Bulletin of the Global Volcanism Network

All reports of volcanic activity published by the Smithsonian since 1968 are available through a monthly table of contents or by searching for a specific volcano. Until 1975, reports were issued for individual volcanoes as information became available; these have been organized by month for convenience. Later publications were done in a monthly newsletter format. Links go to the profile page for each volcano with the Bulletin tab open.

Information is preliminary at time of publication and subject to change.

Recently Published Bulletin Reports

Erta Ale (Ethiopia)

New eruptive event forms lava lake and multiple large flow fields 3 km S of South Pit Crater, January 2017-March 2018

Sinabung (Indonesia)

Large explosion with 16.8 km ash plume, 19 February 2018

Kadovar (Papua New Guinea)

First confirmed historical eruption, ash plumes, and lava flow, January-March 2018

Fournaise, Piton de la (France)

Second eruption of 2017; July-August, fissure with flows on the SE flank

San Cristobal (Nicaragua)

Intermittent ash-bearing explosions during 2017; Ash plume drifts 250 km in August.

Suwanosejima (Japan)

Large explosions with ash plumes and Strombolian activity continue during 2017

Kilauea (United States)

Activity continues at Halema'uma'u lava lake, and at the East Rift Zone 61g flow, July-December 2017

Manam (Papua New Guinea)

Ash plumes and Strombolian explosions increase, March-May 2017

Sangay (Ecuador)

Eruptive episode of ash-bearing explosions and lava on SE flank, 20 July-26 October 2017

Tinakula (Solomon Islands)

Short-lived ash emission and large SO2 plume 21-26 October 2017; historical eruption accounts

Yasur (Vanuatu)

Typical ongoing eruptive activity and thermal anomalies through January 2018

Ambrym (Vanuatu)

Elevated seismicity in early August 2017-early November 2017, lava lakes remain



Erta Ale (Ethiopia) — April 1989 Citation iconCite this Report

Erta Ale

Ethiopia

13.6°N, 40.67°E; summit elev. 613 m

All times are local (unless otherwise noted)


New eruptive event forms lava lake and multiple large flow fields 3 km S of South Pit Crater, January 2017-March 2018

Ethiopia's Erta Ale basaltic shield volcano has had at least one active lava lake since the mid-1960s, and possibly much earlier. Two active craters (North Pit and South Pit) within the larger oval-shaped Summit Caldera have exhibited periodic lava fountaining and lava lake overflows over the years. A new eruptive event located about 3 km SE of the Summit Crater appeared on 21 January 2017. Activity at the eruption site increased during subsequent months, sending lava flows several kilometers NE and SW from a newly formed lava lake. This report discusses activity from February 2017 through March 2018 as the flows traveled as far as 16 km from the main vent. Information comes from satellite thermal and visual imagery, and photographs and reports from ground-based expeditions that periodically visit the site.

Summary of activity, February 2017-March 2018. The 21 January 2017 activity at Erta Ale was the first time a vent outside of the Summit Caldera has been observed (figure 50). The initial vent or vents created multiple lava flows that traveled generally NE and SW from their sources, creating at least one lava lake that persisted for about a year (figure 51). The flows began inside an older caldera at a location about 3 km SE of the South Pit Crater, but eventually overflowed the caldera rim in multiple directions. As the flow fields enlarged, thermal imagery captured hot-spots along the flows that were likely produced by breakouts, skylights into lava tunnels, and hornitos, as well as multiple surges of flows across the growing fields (figure 52). The imagery also showed the locations of the advancing flow fronts which had reached over 5 km SW of the source by August 2017 and over 16 km NE of the source by March 2018, eventually reaching the alluvial plain NE of Erta Ale. Thermal anomaly data indicated that the maximum thermal energy output happened in April 2017, gradually decreasing through March 2018. The far NE front of the northeast flow field was still active at end of March 2018.

Figure (see Caption) Figure 50. The summit of Erta Ale has two oblong NW-trending calderas. The northern Summit Caldera contains the North Pit Crater and the South Pit Crater. The North Pit Crater has had a solidified lava lake with a large hornito emitting magmatic gases and incandescence at night, and the South Pit Crater has had an active lava lake for many years that last overflowed its rim during mid-January 2017. The new eruption began at vents located about 3 km SE of the South Pit Crater near the northern rim of a second caldera referred to here as the Southeast Caldera, on 21 January 2017. The new eruption had not yet begun in this 16 January 2017 image. See figure 46 (BGVN 42:07) for additional images the following week that show the first flows from the new vents. Images copyright by Planet Labs Inc., 3 m per pixel resolution, and used with permission under a Creative Commons license (CC BY-SA 4.0), annotated by GVP.
Figure (see Caption) Figure 51. A new lava lake formed during late January 2017 at the new eruption site about 3 km SE of the South Pit Crater at Erta Ale, inside the Southeast Caldera. This view is likely from the rim of the Southeast Caldera, looking SE or E. Visitors were not able to get closer to the vent due to the active flows for several months. Photo by Stefan Tommasini taken during February 2017, courtesy of Volcano Discovery (Erta Ale volcanic activity: 2017 overview and June update, 27 June 2017).
Figure (see Caption) Figure 52. An active new pahoehoe lava field flowed over older lava flows inside the Southeast Caldera at Erta Ale during February 2017. This photo was likely taken from the northern or western rim of the Southeast Caldera. Photo by Stefan Tommasini, courtesy of Volcano Discovery (Erta Ale volcanic activity: 2017 overview and June update, 27 June 2017).

When the new eruptive episode began, the lava lake at the South Pit Crater drained rapidly to around 80-100 m below the rim, according to visitors to the site a few weeks later. The crater was emitting a strong thermal signal by early March 2017 as the lake level rose again. Visitors in April witnessed a fluctuating lake level rising and falling by up to 20 m every 30 minutes over several days. The thermal signal remained strong at the South Pit Crater through March 2018. Due to significant political instability in the area, ground visits are intermittent, but high-quality photographs were taken in February 2017, December 2017, and January 2018 that show the new lava lake and parts of the new flow fields.

Activity during late January-March 2017. The new eruptive event at Erta Ale began in late January 2017 at the northern end of the Southeast Caldera located; the first lava flows observed were locatedabout 3 km SE from the main Summit Caldera (figure 45 (BGVN 42:07) and figure 50). Two separate vent areas appeared active initially. The northern vent sent lava flows to the NE for several kilometers and to the SW a much shorter distance. The southern vent sent a stream of lava to the S. By the end of January 2017 the North and South Pit Craters at the Summit Caldera were still thermally active, but the signals were much stronger from the new vent areas in the Southeast Caldera (figure 53). A faint thermal signal from about 5 km E of the northern vent suggested the extent of the new flows in that direction.

Figure (see Caption) Figure 53. A Sentinel-2 image from 29 January 2017 shows the initial activity at the new Southeast Caldera vents of Erta Ale (labelled Event 1 and Event 2). Weak thermal signals are apparent from the North and South Pit Craters (Pit Crater Nord, Pit Crater Sud) within the Summit Caldera, and much stronger thermal signals are evident from two areas inside the Southeast Caldera. A faint signal from about 5 km E of the new vents indicates possible flow activity breaking out of lava tubes in that region (Skylight). Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Le point sur l'activité des volcans Etna, Erta Ale, Fuego, Piton de la Fournaise et Bogoslof, 3 février 2017).

A small group of travelers led by Ethiopian geologist Enku Mulugeta visited Erta Ale during the first half of February 2017. They reported that within the main Summit Caldera, the hornito in the North Pit Crater had collapsed and the lava lake in the South Pit Crater was about 80-100 m below the caldera floor level. The eruption in the Southeast Caldera was still very active, and they photographed the sizable new lava field which contained numerous pahoehoe flows, actively spattering hornitos, and a large lava lake (figures 51, 52, and 54). During the following months activity remained high both at the new eruption site and at the Summit Caldera where the lava lake in the South Pit Crater gradually rose back up to about 50 m below the caldera floor. Culture Volcan annotated a series of Sentinel-2 satellite thermal images which show the progression of the lava flows through the following year.

Figure (see Caption) Figure 54. A large new lava field quickly formed inside the Southeast Caldera at Erta Ale after the beginning of the new eruptive event in late January 2017. When photographed here in February 2017, pahoehoe flows had spread outward from a central vent area (glow at top center) for over a kilometer in multiple directions. View is likely to the E from the W rim of the Southeast Caldera. Photo by Stefan Tommasini, February 2017, courtesy of Volcano Discovery (Erta Ale volcanic activity: 2017 overview and June update, 27 June 2017).

By 10 March 2017 only the southern vent area was active inside the Southeast Caldera. It continued to feed the lava field; lava was actively flowing S from the vent towards the W rim of the Southeast Crater, and NE, breaking out from lava tubes which blocked the thermal signal until about 2.6 km NE of the vent (figure 55). Thermal signals from both the North and South Pit Craters were distinct and stronger than in late January.

Figure (see Caption) Figure 55. The thermal signals at both the North and South Pit Craters at Erta Ale were stronger in this 10 March 2017 image than in late January. Only one main source of lava is apparent at the Southeast Caldera. Lava flows directly from the primary vent SW towards the W rim of the caldera, and also surfaces from tunnels about two kilometers NE in an actively moving lava front. Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Un point sur l'activité des volcans Etna et Erta Ale, 13 mars 2017).

A site visit to the South Pit Crater on 20 March 2017 demonstrated that the lake level had risen significantly since its drop in early February, and was once again actively convecting (figure 56). By the end of March 2017, satellite thermal imagery made clear the increasing thermal signal at the South Pit Crater, and in the Southeast Caldera, the major increase in effusion to the NE from the main vent. The width of the flow field had increased to about 1,400 m, and the farthest front was about 3,400 m NE from the vent (figure 57). The lava at the source measured about 180 x 75 m in size, suggesting a lava lake; a smaller overflow to the SW appeared to have reached the W rim of the Southeast Caldera by 30 March 2017 near the area where a new flow had first appeared in a 23 January 2017 satellite image (see figure 46, BGVN 42:07).

Figure (see Caption) Figure 56. The South Pit Crater of Erta Ale on 20 March 2017 had risen significantly from its drop in February and was actively convecting. Photo by Jean-Michel Escarpit, courtesy of Cultur Volcan (Un point sur l'activité des volcans Fuego, Manam et Erta Ale, 22 mars 2017).
Figure (see Caption) Figure 57. The thermal signal at the South Pit Crater continued to increase in this 30 March 2017 satellite image of Erta Ale. The main vent in the Southeast Caldera had dimensions of about 180 x 75 m, suggesting a lake had formed. A large increase in the thermally active area to the NE indicated that the flow field was expanding significantly in that direction, with a few small thermal anomalies between the lake and lava field suggesting a number of small flows or lava tube breakouts. Flow activity also continued to the SW reaching the W rim of the Southeast Crater where lava had flowed past the crater rim in late January (see figure 46, BGNV 42:07). Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Un point sur l'activité des volcans Klyuchevskoy et Erta Ale, 31 mars 2017).

Activity during April-May 2017. In the next Sentinel-2 satellite image from 9 April (figure 58), the distance to the farthest front of the lava flow had increased to about 4,600 m from the lava lake, and a new flow had appeared a few hundred meters east of the lake that extended about 1,100 m ENE from its source. Lava also flowed SW from the source to the SW rim of the Southeast Crater, appearing to pond against and flow slightly beyond the rim.

Figure (see Caption) Figure 58. The lava flows continued to extend NE from their source inside the Southeast Crater at Erta Ale in this Sentinel-2 satellite image from 9 April 2017. The farthest edge of the northeast flow front was about 4,600 m from the lake. A new arm of lava flowed more than a kilometer ENE from its source close to the lake. Another thermal signature SW of the lake indicated an accumulation of lava near or slightly spilling over the SW rim of the Southeast Crater. Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Le point sur l'activité des volcans Erta Ale et Bogoslof, 16 avril 2017).

A group visited Erta Ale during 11-15 April 2017 in collaboration with Addis Ababa University geologist Enku Mulugeta. They noted that fluctuating lava lake levels at the South Pit Crater were cycling every 30 minutes or so between 40 and 50 m below the caldera floor (figures 59 and 60). Lava tubes from the walls of the crater would feed the lake with fresh lava after it drained. Two coalesced hornitos, about 7 m high, were present in the NE part of the crater, emitting SO2 gas and occasional lava. At the North Crater Pit, noisy degassing of SO2 from several hornitos at the center of the solidified crust was apparent. Observers at the Southeast Caldera could see the lava lake with the top about 10 m below its crater rim, and minor fountaining during the night, but they were not able to get closer than about 700 m due to the active flows.

Figure (see Caption) Figure 59. The lava lake level at the South Pit Crater at Erta Ale during April 2017 was fluctuating by 10-20 m every 30 minutes or so. The high-stand of the lava is shown here. Courtesy of Toucan Photo.
Figure (see Caption) Figure 60. The lava lake level at the South Pit Crater at Erta Ale during April 2017 was fluctuating by 10-20 m every 30 minutes or so. The low stand of the lava is shown here as the lava drains away. Courtesy of Toucan Photo.

By the end of April 2017 satellite thermal imagery indicated that the northeast flow field at the Southeast Caldera extended more than 7 km NE from the lake and was curving towards the E (figure 61). The lava lake was still thermally active, as was the South Pit Crater to the NW.

Figure (see Caption) Figure 61. Sentinel-2 satellite imagery of Erta Ale on 29 April 2017 shows the growth of the northeast lava field from earlier in the month to more than 7 kilometers from its source. The South Pit Crater was still active, as was the source of the northeast lava field. Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (L'activité effusive reste soutenue à l'Erta Ale, 3 mai 2017).

Eleven days later, activity was quite different in the Southeast Caldera. Satellite imagery from 9 May 2017 (figure 62) showed a new, relatively narrow but bright lava flow moving NE for 2-3 km originating in a location slightly NE of the original lava lake; activity farther NE had diminished from the previous image. A subsequent image on 18 May looked similar, but by 19 May the narrow flow had been replaced by a much broader area of thermal anomaly in the region immediately E of the source. By 29 May 2017, the source of the lava appeared to have shifted several hundred meters SE of the earlier location, and a strong thermal signal once again extended NE across the northeast flow field from the new source for about two kilometers (figure 63).

Figure (see Caption) Figure 62. A Sentinel-2 satellite image of Erta Ale on 9 May 2017 showed a shift to the NE in the location of the source of the active flows. A new narrow flow had traveled 2-3 km NE from a source located NE of the lava lake. The more distant northeast flow field had a much smaller thermal signature than on 29 April. Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Breakout sur le volcan Erta Ale, 11 mai 2017).
Figure (see Caption) Figure 63. A significant shift to the SE in the location of the lava source from a few weeks earlier is apparent in this Sentinel-2 satellite image of Erta Ale captured on 29 May 2017. A strong thermal anomaly trended NE across the northeast flow field for about two kilometers. Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Erta Ale: une éruption vraiment exceptionnelle, 11 juin 2017).

Activity during June-August 2017. The rapidly changing flow field was significantly different again less than two weeks later in satellite imagery captured on 8 June 2017. Lava was flowing N, SE, and S across the northeast lava field, extending beyond the rim of the Southeast Caldera to the N and E. Another very strong thermal signal emerged from the SW corner of the Southeast Caldera where lava was flowing W and S outside the caldera rim forming a new southwest lava field (figure 64).

Figure (see Caption) Figure 64. A Sentinel-2 satellite image of Erta Ale on 8 June 2017 shows significant changes in the location of the active flow fields from less than two weeks earlier. The South Pit Crater in the Summit Caldera still had a strong thermal signal suggesting an active lake in the crater. Flows in the Southeast Caldera appeared to be moving N, E, and S across the northeast lava field, and a new area with flows moving S and W from the SW rim of the Southeast Caldera formed the new Southwest lava field. Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Erta Ale: une éruption vraiment exceptionnelle, 11 juin 2017).

During June 2017, the most aggressive flow activity contributed to significant growth of the southwest lava field. By 28 June, infrared imaging detected flow fronts 4,500 m SW of the vent; they had extended to about 5,100 m, nearing the base of the SW flank of Erta Ale, by 5 July (figure 65). Flow activity also persisted in the northeast flow field with activity concentrated about 1.5 km NE of the vent on 28 June. Movement increased at the northeast flow field beginning in late June and it had extended to about 3.5 km NE of the lava lake by 5 July 2017.

Figure (see Caption) Figure 65. Lava flow activity at the Southeast Caldera of Erta Ale during June 2017 was concentrated in the growing southwest flow field which had extended about 5,100 m from its lava lake source by 5 July 2017 in this Landsat 8 satellite image. The northeast flow field began extending farther NE during the first week of July, reaching 3,500 m from the lake by 5 July. Courtesy of ESA/Copernicus and NASA/USGS with annotations provided by Culture Volcan (Un point sur l'activité des volcans Copahue et Erta Ale, 8 juillet 2017).

Significant movement to the NE in the northeast flow field was apparent in satellite images beginning on 21 July 2017; the head of the flow had reached about 9.5 km from the lava lake by 28 July 2017, mostly focused in a narrow channel (figure 66). Activity decreased in the southwest flow field during July; the lava front had advanced only a few hundred meters by the end of July from its position on 5 July.

Figure (see Caption) Figure 66. The northeast flow field at Erta Ale lengthened significantly during July 2017; the leading edge was about 9.5 km NE of the lava lake by 28 July 2017, as captured in this Sentinel-2 satellite image. The southwest flow field had extended just a few hundred meters SW from its location on 5 July. The distance between the South Pit Crater and the Southeast Caldera lava lake is about 2.7 km. Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Les actus du jour: Katla en alerte jaune et quelques changements à l'Erta Ale, 29 juillet 2017).

During August 2017, lava continued to flow from the Southeast Caldera lava lake in two directions. The northeast flow front extended to 12 km from the vent by 17 August and had reached over 14 km by 7 September. The southwest flow field, while it remained in roughly the same area, had a decreased but still significant thermal signature in early September, suggesting continued but diminished activity throughout the period (figures 67).

Figure (see Caption) Figure 67. During August 2017, lava continued to flow in two directions from the Southeast Caldera lava lake at Erta Ale. The northeast flow field had reached over 14 km from the lake by 7 September 2017 when this Landsat 8 satellite image was taken. The Southwest flow field, while it remained in roughly the same area, still had a significant thermal signature suggesting continued activity. Courtesy of ESA/Copernicus and NASA/USGS with annotations provided by Culture Volcan (volcan Erta Ale: ça continue; Fernandina: c'est moins sûr, 12 septembre 2017).

Activity during September-December 2017. In a Sentinel-2 satellite image from 26 September 2017, it was clear that the South Crater Pit was still thermally active, and that the southwest flow field had largely cooled with only a small area on its NW edge still producing a thermal anomaly (figure 68). In contrast, the northeast flow field had advanced about 1 km in the previous three weeks and was less than a kilometer from the edge of the valley alluvium. It finally reached the edge of the older lava field and began to advance across the alluvium NE of the volcano, more than 16 km from the lava lake, on 16 October 2017 (figure 69). Based on satellite imagery, Cultur Volcan interpreted that activity slowed significantly during November 2017, and while the thermal signal remained strong near the head of the flow, it did not advance significantly across the alluvium.

Figure (see Caption) Figure 68. The South Pit Crater at Erta Ale still had an active lava lake on 26 September 2017 in this Sentinel-2 satellite image. The southwest lava field had largely cooled, with only a small thermal anomaly along it NW edge. The northeast lava field continued to be active; it had advanced about 1 km NE in about three weeks and was about 650 m from the edge of the alluvium. A significant number of hotspots along the northeast lava flow suggest that several skylights existed into lava tubes or there were small breakouts. Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Les actus du jour: Heard Island, Erta Ale, Pacaya, Fuego, Sangay, Ol Doynio Lengai, 5 octobre 2017).
Figure (see Caption) Figure 69. Erta Ale's northeast flow field reached the alluvium about 16 km E of the Southeast Caldera lava lake by 16 October 2017, as recorded in this Sentinel-2 satellite image. The distance between the ends of the two easternmost tongues of lava is about 1 km. Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Erta Ale: ça y est, le champ de lave entre dans la plaine!, 18 octobre 2017).

Visitors to the South Pit Crater in mid-December 2017 reported that its lava lake continued to be active and its level was about 60 m below the rim. They were also able to visit the Southeast Caldera lava lake, 2.7 km SE of the South Pit Crater, and take photographs from its rim; it was about 200 m long and 100 m wide and filled with slowly convecting lava (figures 70, 71). Satellite imagery from 25 December 2017 showed the active lake at the South Pit Crater, the active lake at the Southeast Caldera, and numerous skylights and overflows along the 16-km-long northeast flow field (figure 72).

Figure (see Caption) Figure 70. The Southeast caldera lava lake at Erta Ale, its surface crusted over with slightly cooled lava, with dimensions of about 200 x 100 m in mid-December 2017. Photograph by FB88, courtesy of Culture Volcan (Un point sur l'activité à l'Erta Ale, 31 décembre 2017).
Figure (see Caption) Figure 71. The Southeast Caldera lava lake at Erta Ale was slowly convecting during mid-December 2017. Photographed by FB88, courtesy of Culture Volcan (Un point sur l'activité à l'Erta Ale, 31 décembre 2017).
Figure (see Caption) Figure 72. Sentinel-2 satellite imagery from 25 December 2017 of Erta Ale showed the active lake at the South Pit Crater (Summit lava lake), the active lake at the Southeast Caldera (Rift-Zone lava lake), and numerous skylights and overflows along the 16-km-long northeast flow field. Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Un point sur l'activité à l'Erta Ale, 31 décembre 2017).

Activity during January-March 2018. By mid-January 2018 thermal activity was concentrated a few kilometers back from the front of the northeast flow, about 12 km from the lava lake (figure 73). A Volcano Discovery tour group visited during 13-26 January 2018 and was able to access and photograph both the North and South Pit Craters and the new lake and flow fields around the Southeast Caldera with ground-based and aerial drone photography (figures 74-84).

Figure (see Caption) Figure 73. By 19 January 2018, thermal activity at Erta Ale's northeast flow field was concentrated a few kilometers back from the front of the flow, about 12 km from the Southeast Caldera lava lake. The South Pit Crater and Southeast Caldera lava lakes are visible on the left. Small hot-spots near the Southeast Caldera lava lake could be hornitos or skylights into lava tubes. Courtesy of ESA/Copernicus with annotations provided by Culture Volcan (Le point sur l'activité des volcans Erta Ale, Kadovar (Mis à jour) et Nevados de Chillan, 21 janvier 2018).
Figure (see Caption) Figure 74. In this aerial view taken in January 2018 by a drone of the central part of Erta Ale's Summit Caldera, steam plumes rose from the North Pit Crater (left) and South Pit Crater (right). The fresh black lava around the South Pit Crater overflowed onto the caldera floor in January 2017 shortly before the beginning of the eruptive events in the Southeast Caldera a few kilometers to the south. Photograph by Stefan Tommasini taken during 13-26 January 2018, courtesy of Volcano Discovery.
Figure (see Caption) Figure 75. The North Pit Crater inside the Summit Caldera at Erta Ale contained a large collapsed vent in January 2018 that formed after the magma drained away from the crater in January 2017. Photograph by Stefan Tommasini taken during 13-26 January 2018, courtesy of Volcano Discovery.
Figure (see Caption) Figure 76. The lava lake in the South Pit Crater of Erta Ale's Summit Caldera was tens of meters below the rim in January 2018. Magma drained away and parts of the crater walls collapsed in January 2017, followed by repeated filling and draining of the lava lake during 2017. Photograph by Stefan Tommasini taken during 13-26 January 2018, courtesy of Volcano Discovery.
Figure (see Caption) Figure 77. This aerial view by drone shows the large lava lake that formed at Erta Ale's Southeast Caldera during 2017; it was still slowly convecting in January 2018. The lake dimensions were about 100 x 200 m. Photograph by Stefan Tommasini taken during 13-26 January 2018, courtesy of Volcano Discovery.
Figure (see Caption) Figure 78. Recently cooled black crust is overrun and consumed by molten lava that quickly cools and crusts over in Erta Ale's Southeast Caldera lava lake in January 2018. Photograph by Stefan Tommasini taken during 13-26 January 2018, courtesy of Volcano Discovery.
Figure (see Caption) Figure 79. Lava appears to flow into the Southeast Caldera lava lake at Erta Ale from a vent at the far edge and slowly spread across the lake during January 2018. Photograph by Stefan Tommasini taken during 13-26 January 2018, courtesy of Volcano Discovery.
Figure (see Caption) Figure 80. Lava splashes as it flows into the Southeast Caldera lava lake at Erta Ale in January 2018. Photograph by Anastasia Ganuschenko taken during 13-26 January 2018, courtesy of Volcano Discovery.
Figure (see Caption) Figure 81. Downwelling consumes lava inside the Southeast Caldera lava lake at Erta Ale in January 2018. Photograph by Stefan Tommasini taken during 13-26 January 2018, courtesy of Volcano Discovery.
Figure (see Caption) Figure 82. Incandescence is visible inside a hornito that formed through lava spattering along the new flows in the Southeast Caldera at Erta Ale in January 2018. Photograph by Anastasia Ganuschenko taken during 13-26 January 2018, courtesy of Volcano Discovery.
Figure (see Caption) Figure 83. Many layers of fresh Pahoehoe lava flows were cool enough to walk on in some areas of the Southeast Caldera lava fields in January 2018. Photograph by Stefan Tommasini taken during 13-26 January 2018, courtesy of Volcano Discovery.
Figure (see Caption) Figure 84. Fresh lava flows were easily distinguished from older ones by their silver hue and dark black crust at Erta Ale's Southeast Caldera lava fields in January 2018. Photograph by Stefan Tommasini taken during 13-26 January 2018, courtesy of Volcano Discovery.

By late March 2018 no thermal signal appeared in satellite imagery at the site of the Southeast Caldera lava lake, although the South Pit Crater was still visible. A large increase in the area of fresh flows and multiple thermal anomalies were present at the flow front of the northeast lava field 14-16 km from the former lava lake (figure 85). During the second half of March, the flow progressed several hundred meters out into the alluvial plain.

Figure (see Caption) Figure 85. Sentinel-2 satellite imagery captured on 15 March 2018 showed a large increase in the area of fresh lava flows at the NE front of the northeast lava field at Erta Ale when compared with an image from 19 January 2018. Over the next ten days, images showed the narrow finger of lava that just touches the alluvium in this image creep about a kilometer out into the alluvial plain. Courtesy of Courtesy of ESA/Copernicus, published by Cultur Volcan (Les actus volcaniques du jour: Erta Ale, Maly-Semiachik, Suwanose-Jima et Ebeko, 28 mars 2018).

MIROVA thermal anomaly data. The MIROVA thermal anomaly data captures information about the distance of the anomalies from the summit as well as the radiative power released from Erta Ale. Both sets of information agree well with observations from the Sentinel-2 and Landsat satellite data. The plot of distance from the summit (figure 86) shows that during August 2016-mid-January 2017 the thermal anomalies were located very close to the summit point, representing heat flow from both the South and North Pit Craters within the Summit Caldera. Beginning on 21 January 2017, the jump in location of the anomalies corresponded with the beginning of the eruption in the Southeast Caldera. The MIROVA thermal anomalies progressed farther from the summit point during March and April 2017, when the northeast flow field was lengthening to the NE. The thermal signal jumps back closer to the summit point in early May corresponding to when new breakouts were spotted near the Southeast Caldera lava lake; the flows again traveled away from the lake during June and July 2017. Active lava flows from mid-August 2017 through March 2018 were visible in satellite imagery 12-16 km from the lava lake, which is reflected in the MIROVA data (figure 86).

Figure (see Caption) Figure 86. MIROVA data showing the distance from the summit point of thermal anomalies at Erta Ale. Upper graph is the year ending 18 July 2017. Lower graph is the year ending 9 March 2018. They correspond well with locations of thermal anomalies that appear in numerous satellite images during that time. Note the distance scale change. See text and earlier figures for details. Courtesy of MIROVA.

The MIROVA data for the radiative power released from Erta Ale during August 2016-March 2018 also corresponds well with satellite and ground observations (figure 87). The levels of radiative power were moderate and constant during August 2016 to mid-January 2017 when only the lava lake and hornitos at the South and North Pit Craters were active (see also figure 47, BGVN 42:07). A moderate spike in the radiative power corresponds to the overflow of the South Pit Crater during 16-20 January 2017, followed by a large spike in radiative power on 21 January when the eruption started in the Southeast Caldera. This was followed by an extended period of increased radiative power as extensive flow fields formed in the Southeast Caldera. The graph is also able to distinguish the movement of the flows from near the Southeast Caldera lava lake to farther away and then near again during March-June 2017. The radiative power graph from 10 March 2017-9 March 2018 clearly shows a gradual decrease in the amount of radiative power over the period, suggesting a decline in flow activity, which corresponds well to satellite observations.

Figure (see Caption) Figure 87. MIROVA plots of radiative power at Erta Ale for 18 July 2016-18 July 2017 (upper) and 9 March 2017-9 March 2018 (lower). Note the different y-axis scales for VRP due to the large spike on 21 January 2017 at the beginning of the Southeast Caldera eruptive episode. The plots record both the movement of the flow fields away from and closer to the summit point during March-June 2017, and then the gradual decrease in radiative energy from May 2017 through early March 2018. Courtesy of MIROVA.

Geologic Background. Erta Ale is an isolated basaltic shield that is the most active volcano in Ethiopia. The broad, 50-km-wide edifice rises more than 600 m from below sea level in the barren Danakil depression. Erta Ale is the namesake and most prominent feature of the Erta Ale Range. The volcano contains a 0.7 x 1.6 km, elliptical summit crater housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera is renowned for one, or sometimes two long-term lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the N flank.

Information Contacts: European Space Agency (ESA), Copernicus (URL: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus; Robert Simon, Sr., Data Visualization Engineer, Planet Labs Inc. (URL: http://www.planet.com/) [Images used under https://creativecommons.org/licenses/by-sa/4.0/]; Cultur Volcan, Journal d'un volcanophile (URL: https://laculturevolcan.blogspot.com); Toucan Photo (URL: www.toucan.photo); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


Sinabung (Indonesia) — April 1989 Citation iconCite this Report

Sinabung

Indonesia

3.17°N, 98.392°E; summit elev. 2460 m

All times are local (unless otherwise noted)


Large explosion with 16.8 km ash plume, 19 February 2018

Indonesia's Sinabung volcano has been highly active since its first confirmed Holocene eruption during August and September 2010; ash plumes initially rose up to 2 km above the summit, and falling ash and tephra caused fatalities and thousands of evacuations (BGVN 35:07). It remained quiet after the initial eruption until 15 September 2013, when a new eruptive phase began that has continued uninterrupted through February 2018. Ash plumes rising several kilometers, avalanche blocks falling several kilometers down the flanks, and deadly pyroclastic flows travelling more than 4 km have all been documented repeatedly during the last several years. Details of events during October 2017-March 2018, including the largest explosion to date on 19 February 2018, are covered in this report. Information is provided by, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), referred to by some agencies as CVGHM or the Indonesian Center of Volcanology and Geological Hazard Mitigation, the Darwin Volcanic Ash Advisory Centre (VAAC), and the Badan Nacional Penanggulangan Bencana (National Disaster Management Authority, BNPB). Additional information comes from satellite instruments and local observers.

When activity began in 2010, and again when eruptions resumed in 2013, many news accounts included statements that Sinabung had last been active 400 years ago, or even saying specifically that the last eruption was in 1600 CE. Those claims appear to have been caused by a misunderstanding related to the boundary time that Indonesian volcanologists use to categorize volcanoes. Those volcanoes with historical activity, defined as being about 400 years ago (corresponding to the beginning of the Dutch East India Company era), are in the "Type A" group. Those in the "Type B" group, including Sinabung prior to 2010, have not had reported activity in more than 400 years. Using charcoal associated with the most recent pyroclastic flow, Hendrasto et al. (2012) determined that the last previous eruptive activity was 1200 years before present using carbon dating techniques, or 740-880 CE (at 1 sigma).

Although activity remained high from October 2017 through March 2018, a gradual decline in the overall eruptive activity from the beginning of 2017 was apparent. The number of explosions per month generally declined, with no explosions reported during March 2018, for the first time since August 2013 (figure 45). The thermal anomaly record was similar; periods of high heat flow persisted through mid-November 2017, followed by a gradual reduction in the amount of thermal activity, although the intensity remained consistent, according to the MIROVA project (figure 46). Much of the heat flow was attributed to the dome growth at the summit; the dome was destroyed in the large explosion of 19 February 2018.

Figure (see Caption) Figure 45. The number of explosions per month at Sinabung as reported by PVMBG from January 2017-March 2018. Only partial data was reported for 18-31 January 2018, and no explosions were observed during March 2018.
Figure (see Caption) Figure 46. Thermal anomaly data at Sinabung from satellite-based MODIS instruments, plotted on a Log Radiative Power scale, persisted through the end of 2017 and then decreased in frequency through the end of February 2018. Much of the heat flow was attributed to a dome near the summit which was destroyed in the 19 February 2018 explosion. Graph shows thermal anomalies between 11 May 2017 and 1 April 2018. Courtesy of MIROVA.

Throughout the period from October 2017 through 19 February 2018, steam plumes were constantly rising to heights of 1,000-2,400 m above the summit. Avalanche blocks were ejected daily down the E and S flanks from 500-3,500 m, and multiple pyroclastic flows each month traveled between 1,000 and 4,600 m down the SE flank. Tens of explosions occurred monthly, generating ash plumes that rose from 500 to 5,000 m above the summit. Explosive activity was more intermittent during February than the previous months, until 19 February when the largest explosion to date occurred; it included an ash plume that rose to at least 16.8 km altitude and at least ten pyroclastic flows. In spite of the size of the explosion, no injuries or fatalities were reported as most nearby communities had been evacuated from the ongoing activity. Activity decreased substantially during March 2018; there were no explosions, block avalanches, or pyroclastic flows reported, only steam plumes rising 1,000 m above the summit.

Activity during October 2017-January 2018. During October 2017, steam plume heights reached 1,500 m above the summit. Avalanche blocks traveled down the E and S flanks 500-2,500 m, and eight pyroclastic flows traveled 1,000-4,500 m down the SE and S flanks. Ash plume heights ranged from 500 to 3,600 m above the summit. The Darwin VAAC issued 38 aviation alerts during the month. On 1 October they reported an ash plume drifting both NW at 4.6 km altitude and NE at 3.7 km. The next day, the webcam observed an ash emission that rose to 5.5 km altitude. On 4 October an ash plume was spotted in the webcam rising to 5.8 km altitude and drifting ENE. Later that day it had detached from the volcano and was seen drifting NW in satellite imagery. An ash plume on 5 October rose to 3.9 km altitude and drifted ESE. Two ash emission were reported on 7 October; the first rose to 3 km altitude, the second rose to 4.3 km, they both dissipated quickly. On 8 October, three plumes were reported. The first rose to 4.6 km and drifted WSW, the second rose to 3 km and drifted S and the third rose to 3.4 km and also drifted S. The following day, an ash plume rose to 4.6 km and drifted E. BNPB stated that on 11 October, an event at Sinabung generated an ash plume that rose 1.5 km above the crater and drifted ESE, causing ashfall in several local villages. On 12 October an event produced an ash plume that rose 2 km above the crater and was followed by pyroclastic flows traveling 1.5 and 2 km down the S and ESE flanks, respectively.

PVMBG reported ash plumes rising to 3.7 km on 11, 12, and 13 October 2017. Later on 13 October the Jakarta MWO reported an ash plume at 4.3 km. The next day PVMBG reported an ash plume at 5.5 km altitude. A plume on 15 October rose to 3 km and drifted E. A steam plume on 16 October drifted down the SE flank before drifting SE no 16 October (figure 47). On 17 October, a discrete emission rose a few hundred meters above the summit drifted NE. Later that day, an ash plume was seen in the webcam moving SE at 3.4 km. On 18 October, two ash emissions were reported. The first rose to 3.7 km and drifted E, the second rose to 3.9 km and drifted W. An ash plume rose to 4.6 km altitude on 21 October, and to 3.9 km, drifting S, on 23 October. The next day, three ash plumes were reported; the first rose to 3 km, the second to 4.6 km, and the third to 3.7, all drifting E. After five days of quiet, the webcam observed ash plumes that rose to 4.3 km on 30 October, and to 3.9 km on 31 October. Only two MODVOLC thermal alerts were issued, on 20 and 27 October.

Figure (see Caption) Figure 47. A steam plume drifted down the SW flank of Sinabung before moving SE on 16 October 2017. View is from the SE. Courtesy of PVMBG.

Steam plumes were higher during November 2017, rising 2,400 m above the summit. Block avalanches traveled 500-3,000 m down the E and S flanks most days, and ten pyroclastic flows traveled between 2,000-3,500 m down the ESE and S flanks. The ash plumes rose 700-3,200 m above the summit. The Darwin VAAC issued 41 aviation alerts in November. Near-daily ash plumes were observed mostly in the webcam and occasionally in satellite imagery. They generally rose to 3.4-4.9 km altitude; the most common drift directions were S and SW. A number of times, multiple ash plumes were reported in a single day. On 14 November, four ash plumes were observed. The first rose to 3.7 km, the second and third rose to 4.6 km and drifted S and SSW, the last rose to 3.9 km and also drifted SSW. On 20 November a discrete emission produced an ash plume that rose to 5.5 km altitude and drifted SSW. Three ash plumes were recorded the next day, rising 3.9-4.6 km and drifting in multiple directions under variable winds. An ash plume on 23 November was reported by PVMBG at 6.7 km altitude drifting W, the highest noted for the month. MODVOLC thermal alerts appeared twice on 5 November, once on 14 November, and three times on 17 November.

Activity during December 2017 was similar to the previous two months; steam plumes rose 2,000 m above the summit, block avalanches traveled 500-3,500 m down the E and S flanks numerous times, and nine pyroclastic flows descended the ESE and S flanks distances ranging from 2,000 to 4,600 m. Ash plume heights were from 700-4,000 m above the summit. The Darwin VAAC issued 43 aviation alerts in December 2017. They reported ash plume heights of 3.4-4.9 km altitude on most days. Every day during 10-19 December, ash plumes were reported at altitudes of 4.6-5.5 km drifting SW, E or SE. PVMBG reported ash plumes on 26, 27 and 28 December that rose to 3.9, 5.2, and 5.5 km, respectively. BNPB reported pyroclastic flows on 27 December that traveled 3.5-4.6 km SE, and ashfall was reported in many nearby villages including Sukanalu Village (20 km SE), Tonggal Town, Central Kuta, Gamber (4 km SE), Berastepu (4 km SE), and Jeraya (6 km SE). The highest ash plume of the month rose to 6.4 km altitude on 29 December and drifted E. This was followed by another discrete ash emission the same day that rose to 5.8 km and two plumes the next day that rose to 5.2 km and drifted W. There was only one MODVOLC thermal alert issued on 7 December.

The Darwin VAAC issued 56 aviation alerts for January 2018. Multiple discrete ash emissions were reported on most days. Plume altitudes generally ranged from 3.4 to 5.5 km. A 6.1 km altitude plume was visible in satellite imagery on 18 January (figure 48). The drift directions were highly variable throughout the month. Most plumes dissipated within six hours. Incandescent blocks were reported by PVMBG falling 500-1,500 m down the ESE flank on most days when the summit was visible. They also reported a pyroclastic flow on 27 January that traveled 2,500 m ESE from the summit (figure 49). Three MODVOLC thermal alerts were issued on 6 January, and one on 12 January.

Figure (see Caption) Figure 48. An ash plume rose 3,000 m from the summit of Sinabung on 18 January 2018 in this view looking at the SE flank. Photographer unknown, courtesy of Sutopo Purwo Nugroho, Twitter.
Figure (see Caption) Figure 49. A pyroclastic flow descended 2,500 m down the SE flank of Sinabung on 27 January 2018 while an ash plume also drifts SE in this view of the SE flank. Photographer unknown, courtesy of Sutopo Purwo Nugroho, Twitter.

Activity during February 2018. During most of February, steam plumes rose only 1,000 m above the summit, and avalanche blocks traveled 500-2,500 m down the ESE and S flanks. Far fewer ash emissions were reported than previous months, but the largest explosive event recorded to date took place on 19 February (figure 50). The Darwin VAAC issued 29 aviation alerts during February 2018. Short-lived ash emissions were reported on 1, 3, 5, 11, and 15 February. The ash plume heights ranged from 3.4-4.6 km altitude, and they drifted S or SW.

Figure (see Caption) Figure 50. A very large ash plume rose to 16.8 km altitude from Sinabung on 19 February 2018. Image is from several tens of kilometers from the volcano a few hours after the eruption. No fatalities were reported. Photographer unknown, courtesy of Sutopo Purwo Nugroho, Twitter.

The large explosion was first reported by the Darwin VAAC at 0255 UTC on 19 February 2018. It produced an ash plume, which was clearly observed in satellite imagery (figure 51), that quickly rose to at least 16.8 km altitude and began drifting NW (figure 52). It also produced a large SO2 plume that was recorded by satellite instruments (figure 53). Over the next 15 hours the plume dispersed in three different directions at different altitudes. The highest part of the plume drifted NW at 13.7 km and was visible over 300 km from the summit. The lower part of the plume drifted S initially at 6.7 km and gradually lowered to 4.3 km; it was visible 75 km from the summit before dissipating. A middle part of the plume drifted NW at 9.1 km during the middle of the day. Three subsequent minor ash emissions were observed on 20 and 25 February that rose to 3.4 km altitude. There were no VAAC reports issued during March 2018. A MODVOLC thermal alert issued on 11 February was the last for several months.

Figure (see Caption) Figure 51. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this natural-color image of the ash plume at Sinabung at 0410 UTC on 19 February 2018, just a few hours after it began. The ash plume rose over 16 km high and drifted in multiple directions. Courtesy of NASA Earth Observatory.
Figure (see Caption) Figure 52. The large ash plume of 19 February 2018 at Sinabung, viewed here from within a few kilometers of the summit in the first hour or so after the eruption, rose quickly to over 16 km altitude. Photographer unknown, courtesy of Sutopo Purwo Nugroho, Twitter.
Figure (see Caption) Figure 53. Two different Ozone Monitoring Instruments measured the SO2 plume released by Sinabung in the explosion on 19 February 2018. The upper left image was recorded about three hours after the explosions (0616-0621 UTC, 19 February 2018) by the Ozone Mapper Profiler Suite (OMPS) instrument on the Suomi NPP satellite. The upper right image was recorded about 27 hours after the explosion (0619-0802 UTC, 19 February 2018) by the Ozone Monitoring Instrument (OMI) on the Aura satellite, and shows the multi-directional dispersal of the SO2 plume during that time. The lower image uses the data captured at the same time as the upper left image and displays it using different software and detailed background information. The maximum gas concentrations reached 140 Dobson Units. Upper images courtesy of NASA Goddard Space Flight Center, and lower image courtesy of NASA Earth Observatory.

As many as 10 pyroclastic flows were observed during the 19 February explosion, traveling as far as 4.9 km SSE and 3.5 km E (figures 54 and 55). Ash and tephra as large as a few millimeters in diameter fell in areas downwind, including Simpang Empat (7 km SE), the Namanteran district, Pqyung (5 km SSW), Tiganderket (7 km W), Munthe, Kutambaru (20 km NW), Perbaji (4 km SW), and Kutarayat (figure 56 and 57).

Figure (see Caption) Figure 54. A pyroclastic flow traveled several kilometers SSE from Sinabung on 19 February 2018 as tephra fell from the rising ash cloud in this view from several kilometers away to the NE. Photographer unknown, courtesy of Sutopo Purwo Nugroho, Twitter.
Figure (see Caption) Figure 55. The dark gray ash plume rose skyward while the large brown pyroclastic flows traveled SE from Sinabung on 19 February 2018 as viewed from the town of Kutarakyat located 5 km NE of the volcano. Photo by Endro Rusharyanto, courtesy of the Associated Press (AP).
Figure (see Caption) Figure 56. Small tephra fragments fell on the village of Gurukinayan (13 km E) and other villages SE of Sinabung during the eruption of 19 February 2018. Photographer unknown, courtesy of Sutopo Purwo Nugroho, Twitter.
Figure (see Caption) Figure 57. Ash from the eruption at Sinabung on 19 February 2018 covered vegetable plants the following day in the village of Payung (5 km SSW). Photograph by Antara Foto, Ahmad Putra via Reuters.

Villagers were temporarily evacuated from nearby villages, but were able to return a few days later (figure 58). Conditions in five districts were so dark that visibility was reduced to about 5 m. In addition, ashfall was recorded as far away as the town of Lhokseumawe, 260 km N. Magma Indonesia reported that the lava dome that had been growing at the summit for some time was destroyed in the 19 February explosion (figure 59). A PVMBG volcanologist reported the volume of the destroyed lava dome was at least 1.6 million cubic meters.

Figure (see Caption) Figure 58. Villagers from Gurukinayan (13 km E) were evacuated as ash spread over the town from the eruption of Sinabung on 19 February 2018, but they returned to their homes a few days later. Photographer unknown, courtesy of Sutopo Purwo Nugroho, Twitter.
Figure (see Caption) Figure 59. The summit of Sinabung, before (top) and after (bottom) the large explosion of 19 February 2018. The dome size in the upper photo is similar to that shown figure 43 (BGVN 42:12) from September 2017. The lower image was taken within a week after the explosion. Courtesy of MAGMA Indonesia, via Twitter.

Reference: Hendrasto M, Surono, Budianto A, Kristianto, Triastuty H, Haerani N, Basuki A, Suparman Y, Primulyana S, Prambada O, Loeqman A, Indrastuti N, Andreas A S, Rosadi U, Adi S, Iguchi M, Ohkura T, Nakada S, Yoshimoto M, 2012. Evaluation of Volcanic Activity at Sinabung Volcano, After More Than 400 Years of Quiet. Journal of Disaster Research, vol. 7, no. 1, p. 37-44.

Geologic Background. Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); Sutopo Purwo Nugroho, Head of Information Data and Public Relations Center of BNPB via Twitter (URL: https://twitter.com/Sutopo_PN); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Associated Press (AP), Endro Rusharyanto, Photographer (URL: http://www.ap.org/); Reuters (http://www.reuters.com/).


Kadovar (Papua New Guinea) — April 1989 Citation iconCite this Report

Kadovar

Papua New Guinea

3.608°S, 144.588°E; summit elev. 365 m

All times are local (unless otherwise noted)


First confirmed historical eruption, ash plumes, and lava flow, January-March 2018

The first confirmed historical eruption at Kadovar began around mid-day local time on 5 January 2018, according to witnesses. The steeply-sloped island is approximately 1.4 km in diameter and is located about 25 km NNE from the mouth of the Sepik River on the mainland of Papua New Guinea (figure 1). This report covers activity from the beginning of the eruption on 5 January through March 2018. Information about the eruption is provided by the Rabaul Volcano Observatory (RVO), the Darwin Volcanic Ash Advisory Center (VAAC), satellite sources, news reports, and local observers. A possible eruption was witnessed by explorers in 1700; no other activity was reported until an outbreak of thermal activity in 1976 (NSEB 01:14-01:11, SEAN 03:09) and a short period of seismic unrest in 2015, according to RVO.

Figure (see Caption) Figure 1. Kadovar Island is located about 25 km NNE from the mouth of the Sepik River on the mainland of Papua New Guinea. Nearby active volcanoes include Blup Blup (12 km N) and Bam (21 km W); residents of Kadovar were evacuated initially to Blup Blup before being moved to an area near Wewak, the nearest community on the mainland, about 105 km W. The red triangles are Holocene volcanoes, and the blue (cyan) triangles are Pleistocene volcanoes. Base map courtesy of Google Earth.

Ash and steam emissions from Kadovar were first reported on 5 January 2018. After about 24 hours, more than half of the island was covered by volcanic debris. Activity intensified over the next two weeks; RVO identified five distinct vents located at the summit and along the SE coast. Dense ash plumes and steam rose from the summit vents, and a slowly-extruding lava flow emerged from a vent near the shoreline on the SE flank. Persistent steam and intermittent ash plumes were produced from the summit vent through the end of March. The lava flow grew outward from the shore for tens of meters before collapsing in early February, but it reappeared a few days later. By the end of the first week of March 2018 the flow was about 17 m above sea level; its growth rate had slowed, adding only one meter by late March.

The NOAA/CIMSS Volcanic Cloud Monitoring system generated an alert for an ash cloud moving WNW, as imaged by S-NPP VIIRS, at 0330 UTC on 5 January 2018; Himawari-8 imagery subsequently showed that the eruption began around 0220 UTC. The Darwin VAAC reported two discrete ash plumes drifting W at 2.1 km altitude during the day. After local reports of the eruption Samaritan Airlines flew administrators from the Wewak district to investigate, enabling photographs of ash and steam emissions (figure 2).

Figure (see Caption) Figure 2. Steam and ash emerged from a vent near the summit of Kadovar Island and drifted WNW on 5 January 2018. The view is looking NW with the SE flank of Kadovar in the foreground. In the upper photo, the island in the background is Viai Island about 30 km NW. Photo by Ricky Wobar, administrator of the Wewak district. Courtesy of Samaritan Aviation, posted on Facebook on 5 January 2018.

The following day, 6 January 2018, photos from a Samaritan Air flight showed that dark gray ash and steam plumes rising from a crater on the SE side of the summit had intensified (figures 3 and 4). It was estimated that 50 or 60% of the island was covered in volcanic debris, which appeared to be primarily ash along with some pyroclastic flows. According to the International Federation of Red Cross and Red Crescent Societies (IFRC), the entire population of Kadovar, about 600 people who lived on the N side of the island, was relocated to nearby Blup Blup Island which is home to about 800 residents. RVO reported minor ashfall on Kairiru and Mushu islands (115 km WNW), and on mainland Papua New Guinea at Mt. Uru in Yangoru (130 km W), Woginara (140 km W), and the Wewak District (100 km W).

Figure (see Caption) Figure 3. Ash and steam plumes rose from distinct vents on the SE side of the summit at Kadovar. View is to the NE, with Blup Blup volcano located about 12 km in the distance. Photo by Ricky Wobar likely taken on 6 January 2018, published by ABC News on 8 January 2018. Courtesy of ABC News.
Figure (see Caption) Figure 4. Ash and steam emissions intensified from vents at the summit of Kadovar Island on 6 January 2018. Posted on Facebook, 6 January 2018 by Samaritan Aviation.

Also on 6 January 2018, missionary Brandon Buser set out from Wewak to visit Bam by boat. He observed the steam and ash plumes of Kadovar from about 75 km away. About 25 km W of the island, he felt falling ash. From a few hundred meters offshore he witnessed the ash and steam plumes rising from near the summit as he circled the S and E sides of the island (figures 5-8).

Figure (see Caption) Figure 5. Locations of the following photographs of the eruption at Kadovar on 6 January 2018 correspond closely to the purple spots where the boat slowed down on its trip around the island. North is to the top. Numbers indicate approximate locations of the following figures 6-12. Courtesy of Brandon Buser. Base map courtesy of Google Earth.
Figure (see Caption) Figure 6. An ash plume drifted NW from the summit of Kadovar as viewed from a boat a few hundred meters off the SW flank on 6 January 2018. Courtesy of Brandon Buser.
Figure (see Caption) Figure 7. Ash drifted WNW from Kadovar and also covered the vegetation on the SSW flank on 6 January 2018 in this view from a boat a few hundred meters off the SSW flank. Courtesy of Brandon Buser.
Figure (see Caption) Figure 8. Dark ash and white steam both rose from vents at the summit of Kadovar on 6 January 2018. Debris and ashfall killed and denuded the trees on the SE flank, and covered the ground. View is from a boat a few hundred meters off the SE flank. Courtesy of Brandon Buser.

While preparing to head E to Bam, Buser witnessed an explosion that sent large plumes of ash and steam skyward from the SE flank, and a significant cloud of volcanic debris was ejected outward and down the SE flank; large boulders fell into the ocean. Heading rapidly E away from the eruption, he took additional photographs (figures 9-12).

Figure (see Caption) Figure 9. Dark gray ash and white steam billowed up from a vent near the summit of Kadovar on 6 January 2018 at the start of an explosion. The denuded vegetation and bare slopes on the SE flank indicated the extent of the recent activity. The view is from a boat a few hundred meters offshore of the NE flank. Courtesy of Brandon Buser.
Figure (see Caption) Figure 10. An explosion witnessed at Kadovar on 6 January 2018. Steam rose from a vent near the summit (right), dark gray ash billowed up from the SE flank, and brown dust and debris descended the SE flank into the ocean (left) in this view from a few hundred meters off the NE flank. Courtesy of Brandon Buser.
Figure (see Caption) Figure 11. A large explosion at Kadovar witnessed on 6 January 2018. Light gray steam and ash rose from near the summit and drifted NW covering the N half of the island in ash; a large eruption of dark gray ash shot upward from a different vent on the SE flank surrounded by dust and debris that traveled outward at its base. Larger debris caused splashing in the water off the SE flank (left). View is from a few kilometers off the NE flank. Courtesy of Brandon Buser.
Figure (see Caption) Figure 12. The plumes of steam, ash, and debris from the explosion moments earlier at Kadovar on 6 January 2018 rose and began to drift NW covering the island. Blocks landing in the ocean on the SE flank created spray along the shoreline (left). View is from a boat a few kilometers NE of the island. Courtesy of Brandon Buser.

The Darwin VAAC reported on 6 January 2018 that a continuous ash plume was identifiable in satellite imagery moving W and WNW at 2.1 km altitude. By 7 January, the plume could be identified about 220 km WNW in satellite images (figure 13). During their return trip from Bam on 8 January 2018, the missionaries again circled the island and noted that the eruption seemed to be occurring from different vents. The island was covered in ash, and they became covered with wet ash as they traveled under the drifting ash plume. The Darwin VAAC reported the plume drifting WNW extending about 185 km on 8 January. They also noted that the influence of the sea breeze was also spreading minor ash to the SW. Continuous ash emissions were observed by the Darwin VAAC through 11 January, drifting W and NW at 2.1 km altitude.

Figure (see Caption) Figure 13. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite captured the eruption of Kadovar that began two days earlier on 7 January 2018 as a plume of ash and steam that streamed NW from its crater. A second smaller plume, also drifting NW, is visible SE of Kadovar from unrelated activity at nearby Manam, one of Papua New Guinea's most active volcanos. Brown-green plumes visible in the water S of Kadovar near the coast of the mainland, are caused by sediment from the Sepik and Ramu rivers on the mainland. Courtesy of NASA Earth Observatory.

RVO reported a significant escalation in activity during 12-13 January 2018. An explosion during the previous night ejected large incandescent boulders from the fracture on the SE flank. Residents on Blup Blup (15 km N) could see incandescence high on the volcano's flank. During a flyover on 13 January, RVO noted variable steam and gas emissions rising to 1 km above the Main Crater and identified five distinct vents (figure 14). The SE Coastal Vent was very active with dense white steam emissions rising 600 m from the vent (figure 15). A dome of lava was visible at the base of the steam plume, but no incandescence was observed. The Southern Coastal Vent had been vigorously steaming a few days earlier, and RVO interpreted it to be the source of the incandescent blocks in the explosion a few days before.

Figure (see Caption) Figure 14. A sketch map of the five newly identified vents at Kadovar, 14 January 2018, from an RVO overflight the previous day. Courtesy of RVO (VOLCANO INFORMATION BULLETIN- No. 08 14/01/2018).
Figure (see Caption) Figure 15. A vigorous steam plume rose from the SE Coastal Vent at Kadovar on 13 January 2018 while an ash plume rose from Main Crater at the summit. Photo by the office of Allan Bird, Governor of East Sepik Province. Courtesy of RVO (VOLCANO INFORMATION BULLETIN- No. 08 14/01/2018).

Reports of continuous ash emissions at 2.1 km altitude drifting WNW from the Darwin VAAC resumed on 16 January. A brief emission to 3.7 km was also noted that day. Pilot reports on 17 and 18 January indicated that ash was still in the area as high as 3-3.7 km altitude drifting W. The reports of emissions from the Darwin VAAC continued through 24 January. Ash emissions were generally continuous at altitudes from 2.4 to 3 km, although low level emissions of primarily steam and gas were observed on 20 January that included intermittent phases of increased ash content. The plume drift direction was variable, with periods when ash drifted S and SE in addition to the generally prevailing NW and W directions.

During 18-22 January 2018, the Main Crater continued to produce moderate to dark gray ash plumes that rose 500-800 m above the summit, drifting locally S and SE, and a continuous steam plume from the SE Coastal Vent rose as high as 800 m above the island. An incandescent lava flow slowly extruded from the SE Coastal Vent. By the last week of January, the ash plumes were only rising about 100 m above the Main Crater and drifting W; weak incandescence was still observed at night. The white steam plume from the SE Coastal Vent rose closer to 400 m above the island. RVO estimated that the lava flow had risen to about 50 m above sea level and extended 150-200 m out from the coast.

In their report on 2 February 2018, RVO noted that the lava flow continued to grow. A distinct lobe had pushed out from the seaward nose of the flow, by about 20-30 m; it appeared to be channeled by levees which had developed at the flow's sides. At 1830 local time on 1 February, a collapse of the side of the flow facing Blup Blup was observed; it resulted in a plume of gray ash and then vigorous steaming at the collapse site, which also was incandescent at night. The main body of the flow significantly bulged upwards, with a distinct 'valley' visible between the bulge and the island's flank.

RVO reported that on 9 February the lava flow at the SE Coastal Vent had collapsed, causing 5-6 minor tsunamis less than 1 m high that were observed by residents on Blup Blup's E and W coasts. The waves were reported at 1050, before the main collapse of the dome. In a 12 February report, RVO noted that activity from Main Crater consisted of white plumes rising 20 m and drifting a few kilometers SE accompanied by weak nighttime crater incandescence. Activity renewed at the SE Coastal Vent shortly after the collapse of the flow on 9 February 2018; lava re-emerged a few days later, connecting a lava island to the coastline again. Continuous steam emissions from both the Main Crater and the SE Coastal Vent were interrupted by dark ash plumes on 16 and 20-22 February, and occasional explosions were heard by residents on nearby islands. Minor ashfall was reported on Blup Blup on 21 and 22 February.

Eruptive activity continued during March 2018, although at a slower rate. The Main Crater generally produced continuous emissions of white steam and intermittent explosions with dark ash plumes; incandescence was usually visible at night from Blup Blup. According to the Darwin VAAC, a pilot reported an ash plume at 3.9 km altitude drifting SE on 2 March; it was not visible in satellite imagery due to meteoric clouds. The lava flow extruding from the SE Coastal Vent continued to grow, creating a dome that grew from 7-8 m above sea level to 10-17 m above sea level by 8 March. Dark ash emissions from the vent and nighttime incandescence were common. The growth rate slowed later in the month, and only one meter of change was observed between 10 and 20 March.

Satellite data. The MIROVA project recorded thermal anomalies from Kadovar in early January and early March 2018 (figure 16). MODVOLC thermal alerts were issued on three days; 15 and 22 January, and 7 February 2018. During January, small SO2 plumes were recorded by NASA satellites on four occasions (figure 17).

Figure (see Caption) Figure 16. The MIROVA project thermal anomaly graph for Kadovar from 11 May 2017 through March 2018. The first anomaly in early January 2018 correlates with observations of the first reported explosion. Courtesy of MIROVA.
Figure (see Caption) Figure 17. SO2 plumes from Kadovar were detected several times during January 2018 by the OMI instrument on NASA's Aura satellite. Courtesy of NASA Goddard Space Flight Center.

Geologic Background. The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. Kadovar is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. The village of Gewai is perched on the crater rim. A 365-m-high lava dome forming the high point of the andesitic volcano fills an arcuate landslide scarp that is open to the south, and submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. No certain historical eruptions are known; the latest activity was a period of heightened thermal phenomena in 1976.

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea, Contact: steve_saunders@mineral.gov.pg, ima_itikarai@mineral.gov.pg; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); NOAA, Cooperative Institute for Meteorological Satellite Studies (CIMSS), Space Science and Engineering Center (SSEC), University of Wisconsin-Madison, 1225 W. Dayton St., Madison, Wisconsin 53706, USA (URL: http://cimss.ssec.wisc.edu/); International Federation of Red Cross and Red Crescent Societies (IFRC) (URL: http://www.ifrc.org/); Samaritan Aviation (URL: http://samaviation.com/, https://www.facebook.com/samaritanaviation/); Brandon Buser (URL: https://ethnos360.org/missionaries/brandon-and-rachel-buser, https://www.facebook.com/brandon.buser.35); ABC News (URL: http://www.abc.net.au/news/2018-01-08/tsunami-warning-for-communities-near-erupting-png-volcano/9311544); Google Earth (URL: https://www.google.com/earth/).


Piton de la Fournaise (France) — April 1989 Citation iconCite this Report

Piton de la Fournaise

France

21.244°S, 55.708°E; summit elev. 2632 m

All times are local (unless otherwise noted)


Second eruption of 2017; July-August, fissure with flows on the SE flank

Short pulses of intermittent eruptive activity have characterized Piton de la Fournaise, the large basaltic shield volcano on Reunion Island in the western Indian Ocean, for several thousand years. The most recent episode occurred during 31 January-27 February 2017 with an active vent located inside the Enclos caldera on the S flank, about 1 km SE of Château Fort and about 2.5 km ENE of Piton de Bert (BGVN 42:07). The next episode, discussed here, began on 14 July 2017 and lasted for about six weeks. Activity through February 2018 is covered in this report. Information is provided by the Observatoire Volcanologique du Piton de la Fournaise (OVPF) and satellite instruments.

A new fissure eruption began on 14 July 2017 on the S flank inside the caldera about 850 m W of Château Fort and lasted through 28 August. The fissure was initially 450 m long with seven active lava fountains. Within 48 hours the flow had reached its farthest extent, about 2.8 km from the fissure. Activity continued from the southernmost cone of the fissure with three active vents for a few weeks. Surface lava flows diminished, and activity was concentrated in lava tubes flowing SE from the cone with occasional breakouts and ephemeral vents along the flow field. The tremor signal briefly spiked with lava fountains on 16-17 August, and then ceased altogether on 28 August. A brief seismic swarm during 24 August-1 September led OVPF to conclude that magma had moved but did not open a new fissure. Inflation was intermittent through December, and then increased significantly during January before leveling off during February 2018.

Activity during June-July 2017. The brief seismic swarm of 17-18 May 2017 was followed by another brief increase in seismicity during the first few days of June 2017, but no surface eruption was reported. The inflation that occurred during the May event tapered off by early June. The volcano remained quiet until seismicity began increasing on 10 July 2017; this was accompanied by inflation recorded at the GPS stations as well. The observatory (OVPF) noted the beginning of seismic tremors, indicative of a new eruption, around 0050 on 14 July 2017. Webcams revealed that eruptive fissures opened on the S flank of the cone inside the Enclos caldera. A reconnaissance flight conducted later in the morning on 14 July indicated that the eruptive site was located 750 m SE of the Kala-Pele peak and 850 m W of Château Fort, about 2.2 km NE of Piton Bert (Figure 110).

Figure (see Caption) Figure 110. Location of the Piton de la Fournaise eruption that began on 14 July 2017. Courtesy of OVPF/IPGP (Bulletin d'activité du vendredi 14 juillet 2017 à 15h30 Heure locale).

By 0930 that morning, the fissure extended over a total length of approximately 450 m. Seven lava fountains with a maximum height of 30 m were active (figure 111). The fountain farthest downstream began to build a cone with two arms of flowing lava. Satellite measurements indicated an initial flow rate of about 22-30 m3/s at the beginning of the eruption.

Figure (see Caption) Figure 111. A new fissure opened on the S flank of the cone inside the Enclos caldera at Piton de la Fournaise on 14 July 2017. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du vendredi 14 juillet 2017 à 15h30 Heure locale).

The tremor intensity decreased significantly the following day; this was reflected in the decrease in the flow rates and the distribution of activity on the fissure. Only three lava fountains were active on 15 July 2017 near the downstream end of the fissure; they began to form two small cones with lava flows that merged into a single channel (figure 112). The fountains did not exceed 30 m in height. By 1400 on 15 July the flow front was 2.2 km SE from the fissure. Satellite instrument measurements suggested the flow rate had dropped to two m3/s. Sulfur dioxide anomalies were measured by the OMI satellite instrument during 14-16 July (figure 113).

Figure (see Caption) Figure 112. Lava emerged from two vents and merged into a single flow at the eruptive site at Piton de la Fournaise on 15 July 2017 at 1400 local time. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 15 juillet 2017 à 16h30 Heure locale).
Figure (see Caption) Figure 113. Sulfur dioxide anomalies were captured by the OMI instrument on the Aura satellite by NASA on 14 (left) and 16 (right) July 2017 at the beginning of the eruption at Piton de la Fournaise. Courtesy of NASA Goddard Space Flight Center.

Tremors fluctuated over the next few days with changes related to the growth and collapse of various the cones along the fissure. On 18 July, there were six active fountains (figure 114). The flow rate remained approximately 1-3 m3/s. Fountains reached 20 m high on 19 July and a third vent was visible forming on the N side of the main cone. During an overflight on 21 July, OVPF noted that all three vents were active, but lava was only flowing SE from the central one (figure 115). Lava tubes had begun to form downstream of the cone, with numerous breakouts creating small lateral expansion arms.

Figure (see Caption) Figure 114. Six fountains were active along the fissure zone on 18 July 2017 at Piton de la Fournaise. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du mardi 18 juillet 2017 à 16h00 Heure locale).
Figure (see Caption) Figure 115. Lava flowed SE from the central vent of three in the fissure zone at Piton de la Fournaise on 21 July 2017. The magmatic gases are drifting SSE to the upper left of the image. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du vendredi 21 juillet 2017 à 16h30 Heure locale).

OVPF measured the flow dimensions on 22 July as 2.8 km long and 0.6 km wide (figure 116); the flow front had not advanced in the previous seven days. A fourth vent on the N side of the cone was periodically emitting ejecta, and two flows were active; one moving SE towards Château Fort and the other moving towards the SW inside a lava tube. On 24 July OVPF measured the flow rate as 1-4 m3/s, and the total volume of lava to date as 5.3 ± 1.9 million m3. On 25 July 2017, local observers reported that the main vent on the SE flank of the cone was visible, as well as a second vent on the N flank of the growing cone. The main lava channel was clearly visible downstream of the cone with frequent overflows (figure 117), and active flow continued inside the lava tubes.

Figure (see Caption) Figure 116. An outline of the active lava flow at Piton de la Fournainse on 22 July 2017. Base map courtesy of Google Earth. Annotations courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du samedi 22 juillet 2017 à 17h00 Heure locale).
Figure (see Caption) Figure 117. The main lava channel flowed SE from the eruptive vent at Piton de la Fournaise on 25 July 2017. Photo copyright by Cité du Volcan/Arthur Vaitilingom). Courtesy of OVPF/IPGP (Bulletin d'activité du mercredi 26 juillet 2017 à 16h00 Heure locale).

By 30 July the flow intensity had decreased to about half of its original flow rate. The cone continued to grow, but no surface lava flows were observed (figure 118). The main vent rarely produced ejecta. Active lava was flowing in tunnels with a few minor breakouts near the cone. The flow front remained 2.8 km from the eruptive vent.

Figure (see Caption) Figure 118. The eruptive vent of Piton de la Fournaise on 30 July 2017 showed no surface flows, but activity continued in lava tunnels. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du dimanche 30 juillet 2017 à 16h00 Heure locale).

Activity during August 2017-February 2018. The intensity of the tremors associated with the eruption continued to taper off into early August to levels below 20% of what they were at the beginning of the eruption, and this corresponded to a decrease in observed activity in the field. During an OVPF overflight on 2 August 2017 no flows or ejecta from the eruptive cone were seen, but a number of surface breakouts from lava tubes were still visible; the nearest to the cone was 520 m to the SE (figure 119). The main vent was completely blocked, but the smaller vent still had visible incandescence and strong degassing (figure 120).

Figure (see Caption) Figure 119. Lava tubes and small breakouts at Piton de la Fournaise on 2 August 2017 (N to the lower right). The breakouts were several hundred meters SE of the main vent. The eroded cone in the upper right is visible in the upper left of figure 115 showing the relative location compared with the main fissure. See also figure 121 for relative location. 1) A hornito formed from overpressure in an underlying lava tube. 2) A 20-m-long flow from a breakout over an active tunnel. 3) Two ephemeral vents had recently opened in the roof of the tunnel just prior to this photo being taken. 4-5-6) The longest breakout flow observed was 220 m long and began at an ephemeral vent located downstream of points 1, 2, and 3. The flow surface was 10 m wide near 4), spreading out and cooling farther downstream (5 and 6). Incandescent lava was still visible near the flow front (6) in two lobes. 7-8) Two other breakout flows from ephemeral vents 520 meters from the main vent were also visible, 50 and 180 m long, respectively. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du mercredi 2 août 2017 à 16h30 Heure locale).
Figure (see Caption) Figure 120. Visible incandescence and strong degassing were apparent from the smaller vent at the eruptive site on 2 August 2017 at Piton de la Fournaise. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du mercredi 2 août 2017 à 16h30 Heure locale).

Estimates of the flow rates during the first week of August were less than 1-2 m3/s, and the total lava volume emitted on the surface was measured at 7.2 +/- 2.3 million m3. A larger breakout from a tunnel on 5 August was visible in the OVPF webcams and fed a surface flow over several hundred meters for several hours. By 6 August 2017 the activity was focused mainly in lava tunnels with a few surface breakouts, although incandescence was visible from the small vent seen in imagery available in Google Earth (figure 121). Small ejecta was observed during 7-9 August from the remaining active small vent on the N flank of the cone (figure 122).

Figure (see Caption) Figure 121. Imagery from Google Earth captured on 6 August 2017 showed incandescence and degassing from the small vent at the S end of the fissure at Piton de la Fournaise (left plume), as well as degassing from surface breakouts along the still active lava tunnels to the SE. Courtesy of Google Earth.
Figure (see Caption) Figure 122. Only the small vent on the N side of the cone was still incandescent at Piton de la Fournaise on 9 August 2017. N is to the upper right. Courtesy of and copyright by OVPF/IPGP (Bulletin d'activité du mercredi 9 août 2017 à 17h00 Heure locale).

Observations made on 14 August 2017 indicated lava was still active in tunnels as pahoehoe flows were observed about 2 km from the active vent. A brief increase in seismic and surface activity occurred on 16 August. The Piton de Bert webcam captured short-lived lava fountains at the E edge of the eruptive cone. Seismic tremor intensity increased rapidly and then oscillated during 16-17 August. The minor inflation of the cone that had been observed since 1 August ceased by 18 August. Field measurements on 21 August demonstrated a significant decrease in flow activity since 12 August. The volcanic tremor signal was stable at a low level on 25 August; it decreased significantly on 27 August and disappeared altogether about 0300 local time on 28 August 2017, leading OVPF to conclude the eruptive phase had ended.

A number of indications led OVPF to conclude that two migrations of magma that did not reach the surface occurred between 16 August and 1 September. Increased seismicity began on 16 August and was accompanied by a measured increase in SO2; satellite measurements showed two areas of inflation SE of the active fissure between 7 and 25 August. A seismic swarm in the same area was recorded during 24 and 25 August (figure 123). Overflights by OVPF on 25 August did not identify any new fissures associated with the seismic events and inflation.

Figure (see Caption) Figure 123. A seismic swarm on 24 and 25 August 2017 at Piton de la Fournaise led OVPF to conclude that magma was moving beneath the surface in an area SE of the active fissure zone. Courtesy of and copyright by OVPF/IPGP (Bulletin mensuel du lundi 2 octobre 2017).

After the seismic swarm, the number of daily seismic events decreased to less than one per day by the end of September 2017. OVPF reported minor inflation during the second half of October along with a slight increase in seismicity. Inflation stabilized in November but increased again during January 2018 (figure 124). A gradual increase in shallow seismicity beneath the summit craters was recorded during the second half of February. It was accompanied by an increase in CO2 concentrations in the soil as well, which rose to some of the highest levels since measurements began in 2015.

Figure (see Caption) Figure 124. Deformation at Piton de la Fornaise from 14 July 2017 to 28 February 2018. The eruption of 14 July- 28 August 2017 is shown in yellow. The y-axis measures the change in length in centimeters of a N-S line crossing the Dolomieu crater between two GPS receivers. The raw data is shown in black and the blue line is the data smoothed over a week. A rise means elongation and therefore swelling of the volcano; conversely, a decrease indicates contraction and therefore deflation of the volcano. Courtesy of and copyright by OVPF/IPGP (Bulletin mensuel du jeudi 1 mars 2018).

Thermal anomaly data. The MIROVA project thermal anomaly record shows both the episodic nature of the activity and the cooling signature of the flows that continued beyond 28 August 2017 when OVPF noted the cessation of tremors associated with eruptive activity (figure 125). The MODVOLC thermal alerts first appeared on 13 July 2017 and continued persistently with multiple daily alerts until 23 August 2017.

Figure (see Caption) Figure 125. MIROVA thermal anomaly data for Piton de la Fournaise for the year ending 5 January 2018. The eruption of February 2017 had very little cooling after the tremors ceased at the end of February, but the July eruption had significant cooling evident for more than two months after the cessation of seismic tremors on 28 August 2017. Courtesy of MIROVA.

Geologic Background. The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Information Contacts: Observatoire Volcanologique du Piton de la Fournaise (OVPF), Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


San Cristobal (Nicaragua) — April 1989 Citation iconCite this Report

San Cristobal

Nicaragua

12.702°N, 87.004°W; summit elev. 1745 m

All times are local (unless otherwise noted)


Intermittent ash-bearing explosions during 2017; Ash plume drifts 250 km in August.

Nicaragua's San Cristóbal volcanic complex has exhibited sporadic eruptive activity dated back to the early 16th century. More consistent modern record keeping has documented short-lived eruptive episodes every year since 1999. Small explosions with intermittent gas-and-ash emissions are typical. Three single-day explosive events were reported in 2015; a series of explosions on 5 March 2015 generated a 500 m high ash plume, 41 explosions on 6 June 2015 ejected ash 200 m above the summit, and the first of two explosions on 12 June 2015 sent an ash plume 2,000 m above the summit. The next eruption did not occur until 22 April 2016 when 11 explosions were recorded, with the largest sending an ash plume 2,000 m above the summit. Activity from July 2016-December 2017 is covered in this report. Information is provided by the Instituto Nicaragüense de Estudios Territoriales (INETER), and the Washington Volcanic Ash Advisory Center (VAAC).

Following little activity during the remainder of 2016 after the 22 April explosions, small explosions with minor ash were reported in February, March, and April 2017. Significant explosions during 18-19 August sent ash plumes over 200 km W and deposited ash in numerous communities. Seismicity was high during October-December 2017, but ash-bearing explosions were only reported on 7 and 11 November.

After the 22 April 2016 explosions, San Cristóbal remained quiet for the remainder of 2016. In the month's they were measured, 45-72 degassing-type seismic events were recorded. During a field visit on 29 November 2016, new landslides around the crater rim, both inside the crater and down the outer flanks, were observed. These were interpreted by INETER scientists as resulting from a major tectonic earthquake that occurred offshore in mid-November that was felt in nearby Chinandega (16 km SW), and not from volcanic activity.

Seismic activity increased slightly in January 2017 with 100 degassing events recorded. INETER reported 15 small ash-and-gas explosions during 18-19 February and 153 degassing events. There were no reports of ashfall in the nearby communities. Only 27 degassing seismic events were reported in March; three small gas explosions with minor ash occurred on 16, 25, and 28 March 2017.

Eight small explosions with gas and minor ash took place during April 2017 on days 13, 15, 16 and 19, but no damage was reported in nearby communities. Very low values of SO2 (averaging 147 tons/day) were measured at the end of April 2017, far less than values of 854 and 642 measured in September and October 2016. Degassing-type seismic events increased sharply beginning on 20 April, totaling 1,931 events; they remained elevated through 25 April.

Volcano-tectonic (VT) earthquakes increased significantly to 235 recorded events during May, from values in the single digits earlier in the year. Minor fumarolic activity occurred at the S side of the summit crater on 27 May 2017 (figure 33). Two small gas explosions were recorded on 20 and 27 May, but no ash emissions were reported. A significant increase to 2,349 degasification-type earthquakes was reported during June 2017; slightly fewer (1,981) were reported during July.

Figure (see Caption) Figure 33. Minor fumarolic activity was observed at the S side of the summit crater at San Cristóbal during a field visit by INETER on 27 May 2017. Courtesy of INETER (Boletín mensual, Sismos y Volcanes de Nicaragua, Mayo 2017).

Significant explosions early on 18 August 2017 were observed from Chinandega with notable gas and ash emissions (figure 34), and ashfall was deposited around the region (figure 35). Communities affected by the ashfall were located to the W and SW of the volcano and included Belén, La Mora, La Bolsa, El Viejo (18 km WSW), La Grecia, Realejo (25 km SW) and Corinto (30 km SW). Ash plumes rose between 300 and 600 m above the crater rim and drifted W and SW. Additional explosions occurred the next day but had ceased by 20 August.

Figure (see Caption) Figure 34. Explosion and ash plume at San Cristóbal at 1330 on 18 August 2017. Courtesy of INETER (Boletín mensual, Sismos y Volcanes de Nicaragua, Agosto, 2017).
Figure (see Caption) Figure 35. Ash was collected by INETER scientists from the 18 August 2017 explosion at San Cristóbal. Courtesy of INETER (Boletín mensual, Sismos y Volcanes de Nicaragua, Agosto, 2017).

A small plume was noted in satellite imagery by the Washington VAAC on 18 August 2017 moving NW. Later imagery showed gas and ash drifting W at an estimated altitude of 2.1 km. It extended approximately 265 km W of the summit before dissipating. Ground measurements of SO2 made during 18-20 August showed increases to a peak of 3,519 metric tons per day on 19 August before dropping back to more typical background values below 700 t/d. INETER scientists used GOES and AVHRR satellite images to identify the maximum extent of the ash plume from the eruptive event. The ash cloud covered the area W of San Cristóbal, approximately 2,960 Km2, and extended more than 80 km offshore, with a total length of 125 km and a maximum width of 33 km (figure 36). Seismometers recorded 3,880 degassing-type seismic events during August 2017. Seismicity decreased slightly during September 2017 to 2,604 measured events, of which 2,415 were degassing-type, 187 were VT events, and two explosions were recorded on 1 September, but no ashfall was reported.

Figure (see Caption) Figure 36. The extent of the ash plume from the 18-20 August 2017 eruptive episode at San Cristóbal, identified in satellite imagery by INETER scientists. Courtesy of INETER (Boletín mensual, Sismos y Volcanes de Nicaragua, Agosto, 2017).

An order-of-magnitude increase in seismicity occurred during October-December 2017, with the monthly totals of the numbers of events ranging from 17,000-21,000 (figure 37). INETER reported a series of 14 explosions during the evening of 7 November. Ashfall was reported to the W in Los Farallones, San Agustín, La Mora, El Naranjo and the city of Chinandega. The Washington VAAC subsequently reported an ash plume that models suggested rose to 6.7 km and drifted W on 11 November.

Figure (see Caption) Figure 37. Numbers of daily seismic events at San Cristóbal during October-December 2017. Event types include VT (volcano-tectonic), degasification, and tremor. Note scale in each graph as different symbols and colors are used for the same type each month. Total seismic events for October (top) was 17,815, November (middle) was 19,206, and December (bottom) was 20,925. Ash bearing explosions were reported by INETER on 7 November, and the Washington VAAC reported an ash plume on 11 November that possibly rose to 6.7 km altitude and drifted W. Courtesy of INETER (Boletín mensual, Sismos y Volcanes de Nicaragua, Octubre, Noviembre, Diciembre, 2017).

Geologic Background. The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km W of San Cristóbal; it and the eroded Moyotepe volcano, 4 km NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html).


Suwanosejima (Japan) — April 1989 Citation iconCite this Report

Suwanosejima

Japan

29.638°N, 129.714°E; summit elev. 796 m

All times are local (unless otherwise noted)


Large explosions with ash plumes and Strombolian activity continue during 2017

Suwanosejima, an andesitic stratovolcano in Japan's northern Ryukyu Islands, was intermittently active for much of the 20th century, producing ash plumes, Strombolian explosions, and ash deposits. Continuous activity since October 2004 (figure 24) has consisted generally of multiple ash plumes most months rising hundreds of meters above the summit to altitudes between 1 and 3 km, and tens of reported explosions. The rate of activity began increasing during 2014; the frequency of explosions and the height of the plumes have continued to increase through 2017, which is covered in this report. Information is provided primarily by the Japan Meteorological Agency (JMA), and the Tokyo Volcanic Ash Advisory Center (VAAC).

Figure (see Caption) Figure 24. Eruptive history at Suwanosejima from January 2003-December 2017. Black bars represent the height of the emissions in meters above the crater rim, gray volcanoes indicate an explosion, usually accompanied by an ash plume, and the red volcanoes represent large explosions with ash plumes. Courtesy of JMA (Suwanosejima volcanic activity report, December 2017).

Activity at Suwanosejima has been persistent and generally increasing during 2014-2017 (figure 25). During 2017, ash emissions rose from a few hundred to nearly 3 km above the Ontake crater rim. Large explosions were reported 32 times by JMA, including 12 during August. Most explosions sent ash emissions to less than 1,000 m above the crater rim, but the highest ash plume, on 3 August 2017, rose 2.8 km above the crater rim, and was the highest recorded since observations began in 2003. Incandescence was observed at the crater from a thermal camera throughout the year and was witnessed locally many times. Many of the explosions, large and small, were heard in the nearby village. Ashfall was confirmed in the village to the SSW on nine different occasions during the year.

Figure (see Caption) Figure 25. Eruptive history at Suwanosejima for 2014-2017. Black bars represent height of steam, gas, or ash plumes in meters above crater rim, gray arrows or volcanoes represent an explosion, usually accompanied by an ash plume, red arrows or volcanoes represent a large explosion with an ash plume, red bars or orange diamonds indicate incandescence observed in webcams. From top to bottom: Eruptive activity during 2014, 2015, 2016, and 2017. Courtesy of JMA (Suwanosejima volcanic activity reports, December 2014, 2015, 2016, and 2017).

Activity during January-April 2017. There were no large explosions at Suwanosejima during January 2017, but occasional minor ash emissions rose as high as 1,300 m above the Ontake crater rim. Incandescence was visible from the webcam on most clear nights. Ashfall was reported in the village 4 km S on 17 and 26 January. The Tokyo VAAC reported ash emissions four times in January. Ash plumes rose to 1.2 km altitude and drifted SE on 4 January; to 1.8 km and drifted W on 5 January; to 1.2 km and drifted S on 16-17 January; and to 2.1 km and drifted SE on 25 January.

In contrast with January, five large explosions were reported by JMA during February 2017. The first, on 9 February, sent an ash plume to 700 m above the crater rim. An ash emission on 18 February rose to 1,200 m above the rim (figure 26). People in the nearby village reported hearing explosions on 18, 20, 27, and 28 February. The largest explosions occurred during 27-28 February when ejecta was scattered 600 m from the crater rim. The Tokyo VAAC reported ash emissions drifting SE several times: on 9 February at 1.5 km altitude, on 16 and 17 February at 1.8 km, and during 27-28 February at 1.5 km.

Figure (see Caption) Figure 26. An ash emission from Suwanosejima was captured by the 'Campground' webcam on 18 February 2017. Courtesy of JMA (Suwanosejima volcanic activity report, February 2017).

Intermittent ash emissions occurred during March 2017, but no large explosive events were reported. Ejecta was scattered around the edge of the crater on 4 March and an ash plume rose 1,000 m. Small ash plumes were noted rising 900 m on 12 and 15 March; explosions were heard in the village on 14 and 16 March, and ashfall was reported there on 25 March. Incandescence was observed at the summit intermittently throughout the month. During a field survey on 21 and 22 March, JMA noted minor thermal anomalies at the Ontake Crater, the N slope of the Ontake crater, and just above the coastline on the E flank (figure 27). The Tokyo VAAC reported ash emissions three times during March; on 3 March ash plumes rose to 1.5-1.8 km altitude and drifted SE and on both 28 and 31 March they rose to 1.8 km altitude and drifted SE and E.

Figure (see Caption) Figure 27. Thermal anomalies were apparent from the Ontake crater (upper left), the north slope of the crater (upper right), and just above the coastline on the E flank (lower left) in this thermal image of Suwanosejima taken on 22 March 2017 from the NE. Courtesy of JMA (Suwanosejima volcanic activity report, March 2017).

Only minor ash emissions and occasional incandescence was reported during April 2017. Two emission events on 1 April sent ash plumes to 1,200 m above the crater rim. A tremor that lasted nine minutes occurred on 11 April and a small seismic swarm was recorded on 13 April. Small explosions were also reported on 17 and 19 April, with the 19 April event heard at the nearby village; another small explosion was reported on 30 April. There were no reports issued by the Tokyo VAAC.

Activity during May-August 2017. Activity increased slightly during May 2017; two large explosions were recorded by JMA. A small explosion was reported on 1 May, and the highest plume rose to 1,900 m above the crater rim on 10 May during a larger event. Incandescence was observed from the local village on 16 May, and explosions were heard from the village on 16 and 18 May, and again on 28 and 29 May; no ashfall was reported. The Tokyo VAAC reported ash emissions on 7, 8, and 10 May. On 7 May they reported an ash plume located 45 km S at 1 km altitude extending SW. A few hours later ash extended N at 1.5 km. An explosion on 8 May sent an ash plume to 2.1 km where it remained stationary over the volcano for much of the day before dissipating. A higher ash plume was reported on 10 May at 2.7 km altitude drifting E.

Small ash explosions occurred at Ontake Crater on 8 and 21 June 2017, but there were no larger explosive events. Ash plume heights rose to only 600 m above the crater rim, and occasional nighttime incandescence was reported. No reports were issued by the Tokyo VAAC. JMA reported that the highest ash plume during July rose 2.1 km above the summit crater on 17 July, but no large explosions were recorded. Incandescence was observed intermittently throughout the month. A small explosion on 2 July sent an ash plume to 1.9 km above the crater rim. Intermittent ash emissions were noted during 17-19, 22 and 25 July. The Tokyo VAAC reported ash emissions during 2 and 16-18 July. They reported the plumes on 2 July at 1.8-2.4 km altitude, extending N for most of the day. A new explosion on 16 July sent an ash plume to 2.7 km altitude that drifted E. Intermittent ash emissions continued to drift E through 18 July at altitudes ranging from 1.8-2.1 km.

Activity increased substantially during August 2017; JMA reported 12 large explosions, nine of which occurred during the last week. Ashfall was reported in the nearby village on 2 August. The highest plume of the month was reported on 3 August, 2.8 km above the crater rim. Explosions were heard in the village on 3 and 19 August. A small explosion was reported on 12 August. Large explosions occurred on 19, 20, and 24 August in addition to the nine events during the last week. A single MODVOLC thermal alert was reported on 18 August, and the MIROVA system reported thermal anomalies during several days of the last week of the month (figure 28). The Washington VAAC reported ash on 1 August that rose to 2.4 km altitude and drifted SW. A higher plume on 3 August rose to 3.7 km and drifted W. They reported another ash plume that first rose to 3.0 km on 24 August; subsequent emissions that day were drifting NE at 2.1-2.4 km altitude. A new plume on 25 August extended E at 2.4 km. Continuing ash emissions from multiple explosions during 28-31 August rose to 1.2-3.0 km altitude and drifted SE.

Figure (see Caption) Figure 28. Log Radiative Power plot from the MIROVA project for Suwanosejima for 24 May 2017-15 February 2018 shows increased thermal activity during late August 2017, and intermittent pulses of activity from late May-September. Courtesy of MIROVA.

Activity during September-December 2017. Four large explosions were recorded during the first week of September 2017, after which a number of smaller ash emission events were reported. Ashfall was reported four times in the nearby village on 2, 4, 29, and 30 September. The Tokyo VAAC reported explosions on 1, 4, 6, and 29 September. The ash plume from the explosion on 6 September rose to 1.5 km altitude and drifted E; on 29 September, it rose to 2.4 km altitude, also drifting E.

JMA reported four large explosions during October 2017. Two explosions occurred on 11 October; one of the ash plumes rose 1,900 m above the crater rim (figure 29). Explosions were heard in the nearby village on 12 and 31 October, and ashfall was reported on 13 October. During the large explosion of 31 October incandescent ejecta was scattered around the crater rim and the ash plume rose 1,900 m. The Tokyo VAAC reported an explosion with ash on 10 October (UTC) that rose to 2.7 km altitude and remained stationary until dissipating a few hours later. They noted that the explosion on 31 October produced a plume that rose over 1.5 km and drifted NW.

Figure (see Caption) Figure 29. An ash plume from an explosion on 11 October 2017 rises 1.9 km above the Ontake crater of Suwanosejima. Courtesy of JMA (Suwanosejima volcanic activity report, October 2017).

JMA reported five large explosions during November 2017. Incandescent ejecta was seen around the crater rim during the explosion of 1 November, and the plume rose to 2 km above the rim. Loud explosions were heard from the nearby village on 3, 5, 6, 15, and 16 November, and ashfall was reported there on 14, 15, and 20 November. A small explosion was reported on 10 November; intermittent explosions with ash plumes rising 700 m were observed on 20 and 21 November. The Tokyo VAAC reported ash plumes at 1.5 km drifting W on 1 and 5 November, and at 1.8 km altitude drifting NW on 10 November, the last VAAC report issued for 2017.

Only small explosions were reported from Ontake crater during December 2017. The highest plume rose 700 m above the crater rim. Small explosions were heard a number of times in the nearby village on 8-9, 11-13, and 26-30 December. JMA scientists visiting during 8-10 December heard intermittent explosions and witnessed incandescence visible to the naked eye. They also observed ashfall in the village on the morning of 10 December. During a field survey on 14 December, no significant changes were noted from the previous survey in March 2017 (figures 30 and 31).

Figure (see Caption) Figure 30. The summit of Suwanosejima with steam rising from Ontake Crater taken from the W on 14 December 2017. Courtesy of JMA (Suwanosejima volcanic activity report, December 2017).
Figure (see Caption) Figure 31. Steam rises from the Ontake Crater of Suwanosejima viewed from the E on 14 December 2017. Courtesy of JMA (Suwanosejima volcanic activity report, December 2017).

Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Kilauea (United States) — April 1989 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


Activity continues at Halema'uma'u lava lake, and at the East Rift Zone 61g flow, July-December 2017

Hawaii's Kilauea volcano continued its eruptive activity, intermittent for thousands of years and continuous since 1983, throughout 2017. The summit caldera formed about 500 years ago, and the East Rift Zone (ERZ) has been active for much longer. Lava lakes were intermittent in and around Halema'uma'u crater at the summit until 1982. Lava has been continuously flowing from points along the ERZ since 1983, and the episode 61g flow was still vigorous through the end of 2017. A large explosion within Halema'uma'u Crater in March 2008 resulted in a new vent with a lava lake that has been continuously active through 2017.

The US Geological Survey's (USGS) Hawaii Volcano Observatory (HVO) has been monitoring and researching the volcano for over a century, since 1912. Quarterly Kilauea reports for July-December 2017, written by HVO scientists Carolyn Parcheta and Lil DeSmither, form the basis of this report. MODVOLC, MIROVA, and NASA Goddard Space Flight Center (GSFC) provided additional satellite information about thermal anomalies and SO2 plumes.

The lava lake inside the Overlook vent at Halema'uma'u Crater continued to rise and fall during the second half of 2017 with no significant lake level changes and a few periods of spattering. The lake level overall was lower at the end of the year than during much of the year, reflecting long-term deflation of the summit. There were no major explosive events from rockfalls, but smaller sloughs of veneer (thin layers of recently cooled lava that adhere to the vent walls) without accompanying explosions were common. Ongoing subsidence at Pu'u 'O'o, especially around the West Pit prompted moves of monitoring equipment, but little else changed at the cone.

The episode 61g lava flow continued with numerous surface breakouts from areas near the vent all the way down over the pali and into the ocean at the Kamokuna delta during July-December 2017. Changes in the subsurface flow in lava tubes contributed to changing locations of surface breakouts, which were still active at the end of the year. The lava flowing into the ocean at Kamokuna slowed and finally ended in November with changes occurring on the delta in the final weeks of its activity.

Activity at Halema'uma'u. For the second half of 2017, activity at the lava lake inside the Overlook crater continued with little change from January-June. The lake's surface circulation pattern was typical, with upwelling in the N and subsidence of the crust along the southern lake margin, but also around the entire edge of the lake depending on the upwelling location (figure 292). There were often "sinks" a few tens of meters from the SW edge of the lake where the crust folds in on itself and sinks, pulling material away from the wall. A noticeable lava veneer buildup often occurred on the southern margin, where the surface crust was most consistently subducting. Short-term spattering events lasted minutes to hours and occasionally altered the surface crust motion by creating localized subsidence. Throughout the period, spattering was often confined to a grotto at the SE sink. On most days, two or more spattering sites were active simultaneously.

Figure (see Caption) Figure 292. Commonly referenced features and geographic nomenclature at the Halema'uma'u lava lake which is inside the Overlook vent at Kilauea. Geographic directions are faded gray arrows inside the lake with white labels N, S, E, and W, and are distinct from nomenclature cardinal directions (black arrows) used in the text. Satellite image from DigitalGlobe taken on 20 October 2017. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

The lava lake level generally rose and fell over periods of hours to days in response to gas-piston action and to inferred changes in summit lava pressure indicated by deflation-inflation (DI) events. There were a few periods with exceptions when the lake level remained constant for many days at a time, heating up the surrounding walls enough to produce thermal cracking and popping sounds. The total range of the lake level varied between 35 and 40 m during July-December 2017, with the highest level about 17 m below the rim in early September (elevation 1,020 m), and the lowest levels, about 57 m below the rim in late July and September (elevation 977 m) (figure 293).

Figure (see Caption) Figure 293. Halema'uma'u lava lake level measurements for 2017 in meters above sea level at Kilauea. X-axis represents the count of the calendar days, 0 is 1 January 2017. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

There were no significant explosive events triggered by rockfalls, but smaller collapses of veneer and the wall were common, particularly during deflationary phases when the lake level was low and exposed larger areas of the walls. A few larger collapses in September 2017 were big enough to change the geometry of the lake slightly (figure 294). The first, on 8 September at 1806 HST, was a collapse of the large ledge attached to the wall in the southern corner of the lake. This event produced a plume containing ash, a composite seismic event, and lake surface agitation. The following day, 9 September, there was another collapse at 0509. This involved an area of the E Overlook rim composed of mainly lithic deposits, directly above the Southeast sink, which produced a dusty plume, a composite seismic event, and lake surface agitation. On 12 September a thin slice of the southwest lake rim collapsed at 1420, producing a dusty plume, an agitated lake surface for about 10 minutes, and a composite seismic event.

Figure (see Caption) Figure 294. Small changes were visible in the geometry of the Overlook vent at Halema'uma'u from veneer and wall collapses in September 2017 at Kilauea. Left image taken 31 May 2017 by T. Orr shows the areas where the largest collapses took place in September 2017. A large shelf collapsed on 8 September, and the other two dates highlight areas where portions of the lake's lithic wall collapsed. The right photo was taken on 21 September 2017 by L. DeSmither. The photo views are looking SE. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

An interesting effect observed on two veneer collapses occurred on 24 October 2017 at 1617 and 1623. Both were silent events but were noticed because they visually depressed the lake as they fell in and sent a small "wave" propagating outward before spattering began a few seconds later. The wave did not make it more than half way across the lake in either case, and both spattering events lasted only a few minutes. Several veneer ledges built up and subsequently collapsed around the lakes perimeter but were most notable on the SW corner of the lake. Three collapses, on 5 December at 0400 and 7 December at 1856 and 2024, enlarged the NNE edge of the lake towards true N, but did not produce a spatter deposit or explosion (figure 295). Another rockfall occurred on the N margin of the lake on 23 December 2017 at 1552 and triggered a large spattering event.

Figure (see Caption) Figure 295. View from the SW time-lapse camera at Kilauea into the lava lake at Halema'uma'u showing the locations of two collapses in early December 2017 that expanded the Overlook vent towards the NNE. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

Activity at Pu'u 'O'o. During July-December 2017, there were only minor changes in the main crater of Pu'u 'O'o as recorded by the PO webcam, PT webcam, and the West Pit time-lapse camera. Due to slight subsidence, altered ground, and widening cracks first noted in August, the West Pit time-lapse camera was relocated 20 m to the SE on 12 October, and roughly 25 m further back from the rim on 1 November after new crack expansion was observed.

During the month of August 2017 there was slight subsidence of the W portion of the crater floor, and around 20 August a crack opened up in the S embayment with three heat locations. There appeared to be slight subsidence of the E side of West Pit from the time-lapse imagery spanning 22 November to 12 December. This subsidence accelerated during 15-17 December, but then was slower through the end of the year. The deformation data confirmed subsidence at Pu'u 'O'o, but it seemed to be confined to the land bridge separating the main crater and the West Pit lava pond. The lava pond inside of the west pit rose slightly during the period from around an elevation of 847 m in early August to 849.5 m on 12 December when measured during site visits about every three weeks. A thick surface crust and sluggish plate motion was typical at the lava pond.

The time-lapse camera located on the E rim of the lava pond (through October) captured three rockfalls in July and two in August that disturbed the pond's surface. On 30 September 2017 a collapse of the west pit's SE rim also broke off a portion of the ledge below, as it was impacted by the falling rocks (figure 296). The collapse was large enough to agitate the pond surface for several tens of minutes, and produced a small step in the tilt at the POC tiltmeter.

Figure (see Caption) Figure 296. The West Pit lava pond time-lapse camera at Kilauea's Pu'u 'O'o crater captured the area of the rim that collapsed (circled in upper left corner) at 0054 HST on 30 September 2017. The larger circle shows where the lower ledge broke off as a result of the impact. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

The pond surface was also disturbed from rockfalls on 22, 28, and 31 October 2017. The first two events were on the N side of the West Pit rim, and the events on 31 October were on the S side of the rim. A small rockfall that triggered minor spattering was witnessed during an overflight on 1 November (figure 297). After 1 November, when the camera was moved away from the rim, it no longer had direct views of the pond. One of the E spillway spatter cones collapsed into the lava tube that was feeding the 61g flow on 20 November and provided a skylight into the tube for a day before it crusted over. On 12 December, a large talus pile on the NNE side of West Pit was evidence of rock falls near the original time-lapse camera site. The talus, likely resulting from several rock falls, piled up onto the lava coated bench.

Figure (see Caption) Figure 297. A rockfall witnessed at Kilauea's Pu'u 'O'o cone during a 1 November 2017 overflight. A small event on the W side of the pond triggered minor spattering. The surface of the pond had large plates with wide cracks. Left photo by L. DeSmither, right photo by C. Parcheta. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

Activity at the East Rift Zone, episode 61g flow field. The 13 June 2017 breakout that had started on the upper flow field, approximately 1.1 km from the vent, was the largest area of active surface flows on the 61g flow during July-September. Ranging between 2.6–5.8 km from the vent, the breakout significantly expanded the upper flow fields western flow margin. This breakout remained active through the end of September (figure 298). On 26 June 2017 a breakout started near the top of Royal Gardens and quickly advanced down the pali, east of the main flow field. By 6 July the front of the breakout had extended 500 m beyond the pali base with fluid pahoehoe at the front, and a small a'a channel on the steep part of the pali. Slow advancement of the flow placed it approximately 1.5 km from the emergency road near the coast by 9 August before the flow front stalled. When mapped again on 15 August, the closest active flows were about 2.1 km uphill from the road. Intermittently during 1-20 September the breakout produced channelized flows on the steep part of the pali, sometimes as often as every 24 hours. By the end of September active surface flows had advanced to approximately 1.6 km from the emergency road (figure 298).

Figure (see Caption) Figure 298. Changes to the extent of Kilauea's active episode 61g flow field between 2 July and 28 September 2017, showing the flow margin expansion in red. The yellow line indicates the active lava tube beneath the surface flow. During this time, the flow field expanded an additional 165 hectares from the previous 1,007 hectares (as of 2 July), to a total of 1,172 hectares, increasing the flow field area by 16 percent. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

Two other breakouts that started near the episode 61g vent were also active during July-September 2017. The 5 March breakout, which had advanced downslope during its 4 months of activity, was weakly active on 10 July, with two small lava pads observed approximately 4.8 km from the vent. By the time of the overflight on 9 August, the breakout was inactive. On 26 July around 1025 HST, a new breakout started about 1.1 km from the vent and remained active through the end of September with flow activity located 1.1-2.5 km from the vent. On 27 August at roughly 0945 a breakout began on the steep part of the pali originating from the main 61g tube. By 1 September the breakout was at the base of the pali and spreading onto the coastal plain. A few other channels were reported on this area of the pali, and activity continued through the end of September with very little advancement across the coastal plain (figure 299).

Figure (see Caption) Figure 299. A view looking NW at the breakouts on the Pulama Pali and the coastal plain of Kilauea's East Rift Zone. The majority of the 61g surface flows that spread across the coastal plain were supplied by the 26 June 2017 breakout (right of the kipuka, green area, center right); the breakout that started on 27 August (left of the kipuka, steaming) supplied a smaller pad of flows closer to the base of the pali. A 'kipuka' is an Hawai'ian term for an "island" of land completely surrounded by one or more younger lava flows. Photo taken on 21 September 2017 by L. DeSmither. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

The 26 June 2017 breakout remained active and stable through the end of 2017, forming a tube from its breakout point to midway down the pali on the E side of the 61g flow. The area where breakouts from 5 March, 13 June, and 26 July occurred (1.1 km from vent) also remained intermittently active through the end of 2017 (figure 300).

Figure (see Caption) Figure 300. The lava flow field expansion for the 61g lava flow at Kilauea between 1 October and 31 December 2017. In addition to continued activity from the longer-lived breakouts fueling the expansion shown in red, nearly 90 known shorter-lived surface breakouts occurred, based on observations from webcams, overflights, and satellite data. Changes in the breakout locations are seen in the progression of orange, red, and purple dots after the 61g tube became blocked by a graben collapse on the delta near the end of September (see discussion in next section). The yellow lines indicate lava tube locations underneath the surface flow. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

Numerous overflows originating on the sea cliff began in early October 2017. These breakouts occurred within 310 m of the sea cliff and persisted for nearly a month. There were also approximately 20 short-lived breakouts in October above the sea cliff, each lasting 1-3 days. They were located mostly in clusters on the upper flow field at 1, 2, and 3.5 km from the vent, along the top and base of the pali, and from the coastal tube.

An estimated 35 tube breakouts occurred during November 2017; they typically lasted 2- 10 days, and were located inland of the October breakouts. Locations of activity were in the upper flow field almost entirely between 2 and 3.5 km from vent, with three closer breakouts at 0.5, 0.8, and 1 km from vent. The two active tubes on the pali continued to have breakouts at the top and base of the cliff, but also started breakouts midway downslope (figure 301). At 0805 on 7 November, a viscous breakout occurred approximately 500 m above the sea cliff. The small breakout came directly from the 61g tube and lasted for roughly four and a half days. Another viscous breakout from the tube occurred approximately 950 m upslope of the sea cliff from 18-23 November. A week after that, a third viscous breakout occurred about 2 km from the sea cliff. By the end of November, there was no further breakout activity on the delta or the distal half of the coastal plain.

Figure (see Caption) Figure 301. A pali breakout from the 61g lava tube observed during a 20 November 2017 overflight at Kilauea. The photographer estimated the active breakout at tens of meters across. Photograph by C. Parcheta. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

During December 2017, an estimated 30 breakouts were recorded from the 61g flow tube, however these were often longer, lasting up to a week on the upper flow field, and with near perpetual breakouts on the pali throughout the month, which made quantifying the exact number difficult. A new breakout occurred 500 m from the 61g vent on 1 December and lasted through 20 December. This breakout, and the whole area between 500-1,200 m from the vent, poured lava onto the eastern upper flow field (figure 300). Most of the upper flow field activity was focused very close to the vent, between 350-800 m; additional activity also occurred at the 1 km location and a few continued breakouts were noted from the 2-3.5 km region. The coastal flow field activity was sluggish and mostly a result of the near-constant pali tube breakouts reaching the base. On 9 December a new voluminous breakout began near the top of the pali that burned through the kipuka near the center of the flow field (figures 302 and 303). This major breakout lasted through the end of the year and produced mostly 'a'a channels on the pali with pahoehoe at the pali base. Pali tube breakouts occurred at nearly every elevation but seemed to move higher up the slope as the month came to a close. Activity did not advance more than 400 m from the base of the pali.

Figure (see Caption) Figure 302. A small channel of lava burned through the kipuka on Kilauea's Pulama Pali on 21 December 2017. Figure 299 shows the kipuka on 21 September, still intact. Photograph by C. Parcheta. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).
Figure (see Caption) Figure 303. Close up of the 'a'a flow front near the base of the pali at Kilauea, which burned the remaining trees within the kipuka. Photograph by M. Patrick on 21 December 2017. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

Time series thermal maps of the 61g flow field overlaid on all of the tubes mapped from the field to date suggested to HVO scientists that some of the many breakouts during October-December 2017 may have come from reactivation of an earlier tube thought to be inactive since at least April 2017 (figure 304). Breakout locations coincided with the former tube trace, and happened at least five times between 21 September and 5 January 2018.

Figure (see Caption) Figure 304. A time series of thermal maps from overflights at Kilauea with all 61g tubes overlaid. Solid white lines are tubes active as of the image date, indicated by a thermal trace. Long dashed white line is the main (western) tube that became blocked at the end of September 2017. Dotted lines are older tubes from 2016 that were active when the 61g flow first crossed the coastal plain. These tubes were no longer noted in public maps by April 2017. In all thermal maps from October-December 2017, there was activity (indicated by black arrows) located above the older tube down the center of the flow field suggesting to HVO scientists that this tube may have been still producing breakouts from backlogged lava in the system. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

Activity at the East Rift Zone, Kamokuna ocean entry. By the end of June 2017, flows from multiple breakouts had resurfaced the delta of the Kamokuna ocean entry, covering earlier cracks, and building up and steepening the delta's landward side. These surface breakouts continued into early July, but by 10 July several new cracks had appeared, two of which visibly spanned the width of the delta (figure 305). Slumping of the seaward half of the delta and expansion of the cracks was visible in time-lapse camera images until the end of September.

Figure (see Caption) Figure 305. The Kamokuna ocean entry delta at Kilauea with visible large coast-parallel cracks which span most of the delta's width. On the W (left) side of the delta, the largest crack has been partially buried by the 'a'a flow produced by the 19 August 2017 breakout which started on the sea cliff roughly 100 m inland (lighter in color). Photo taken on 1 September 2017 by L. DeSmither. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

On 19 August 2017 around 0405 HST a breakout started on the sea cliff approximately 100 m upslope of the ramp, and five minutes later lava was spilling over the sea cliff and onto the delta. The breakout point and the lava falls over the cliff were both on the W side of the 61g tube. The lava produced a small 'a'a flow on the delta (figure 305), during its short-lived activity that lasted roughly 9.5 hours. Late on 19 August, the time-lapse camera also captured two images of littoral explosions in the center of the delta that produced a large spatter deposit on the delta's surface.

Three more sea cliff breakouts started on 23 September 2017. The first was brief "firehose-like" activity that began in the early morning hours. Based on the delta surface flows it produced, activity lasted less than 24 hours. Later views of the cliff face revealed that the "firehose" came out of a narrow horizontal crack E of the ramp, that was less than a meter below the top of the cliff. Later that day, on the sea cliff near the ocean entry, two new breakouts started, one to the E and one to the W of the tube. The E breakout originated roughly 70 m upslope of the sea cliff, and the breakout point had been fractured and depressed. Its thin pahoehoe flow spread out behind the littoral cone and came close to the edge of the cliff but did not spill over. The W breakout was visible in the time-lapse camera images on 23 September from around noon until midnight, producing only a few small dribbles of lava over the sea cliff. The breakout point was roughly 100 m upslope of the sea cliff, and buried the breakout from 19 August with thick, viscous pahoehoe. By the end of September, surface flows again covered much of the delta until most of the cracks were obscured, and only the ramp and a small area of the eastern delta close to the sea cliff were still uncovered.

Beginning in late August 2017, the ocean entry plume started to fluctuate regularly, and the plume was often weak or would briefly shut down. A shatter ring (a raised rim depression that forms over active lava tubes) began forming near the front of the delta on 21 August. By 30 August, the repeated uplifting and subsidence of the delta had broken the surface flows and built up a large rubble pile. On 26 September 2017 a bulge formed on the back half of the delta where the slope was steepest (figure 306). This inflationary feature produced steam and a delta surface flow from a crack at its base.

Figure (see Caption) Figure 306. Changes at the Kamokuna ocean entry at Kilauea between 26 June (left) and 26 September 2017 (right). The delta grew about 1.62 hectares (4 acres) in size, but also thickened from multiple breakouts resurfacing the delta. The delta cracks are not visible in either photo because the delta had been newly resurfaced in both images. Photos taken by L. DeSmither. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for July-September 2017).

HVO scientists concluded that the bulge observed on 26 September 2017 was the result of the formation of a spreading-induced graben in the middle of the delta that obstructed the 61g tube between 23 and 26 September 2017 (figure 307, top row). During the first part of October, additional breakouts from the tube above the sea cliff produced lava falls that poured down on the W side of the tube (figure 307, middle row). A few breakouts in the latter half of October flowed to the E side of the tube (figure 307, bottom row). The delta did not expand much in area during October-December 2017, but it thickened greatly due to the added volume from the lava falls breakouts and several small sluggish breakouts on the delta. The maximum extent that the delta reached was a little over 4 hectares in October, and then it began to shrink from waves crumbling its edges. By the end of December, the delta had lost about 0.4 hectares (1 acre) of land.

Figure (see Caption) Figure 307. Activity at the Kamokuna ocean entry of Kilauea during September-October 2017. Top: before (left, 19 September 2017) and after (right, 26 September 2017) the graben formation induced by delta slumping. The yellow (left) and orange (right) lines indicate the topographic profile through the middle of the delta. Middle: Aerial photograph (left, C. Parcheta) and thermal image (right, M. Patrick) from a 12 October 2017 overflight showing the extent of lava falls both E and W of the tube. Once the tube became blocked, the whole delta was resurfaced by this outpouring of lava. Bottom: The last of the lava falls occurred on the E side of the tube. The western falls had solidified but were illuminated on the left in this image during the first activity of the eastern lava falls. Image taken by the Kamokuna time-lapse camera on 10 October 2017 at 1842. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

The ocean entry was thought to have fully ceased activity shortly after 12 November 2017. The plume had its first pause in activity on 23 September, and quickly resumed but with decreasing vigor. By 26 September the plume was noticeably weaker and beginning to show intermittent pauses, which continued and became more prolonged through 4 November. The following day (5 November) was the first day with no plume visible in the HPcam, and 6 November was the last day an ocean entry plume was visible in the HP webcam. Ocean entry was active and observed during field visits between 6-11 November, but its weak, diffuse plume was not visible to the HP camera. The time-lapse camera stopped taking photos during the end of the Kamokuna delta activity in the late afternoon on 11 November (figure 308). This malfunction was discovered during a field visit on 12 November; the batteries were replaced a week later. The last photo of known lava activity on the delta was taken on 12 November, and the delta was likely completely inactive within a day or two.

Figure (see Caption) Figure 308. Kamokuna delta at Kilauea on 11 November 2017 shortly before the edges began to crumble from the continuous wave action. Photograph by Kamokuna time-lapse camera. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for October-December 2017).

During a 12 December 2017 overflight, an HVO scientist witnessed a collapse of a small portion of the sea cliff east of the tube into a yellow talus pile on the back portion of the delta, removing the evidence of the lava falls.

Satellite thermal and SO2 data. In addition to field observations, satellite-based thermal and SO2 data provide important insights into the ongoing activity at Kilauea. The many MODVOLC thermal alerts issued during July-December 2017 show the varying intensity and locations through time of the many breakouts along the episode 61g flow field from near the vent at the base of Pu'u 'O'o all the way down to the Kamokuna ocean entry delta (figure 309).

Figure (see Caption) Figure 309. MODVOLC thermal alert pixels for the episode 61g lava flow at Kilauea during various weeks of July-December 2017. Green grid squares each represent 1 square km. Areas of activity discussed in the earlier text are labelled. Each image represents seven days of thermal alerts. Upper left: 2-8 July 2017, the 13 June breakout expands the upper flow field, and the front of the 26 June breakout has extended beyond the base of the pali. Upper right: 23-29 July 2017, the 26 July breakout appears about 1 km E of the vent, breakouts are active on the pali, and surface flows are active on the Kamokuna delta. Center left: 27 August-2 September 2017, extensive new breakouts along the base of the pali created multiple alerts in that area. Center right: 1-7 October 2017, abundant breakouts just above the delta create lava falls over the delta after the graben formed in late September. Lower left: 12-18 November 2017, many breakouts were observed near the vent and on the pali during November. Lower right: 17-23 December 2017, breakouts were focused on the upper slope and the pali where the kipukas burned up in December, and lava was no longer flowing into the ocean at the delta. Courtesy of HIGP, MODVOLC.

The MIROVA project thermal anomaly graph of distance from the summit also shows the multiple sources of heat at Kilauea and the migration of those sources over time (figure 310). The MIROVA center point for relative distances described here is about 10 km (0.1°) E of Halema'uma'u crater. The anomaly locations at about 10 km distance from this point correspond to both the lava pond at Pu'u 'O'o crater and the Halema'uma'u crater lava lake. Those about 20 km away correspond to the Kamokuna ocean entry. Anomalies that migrate over time between 10 and 20 km distance trace the movement of the many episode 61g flow breakouts between Pu'u 'O'o and the Kamokuna ocean entry during July-December 2017.

Figure (see Caption) Figure 310. The MIROVA project thermal anomaly graph of distance from the summit shows the multiple sources of heat at Kilauea and the migration of those sources from 1 June 2017-15 January 2018. The MIROVA center point for relative distances described here is about 10 km (0.1°) E of western Halema'uma'u crater. The anomaly locations at about 10 km distance (y-axis) correspond to both the lava pond at Pu'u 'O'o crater and the Halema'uma'u crater lava lake. Those about 20 km away correspond to the Kamokuna ocean entry. Anomalies that migrate over time between 10 and 20 km distance trace the movement of the many episode 61g flow breakouts between Pu'u 'O'o and the Kamokuna ocean entry during July-December 2017.

Kilauea emits significant SO2 that is recorded by both ground-based and satellite instruments. Sulfur dioxide emissions exceeded density levels of two Dobson Units (DU) multiple times every month during the period (figure 311). Increases in SO2 flux are caused by many factors including increases in the number and size of surface lava breakouts as well as activity at the summit crater.

Figure (see Caption) Figure 311. Sulfur dioxide emissions generally exceeded density levels of two Dobson Units (DU) multiple times every month at Kilauea and are recorded daily in satellite data. Increases in SO2 emissions are caused by many factors including increases in the number and size of surface lava breakouts as well as activity at the summit crater. A few of the SO2 plumes captured by the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite with DU greater than 2 during July-December 2017 are shown. The prevailing winds on Hawaii blow from NE to SW, so plumes generally drift SW. UR: 23 July 2017, UL: 12 September 2017, LR: 9 October 2017 and LL: 28 December 2017. Courtesy of NASA Goddard Space Flight Center.

Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: http://hvo.wr.usgs.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Manam (Papua New Guinea) — April 1989 Citation iconCite this Report

Manam

Papua New Guinea

4.08°S, 145.037°E; summit elev. 1807 m

All times are local (unless otherwise noted)


Ash plumes and Strombolian explosions increase, March-May 2017

Manam is a basaltic-andesitic stratovolcano that lies 13 km off the northern coast of mainland Papua New Guinea; it has a 400-year history of recorded evidence for recurring low-level ash plumes and occasional Strombolian emissions, lava flows, pyroclastic avalanches, and large ash plumes. Activity during 2016 included only two episodes of ash emissions, during early March and mid-July, but persistent thermal activity (strongest between March and July 2016) was intermittent throughout the year (BGVN 42:03). Activity from January 2017-January 2018, discussed below, included increased Strombolian activity, lava flows, and ash emissions during February-May 2017 that led to evacuations and concern for local residents. Information about Manam is primarily provided by Papua New Guinea's Rabaul Volcano Observatory (RVO), part of the Department of Mineral Policy and Geohazards Management (DMPGM). This information is supplemented with aviation alerts from the Darwin Volcanic Ash Advisory Center (VAAC). MODIS thermal anomaly satellite data is recorded by the University of Hawai'i's MODVOLC thermal alert recording system, and the Italian MIROVA project; sulfur dioxide monitoring is done by instruments on satellites managed by NASA's Goddard Space Flight Center.

Summary of 2017 activity. A strong surge in thermal activity beginning in mid-February 2017 lasted through mid-June. Low levels of intermittent activity continued for the rest of 2017, with a short-lived increase during late December 2017 and early January 2018 (figure 35). Strong multi-pixel daily MODVOLC thermal alerts began on 17 February and continued through 29 May 2017. Plumes of SO2 were detected with satellite instruments in late February, early March, and during the second half of May.

Figure (see Caption) Figure 35. The MIROVA project Log Radiative Power signal for Manam increased significantly during late February 2017 and remained elevated through mid-June. Significant ash plumes and Strombolian activity were reported from early March-late May, after which only a few low-level ash plumes were reported through the end of 2017. Log Radiative Power graph of the year ending 17 January 2018. The occasional points shown in black indicate thermal sources located more than 5 km from the summit, and are likely unrelated to volcanic activity. Courtesy of MIROVA.

The first report of ash emissions in 2017 was on 2 March. Activity increased in late March, and again during the second half of April. Most of the many ash plume events that took place during May rose to 2-5 km altitude, but on 4 and 26 May they rose to over 12 km altitude. Ash plumes were noted on only two days during June, and none during July. Minor low-level ash emissions resumed in early and mid-August. The final VAAC report of 2017 was issued on 2 September.

RVO reported incandescent activity, Strombolian explosions, lava and pyroclastic flows, and ash emissions during February-May 2017 from both the Main and Southern craters (figures 36 and 37), and steam-and-gas emissions throughout the year. Activity during late February to mid-April occurred at both craters; most of the activity during late April and May came from Southern Crater. The events of mid-May caused ashfall across the island. Lava flows and pyroclastic flows in mid-April and mid-May led to evacuations from several villages. Incandescence was observed once from Southern Crater in November and once from Main Crater in December.

Figure (see Caption) Figure 36. Activity at Main Crater of Manam during 2017. The five graphs represent the rate (right y-axis) and intensity (left y-axis) of various activity at the volcano. Steam-and-gas emissions were observed throughout the year (bottom graph; green bars, blue circles). Explosions were heard during mid-February-April (second from bottom graph; blue bars, green circles). Ash emissions were reported from mid-February through April, and at the end of May (middle graph; purple bars, black crosses). Incandescence was observed from mid-February-April, once at the end of May and once in early December (second from top graph; black bars, red x's). Incandescent bombs, lava flows or pyroclastic flows were observed during mid-February-April and at the end of May (top graph; red bars, black diamonds). Courtesy of Steve Saunders, RVO.
Figure (see Caption) Figure 37. Activity at Southern Crater of Manam during 2017. The five graphs represent the rate (right y-axis) and intensity (left y-axis) of various activity at the volcano. Steam-and-gas emissions were observed throughout the year (bottom graph; green bars, blue circles). Explosions were heard during February-May and in mid-July (second from bottom graph; blue bars, green circles). Ash emissions were reported from mid-January through May (middle graph; purple bars, black crosses). Incandescence was observed in early January, from late January-May, and once in early November (second from top graph; black bars, red x's). Incandescent bombs, lava flows, or pyroclastic flows were observed from mid-February-mid May (top graph; red bars, black diamonds). Courtesy of Steve Saunders, RVO.

Activity during February-March 2017. After a break during much of December 2016, low-to-moderate pulses of thermal anomalies were recorded briefly by the MIROVA project early in January 2017 (BGVN 42:03, figure 34). Activity increased again in mid-February with stronger MIROVA anomalies and multi-pixel MODVOLC thermal alerts. Sulfur dioxide plumes were released on 25 February and 4 March 2017 (figure 38).

Figure (see Caption) Figure 38. Sulfur dioxide emissions from Manam increased in late February 2017 along with increased thermal activity. SO2 plumes were captured by the OMI instrument on the Aura satellite on 25 February 2017 (left) and 4 March 2017 (right). Another emission, partly obscured, on 4 March is likely from Bagana on Bougainville Island to the SE. Courtesy of NASA Goddard Space Flight Center.

MODVOLC thermal alerts were issued on 13 days during March, many days had 3-6 alerts. The Darwin VAAC issued the first Volcanic Ash Advisory of 2017 on 2 March based on a pilot report of ash extending N of the volcano at 3 km altitude. The next report, on 20 March, indicated an ash plume visible in satellite imagery moving NE at 2.4 km altitude. It extended 80 km E of the summit the following day. Mostly-steam emissions with minor ash content were reported on 23 March, extending 75 km SE at the same altitude.

Activity during April 2017. Intense multi-pixel MODVOLC thermal alerts continued into April 2017; days with multiple alerts included 2, 14, 22-23, and 25-26 April. RVO released a Volcano Information Bulletin on 16 April 2017 noting a sudden increase in RSAM values beginning on 15 April, and indicating that a small-to-moderate eruption was ongoing from Main Crater. Incandescence was visible during most nights of April from both Main and Southern craters. RSAM values increased by two orders of magnitude during 16-17 April (figure 39). During that night, a brief report from Dugulava village on the SE side of the island indicated that large incandescent lava fragments were falling into valleys to the N and SW, accompanied by loud explosions. Strombolian activity at Southern Crater increased on 18 April, and was accompanied by emissions of dark ash plumes that rose a few hundred meters above the crater and drifted NW. Two small pyroclastic flows were channeled into valleys on the SE and SW flanks, and terminated at about 1,000 m elevation. Strombolian activity subsided by late afternoon, but weak gray ash emissions continued. At Main Crater, white-gray ash plumes continued with bursts of incandescence at about 5-minute intervals.

Figure (see Caption) Figure 39. A spike in RSAM values during 16-17 April 2017 coincided with increased Strombolian activity from Southern Crater at the summit of Manam. Courtesy of RVO-DMPGM (Volcano Information Bulletin-No. 06-042017, Issue Date: 19th April 2017).

RVO reported that activity diminished after 18 April but continued at low levels through 21 April; explosions were still heard from both Main and Southern Craters. Both craters were incandescent, but only Southern Crater ejected incandescent tephra, which became briefly intense during the morning of 20 April. Pale gray-to-brown plumes containing minor amounts of ash rose from both craters and drifted SE. RSAM values began to rise again on 22 April, and Strombolian activity continued during 22-24 April (figure 40). According to a news article from 25 April (The National) the Alert Level was raised to Stage 3, and an official on the island noted that evacuations of women and children had begun to Bogia, about 16 km SW on the mainland.

Figure (see Caption) Figure 40. An explosion at Manam on 22 April 2017. Incandescence at the summit and steam emissions are visible beneath the meteoric clouds. Photo: USGS/Landsat-8 OLI. Courtesy of Radio New Zealand.

The Darwin VAAC reported an ash plume at 4.6 km altitude extending about 35 km SE from the summit on 24 April. The next day, an ash plume was observed drifting a similar distance SW at 3 km altitude. The drift direction changed to WSW then W during 26 April, and the plume was last observed about 65 km from the summit. Infrared imagery indicated ongoing activity at the summit.

Strombolian activity and strong, dark-gray ash emissions continued during 24-25 April; activity declined for a few days before the next pulse began during the early morning of 28 April with Strombolian explosions that were heard at the Bogia Government Station. Most of the lava fell back into the crater, but some traveled down the SW and SE valleys, and minor amounts of ash fell on the SE and W parts of the island.

A pulse of moderately-high Strombolian activity occurred from Southern Crater during the early morning of 30 April 2017. The episode lasted about two hours and produced a small pyroclastic flow that was channeled into the SW valley and stopped at about 200 m elevation. Ejected incandescent lava fragments landed mostly within the crater, but some traveled down the SW and SE valleys. Ash and scoria up to 40 mm in diameter fell on the E side of the island in Abaria and Boakure.

Activity during May 2017. The strongest thermal activity of the year was recorded during May 2017. MODVOLC thermal alerts were issued on 4, 5, 9, 13, 14, 17, 18, 25, and 29 May, with 21 alerts issued on 18 May and a single alert on 29 May that was the last issued for the year. RVO reported a Strombolian event from Southern Crater, lasting from about 1700 on 4 May to 0700 the following morning. A lava flow descended into the SW valley to 600 m above sea level, and minor amounts of ash fell in areas stretching between Warisi to the E, Dugulaba on the S, and Boda and Baliab on the NW parts of the island.

The Darwin VAAC reported an ash plume drifting E at 3 km altitude late on 4 May 2017 (UTC). About an hour later, they reported a much higher altitude ash plume moving S from the summit at 12.5 km altitude, in addition to continuous ash moving E at 3 km altitude. The high-level ash plume dissipated after about five hours, but the lower-level emission continued to be visible in satellite imagery drifting E, then NE at least 25 km from the summit through 7 May, after which activity subsided. RVO reported steam-and-gas emissions from Southern Crater on 13 May. Incandescent lava fragments were ejected during the early morning of 14 May, generating a lava flow that traveled down the SW valley to an elevation of 600-700 m.

The next VAAC report, on 14 May 2017, noted an ash plume drifting NW at 4.6 km altitude 35 km from the summit. Later in the day, they reported another short-lived ash plume that rose to 5.5 km altitude drifting almost 100 km W, and a large hotspot over the summit. The lower-altitude plume lasted for another day before dissipating. RVO reported light gray to dark gray ash plumes during 15-18 May. The Darwin VAAC reported multiple plumes moving W at 2.1-2.4 km altitude on 17 May, and continuous emissions extending WNW on 18 May. RVO reported explosive activity on 18 May; a small lava flow traveled down the SW valley, but not as far as the 13-14 May flow. A weak ash emission, which dissipated after a few hours, was reported on 19 May drifting W at 2.7 km altitude. The Darwin VAAC reported that a substantial ash emission on 26 May 2017 was seen in satellite images drifting 55-75 km W at 12.2 km altitude. A second plume from a continuous lower-level eruption was reported later in the day rising to 4.6 km altitude. Both plumes dissipated by the end of the day. Sulfur dioxide emissions were captured by satellite instruments on 18 and 27 May (figure 41).

Figure (see Caption) Figure 41. SO2 plumes from Manam were captured on 18 (left) and 27 (right) May 2017 by the OMI instrument on the Aura satellite. Eruptive activity was reported by RVO and ash emissions were reported by the Darwin VAAC on 18 May, and a large ash emission was reported by the Darwin VAAC on 26 May. Courtesy of NASA Goddard Space Flight Center.

Activity during June-December 2017. Activity decreased significantly after May 2017 and was low for the remainder of the year. RVO noted weak-to-moderate steam plumes on the rare clear-weather days during June; there was no observed incandescence, and very low seismicity. The Darwin VAAC reported an ash plume that rose to 5.5 km altitude and drifted W on 6 June. Later in the day the plume extended WNW at about 2.4 km altitude. It was last observed early on 7 June before dissipating. No further ash emissions were noted by the Darwin VAAC or RVO until 5 August 2017 when the Darwin VAAC observed minor ash emissions moving NW at 2.1 km altitude. The emissions were visible that day and the next before dissipating. A new ash emission was reported late on 7 August, drifting W at 1.8 km altitude for about 8 hours before dissipating early the next day. Another minor plume on 12 August briefly extended 35 km NW at 2.1 km altitude. During 21-22 August, a similar plume was seen at the same altitude. A minor ash emission on 1 September, which also rose to 2.1 km altitude, was only visible for a few hours before dissipating, and was the last emission reported in 2017.

RVO noted incandescence at Southern Crater once in early November, and once at Main Crater in early December. The MIROVA data showed a cluster of thermal anomalies during late December2017 and early January 2018 (figure 35) suggesting a renewed pulse of thermal activity during that time.

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Radio New Zealand (URL: http://www.radionz.co.nz); The National (URL: http://www.thenational.com.pg).


Sangay (Ecuador) — April 1989 Citation iconCite this Report

Sangay

Ecuador

2.005°S, 78.341°W; summit elev. 5286 m

All times are local (unless otherwise noted)


Eruptive episode of ash-bearing explosions and lava on SE flank, 20 July-26 October 2017

Periodic eruptive activity at Ecuador's remote Sangay has included frequent explosions with ash emissions and occasional andesitic block lava flows. Eruptive activity from late March to mid-November 2016 included multiple ash emissions and persistent thermal signals through July 2016 (BGVN 42:08). A new episode of ash emissions and thermal anomalies, that began on 20 July 2017 (BGVN 42:08) and lasted through late October 2017, is covered in this report. Subsequent activity through February 2018 included a single ash-emission event near the end of the month. Information is provided by Ecuador's Instituto Geofísico (IG) and the Washington Volcanic Ash Advisory Center (VAAC); thermal data from the MODIS satellite instrument is recorded by the University of Hawaii's MODVOLC system and the Italian MIROVA project.

The first ash plume of the latest eruptive episode at Sangay was reported on 20 July 2017. VAAC reports were issued on 20 and 21 July, eleven days in August, six days in September, and on 13 October. Thermal activity first appeared in a MIROVA plot during the last week of July and continued through 26 October. Multiple MODVOLC thermal alerts were issued between 2 August and 19 October. IG reported that low-energy ash emissions rising 1 km or less above the summit crater were typical throughout the period. They also repeatedly noted two distinct thermal hot spots in satellite data. A single ash emission on 25 February 2018 was the only additional activity through the end of February 2018.

Activity during July-October 2017. The Washington VAAC reported an ash emission on 20 July 2017 that rose to 8.2 km altitude and drifted about 80 km W. A plume was reported on 1 August by the Guyaquil MWO near the summit at about 5.3 km altitude, but was obscured by clouds in satellite imagery. The following day an ash plume was observed at 7.6 km altitude centered about 15 km NW of the summit. An ash emission was reported on 6 August, but was not visible in satellite imagery. The MWO reported an ash emission on 12 August at 6.4 km altitude moving SW, but no ash was detected in satellite imagery under partly cloudy conditions. The Washington VAAC observed an ash plume on 13 August extending around 50 km SW at 6.1 km altitude and a well-defined hotpot. IG reported an ash emission drifting W on 16 August, but clouds obscured satellite views of the plume. Hotspots continued to be observed in shortwave infrared (SWIR) imagery. The Washington VAAC reported an ash plume at 8.2 km altitude on 17 August. The imagery showed an initial puff moving NW followed by several smaller puffs. On 19 August, the Guayaquil MWO reported an ash plume at 5.8 km altitude drifting SW. The next day, another explosion was reported with ash rising again to 5.8 km and drifting W, and a hotspot was observed in satellite imagery.

The Washington VAAC reported a possible ash plume extending 30 km SW of the summit at 7 km altitude on 22 August. It had dissipated the next day, but they noted that a hotspot was visible in SWIR imagery. The next ash plume was reported by the MWO on 1 September at 5.2 km altitude but was not observed in satellite imagery. The next day, the Washington VAAC observed an ash plume at 6.1 km altitude extending 15 km NW of the summit. The Guayaquil MWO reported an ash plume to 7.3 km altitude on 6 September. On 20 September, a possible ash plume could be seen in GOES-16 imagery extending about 150 km W from the summit at 6.1 km altitude. Another plume extended 15 km SW from the summit later in the day at the same altitude. By the end of the day, continuous ash emissions were reported drifting W at 5.8 km altitude. The following day, occasional ash emissions were still reported drifting W and dissipating within 35 km of the summit. A new emission late on 21 September sent an ash plume 25 km W of the summit at 6.1 km altitude. Possible ongoing emissions were reported on 22 September, but not visible in satellite imagery. After three weeks of quiet, the Washington VAAC reported an ash emission on 13 October drifting S at 6.1 km altitude along with a bright hot spot visible for part of the day. This was the last report of ash emissions for 2017.

The eruption that began on 20 July 2017 was characterized by explosions from the central crater and lava emissions from the Ñuñurco dome on the E side of the summit. IG reported two areas of hot spots visible in thermal images during August and September. Around 65 seismic explosions and 25 long-period events were recorded daily during most of this time, along with a few harmonic tremors. Low-energy ash emissions rising 1 km or less above the summit crater were typical. Ashfall was reported to the SW and NW in Culebrillas (75 km SW), and Licto (35 km NW). New lava flows were interpreted to be on the ESE flank by IG based on the repeated hot spots visible in satellite imagery and darkened areas in the snow in the webcam images (figure 20).

Figure (see Caption) Figure 20. A dark streak in the snow near the summit (left side, arrow) of Sangay indicates recent ejecta of blocks or flows on the upper ESE flank of the cone on 1 October 2017. View is from the ECU911 webcam located in Huamboya, 40 km E. Courtesy of IG-EPN (Informe Especial del Volcán Sangay, 2017-2, Continúa la erupción, se observan dos ventos, 4 de octubre del 2017).

Thermal activity measured from satellite instruments support the interpretation of significant lava emissions as blocks or flows at Sangay during late July-October 2017. The MODVOLC system reported 11 thermal alerts beginning on 14 August, 15 during September, and 13 between 3 and 19 October. A similar signal of thermal activity was recorded by the MIROVA system during the same period (figure 21).

Figure (see Caption) Figure 21. The MIROVA project graph of thermal anomalies in MODIS data from Sangay for the year ending on 17 November 2017 (lower graph) clearly shows the period of increased heat flow between late July and late October. The last anomaly appeared on 26 October 2017 (upper graph). Courtesy of MIROVA.

Activity on 25 February 2018. The Washington VAAC reported an ash plume rising to 6.1 km altitude and drifting NE from the summit on 25 February 2018. The plume was visible 170 km NE before dissipating by the end of the day.

Geologic Background. The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Information Contacts: Instituto Geofísico (IG), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec ); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


Tinakula (Solomon Islands) — April 1989 Citation iconCite this Report

Tinakula

Solomon Islands

10.386°S, 165.804°E; summit elev. 796 m

All times are local (unless otherwise noted)


Short-lived ash emission and large SO2 plume 21-26 October 2017; historical eruption accounts

Remote Tinakula lies 100 km NE of the Solomon Trench at the N end of the Santa Cruz Islands, part of the country of the Solomon Islands, which generally lie 400 km to the W. It has been uninhabited since an eruption with lava flows and ash explosions in 1971 when the small population was evacuated (CSLP 87-71). The nearest inhabitants live on Te Motu (Trevanion) Island (about 30 km S), Nupani (40 km N), and the Reef Islands (60 km E); they occasionally report explosion noises from Tinakula. Ashfall from larger explosions has historically reached these islands. The last reported evidence of activity came from MODVOLC thermal alerts between August 2010 and October 2012, and observations of incandescent lava blocks rolling into the sea in May 2012. A new eruptive episode with a large ash explosion and substantial SO2 plume during 21-26 October 2017 is reported below, along with newly available historical newspaper accounts of earlier eruptions.

Reports of ash plumes are issued by the Wellington Volcanic Ash Advisory Center (VAAC); the National Disaster Management Office (NDMO) of the Solomon Islands Government also issues situation reports when significant activity is reported. Satellite data from infrared, visual, and SO2 monitoring instruments are an important source of information for this remote volcano. News reports from local (and social) media are often the only sources of information for the smaller events. Recently identified 19th- and 20th-century newspaper accounts of eruptive activity witnessed by sailors passing nearby is a valuable new resource for previously unreported events.

Eruption of 21-26 October 2017. Reports of a substantial explosion with an ash plume from Tinakula appeared on social media and in the local press during 22-26 October 2017. Staff from the Lata Met Service Office approached the island by boat on 23 October to make direct observations (figures 17-19). A video clip from the Himawari8 Satellite showing the ash plume explosion was posted by Stephan Armbruster on Twitter on 22 October. The Solomon Islands NDMO issued a situation report on 26 October showing ashfall covering vegetation on the island. According to the NDMO, ashfall was concentrated on the island, although a small amount of ash drifted SE and was reported to briefly contaminate drinking water in several communities in the nearby Reef Islands (60 km ENE) . Ashfall was also reported on Fenualoa Island (50 km ENE) (Radio New Zealand). The eruption was categorized by NMDO as a VEI 3. A team of geologists from NDMO brought seismic monitoring equipment to Tinakula in early November, and measured a high frequency volcanic tremor on 5 November 2017.

Figure (see Caption) Figure 17. View from the SE of the eruption at Tinakula on 23 October 2017 during a site visit by staff from the Lata Office of the Solomon Islands Meteorological Service. Photo by Okano Gamara.
Figure (see Caption) Figure 18. Ash and steam emissions rose from Tinakula on 23 October 2017 during a site visit by staff from the Lata Office of the Solomon Islands Meteorological Service. Photo by Okano Gamara.
Figure (see Caption) Figure 19. Ash emission from Tinakula on 23 October 2017 during a site visit by staff from the Lata Office of the Solomon Islands Meteorological Service. Photo by Okano Gamara.

The Wellington VAAC first reported an ash plume visible in satellite imagery shortly after midnight (UTC) on 21 October 2017. The plume was estimated to be at 4.6 km altitude and drifting N. About 90 minutes later they reported a second eruption with a much higher plume drifting SE at 10.7 km altitude using IR imagery cloud top temperatures to estimate the altitude. They reported ongoing ash emissions visible in satellite imagery drifting SE at 6.1 km altitude throughout the morning, dropping to 3 km altitude by the end of the day. The following day, 22 October, intermittent ash emissions were reported at 3.7 km altitude moving E. By that afternoon, they had dropped to 2.4 km, and had lowered to 1.8 km by late on 23 October. Ongoing low-level ash emission (2.1 km altitude) continued through 25 October; by early on 26 October, there was no further evidence of ongoing activity.

No MODVOLC thermal alerts were associated with this event, but there was a brief MIROVA signal from the MODIS infrared data during 20-23 October 2017 (figure 20). A major SO2 plume was released from Tinakula on 21 October, and a smaller one was recorded on 28 October as well (figure 21).

Figure (see Caption) Figure 20. Moderate thermal signals were recorded from Tinakula on 20 and 23 October 2017 (top graph) by the MIROVA system that captures MODIS infrared satellite data. Another signal reported during the first week of March 2017 (bottom graph) could also have been an eruptive event, but no other corroborating evidence is available. Courtesy of MIROVA.
Figure (see Caption) Figure 21. Major SO2 plumes from Tinakula and the Vanatu volcanoes of Ambae and Ambrym were released during October 2017. A substantial SO2 plume drifted in several directions from Tinakula on 21 October 2017 (left). Much smaller plumes are also visible from Ambae and Ambrym which are located farther south. On 28 October (right), a smaller SO2 plume was drifting SE from Tinakula while much larger plumes were apparent from Ambae and Ambrym. Data gathered by the OMI instrument on the Aura Satellite. Courtesy of NASA Goddard Space Flight Center.

Summary of activity during 1971-2012. After the 1971 eruption, intermittent ash emissions, lava bombs, and pyroclastic flows were reported by geologists and sailors passing nearby in 1984, 1985, 1989-1990, 1995, and 1999. Infrared MODIS thermal data was first reported as MODVOLC thermal alerts beginning in 2000 and has provided satellite-based confirmation of thermal activity since then. Months with thermal activity included February 2000-May 2001, February 2006-November 2007, September-November 2008, August 2009, and January 2010-October 2012 (figure 22). No additional thermal alerts were issued through 2017. Since 2004, SO2 data has been gathered by satellite instruments and processed by NASA Goddard Space Flight Center; in February and April 2006 small SO2 plumes were recorded (figure 23).

Figure (see Caption) Figure 22. Months with MODVOLC thermal alerts from MODIS infrared data for Tinakula, during January 2000-December 2017. The orange boxes indicate months where at least one MODVOLC thermal alert was issued; the number of alerts is indicated inside the square. Months highlighted in green represent contiguous periods of time of three months or greater with no recorded MODVOLC thermal alerts. Pale orange squares indicate months with no MODVOLC thermal alerts issued, but within a three-month buffer of an earlier thermal alert. Data courtesy of MODVOLC.
Figure (see Caption) Figure 23. SO2 emission data captured by the OMI instrument on the Aura satellite indicated small plumes from Tinakula (top center of images) on 12 and 14 February 2006 (top) and 21 and 23 April 2006 (bottom). Small plumes were also visible from Ambrym on 12 February, and from Ambae and Ambrym on 14 February and 21 and 23 April 2006. Courtesy of NASA Goddard Space Flight Center.

Eruption reports during 1868-1932. Reports of eruptions at Tinakula between 1868 and 1932 have recently been found in 19th and 20th century newspaper accounts from Australia and New Zealand (table 6). The accounts describe incandescence, water discoloration of the sea, explosions, ash plumes, and lava flows extending from the summit to the ocean.

Table 6. Newly discovered historical newspaper accounts of volcanic activity from ships passing near Tinakula between 1868 and 1932. This is not a full eruptive history for the time period. Online links provided in the References section. Courtesy of Steve Hutcheon.

Date Account Reference
17 Oct 1868 Passed Volcano Island, one of the South (sic) Cruz group, on the 17th of October. It was then in active operation, vomiting forth immense volumes of fire and smoke. Note; Volcano Island is another name for Tinakula. The Age, Melbourne, 10 November 1868, page 2b; also in The Argus, Melbourne, 10 November 1868, page 4b
9 Oct 1869 On the 9th October sighted three low islands, also Volcano Island; the discharge from the latter was plainly visible. The Empire, Sydney, 27 October 1869, page 2a
29/30 Nov 1871 During the night, the active volcano, Tinakula, was passed. Large masses of red hot lava were emitted; and the sight is described as being very imposing and grand. The Sydney Morning Herald, 19 February 1872, page 6a
20 Jun 1887 When his vessel was off the Santa Cruz group Mount Tinakula became an active volcano. It broke out at 4 o'clock on the morning of June 20 and viewed from the ship's deck presented a most grand spectacle. The water for miles round was of a pea green color and had the appearance of being very shallow. The Daily Telegraph, Sydney, NSW, 20 July 1887, page 4f
~23 Aug 1910 Tinakula Island was found to be in an active state of eruption, and presented a fine sight. The ship Tambo departed Tarawa 19 August and arrived in Sydney on 31 August 1910. The Daily Telegraph, Sydney, NSW, 1 September 1910, page 7a
2/3 May 1932 The steamer passed within half a mile of the active volcano of Tinakula. It was at night, and the passengers obtained a remarkable view of the red hot lava streams flowing from the summit, which is 2000 ft. high, to the water's edge. Three eruptions occurred while the vessel was within view of the island, each preceded by an explosion which sounded like thunder. The New Zealand Herald, Auckland, NZ, 27 June 1932, page 6a; The Auckland Star, 10 September 1932 page 1h (Supplement)

References. The Age (Melbourne, Victoria) 10 November 1868, page 2b (URL: http://nla.gov.au/nla.news-article177002744).

The Empire (Sydney, NSW) 27 October 1869, page 2a, (URL: http://nla.gov.au/nla.news-article60895166).

The Sydney Morning Herald (NSW) 19 Februay 1872, page 6a (URL: http://nla.gov.au/nla.news-article13252748).

The Daily Telegraph (Sydney, NSW) 1887 20 July, page 4f (URL: http://nla.gov.au/nla.news-article239817295).

The Daily Telegraph (Sydney, NSW) 1 September 1910, page 7a (URL: http://nla.gov.au/nla.news-article237993807; http://nla.gov.au/nla.news-article15183461 ).

The New Zealand Herald (Auckland, NZ) 27 June 1932, page 6a (URL: https://paperspast.natlib.govt.nz/newspapers/NZH19320627.2.19 ).

The Auckland Star (NZ) 10 September 1932, page 1h (Supplement) (URL: https://paperspast.natlib.govt.nz/newspapers/AS19320910.2.180.6 ).

Geologic Background. The small 3.5-km-wide island of Tinakula is the exposed summit of a massive stratovolcano at the NW end of the Santa Cruz islands. Similar to Stromboli, it has a breached summit crater that extends from the summit to below sea level. Landslides enlarged this scarp in 1965, creating an embayment on the NW coast. The satellitic cone of Mendana is located on the SE side. The dominantly andesitic volcano has frequently been observed in eruption since the era of Spanish exploration began in 1595. In about 1840, an explosive eruption apparently produced pyroclastic flows that swept all sides of the island, killing its inhabitants. Frequent historical eruptions have originated from a cone constructed within the large breached crater. These have left the upper flanks and the steep apron of lava flows and volcaniclastic debris within the breach unvegetated.

Information Contacts: National Disaster Management Office (NDMO), Solomon Islands Government, Prince Philip Highway, Ranadi, Solomon Islands (URL: http://www.ndmo.gov.sb); Wellington Volcanic Ash Advisory Centre (VAAC), Meteorological Service of New Zealand Ltd (MetService), PO Box 722, Wellington, New Zealand (URL: http://www.metservice.com/vaac/, http://www.ssd.noaa.gov/VAAC/OTH/NZ/messages.html); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: http://so2.gsfc.nasa.gov/index.html ); Radio New Zealand (URL: http://www.radionz.co.nz/international/pacific-news/342267/solomons-pm-calls-for-calm-in-communities-close-to-volcano); Solomon Islands Broadcasting Corporation, SIBC Voice of the Nation, Honiara, Solomon Islands (URL: http://www.sibconline.com.sb/no-its-not-snow-in-the-solomons-its-ash-from-the-tinakula-volcano/); Andy Prata, AIRES Atmospheric Industrial Research and Environmental Solutions, Melbourne, Australia (URL: https://www.aires.space/, https://twitter.com/andyprata/status/922177129944625157); Gamara Okzman Bencarson, Facebook.


Yasur (Vanuatu) — April 1989 Citation iconCite this Report

Yasur

Vanuatu

19.532°S, 169.447°E; summit elev. 361 m

All times are local (unless otherwise noted)


Typical ongoing eruptive activity and thermal anomalies through January 2018

Regular monitoring reports about Yasur from the Vanuatu Meteorology and Geo-Hazards Department (VMGD) indicated that the centuries-long eruptive activity continued from mid-June 2017 through January 2018. VMGD volcano bulletins on 21 July, 30 August, 29 September, 31 October, and 8 December 2017, and 30 January 2018, stated that major unrest was continuing, and the Alert Level remained at 2 (on a scale of 0-4). Based on seismic data, explosions continued to be intense. Visitors were reminded of the closed 395-m-radius Permanent Exclusion Zone (figure 48) and that volcanic ash and gas could impact other areas near the volcano due to trade winds.

Figure (see Caption) Figure 48. Oblique aerial photograph of Yasur with an overlay of designated hazard zones that may be closed depending on the level of eruptive activity. Courtesy of Vanuatu Meteorology and Geo-Hazards Department.

During the reporting period thermal anomalies based on MODIS satellite instruments analyzed using the MODVOLC algorithm were numerous every month. The MIROVA (Middle InfraRed Observation of Volcanic Activity) system also detected numerous hotspots every month (figure 49).

Figure (see Caption) Figure 49. Thermal anomalies detected in MODIS data by the MIROVA system (log radiative power) at Yasur for the year ending 23 February 2018. Courtesy of MIROVA.

Geologic Background. Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department, Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory/); Radio New Zealand (URL: https://www.radionz.co.nz); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


Ambrym (Vanuatu) — April 1989 Citation iconCite this Report

Ambrym

Vanuatu

16.25°S, 168.12°E; summit elev. 1334 m

All times are local (unless otherwise noted)


Elevated seismicity in early August 2017-early November 2017, lava lakes remain

Occasional weak eruptions and low-level ash emissions are typical of activity at Ambrym. The most recent ash emission was on 3 April 2017 (BGVN 42:05). The current report summarizes activity from late April through December 2017.

On 30 August 2017, the Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported that "drastic changes" at Ambrym prompted an increase in the Alert Level from 2 to 3 (on a scale of 0-5). Areas deemed hazardous were near and around the active vents (Benbow, Maben-Mbwelesu, Niri-Mbwelesu and Mbwelesu), and in downwind areas prone to ashfall. According to a news report (Radio New Zealand), a representative of VMGD indicated that the Alert Level change was based on increased seismicity detected since the beginning of August, but which became more notable on 25 August.

According to VMGD, aerial observations on 24 and 30 September, and 1 and 6 October, combined with analysis of seismic data, confirmed that minor eruptive activity within the caldera was characterized by hot volcanic gas and steam emissions. Areas deemed hazardous were within a 2-km radius from Benbow Crater and a 3-km radius from Marum Crater.

A news report (The Vanuatu Independent) quoted an official from VMGD as stating that on 8 November 2017 at 0500, the Niri-Mbwelesu eruptive vent emitted a minor ash plume. On 7 December 2017, VGO lowered the Alert Level to 2, noting that activity had stabilized by the end of November and was characterized by gas-and-steam emissions. Seismicity had also declined. The report reminded the public to stay outside of the Permanent Danger Zone, defined as a 1-km radius from Benbow Crater and a 2.7-km radius from Marum Crater.

During the reporting period, thermal anomalies based on MODIS satellite instruments and analyzed using the MODVOLC algorithm, continued to be numerous every month, possibly reflecting lava lakes in Benbow and Marum craters. The MIROVA (Middle InfraRed Observation of Volcanic Activity) system also detected numerous hotspots every month within 5 km of the volcano.

Geologic Background. Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides arc. A thick, almost exclusively pyroclastic sequence, initially dacitic, then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major plinian eruption with dacitic pyroclastic flows about 1900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the caldera floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department, Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory/); Radio New Zealand (URL: https://www.radionz.co.nz); The Vanuatu Independent (URL: https://vanuatuindependent.com/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Middle InfraRed Observation of Volcanic Activity (MIROVA), Mirova (collaborative project between the Universities of Turin and Florence, Italy)(URL: http://www.mirovaweb.it).

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Scientific Event Alert Network Bulletin - Volume 14, Number 04 (April 1989)

Managing Editor: Lindsay McClelland

Aira (Japan)

Summit explosions diminish

Akutan (United States)

Small ash ejections resume

Ambrym (Vanuatu)

Ash plume and lava flow; recent eruption history

Apoyeque (Nicaragua)

Lake temperature measured

Asosan (Japan)

Brief ash emission

Bagana (Papua New Guinea)

Lava flow advances; new avalanche deposits

Concepcion (Nicaragua)

Strong fuming

Galeras (Colombia)

Ash emission and strong seismicity; area residents alerted

Kilauea (United States)

Lava flows threaten houses

Langila (Papua New Guinea)

Moderate ash ejections and glow

Lengai, Ol Doinyo (Tanzania)

January inspection reveals no new lava

Lonquimay (Chile)

Continued tephra emission; cattle sickened by ash

Manam (Papua New Guinea)

Incandescent ejections and vapor release

Masaya (Nicaragua)

Lava lake drains; rockslides; gas emission

Momotombo (Nicaragua)

Burning gases from fumaroles

Niigata-Yakeyama (Japan)

Increased steaming, small ash eruption

Nyamuragira (DR Congo)

Lava erupts from summit and E flank

Poas (Costa Rica)

Crater lake gone; explosions and molten sulfur ponds

Popocatepetl (Mexico)

New fumaroles and large sulfur deposits

Rabaul (Papua New Guinea)

Seismicity and deformation at background level

Rincon de la Vieja (Costa Rica)

Crater lake sampled

Ruapehu (New Zealand)

Heat flow declines

Ruiz, Nevado del (Colombia)

Seismicity decreases

Soputan (Indonesia)

Ashfall damages houses and crops

Ulawun (Papua New Guinea)

Small ash emissions, minor seismic increases

White Island (New Zealand)

Tephra ejections continue



Aira (Japan) — April 1989 Citation iconCite this Report

Aira

Japan

31.593°N, 130.657°E; summit elev. 1117 m

All times are local (unless otherwise noted)


Summit explosions diminish

Activity . . . in April was lower than in previous years. Single explosions were registered on the 1st, 5th, and 13th. The highest cloud rose 1,600 m on 13 April. Monthly ash accumulation at the observatory was 119 g/m2.

Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Information Contacts: JMA.


Akutan (United States) — April 1989 Citation iconCite this Report

Akutan

United States

54.134°N, 165.986°W; summit elev. 1303 m

All times are local (unless otherwise noted)


Small ash ejections resume

Small ash ejections resumed in February 1989. Observer's initials, in brackets, follow their information in the chronology below.

27 February, 1200: A small, short-lived, vertical blast of ash and steam from the summit tephra cone was observed from a small boat on the N side of Akutan Island. The plume was probably <500 m high [LP].

15 March: An atmospheric shock wave was felt at 0900 by a pilot [NS] over the W shore of Akutan volcano. A black summit eruption plume rose rapidly, its top disappearing into cloud cover at 1,800 m altitude. Near Akutan village, the plume was observed at 0900 [RP] through a break in the clouds. Black ash quickly reached an estimated 2,300 m above the volcano. During the next several hours, emissions diminished and turned gray, with only a small white steam plume evident just before noon. At 1430, a small dark-gray eruption plume was observed from the village, drifting S [DM]. During an overflight at 1500, the summit tephra cone emitted dark steam [NS and HW]. Observations of the W and SW flanks revealed fresh ash covering the snow above 600 m elevation.

16 March, morning: A very light dusting of ash that had fallen the previous night was noticed in Akutan village [DM]. At 1100 the volcano's summit region was white with fresh snow [HW].

Between 17 and 31 March: A crater on the E side of the summit cone began to emit steam at some time during this period [DM]. Previously, steam had emerged only from the cone's W side.

28-29 March: Akutan's summit was black with fresh-looking ash. Minor amounts of steam were emitted [CL].

31 March, about 1945: A large white plume was observed at least 600 m above Akutan from a U.S. Coast Guard plane [SR]. The plume top had drifted 7 km S. No eruptive activity had been seen from near the village at 1900 [LL]. No further activity was observed from 31 March until the end of the report period on 7 April.

Observers (initials in brackets): Lawrence Prokopioff, Richard Petre, David McGlashan, Harold Wilson, and Linda Logan, Akutan Village and vicinity; Nick Sias, Peninsula Airways; Craig Leth, FAA; Lieutenant Commander Steve Rapalus and his crew, U.S. Coast Guard.

Geologic Background. One of the most active volcanoes of the Aleutian arc, Akutan contains 2-km-wide caldera with an active intracaldera cone. An older, largely buried caldera was formed during the late Pleistocene or early Holocene. Two volcanic centers are located on the NW flank. Lava Peak is of Pleistocene age, and a cinder cone lower on the flank produced a lava flow in 1852 that extended the shoreline of the island and forms Lava Point. The 60-365 m deep younger caldera was formed during a major explosive eruption about 1600 years ago and contains at least three lakes. The currently active large cinder cone in the NE part of the caldera has been the source of frequent explosive eruptions with occasional lava effusion that blankets the caldera floor. A lava flow in 1978 traveled through a narrow breach in the north caldera rim almost to the coast. Fumaroles occur at the base of the caldera cinder cone, and hot springs are located NE of the caldera at the head of Hot Springs Bay valley and along the shores of Hot Springs Bay.

Information Contacts: J. Reeder, ADGGS.


Ambrym (Vanuatu) — April 1989 Citation iconCite this Report

Ambrym

Vanuatu

16.25°S, 168.12°E; summit elev. 1334 m

All times are local (unless otherwise noted)


Ash plume and lava flow; recent eruption history

On 31 April at 0730, the meteorological service in Wellington, New Zealand detected volcanic ash clouds near 16.1°S, 168.1°E on satellite images. The main cloud had an estimated diameter of 15-30 km, with streamers to 115 km NNE, and moved at a speed of ~30 km/hour. The plume height was estimated at ~6 km from an aircraft at 0350. The meteorological service in Darwin, Australia also located a steam/ash cloud on visible satellite images at 1030. NOAA infrared and visible images showed only a small cloud on 31 April at 1344 during clear weather. The following is a report from J.P. Eissen, M. Lardy, M. Monzier, L. Mollard, and D. Charley of ORSTOM (Nouméa and Port Vila).

Description and history. "Ambrym, a large stratovolcano with a 15-km-wide caldera (figure 1), is one of the most active volcanoes of the New Hebrides arc, which includes Yasur (Tanna Island), Lopevi (Lopevi Island), and the shallow submarine volcano Karua (between Epi and Tongoa Islands).

Figure (see Caption) Figure 1. Geologic features of Ambrym caldera. The 1988 and 1989 lava flow paths have been modified after Monzier and Douglas (1989). Q1 = Tuvio volcanics (old northern Ambrym volcano), Q2 = older flank volcanics, Q3 = younger flank volcanics, Q4 = Tower Peak volcanics, Q5 = undifferentiated recent caldera and flank volcanics, Q6 = NE and E Marum basaltic flows and related old cones. The area shown is outlined on the index map (inset) of the main topographic features of Ambrym Island. B = Benbow, M = Marum (active cones), To = Tower Peak, Tu = Mt. Tuvio (old volcanic centers), E = Endu village, O = Otas village, S = Sevisi village. Maps modified after geological (New Hebrides Geological Survey, 1976) and pedomorphological (Quantin, 1978) maps.

". . . . In the historical period, at least five types of activity can be distinguished. From the most to least frequent, these are: 1) intra-caldera, intermittent, Strombolian-type activity with mild extra-caldera ashfalls, but without lava flows (occurs almost every year); 2) intracaldera eruption frequently preceded by lava lake formation in the crater — generally starts with emission of a Plinian column that produces extra-caldera ashfalls, followed by intra-caldera lava flows; 3) activity similar to (2) followed by lava overflowing from the caldera (1863 (?), 1913-14, 1942 eruptions); 4) extra-caldera lava emission from fissures (1894, 1913, 1929, 1936 eruptions) — sometimes evolves toward 5) formation of pyroclastic cones, sometimes accompanied by lava flows (1888, 1915, 1929 eruptions). Several of these types of actvity have occurred consecutively in the different phases of a single eruption (as in 1913-14 and 1929, the two major Ambrym eruptions).

"On 13 November 1986, an aircraft pilot reported an increase in activity at the volcano. Ash emission became significant 17 November, but activity decreased 19-20 November. A new cone formed (Cheney, 1986) 3 km E of the active Marum cone (figure 1) and produced an intra-caldera lava flow ~4 km long (Melchior, 1988).

May 1988 activity. "On 27 May 1988, a lava lake ~50 m in diameter was observed in Mbwelesu's crater. Benbow was emitting white clouds whereas Marum and Mbwelesu were emitting dark grey clouds (Melchior, 1988). On 10 August, intracaldera lava flowed S more than 1.5 km from what appeared to be a new cone, but was possibly an extension of Mbwelesu (Cheney, 1988). The flow (still warm) extended ~5 km S (Charley, 1988). This eruption had ended by 23 August.

April 1989 activity. "At 1000 on 24 April 1989, a pilot observed a large plume rising ~3,500 m above the volcano. A lava flow from the the 1988 cone was following the same path as the 1988 flow but was a few kilometers longer. It followed the creek near Endou village (figure 1) and may or may not have extended outside the caldera [but see 14:10]. About 1 km2 of Otas village was reported to be burned. On the night of 29 April, large areas of red glow were seen from boats cruising in the area, and winds carried ash NW. Young vegetation on the S flank was burned (possibly by acid rain), and rain water had a strong taste. Local inhabitants said that the eruption was normal for the volcano even though there were more loud roaring noises and small earthquakes than in 1986 or 1988. A local pilots' strike prevented further observation of the eruption, but on 10 May the volcano was still active." The eruption apparently stopped sometime before 14 May.

References. Charley, D., 1988, Rapport de Mission à Ambrym en Aout 1988: Document ORSTOM, Port Vila, 5 p.

Cheney, C.S., 1986, New volcanic eruption near Endu, SE Ambrym: Geology Dept Memo, 24 November 1986, 1 p.

Cheney, C.S., 1988, Volcanic activity report, Ambrym and Epi: Geology Dept Memo, 17 August 1988, 1 p.

Melchior, A.H., 1988, Rapport de Mission de Reconnaissance Volcanologique Ambrym (25-28 May 1988) et à Tanna (14 May 1988): Document ORSTOM, Nouméa, 10 p.

Quantin, P., 1978, Archipel des Nouvelles-Hébrides: Atlas des Sols et de quelques Données du Milieu: Cartes Pédologiques, des Formes du Relief, Géologiques et de la Végétation; ORSTOM (18 sheets).

Stephenson, P.J., McCall, G.J.H., Le Maitre, R.W., and Robinson, G.P., 1968, The Ambrym Island Research Project, in Warden, A.J., ed., New Hebrides Geological Survey Annual Report 1966: Port Vila, p. 9-15.

Geologic Background. Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides arc. A thick, almost exclusively pyroclastic sequence, initially dacitic, then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major plinian eruption with dacitic pyroclastic flows about 1900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the caldera floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Information Contacts: J. Eissen, M. Lardy, M. Monzier, ORSTOM, New Caledonia; L. Mollard, and D. Chaney, ORSTOM, Vanuatu; J. Latter, DSIR Geophysics, Wellington; S. Kusselson, SAB; J. Temakon, Dept of Geology, Mines, and Rural Water Supply, Port Vila.


Apoyeque (Nicaragua) — April 1989 Citation iconCite this Report

Apoyeque

Nicaragua

12.242°N, 86.342°W; summit elev. 518 m

All times are local (unless otherwise noted)


Lake temperature measured

Surface temperature of the lake (measured with an 8-14 micrometer bandpass radiometer) varied between 28 and 30°C during fieldwork 8 April. A water temperature measured near the N shore was 25.5°C.

Geologic Background. The Apoyeque volcanic complex occupies the broad Chiltepe Peninsula, which extends into south-central Lake Managua. The peninsula is part of the Chiltepe pyroclastic shield volcano, one of three large ignimbrite shields on the Nicaraguan volcanic front. A 2.8-km wide, 400-m-deep, lake-filled caldera whose floor lies near sea level truncates the low Apoyeque volcano, which rises only about 500 m above the lake shore. The caldera was the source of a thick mantle of dacitic pumice that blankets the surrounding area. The 2.5 x 3 km wide lake-filled Xiloá (Jiloá) maar, is located immediately SE of Apoyeque. The Talpetatl lava dome was constructed between Laguna Xiloá and Lake Managua. Pumiceous pyroclastic flows from Laguna Xiloá were erupted about 6100 years ago and overlie deposits of comparable age from the Masaya plinian eruption.

Information Contacts: C. Oppenheimer, Open Univ.


Asosan (Japan) — April 1989 Citation iconCite this Report

Asosan

Japan

32.884°N, 131.104°E; summit elev. 1592 m

All times are local (unless otherwise noted)


Brief ash emission

On 27 April, the staff of AWS visited the crater rim as they have every day for the past 20 years. A vent on the SE floor of Crater 1 was releasing yellow vapor and ash to 30 m, accompanied by larger tephra. The Aso Volcano Disaster Prevention Authority closed a 1-km area near the crater to tourists. The area was reopened 2 May, when a field survey revealed only white vapor reaching ~5-6 m above the vent.

Glow on the crater floor has been observed every night since October 1988. A maximum temperature of 232°C was measured (with a infrared radiation thermometer) at a glowing site on 18 April.

Isolated tremor remained frequent in April. The daily number of tremor episodes was 100-250, with a monthly total of ~5,760 (figure 10). Amplitude of continuous tremor remained the same.

Figure (see Caption) Figure 10. Monthly number of isolated volcanic tremor episodes at Aso (top), earthquakes (bars, bottom), and maximum plume heights (curve, bottom), 1966-April 1989. Arrows mark periods of explosions. Courtesy of JMA.

Geologic Background. The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 km3 of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 CE. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.

Information Contacts: JMA.


Bagana (Papua New Guinea) — April 1989 Citation iconCite this Report

Bagana

Papua New Guinea

6.137°S, 155.196°E; summit elev. 1855 m

All times are local (unless otherwise noted)


Lava flow advances; new avalanche deposits

"Observer reports and recorded seismicity indicate that increased activity . . . is continuing. Inspections on 3 and 4 March by personnel from Bougainville Island Copper Ltd. revealed that a new deposit of avalanche debris was present on the SE flank. The deposit was dark in colour and extended from the summit . . . to the mid-flank level (~1,000 m altitude). Vegetation around the edges of the deposit had been killed. The avalanche occurred sometime between 3 February and 3 March. The profile of E flank lava flow's terminus had changed, suggesting overriding of older parts of the flow by new lobes and possible advance of the flow nose.

"On 18 March, the pilot of a passing aircraft reported a lava flow on the SE flank and copious ash around and above the volcano. However, an inspection on 12 April indicated that the deposit was probably formed by a rockfall from the inactive nose of of the E flank lava flow (at ~880 m altitude). The proximal part of the flow was still active. It appeared that a new thin lobe was overriding older lava in the main flow channel. An ash mantle on the upper E flank indicated that rockfalls (detected seismically) were occurring in this area. The flow was bent to the S at ~1,150 m altitude. It may be significant that the first lobe of this now compound flow terminated at about this point.

"Since 8 March (when seismic recording . . . was restored) seismicity has been dominated by relatively long-duration, low-frequency, spindle-shaped events. This activity is attributed to rockfalls on the margin of the active lava flow. Daily totals of these events ranged between ~90 and 300. Summit activity has continued to consist of moderate to strong emission of white vapour rich in sulphur dioxide."

Geologic Background. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides.

Information Contacts: C. McKee, RVO.


Concepcion (Nicaragua) — April 1989 Citation iconCite this Report

Concepcion

Nicaragua

11.538°N, 85.622°W; summit elev. 1700 m

All times are local (unless otherwise noted)


Strong fuming

During fieldwork 24 March, fuming obscured the interior of the summit crater. Most of the gas appeared to originate below a step in the crater's inner NE wall. A zone of weak fumaroles about 30 m below the rim on the inner E crater wall had a maximum surface temperature of 42°C (measured by an 8-14 micrometer bandpass infrared thermometer from a distance of about 300 m), suggesting gas temperatures of around 100°C.

Geologic Background. Volcán Concepción is one of Nicaragua's highest and most active volcanoes. The symmetrical basaltic-to-dacitic stratovolcano forms the NW half of the dumbbell-shaped island of Ometepe in Lake Nicaragua and is connected to neighboring Madera volcano by a narrow isthmus. A steep-walled summit crater is 250 m deep and has a higher western rim. N-S-trending fractures on the flanks have produced chains of spatter cones, cinder cones, lava domes, and maars located on the NW, NE, SE, and southern sides extending in some cases down to Lake Nicaragua. Concepción was constructed above a basement of lake sediments, and the modern cone grew above a largely buried caldera, a small remnant of which forms a break in slope about halfway up the N flank. Frequent explosive eruptions during the past half century have increased the height of the summit significantly above that shown on current topographic maps and have kept the upper part of the volcano unvegetated.

Information Contacts: C. Oppenheimer, Open Univ.


Galeras (Colombia) — April 1989 Citation iconCite this Report

Galeras

Colombia

1.22°N, 77.37°W; summit elev. 4276 m

All times are local (unless otherwise noted)


Ash emission and strong seismicity; area residents alerted

Frequent ash ejection in early May was accompanied by increased seismicity (figure 1) and SO2 emission. The strong seismic swarm that began 5 April at 1000 and saturated one seismograph was not associated with eruptive activity. COSPEC measurements the next day showed a sharp rise in SO2 emission to > 1,200 metric tons/day (t/d) from 30-40 t/d 19-20 March [SO2 flux rose above 1,000 t/d on four days in April, see figure 12]. Glow was observed within the active (El Pinta) vent and by mid-April rocks 2 m below the rim had reached almost 600°C. The seismic swarm and glow prompted officials to increase the alert status to "yellow." A hazard map was published in a local newspaper and residents of areas designated as hazardous were urged to move, if possible, to a safer region. As of late April, a dense water-rich gas plume continued to rise 1-2 km above the crater and low-level seismicity persisted, but no deformation was evident.

Figure (see Caption) Figure 1. Number of recorded seismic events at Galeras, 27 February-5 May 1989. Courtesy of the Observatorio Vulcanológico de Colombia and the USGS Volcano Disaster Assistance Program.

4-5 May. After 10 hours of gradual increases in both background tremor (<1 mm peak to peak) and small long-period seismic events, ash was erupted between 0613 and 0830 on 4 May. Although emission rates were low, column heights reached 3.3 km. Ash composed of lithic particles and some plagioclase crystals fell towards the SW and E; a light dusting of ash fell on Pasto (population 350,000) at the volcano's E foot. Seismicity fluctuated between low and moderate levels for the next 11 hours before ash emission resumed at 1743. There were no recognizable immediate seismic precursors but the onset of the activity was accompanied by increased tremor. The rate of ash emission was again low, with the column pulsing at times to 2.9 km height. Both the plume and tremor diminished to low levels at 1855, but ash emission continued until 1940. Most of the ash was blown SW, and 1 mm of dust-sized tephra fell on Consaca, roughly 13 km WSW of the vent. EDM lines showed no change during the activity.

Personnel at the summit TELECON station reported hearing an explosion and smelling sulfur at 2040, after about an hour of seismic quiet. Background tremor began a progressive increase at about the same time, while long-period earthquakes gradually became larger and more frequent. Ash emission accompanied by 1.4-Hz tremor resumed at 2214 and continued until 2310. Another ash eruption began at 0118 from the active cone's main vent; previous episodes had originated from a 20-m-diameter fumarole ~30 m to the E. Tremor frequencies were initially ~4 Hz, but decreased slowly; maximum amplitude reached 10 mm peak-to-peak. A 50-minute band of 4-Hz tremor began at 0357. Its amplitude varied but reached 22 mm. TELECON personnel reported that incandescent blocks were being thrown 30-40 m over the crater rim into the moat between the cone and the caldera wall, and that the cone was covered with incandescent material. However, fieldwork indicated that the tephra was heated to glowing temperatures by gas, and apparently did not contain fresh magma. Ash initially rose ~1 km and was blown SW, then NW over Sandona (roughly 15 km from the vent). Tremor decreased to very low levels at 0500, remaining low until 0630. During the period of seismic quiet, plume emission was very weak.

The ash eruption resumed at 0638, accompanied by an impulsive seismic signal, and tremor increased rapidly to an average peak-to-peak amplitude of 2 mm. The column grew to 1.2 km height by 0712, 1.9 km by 0726, and stabilized as a pulsing column to 2.8 km height between 0728 and 0825. The eruption column and tremor then decreased rapidly to low levels. The plume was broad and dense, dropping sheets of ash mainly within a few kilometers W of the vent. On the vent's E rim, the new deposit was ~25 cm thick, with the first layer a wet mud, probably from the lake that had occupied the bottom of the vent. Surge units were found in the deposit, as were lithic blocks that averaged about 15 cm in diameter. Only a thin film of ash fell at Consaca and other areas to the W and SW. However, the press reported that rescue workers evacuated ~2,000 residents of the Consacá area because of the ashfall. Activity around 1100 was accompanied by pulses of 4-5-Hz tremor and some long-period events. Ash was blown to the N, falling over La Florida and Nariño (8 km NNW and 7.5 km N of the vent). The EDM line across the caldera showed no change after the 4-5 May activity, but there may have been slight deflation on lines from the caldera rim to the active cone.

6 May. Ash emission resumed on 6 May at about 0900, producing a broad, pulsing column that fluctuated between 2.5 and 3.2 km height until darkness prevented further observations (about 1800). The rate of ash emission was intermediate between that of 4 May and the more vigorous activity of 5 May. Only low-level tremor and occasional long-period events accompanied the 6 May activity.

7-9 May. Harmonic tremor (1.3-1.4 Hz) began on 7 May at 0730 and continued for 38 minutes. Amplitudes reached 5 mm peak-to-peak and the tremor could be detected throughout the seismic net to 10 km from the vent. A similar signal reappeared at 0900, lasting for 40 minutes, and a pattern of intermittent tremor continued until 1400, with each episode building to larger amplitudes (as much as 1.5 cm peak-to-peak). The tremor typically occurred in 1.35-Hz packets with wavelengths of 10 seconds. The next-to-last tremor episode ceased abruptly after two large A-type events were recorded. During the last and strongest episode, many small A-type shocks were imbedded in the tremor. The A-type events were centered 3-3.5 km below the vent and 1-7 km to its S. The strong tremor was succeeded by bands of higher frequency tremor with much lower amplitude (<1 mm peak-to-peak). Minor ash emission continued 7 and 8 May. Ash was blown N on 7 May but did not reach La Florida, Nariño, or Jenoy (6 km NNE of the vent). The 8 May ash fell only near the crater. Frequent tremor episodes continued 8 May: 45 minutes of 2-3-Hz tremor that began gradually at 0614; low-frequency (1.54 Hz) banded tremor that began at 0800 and reached 23 mm amplitude about noon, decreasing in amplitude around 1540; amplitude increased again at 1600, to 20 mm, before declining at 1650 and stabilizing at 2-3 mm. Tremor decreased gradually from 9 May at 2000, to a maximum of 1 mm amplitude. Ash emission then stopped, and eruptive activity had not resumed as of 16 May.

The five days of ash emission prompted school closings and an increase in alert status to "orange" on 9 May. No immediate evacuations were ordered but officials asked residents to be ready for instructions if an eruption occurs. The Galeras Volcano Workshop that began 8 May with 50 participants from Central and South America will study the activity and hazards response.

Tephra deposits. An area of ~33 km2 was enclosed within the 3 mm ashfall isopach, including the TELECOM and television sites, 1.5 km to the S, and Nariño, 7.5 km N of the crater. The volume of tephra deposits was calculated at ~4 x 105 m3. The 7 cm of fine ash deposited at the S rim of El Pinta crater 19 February-3 May was overlain by more than 5 m of tephra that accumulated 4-9 May. A preliminary grain-size analysis shows a large fraction of fine (<1 mm) material (table 1). Some coarser layers of the early May tephra included scoria; in one layer (G) it was clearly altered, but in another horizon (E) it included abundant crystals in a very glassy matrix.

Table 1. Grain-size distribution of tephra deposited 4-9 May at Galeras, on the S rim of El Pinta crater. Thicknesses of individual layers (in cm) are supplemented by cumulative thickness of post-19 February tephra; only 7 cm of the section fell 19 February-3 May. The weight percent of six size fractions: <0.5, 0.5-1, 1-2, 2-4, 4-6.5, and >6.5 cm are shown. Courtesy of INGEOMINAS.

[Skip text table]
       Thickness (cm)      Size Fraction (cm)
       Layer  Cumulative   0 <--> 0.5 <--> 1 <--> 2 <--> 4 <--> 6.5 <-->

    B    3       501         26.6     32.2   27.3    8.6    5.5      --
    C    7       498         96.0      2.3    1.0    0.5    0.3      --
    D   12       491         44.6     27.3   20.4    6.1    1.6      --
    E   22       469          5.0      4.1    6.1    7.9   30.9     46.0
    F   32       447         38.8     33.0   17.9    5.2    5.2      --
    G   43       415          6.9      8.1    7.5    6.5    6.5     24.1

Geologic Background. Galeras, a stratovolcano with a large breached caldera located immediately west of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Long-term extensive hydrothermal alteration has contributed to large-scale edifice collapse on at least three occasions, producing debris avalanches that swept to the west and left a large horseshoe-shaped caldera inside which the modern cone has been constructed. Major explosive eruptions since the mid-Holocene have produced widespread tephra deposits and pyroclastic flows that swept all but the southern flanks. A central cone slightly lower than the caldera rim has been the site of numerous small-to-moderate historical eruptions since the time of the Spanish conquistadors.

Information Contacts: H. Cepeda and B. Pulgarin, INGEOMINAS, Popayán; M. Calvache, F. Muñoz, and R. Méndez, INGEOMINAS, Manizales; I. Mejía and E. Parra, INGEOMINAS, Medellín; M. Mercado, Popayán; N. Banks, USGS; Deutche Presse-Agentur; Agence France-Presse.


Kilauea (United States) — April 1989 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


Lava flows threaten houses

Kilauea's . . . eruption continued to feed lava through tubes into the ocean near Kupapau Point during April. Surface lava breakouts along the W tube were active 1-12 April and extended from ~300 m (top of the fault scarp) to 70 m altitude. Lava traveled along the W side of the flow field, entering the E margin of the Royal Gardens subdivision (figure 60). A major breakout on the 13th at ~500 m elevation remained active throughout the month. Large surface flows burned forest to the W and on 25 April passed within 50 m of an occupied home . . . . Access to the upper subdivision, as well as several houses, were threatened. By the end of the month, the flow had reached 60 m elevation and slowed, but was still active. Surface activity from the E tube at the top of the fault scarp was sporadic in early April but ceased after the 10th. The terminus of a breakout from the central tube was active just above the Kapaahu kipuka but stagnated after the 12th. The lava breakouts from the W tube on the 13th apparently lowered the magma supply to the E and central tubes, causing their flows to stagnate. The active portion of the seacoast bench that had formed since the 23 March collapse measured 160 x 60 m at the beginning of the month. Following two large collapses on 13 April (at 2024) and 22 April (at 2307), the bench continued to rebuild.

Figure (see Caption) Figure 60. Sketch map showing lava flows produced from Kupaianaha, July 1986-April 1989, and the current lava tube system. The April surface flows were mostly confined to the 1986-89 flow field. Courtesy of HVO.

The lava pond at Kupaianaha was 20-25 m below the rim during April. Lava was observed in the crater bottom of Pu`u `O`o . . . for most of the month, ranging from spatter to a sizeable lava pond that covered much of the crater floor. Gas pistoning events were witnessed at mid-month. By the 25th, only glowing holes in the rubble at the crater bottom could be seen.

Most of April's 18 strongly recorded seismic events . . . were tightly clustered beneath Kilauea's summit and S flank. Shallow events (0-5 km depth) continued to be recorded. The number of intermediate-depth long-period events beneath the summit decreased and developed a fluctuating pattern after a persistent high rate in March. Increasingly longer bursts of deep tremor (40-60 km depth), at near-regular time intervals during the first half of the month decreased thereafter. Low-level tremor continued beneath Pu`u `O`o and Kupaianaha. Relatively steady tremor amplitude beneath Pu`u `O`o was interrupted 13-17 April by short gas piston bursts and long intervals of banded tremor, correlated with increased activity in the crater. Tremor returned to a relatively steady state in the latter part of the month. Low-amplitude signals from lava entering the sea near Kupapau Point continued to be recorded.

Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: C. Heliker and R. Koyanagi, HVO.


Langila (Papua New Guinea) — April 1989 Citation iconCite this Report

Langila

Papua New Guinea

5.525°S, 148.42°E; summit elev. 1330 m

All times are local (unless otherwise noted)


Moderate ash ejections and glow

"The slightly stronger activity from Crater 2 reported in March continued in April, although fluctuations in the level of activity were evident. The volcano was quiet at the beginning of the month. Between 5 and 23 April, moderate ash emissions were observed, accompanied by weak to strong rumbling sounds. Most ash fell near the volcano. On most nights during this period, weak red glow was observed above Crater 2. Activity subsided between 24 and 28 April, but on the 29th and 30th returned to the levels seen at mid-month. Seismic records were unavailable between 14 and 30 April. During the first half of the month, seismicity was at a low level with only 0-1 explosion earthquakes/day."

Geologic Background. Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Information Contacts: C. McKee, RVO.


Ol Doinyo Lengai (Tanzania) — April 1989 Citation iconCite this Report

Ol Doinyo Lengai

Tanzania

2.764°S, 35.914°E; summit elev. 2962 m

All times are local (unless otherwise noted)


January inspection reveals no new lava

On 12 January, a field party heard magma bubbling at depth but saw no liquid lava. Photographs taken from the E rim by Mr. [Bay] Forrest indicated that hornitos within the crater remained unchanged since the last inspections in late November and mid-December 1988. The extent of lava that had entered the S crater in December had not changed, and the crater floors were covered by light-colored, older lava, with no signs of dark, fresh flows. The darkest feature was a cone (T10) near the base of the E wall. Although minor spattering similar to that observed at T4/T7 in June 1988 could have covered T10's surface, there had been no significant change in its shape. Fumaroles were visible on the E part of the saddle, but the crater walls and W part of the saddle were largely cloud-covered.

Geologic Background. The symmetrical Ol Doinyo Lengai is the only volcano known to have erupted carbonatite tephras and lavas in historical time. The prominent stratovolcano, known to the Maasai as "The Mountain of God," rises abruptly above the broad plain south of Lake Natron in the Gregory Rift Valley. The cone-building stage ended about 15,000 years ago and was followed by periodic ejection of natrocarbonatitic and nephelinite tephra during the Holocene. Historical eruptions have consisted of smaller tephra ejections and emission of numerous natrocarbonatitic lava flows on the floor of the summit crater and occasionally down the upper flanks. The depth and morphology of the northern crater have changed dramatically during the course of historical eruptions, ranging from steep crater walls about 200 m deep in the mid-20th century to shallow platforms mostly filling the crater. Long-term lava effusion in the summit crater beginning in 1983 had by the turn of the century mostly filled the northern crater; by late 1998 lava had begun overflowing the crater rim.

Information Contacts: C. Nyamweru, Kenyatta Univ; B. Forrest, Rift Valley Academy, Kijabe, Kenya.


Lonquimay (Chile) — April 1989 Citation iconCite this Report

Lonquimay

Chile

38.379°S, 71.586°W; summit elev. 2832 m

All times are local (unless otherwise noted)


Continued tephra emission; cattle sickened by ash

The eruption . . . was continuing in early May. Eruption clouds in April and early May, composed mainly of dark brown ash and water vapor, rose 500-1,500 m from Navidad Crater. The number of recorded seismic events had declined to 2-3/day.

Estimates of the volume of the lava flow vary, and are made difficult by the flow's very irregular thickness, which has been increasing faster than the area covered by lava. Hugo Moreno estimated that through March ~150 x 106 m3 of lava had been extruded. The lava flow's W lobe essentially stopped advancing in mid-February, but the E front continued to move down the Lolco River valley. Little additional advance of the lava flow was noted in April and early May. The position of the flow as of 5 April is shown in figure 11.

Figure (see Caption) Figure 11. Map showing the lava flows as of 5 April 1989. Courtesy of Hugo Moreno Roa.

About 10,000 cattle have been suffering the effects of ashfall since December. Many have lost >100 kg in weight and are dying. Analyses by specialists at the Univ Austral determined that the animals are being affected by overdoses of fluorine from the ash. Ash has fallen in various directions (see table 5). The localities most affected are Maillin del Treile, El Naranjo (both roughly 20 km ESE of the active crater), and Comunidad Bernardo Nanco, home to about 80 families, the majority of which depend for their livelihoods on animal raising. Losses are estimated at about $2,000,000 (US). Local authorities and the Ministries of Agriculture and Health are taking emergency measures. Forest fires have burned valuable native trees, including coigüe (Nothfogus dombeyi) and araucaria (Araucaria araucana).

Geologic Background. Lonquimay is a small, flat-topped, symmetrical stratovolcano of late-Pleistocene to dominantly Holocene age immediately SE of Tolguaca volcano. A glacier fills its summit crater and spills down the S flank. It is dominantly andesitic, but basalt and dacite are also found. There is an E-W fissure, although the prominent NE-SW Cordón Fissural Oriental fissure zone cuts across the entire volcano, that produced a series of NE-flank vents and cinder cones, some of which have been the source of voluminous lava flows, including those during 1887-90 and 1988-90 that traveled up to 10 km.

Information Contacts: O. González-Ferrán, Univ de Chile; G. Fuentealba and P. Riffo, Univ de la Frontera; H. Moreno, Univ de Chile.


Manam (Papua New Guinea) — April 1989 Citation iconCite this Report

Manam

Papua New Guinea

4.08°S, 145.037°E; summit elev. 1807 m

All times are local (unless otherwise noted)


Incandescent ejections and vapor release

"Activity remained at a low inter-eruptive level during April. Both Southern and Main Craters released white vapours at weak to moderate rates. Blue vapour was also emitted from Southern Crater on 9, 13, and 22-23 April. Weak deep rumbling sounds from Southern Crater were heard occasionally 11-30 April. The summit was obscured by clouds on most nights, but during clear conditions on the 11th, glow and weak ejections of incandescent lava fragments were observed above Southern Crater. Volcano-seismicity remained at a normal inter-eruptive level with daily earthquake totals ranging between ~700 and 1,200. Tilt measurements showed no trends."

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Information Contacts: C. McKee, RVO.


Masaya (Nicaragua) — April 1989 Citation iconCite this Report

Masaya

Nicaragua

11.984°N, 86.161°W; summit elev. 635 m

All times are local (unless otherwise noted)


Lava lake drains; rockslides; gas emission

A local newspaper (the Barricada, citing Alain Creusot) reported that on 7 March, the level of the active lava lake in Santiago's crater had dropped considerably (since late February). Spatter was occasionally ejected outside the vent. The lake apparently drained on 9 March. Geologists visited the crater on 14 March and measured a temperature of 76.6°C on the surface of the frozen lake (all reported temperatures were measured by an 8-14 micrometer bandpass infrared thermometer from a distance of about 300 m unless otherwise stated). The two incandescent vents that first appeared on 23 February (14:02) were still present in the lake's N corner. The temperature of the hottest glowing vent was 667°C. On 16 and 18 March, fumes collected in the crater and limited observations. By 28 March, debris from rockslides on the SW inner wall of the crater had covered the site of the former lake, at least 175 m below the floor of Santiago Crater. Gas emission was strong. The two incandescent vents (maximum surface temperature 607°C) remained visible at night. On 12 April, the frequency of rockslides (audible about every 5 minutes) had increased significantly. Most occurred on the SW inner wall of the crater and many lasted for minutes. When geologists drove past Masaya on 18 April the amount of fuming appeared to have dramatically decreased.

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.

Information Contacts: C. Oppenheimer, Open Univ.


Momotombo (Nicaragua) — April 1989 Citation iconCite this Report

Momotombo

Nicaragua

12.423°N, 86.539°W; summit elev. 1270 m

All times are local (unless otherwise noted)


Burning gases from fumaroles

A maximum gas temperature of 880°C was measured (by a thermocouple) at fumarole ##9, inside the crater, on 15 April. Flames that extended up to 40 cm from vents were visible at night. Most were pale orange but some gases burned with a blue flame.

Geologic Background. Momotombo is a young stratovolcano that rises prominently above the NW shore of Lake Managua, forming one of Nicaragua's most familiar landmarks. Momotombo began growing about 4500 years ago at the SE end of the Marrabios Range and consists of a somma from an older edifice that is surmounted by a symmetrical younger cone with a 150 x 250 m wide summit crater. Young lava flows extend down the NW flank into the 4-km-wide Monte Galán caldera. The youthful cone of Momotombito forms an island offshore in Lake Managua. Momotombo has a long record of Strombolian eruptions, punctuated by occasional stronger explosive activity. The latest eruption, in 1905, produced a lava flow that traveled from the summit to the lower NE base. A small black plume was seen above the crater after a 10 April 1996 earthquake, but later observations noted no significant changes in the crater. A major geothermal field is located on the south flank.

Information Contacts: C. Oppenheimer, Open Univ.


Niigata-Yakeyama (Japan) — April 1989 Citation iconCite this Report

Niigata-Yakeyama

Japan

36.921°N, 138.036°E; summit elev. 2400 m

All times are local (unless otherwise noted)


Increased steaming, small ash eruption

A white steam plume was rising from the volcano's upper E flank during observations by the staff of Takada Weather Station (from sites 10-20 km away) 1 May 1987-September 1988. Emissions gradually declined, and after a 9 November 1988 visit, no plume was observed.

Moderate steam emission was seen again on 30 March 1989, with a white vapor plume rising 100-150 m from 2 areas on the upper E flank. Steam from the upper NE flank rose about 30-50 m on 15 April. Four days later, steam with a small amount of ash was emitted to about 100-150 m above the upper E flank, the first sighting of a gray plume since May 1987. Observations from Sasagamine (about 8 km SE) on 26 April revealed gray plumes rising 250-300 m from many sites on the upper E flank. A 30 April steam plume, about 300-400 m high and blown 600 m by the wind (figure 2), was the highest since May 1987. Access to the volcano has been closed to tourists.

Figure (see Caption) Figure 2. Height of steam plumes at Niigata-Yake-yama, 1987-91. Courtesy of JMA.

Geologic Background. Niigata-Yakeyama, one of several Japanese volcanoes named Yakeyama ("Burning Mountain"), is a very young andesitic-to-dacitic lava dome in Niigata prefecture in central Honshu, near the Japan Sea. The small volcano rises to 2400 m and was constructed on a base of Tertiary mountains 2000 m high beginning about 3100 years ago. Three major magmatic eruptions took place in historical time, producing pyroclastic flows and surges and lava flows that traveled mainly down the Hayakawa river valley to the north and NW. The first of these eruptions took place about 1000 years ago (in 887 and possibly 989 CE) and produced the Hayakawa pyroclastic flow, which traveled about 20 km to reach the Japan Sea, and the massive Mae-yama lava flow, which traveled about 6.5 km down the Hayakawa river valley. The summit lava dome was emplaced during the 1361 eruption, and the last magmatic eruption took place in 1773 CE. Eruptive activity since 1773 has consisted of relatively minor phreatic explosions from several radial fissures and explosion craters that cut the summit and flanks of the dome.

Information Contacts: JMA.


Nyamuragira (DR Congo) — April 1989 Citation iconCite this Report

Nyamuragira

DR Congo

1.408°S, 29.2°E; summit elev. 3058 m

All times are local (unless otherwise noted)


Lava erupts from summit and E flank

An eruption that began on 23 April in Nyamuragira's summit crater was reported by the Vice Conservator of the Institut Zairois pour la Conservation de la Nature, Parc National des Virunga. On the 24th at 1418, three lava fountains emerged from a fissure on the SSE flank of the volcano. Incandescence was visible from the village of Gisenyi, Rwanda, roughly 30 km from the vent. The resulting lava flow passed between Kitazungurwa and Rugarambiro cones, diverted around Gitebe cone, and flowed along lava erupted in 1981-82 from Rugarambiro (figure 6). By the 26th, the flow had reached Nyasheke-South and was ~6 km from Kakomero, the base camp for climbers at the park entrance.

On the night of the 26th, lava emerged from the W side of the Kanamaharagi cone (formed during the 1905 eruption), building a new parasitic cone (also named Kanamaharagi) at ~1,860 m altitude. Lava fountains up to 200 m high and large amounts of tephra were emitted 30 April-1 May. As of 6 May, the volcano was still erupting.

Geologic Background. Africa's most active volcano, Nyamuragira, is a massive high-potassium basaltic shield about 25 km N of Lake Kivu. Also known as Nyamulagira, it has generated extensive lava flows that cover 1500 km2 of the western branch of the East African Rift. The broad low-angle shield volcano contrasts dramatically with the adjacent steep-sided Nyiragongo to the SW. The summit is truncated by a small 2 x 2.3 km caldera that has walls up to about 100 m high. Historical eruptions have occurred within the summit caldera, as well as from the numerous fissures and cinder cones on the flanks. A lava lake in the summit crater, active since at least 1921, drained in 1938, at the time of a major flank eruption. Historical lava flows extend down the flanks more than 30 km from the summit, reaching as far as Lake Kivu.

Information Contacts: S. Peyer and H. Peyer, Gisenyi, Rwanda; H-L. Hody, GEOVAR, Kigali, Rwanda.


Poas (Costa Rica) — April 1989 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Crater lake gone; explosions and molten sulfur ponds

Until mid-April, thermal activity remained similar to that observed in March, with boiling mud springs and vigorous fumaroles in the crater lake, which has been shrinking since early 1987. Two ponds of molten sulfur (115°C) have persisted since 16 March at the former site of small sulfur and mud cones 50 m SE of the center of the inner crater (figure 14). Small pyroclastic sulfur cones surrounded the lakes, collapsing occasionally.

Figure (see Caption) Figure 14. Sketch map of the inner crater at Poás and its features, April 1989. Courtesy of Gerardo Soto.

On 12 April, the crater lake was convecting vigorously, but shallow areas were visible. The lake level dropped about 2 m during the following week, and by 19 April only a few small mud pools remained. The characteristic geyser-type phreatic activity through the crater lake changed 18-19 April with the lake's near disappearance. Cypressoid vertical columns continuously rose about 25 m above the former center of the lake and began to build a mud/pyroclastic cone. On 19 April, small bursts of gas and mud that contained sulfur particles emerged through the mud surface to heights of about 10 m, rarely to 25-30 m. Steaming was continuous. Activity had increased slightly the next day, but magnetometer traverses that passed about 100 m from the active area showed no changes since the last measurements on 3 April. Phreatic bursts reached about 50 m height on 21 April. Using a thermocouple, Jorge Barquero measured a liquid temperature of 116°C in one of the sulfur ponds. On 22 April at around 1000, a dark mushroom-shaped column developed, convecting to 200-300 m height. Fine mud, sulfur, and burning gases (possibly hydrogen) were ejected until 1032. Fine yellow material fell on the W side of the inner crater [see also 14:05]. Ejection of lithic material stopped suddenly and the plume reverted to its normal white color. About 15 minutes later, continuous geysering of dark sediment and gas was observed for 2-3 minutes. Clouds obscured the summit at 1130. At 2100, after weather had cleared, the base of the plume was suddenly illuminated by a pink-orange light for about 2 minutes. No sounds were audible other than those accompanying the continuing phreatic activity. The light stopped suddenly and was thought to have been generated by burning gases.

During observations on 23 April, a thick white plume coalesced from numerous vents, two of which were discharging a mixture of white condensed steam and yellow sulfur. Dark cypressoid plumes were emitted every few seconds. At least one vent continuously discharged fine dark material. At 0717, a pink-orange light was again seen at the base of a continuous white plume on the SW side of the crater bottom. The light remained visible for 2.5 minutes, and geologists believed that it was generated by burning gases. A brightness temperature of 158°C was recorded (with an 8-14 micrometer bandpass infrared thermometer), but the measurement was made from almost 1 km distance and geologists suspected that the temperature was probably several hundred degrees higher. Phreatic activity from at least six of the vents expelled blocks to about 50 m height and occasionally to 100 m or more, generally vertically but sometimes obliquely. Most of the ejecta fell within 10-20 m of the vents, building cones to about 10 m height with funnel-shaped craters up to 5 m in diameter. The ejecta appeared dry and included blocks more than 20 cm across. Radiant temperatures of dark plumes were only about 80°C as measured from about 150 m away. Activity occasionally reached a level at which at least one of the six or more phreatic vents was erupting at a given time. Booming noises and sounds like a jet engine were occasionally heard. From nearer the vents, sounds like pistol shots were audible.

The two ponds of dark brown, very fluid, bubbling liquid, apparently sulfur, were about 50 cm below the former crater lake floor in steep-sided pits. One, roughly elliptical, was about 20 m across, while the other was dumbbell-shaped and about 10 m long. A terrace of solid sulfur had developed at the edge of the liquid, and the sides and rims of the pits were coated by bright yellow sulfur sublimates. A moderate amount of visible condensate rose from their surfaces and the smell of SO2 was strong. No surface burning was evident. Blocks of pale-colored altered rock (probably former lake sediments) floated on the sulfur ponds, suggesting a density substantially above 1 g/cm3. Remnants of the former crater lake had a maximum surface infrared radiometer temperature of 97°C.

Four geologists (G. Alvarado, M. Fernández, G. Soto, and D. Stevenson) descended to the bottom of the inner crater on 25 April. The activity had built at least three new cones, aligned with the sulfur ponds along a N30°W trend. The cones, 10-12 m high, were continuously active, emitting vertical columns of mud, sulfur, gases, and rocks to 30-70 m (occasionally 100 m) height for some seconds. Optical radiometer temperatures of the plumes were 75-90°C. Lesser thermal features (fumaroles, small hot lakes, and boiling mud springs) were found around the periphery of the cones. A small fault scarp, parallel to the line of cones, cut the sediments. The faulting was interpreted as the result of subsidence caused by the removal of the eruptive products, and a decrease in the internal pore pressure of the subsurface hydrothermal regime. At noon, the geologists were surprised by (but escaped unscathed from) a sudden eruption of sulfur, mud, and gases (some burning) that formed a thick vertical column nearly 400 m high, with a minimum radiometer temperature of 459°C. Sulfur and mud fell on the W wall of the crater and over the rim (toward Cerro Pelón). Other similar eruptions deposited greenish-gray mud within the crater.

The column from a larger eruption on 28 April between 0500 and 0600 reached an estimated height of 1.5-2 km and dropped fine mud to 2.5 km S of the source [see also 14:05]. The next day, the central mud cone (which had reached about 20 m height) ejected vertical columns of mud and sulfur to 200 m height. The small SW mud cone was in nearly continuous activity, emitting brown-gray lithic ash that was carried W by the wind. The gases were sulfurous, strongly yellow- and orange-colored, and rose in a vertical convective column to 350 m height. Eruptive characteristics were similar on 30 April and 1 May, but with columns to 1-1.5 km high on the 1st. The wind carried the fine lithic ash and mud toward the W onto various towns (including Bajos de Toro, Zarcero, and Sarchí).

Activity decreased 2 and 3 May. On the 3rd, ash was measured on the crater rim, reaching 1 mm thickness at point A (figure 15) and 2 mm at point B. Particles reached medium-grained ash size and were lithic, dominantly mud/clay granules of sulfide/sulfate sediments with a high percentage of solutes.

Figure (see Caption) Figure 15. Distribution of ash at Poás, and sites where thicknesses were measured 3 May 1989. Sketch and data from G. Soto.

Seismicity has visibly declined. Volcanic earthquakes totaled 4,240 in April, for a mean of 141/day (figure 16). Seismicity continued to be dominated by B-type events, although their number had decreased. The most significant change was the appearance of tremor episodes with durations of 4-10 minutes. The change in seismic pattern was interpreted by Morales et al. (1988) as the change from magma-water interaction in a medium that is not open (B-type signals) to one that is partially open (continuous train of B-type signals or tremors).

Figure (see Caption) Figure 16. Number of seismic events recorded/day at Poás by the Red Sismológica Nacional, April 1989. Courtesy of Mario Fernández.

Reference. Morales, L.D., Soley, J.F., Alvarado, G.E., Borgia, A., and Soto, G., 1988, análisise espectral de algunas señales sísmicas y su relación con la actividad de los volcanes Arenal y Poás, Costa Rica: Boletín del Observatorio Vulcanológico del Arenal, año 1, no. 2, p. 1-25.

Geologic Background. The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: G. Soto, Mario Fernández, and Héctor Flores, UCR; Guillermo Alvarado, R. Barquero, and Ileana Boschini, ICE; David Stevenson and C.M.M. Oppenheimer, Open Univ.


Popocatepetl (Mexico) — April 1989 Citation iconCite this Report

Popocatepetl

Mexico

19.023°N, 98.622°W; summit elev. 5393 m

All times are local (unless otherwise noted)


New fumaroles and large sulfur deposits

During 1986-87, a seasonal, nearly circular lake occasionally occupied the summit crater. The lake's pH was 2-2.7 and the temperature was 30°C. Continuous fumarolic activity began in August 1988. A March 1989 summit visit by Alejandro Rivera Domínguez revealed large sulfur deposits in the main and inner craters. New fumaroles (not observed in 1987-88) on the main crater wall emitted high-pressure sulfurous gas and steam to 300 m. No significant microseismicity or tilt was detected.

The Grupo de Montañismo y Exploración de la UNAM, led by Prof. José Manuel Casanova Becerra, climbed the volcano on 9 April. More than 20 new fumaroles were observed on the outer S flank about 200 m below the crater rim. These vents (up to 1 m in diameter) were not observed when the group visited the area 2 years ago. Steam columns reached 20 m height and there was a mild sulfur odor. The steam's temperature was probably near the boiling point (at about 5,100 m altitude). The average altitude of the crater rim was 5,300 m with the crater bottom 340 m below. Increased steaming (common during the season) was observed inside the crater.

One seismograph is sited near the volcano . . . . Researchers hope to build an observatory 12 km from the volcano with telemetric data capture. Current monitoring is from the Meteorological Observatory, Geophysics Dept, Univ Autónoma de Puebla, and from Yancuitlalpan Village, S of the volcano.

Geologic Background. Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Information Contacts: S. De la Cruz-Reyna, UNAM; Alejandro Rivera Domínguez, Univ Autónoma de Puebla.


Rabaul (Papua New Guinea) — April 1989 Citation iconCite this Report

Rabaul

Papua New Guinea

4.271°S, 152.203°E; summit elev. 688 m

All times are local (unless otherwise noted)


Seismicity and deformation at background level

"Activity remained at a low (background) level in April. The total number of caldera earthquakes was 146. All of the events were small (ML 0.5-1.5) and none could be located. The daily earthquake count ranged from 0 to 17. Ground deformation measurements showed no significant changes."

Geologic Background. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island's largest city prior to a major eruption in 1994. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.

Information Contacts: C. McKee, RVO.


Rincon de la Vieja (Costa Rica) — April 1989 Citation iconCite this Report

Rincon de la Vieja

Costa Rica

10.83°N, 85.324°W; summit elev. 1916 m

All times are local (unless otherwise noted)


Crater lake sampled

Geologists sampled the crater lake on 6 April. The lake temperature was 45°C, determined by throwing a bottle 100 m into the lake, measuring the resulting sample with a thermocouple, and applying a cooling correction.

Geologic Background. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge that was constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of 1916-m-high Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A plinian eruption producing the 0.25 km3 Río Blanca tephra about 3500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Information Contacts: David Stevenson, Open Univ.


Ruapehu (New Zealand) — April 1989 Citation iconCite this Report

Ruapehu

New Zealand

39.28°S, 175.57°E; summit elev. 2797 m

All times are local (unless otherwise noted)


Heat flow declines

Since February, no discrete eruptions have been reported although steam passively rising from Crater Lake has occasionally been witnessed. When geologists visited the volcano 21-22 March, slight upwelling in the N vent area formed broken sulfur slicks. Crater Lake's temperature had fallen to 32°C (a 10.5° drop over 23 days) representing a decline in heat flow to ~10% of its previous rate. Lake level had decreased to 100-150 mm below overflow. Lake chemistry was stable, showing little change in Mg/Cl since 11 January. Minor inflation was measured across the N crater rim. On 5 April, geologists observed slightly increased upwelling in the N vent area. The lake temperature was 31.3°C. N-rim inflation had largely disappeared. NZGS geologists noted that some previous pulses of inflation/deflation have been followed by renewed lake heating (or strong seismicity). Few tremor episodes and volcanic earthquakes were recorded on seismic records through . . . 5 April.

Geologic Background. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The 110 km3 dominantly andesitic volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 km3 ring plain of volcaniclastic debris, including the Murimoto debris-avalanche deposit on the NW flank. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. A single historically active vent, Crater Lake, is located in the broad summit region, but at least five other vents on the summit and flank have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent, and tephra characteristics suggest that the crater lake may have formed as early as 3000 years ago. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to lower river valleys.

Information Contacts: P. Otway, NZGS Wairakei.


Nevado del Ruiz (Colombia) — April 1989 Citation iconCite this Report

Nevado del Ruiz

Colombia

4.892°N, 75.324°W; summit elev. 5279 m

All times are local (unless otherwise noted)


Seismicity decreases

Seismic activity (high- and low-frequency earthquakes, long-period events, and tremor) significantly decreased in April, continuing a 2-month trend. SO2 emissions measured by COSPEC varied between 700 and 3,700 t/d with a monthly average of 1,800 t/d (figure 26). No significant changes in deformation were measured.

Figure (see Caption) Figure 26. Rates of SO2 emission measured by COSPEC at Ruiz, July 1986-April 1989. Courtesy of the Observatorio Vulcanológico de Colombia.

Geologic Background. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


Soputan (Indonesia) — April 1989 Citation iconCite this Report

Soputan

Indonesia

1.112°N, 124.737°E; summit elev. 1785 m

All times are local (unless otherwise noted)


Ashfall damages houses and crops

On 22 April, Soputan erupted for the first time since May 1985 (10:05), sending ash and lapilli to 1,000-1,500 m above the summit. Newspapers, quoting VSI director Subroto Modjo, reported that the eruption consisted of three explosions (at 1027, 1535, and 1752), the second of which ejected most of the tephra. Earthquakes were recorded by a nearby seismograph and were felt 25 km away. As much as 15-20 cm of ash (carried E by the wind) fell nearby in parts of Tumaratas (11 km NE of Soputan) and Taraitak, and in Ampreng, Raringis, and Noongan. At least 500 houses were damaged and three classrooms collapsed [but see 14:5] in Noongan, a gathering hall collapsed in Paslaten Langowan (13 km ENE), and many trees, especially in the Gunung Potong forest area (7 km E) were knocked down. No ashfall was reported in Manado, 45 km NNE. Damage to buildings and crops was estimated at about $114,000. As a precaution, hazard warning maps were given to residents. . . . No casualties or additional explosions had been reported as of 26 April.

Geologic Background. The Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano rises to 1784 m and is located SW of Riendengan-Sempu, which some workers have included with Soputan and Manimporok (3.5 km ESE) as a volcanic complex. It was constructed at the southern end of a SSW-NNE trending line of vents. During historical time the locus of eruptions has included both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.

Information Contacts: OFDA; R. Austin, Englehard Engineering, USA.


Ulawun (Papua New Guinea) — April 1989 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Small ash emissions, minor seismic increases

"Mild, intermittent, eruptive activity continued in April. Ash emissions occurred 6, 8, 11, 20-22, and 28 April, but their ash content was low, and no significant ashfalls were reported. A strong correlation between activity and preceding heavy rainfall (as observed in March) was not evident. When not producing ash, the volcano emitted white vapours at moderate rates.

"For most of the month, the volcano-seismicity consisted of occasional, small, low-frequency events. Periods of low-amplitude, discontinuous and irregular tremor were recorded between 16 and 18 April. During the last week of April (perhaps correlating with a period of moderate rainfall) discrete events were more numerous, with periods of continuous and discontinuous irregular tremor of low-moderate amplitude."

Geologic Background. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the north coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Information Contacts: C. McKee, RVO.


White Island (New Zealand) — April 1989 Citation iconCite this Report

White Island

New Zealand

37.52°S, 177.18°E; summit elev. 321 m

All times are local (unless otherwise noted)


Tephra ejections continue

Donald Duck vent has intermittently ejected tephra since its formation in late January in a zone of strong fumarolic activity ~100 m NE of eruptive vents in 1978 crater (figure 11). Photographs by Geoff Green of a 4 March eruption (at about 1500-1530) show a 500-m, vigorously convoluting ash column with an incandescent base. The eruption continued for at least 45 minutes, and ash emission also began from R.F. Crater. A larger eruption between 16 and 20 March, apparently not witnessed, presumably generated a larger column. During April, Donald Duck vent continued to eject ash and threw lithic blocks to as much as 200 m S. Intermittent ash, block, and bomb ejections also continued from R.F. Crater during the month. Two bomb-ejecting eruptions from R.F. Crater since 20 March were followed by widespread ash deposition.

During 26 April fieldwork, Donald Duck vent emitted voluminous clouds of light gray gas from a vent at the base of its N wall. New ash-covered scoria bombs (first noted in early April) were present S of Donald Mound, reaching more than l m in diameter near the 1978 Crater rim. R.F. Crater (appearing deep with vertical walls) discharged a dilute cloud of gas and fine pink ash. Ash covered much of the main crater floor and walls. Impact craters and lithic blocks a few days old were abundant around Donald Mound and Donald Duck vent. Congress Crater was quiet.

Fumarole temperatures and emissions had decreased at most vents except Noisy Nellie, which continued to emit voluminous high-pressure gas. Geologists suggested that Donald Duck and R.F. Crater have been capturing heat from surrounding areas, which are cooling as a result. General deflation, in progress since mid-l987, continued with strong subsidence of the Donald Mound area. Seismicity through late April remained similar to previous months, with microearthquakes recorded most days. Activity was conspicuously banded, with individual bands lasting 1.5-24 hours, containing up to 10 medium-frequency events/minute. Activity was most prolonged around 1-2 April. Small E-type events were recorded in April on the 3rd (0854) and 8th (0115, 0931, and 2008), while small A-types occurred most days. Very few B-types were recorded.

Geologic Background. Uninhabited 2 x 2.4 km White Island, one of New Zealand's most active volcanoes, is the emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes; the summit crater appears to be breached to the SE, because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, four sea stacks that are remnants of a lava dome, lie 5 km NNE. Intermittent moderate phreatomagmatic and strombolian eruptions have occurred throughout the short historical period beginning in 1826, but its activity also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project.

Information Contacts: I. Nairn, NZGS Rotorua.

Atmospheric Effects

The enormous aerosol cloud from the March-April 1982 eruption of Mexico's El Chichón persisted for years in the stratosphere, and led to the Atmospheric Effects section becoming a regular feature of the Bulletin. Descriptions of the initial dispersal of major eruption clouds remain with the individual eruption reports, but observations of long-term stratospheric aerosol loading will be found in this section.

View Atmospheric Effects Reports

Special Announcements

Special announcements of various kinds and obituaries.

View Special Announcements Reports

Additional Reports

Reports are sometimes published that are not related to a Holocene volcano. These might include observations of a Pleistocene volcano, earthquake swarms, or floating pumice. Reports are also sometimes published in which the source of the activity is unknown or the report is determined to be false. All of these types of additional reports are listed below by subregion and subject.

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


Central Chile and Argentina


Estero de Parraguirre


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

08/1997 (SEAN 22:08) False Report of Mount Pinokis Eruption

False report of volcanism intended to exclude would-be gold miners

12/1997 (SEAN 22:12) False Report of Somalia Eruption

Press reports of Somalia's first historical eruption were likely in error

11/1999 (SEAN 24:11) False Report of Sea of Marmara Eruption

UFO adherent claims new volcano in Sea of Marmara

05/2003 (SEAN 28:05) Har-Togoo

Fumaroles and minor seismicity since October 2002

12/2005 (SEAN 30:12) Elgon

False report of activity; confusion caused by burning dung in a lava tube



False Report of Mount Pinokis Eruption (Philippines) — August 1997

False Report of Mount Pinokis Eruption

Philippines

7.975°N, 123.23°E; summit elev. 1510 m

All times are local (unless otherwise noted)


False report of volcanism intended to exclude would-be gold miners

In discussing the week ending on 12 September, "Earthweek" (Newman, 1997) incorrectly claimed that a volcano named "Mount Pinukis" had erupted. Widely read in the US, the dramatic Earthweek report described terrified farmers and a black mushroom cloud that resembled a nuclear explosion. The mountain's location was given as "200 km E of Zamboanga City," a spot well into the sea. The purported eruption had received mention in a Manila Bulletin newspaper report nine days earlier, on 4 September. Their comparatively understated report said that a local police director had disclosed that residents had seen a dormant volcano showing signs of activity.

In response to these news reports Emmanuel Ramos of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) sent a reply on 17 September. PHIVOLCS staff had initially heard that there were some 12 alleged families who fled the mountain and sought shelter in the lowlands. A PHIVOLCS investigation team later found that the reported "families" were actually individuals seeking respite from some politically motivated harassment. The story seems to have stemmed from a local gold rush and an influential politician who wanted to use volcanism as a ploy to exclude residents. PHIVOLCS concluded that no volcanic activity had occurred. They also added that this finding disappointed local politicians but was much welcomed by the residents.

PHIVOLCS spelled the mountain's name as "Pinokis" and from their report it seems that it might be an inactive volcano. There is no known Holocene volcano with a similar name (Simkin and Siebert, 1994). No similar names (Pinokis, Pinukis, Pinakis, etc.) were found listed in the National Imagery and Mapping Agency GEOnet Names Server (http://geonames.nga.mil/gns/html/index.html), a searchable database of 3.3 million non-US geographic-feature names.

The Manila Bulletin report suggested that Pinokis resides on the Zamboanga Peninsula. The Peninsula lies on Mindanao Island's extreme W side where it bounds the Moro Gulf, an arm of the Celebes Sea. The mountainous Peninsula trends NNE-SSW and contains peaks with summit elevations near 1,300 m. Zamboanga City sits at the extreme end of the Peninsula and operates both a major seaport and an international airport.

[Later investigation found that Mt. Pinokis is located in the Lison Valley on the Zamboanga Peninsula, about 170 km NE of Zamboanga City and 30 km NW of Pagadian City. It is adjacent to the two peaks of the Susong Dalaga (Maiden's Breast) and near Mt. Sugarloaf.]

References. Newman, S., 1997, Earthweek, a diary of the planet (week ending 12 September): syndicated newspaper column (URL: http://www.earthweek.com/).

Manila Bulletin, 4 Sept. 1997, Dante's Peak (URL: http://www.mb.com.ph/).

Simkin, T., and Siebert, L., 1994, Volcanoes of the world, 2nd edition: Geoscience Press in association with the Smithsonian Institution Global Volcanism Program, Tucson AZ, 368 p.

Information Contacts: Emmanuel G. Ramos, Deputy Director, Philippine Institute of Volcanology and Seismology, Department of Science and Technology, PHIVOLCS Building, C. P. Garcia Ave., University of the Philippines, Diliman campus, Quezon City, Philippines.


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


Press reports of Somalia's first historical eruption were likely in error

Xinhua News Agency filed a news report on 27 February under the headline "Volcano erupts in Somalia" but the veracity of the story now appears doubtful. The report disclosed the volcano's location as on the W side of the Gedo region, an area along the Ethiopian border just NE of Kenya. The report had relied on the commissioner of the town of Bohol Garas (a settlement described as 40 km NE of the main Al-Itihad headquarters of Luq town) and some or all of the information was relayed by journalists through VHF radio. The report claimed the disaster "wounded six herdsmen" and "claimed the lives of 290 goats grazing near the mountain when the incident took place." Further descriptions included such statements as "the volcano which erupted two days ago [25 February] has melted down the rocks and sand and spread . . . ."

Giday WoldeGabriel returned from three weeks of geological fieldwork in SW Ethiopia, near the Kenyan border, on 25 August. During his time there he inquired of many people, including geologists, if they had heard of a Somalian eruption in the Gedo area; no one had heard of the event. WoldeGabriel stated that he felt the news report could have described an old mine or bomb exploding. Heavy fighting took place in the Gedo region during the Ethio-Somalian war of 1977. Somalia lacks an embassy in Washington DC; when asked during late August, Ayalaw Yiman, an Ethiopian embassy staff member in Washington DC also lacked any knowledge of a Somalian eruption.

A Somalian eruption would be significant since the closest known Holocene volcanoes occur in the central Ethiopian segment of the East African rift system S of Addis Ababa, ~500 km NW of the Gedo area. These Ethiopian rift volcanoes include volcanic fields, shield volcanoes, cinder cones, and stratovolcanoes.

Information Contacts: Xinhua News Agency, 5 Sharp Street West, Wanchai, Hong Kong; Giday WoldeGabriel, EES-1/MS D462, Geology-Geochemistry Group, Los Alamos National Laboratory, Los Alamos, NM 87545; Ayalaw Yiman, Ethiopian Embassy, 2134 Kalorama Rd. NW, Washington DC 20008.


False Report of Sea of Marmara Eruption (Turkey) — November 1999

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

Following the Ms 7.8 earthquake in Turkey on 17 August (BGVN 24:08) an Email message originating in Turkey was circulated, claiming that volcanic activity was observed coincident with the earthquake and suggesting a new (magmatic) volcano in the Sea of Marmara. For reasons outlined below, and in the absence of further evidence, editors of the Bulletin consider this a false report.

The report stated that fishermen near the village of Cinarcik, at the E end of the Sea of Marmara "saw the sea turned red with fireballs" shortly after the onset of the earthquake. They later found dead fish that appeared "fried." Their nets were "burned" while under water and contained samples of rocks alleged to look "magmatic."

No samples of the fish were preserved. A tectonic scientist in Istanbul speculated that hot water released by the earthquake from the many hot springs along the coast in that area may have killed some fish (although they would be boiled rather than fried).

The phenomenon called earthquake lights could explain the "fireballs" reportedly seen by the fishermen. Such effects have been reasonably established associated with large earthquakes, although their origin remains poorly understood. In addition to deformation-triggered piezoelectric effects, earthquake lights have sometimes been explained as due to the release of methane gas in areas of mass wasting (even under water). Omlin and others (1999), for example, found gas hydrate and methane releases associated with mud volcanoes in coastal submarine environments.

The astronomer and author Thomas Gold (Gold, 1998) has a website (Gold, 2000) where he presents a series of alleged quotes from witnesses of earthquakes. We include three such quotes here (along with Gold's dates, attributions, and other comments):

(A) Lima, 30 March 1828. "Water in the bay 'hissed as if hot iron was immersed in it,' bubbles and dead fish rose to the surface, and the anchor chain of HMS Volage was partially fused while lying in the mud on the bottom." (Attributed to Bagnold, 1829; the anchor chain is reported to be on display in the London Navy Museum.)

(B) Romania, 10 November 1940. ". . . a thick layer like a translucid gas above the surface of the soil . . . irregular gas fires . . . flames in rhythm with the movements of the soil . . . flashes like lightning from the floor to the summit of Mt Tampa . . . flames issuing from rocks, which crumbled, with flashes also issuing from non-wooded mountainsides." (Phrases used in eyewitness accounts collected by Demetrescu and Petrescu, 1941).

(C) Sungpan-Pingwu (China), 16, 22, and 23 August 1976. "From March of 1976, various large anomalies were observed over a broad region. . . . At the Wanchia commune of Chungching County, outbursts of natural gas from rock fissures ignited and were difficult to extinguish even by dumping dirt over the fissures. . . . Chu Chieh Cho, of the Provincial Seismological Bureau, related personally seeing a fireball 75 km from the epicenter on the night of 21 July while in the company of three professional seismologists."

Yalciner and others (1999) made a study of coastal areas along the Sea of Marmara after the Izmet earthquake. They found evidence for one or more tsunamis with maximum runups of 2.0-2.5 m. Preliminary modeling of the earthquake's response failed to reproduce the observed runups; the areas of maximum runup instead appeared to correspond most closely with several local mass-failure events. This observation together with the magnitude of the earthquake, and bottom soundings from marine geophysical teams, suggested mass wasting may have been fairly common on the floor of the Sea of Marmara.

Despite a wide range of poorly understood, dramatic processes associated with earthquakes (Izmet 1999 apparently included), there remains little evidence for volcanism around the time of the earthquake. The nearest Holocene volcano lies ~200 km SW of the report location. Neither Turkish geologists nor scientists from other countries in Turkey to study the 17 August earthquake reported any volcanism. The report said the fisherman found "magmatic" rocks; it is unlikely they would be familiar with this term.

The motivation and credibility of the report's originator, Erol Erkmen, are unknown. Certainly, the difficulty in translating from Turkish to English may have caused some problems in understanding. Erkmen is associated with a website devoted to reporting UFO activity in Turkey. Photographs of a "magmatic rock" sample were sent to the Bulletin, but they only showed dark rocks photographed devoid of a scale on a featureless background. The rocks shown did not appear to be vesicular or glassy. What was most significant to Bulletin editors was the report author's progressive reluctance to provide samples or encourage follow-up investigation with local scientists. Without the collaboration of trained scientists on the scene this report cannot be validated.

References. Omlin, A, Damm, E., Mienert, J., and Lukas, D., 1999, In-situ detection of methane releases adjacent to gas hydrate fields on the Norwegian margin: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Yalciner, A.C., Borrero, J., Kukano, U., Watts, P., Synolakis, C. E., and Imamura, F., 1999, Field survey of 1999 Izmit tsunami and modeling effort of new tsunami generation mechanism: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Gold, T., 1998, The deep hot biosphere: Springer Verlag, 256 p., ISBN: 0387985468.

Gold, T., 2000, Eye-witness accounts of several major earthquakes (URL: http://www.people.cornell.edu/ pages/tg21/eyewit.html).

Information Contacts: Erol Erkmen, Tuvpo Project Alp.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

48.831°N, 101.626°E; summit elev. 1675 m

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

In December 2002 information appeared in Mongolian and Russian newspapers and on national TV that a volcano in Central Mongolia, the Har-Togoo volcano, was producing white vapors and constant acoustic noise. Because of the potential hazard posed to two nearby settlements, mainly with regard to potential blocking of rivers, the Director of the Research Center of Astronomy and Geophysics of the Mongolian Academy of Sciences, Dr. Bekhtur, organized a scientific expedition to the volcano on 19-20 March 2003. The scientific team also included M. Ulziibat, seismologist from the same Research Center, M. Ganzorig, the Director of the Institute of Informatics, and A. Ivanov from the Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences.

Geological setting. The Miocene Har-Togoo shield volcano is situated on top of a vast volcanic plateau (figure 1). The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Pliocene and Quaternary volcanic rocks are also abundant in the vicinity of the Holocene volcanoes (Devyatkin and Smelov, 1979; Logatchev and others, 1982). Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Figure (see Caption) Figure 1. Photograph of the Har-Togoo volcano viewed from west, March 2003. Courtesy of Alexei Ivanov.

Observations during March 2003. The name of the volcano in the Mongolian language means "black-pot" and through questioning of the local inhabitants, it was learned that there is a local myth that a dragon lived in the volcano. The local inhabitants also mentioned that marmots, previously abundant in the area, began to migrate westwards five years ago; they are now practically absent from the area.

Acoustic noise and venting of colorless warm gas from a small hole near the summit were noticed in October 2002 by local residents. In December 2002, while snow lay on the ground, the hole was clearly visible to local visitors, and a second hole could be seen a few meters away; it is unclear whether or not white vapors were noticed on this occasion. During the inspection in March 2003 a third hole was seen. The second hole is located within a 3 x 3 m outcrop of cinder and pumice (figure 2) whereas the first and the third holes are located within massive basalts. When close to the holes, constant noise resembled a rapid river heard from afar. The second hole was covered with plastic sheeting fixed at the margins, but the plastic was blown off within 2-3 seconds. Gas from the second hole was sampled in a mechanically pumped glass sampler. Analysis by gas chromatography, performed a week later at the Institute of the Earth's Crust, showed that nitrogen and atmospheric air were the major constituents.

Figure (see Caption) Figure 2. Photograph of the second hole sampled at Har-Togoo, with hammer for scale, March 2003. Courtesy of Alexei Ivanov.

The temperature of the gas at the first, second, and third holes was +1.1, +1.4, and +2.7°C, respectively, while air temperature was -4.6 to -4.7°C (measured on 19 March 2003). Repeated measurements of the temperatures on the next day gave values of +1.1, +0.8, and -6.0°C at the first, second, and third holes, respectively. Air temperature was -9.4°C. To avoid bias due to direct heating from sunlight the measurements were performed under shadow. All measurements were done with Chechtemp2 digital thermometer with precision of ± 0.1°C and accuracy ± 0.3°C.

Inside the mouth of the first hole was 4-10-cm-thick ice with suspended gas bubbles (figure 5). The ice and snow were sampled in plastic bottles, melted, and tested for pH and Eh with digital meters. The pH-meter was calibrated by Horiba Ltd (Kyoto, Japan) standard solutions 4 and 7. Water from melted ice appeared to be slightly acidic (pH 6.52) in comparison to water of melted snow (pH 7.04). Both pH values were within neutral solution values. No prominent difference in Eh (108 and 117 for ice and snow, respectively) was revealed.

Two digital short-period three-component stations were installed on top of Har-Togoo, one 50 m from the degassing holes and one in a remote area on basement rocks, for monitoring during 19-20 March 2003. Every hour 1-3 microseismic events with magnitude <2 were recorded. All seismic events were virtually identical and resembled A-type volcano-tectonic earthquakes (figure 6). Arrival difference between S and P waves were around 0.06-0.3 seconds for the Har-Togoo station and 0.1-1.5 seconds for the remote station. Assuming that the Har-Togoo station was located in the epicentral zone, the events were located at ~1-3 km depth. Seismic episodes similar to volcanic tremors were also recorded (figure 3).

Figure (see Caption) Figure 3. Examples of an A-type volcano-tectonic earthquake and volcanic tremor episodes recorded at the Har-Togoo station on 19 March 2003. Courtesy of Alexei Ivanov.

Conclusions. The abnormal thermal and seismic activities could be the result of either hydrothermal or volcanic processes. This activity could have started in the fall of 2002 when they were directly observed for the first time, or possibly up to five years earlier when marmots started migrating from the area. Further studies are planned to investigate the cause of the fumarolic and seismic activities.

At the end of a second visit in early July, gas venting had stopped, but seismicity was continuing. In August there will be a workshop on Russian-Mongolian cooperation between Institutions of the Russian and Mongolian Academies of Sciences (held in Ulan-Bator, Mongolia), where the work being done on this volcano will be presented.

References. Devyatkin, E.V. and Smelov, S.B., 1979, Position of basalts in sequence of Cenozoic sediments of Mongolia: Izvestiya USSR Academy of Sciences, geological series, no. 1, p. 16-29. (In Russian).

Logatchev, N.A., Devyatkin, E.V., Malaeva, E.M., and others, 1982, Cenozoic deposits of Taryat basin and Chulutu river valley (Central Hangai): Izvestiya USSR Academy of Sciences, geological series, no. 8, p. 76-86. (In Russian).

Geologic Background. The Miocene Har-Togoo shield volcano, also known as Togoo Tologoy, is situated on top of a vast volcanic plateau. The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Information Contacts: Alexei V. Ivanov, Institute of the Earth Crust SB, Russian Academy of Sciences, Irkutsk, Russia; Bekhtur andM. Ulziibat, Research Center of Astronomy and Geophysics, Mongolian Academy of Sciences, Ulan-Bator, Mongolia; M. Ganzorig, Institute of Informatics MAS, Ulan-Bator, Mongolia.


Elgon (Uganda) — December 2005

Elgon

Uganda

1.136°N, 34.559°E; summit elev. 3885 m

All times are local (unless otherwise noted)


False report of activity; confusion caused by burning dung in a lava tube

An eruption at Mount Elgon was mistakenly inferred when fumes escaped from this otherwise quiet volcano. The fumes were eventually traced to dung burning in a lava-tube cave. The cave is home to, or visited by, wildlife ranging from bats to elephants. Mt. Elgon (Ol Doinyo Ilgoon) is a stratovolcano on the SW margin of a 13 x 16 km caldera that straddles the Uganda-Kenya border 140 km NE of the N shore of Lake Victoria. No eruptions are known in the historical record or in the Holocene.

On 7 September 2004 the web site of the Kenyan newspaper The Daily Nation reported that villagers sighted and smelled noxious fumes from a cave on the flank of Mt. Elgon during August 2005. The villagers' concerns were taken quite seriously by both nations, to the extent that evacuation of nearby villages was considered.

The Daily Nation article added that shortly after the villagers' reports, Moses Masibo, Kenya's Western Province geology officer visited the cave, confirmed the villagers observations, and added that the temperature in the cave was 170°C. He recommended that nearby villagers move to safer locations. Masibo and Silas Simiyu of KenGens geothermal department collected ashes from the cave for testing.

Gerald Ernst reported on 19 September 2004 that he spoke with two local geologists involved with the Elgon crisis from the Geology Department of the University of Nairobi (Jiromo campus): Professor Nyambok and Zacharia Kuria (the former is a senior scientist who was unable to go in the field; the latter is a junior scientist who visited the site). According to Ernst their interpretation is that somebody set fire to bat guano in one of the caves. The fire was intense and probably explains the vigorous fuming, high temperatures, and suffocated animals. The event was also accompanied by emissions of gases with an ammonia odor. Ernst noted that this was not surprising considering the high nitrogen content of guano—ammonia is highly toxic and can also explain the animal deaths. The intense fumes initially caused substantial panic in the area.

It was Ernst's understanding that the authorities ordered evacuations while awaiting a report from local scientists, but that people returned before the report reached the authorities. The fire presumably prompted the response of local authorities who then urged the University geologists to analyze the situation. By the time geologists arrived, the fuming had ceased, or nearly so. The residue left by the fire and other observations led them to conclude that nothing remotely related to a volcanic eruption had occurred.

However, the incident emphasized the problem due to lack of a seismic station to monitor tectonic activity related to a local triple junction associated with the rift valley or volcanic seismicity. In response, one seismic station was moved from S Kenya to the area of Mt. Elgon so that local seismicity can be monitored in the future.

Information Contacts: Gerald Ernst, Univ. of Ghent, Krijgslaan 281/S8, B-9000, Belgium; Chris Newhall, USGS, Univ. of Washington, Dept. of Earth & Space Sciences, Box 351310, Seattle, WA 98195-1310, USA; The Daily Nation (URL: http://www.nationmedia.com/dailynation/); Uganda Tourist Board (URL: http://www.visituganda.com/).