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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

Klyuchevskoy (Russia) Intermittent moderate gas, steam, and ash emissions; no ash seen after 15 June 2018

Ambae (Vanuatu) Major explosions during March-April 2018 cause heavy ashfall on island; significant lahar damages to infrastructure

Kilauea (United States) Overflows of lava lake in Halema'uma'u crater; Pu'u 'O'o crater floor collapses 30 April 2018; inflation and increased seismicity

San Cristobal (Nicaragua) Moderate explosion on 22 April 2018

San Miguel (El Salvador) Intermittent small ash emissions between 14 January and 30 May 2018

Kirishimayama (Japan) Ash plumes and lava flows at Shinmoedake starting in March 2018; explosion at Iwo-yama

Sabancaya (Peru) Strong, sporadic explosions with ash plumes throughout December 2017-May 2018

Masaya (Nicaragua) Lava lake persists during July 2017-April 2018

Chillan, Nevados de (Chile) Hundreds of ash-bearing explosions; dome appears in crater in mid-December 2017

Marapi (Indonesia) Two explosions during April-May 2018 cause ashfall to the southeast

Nyiragongo (DR Congo) Thermal anomalies show that lava lake remains active through May 2018

Ebeko (Russia) Ash explosions remained frequent through May 2018, with plumes typically rising more than 1 km



Klyuchevskoy (Russia) — August 2018 Citation iconCite this Report

Klyuchevskoy

Russia

56.056°N, 160.642°E; summit elev. 4754 m

All times are local (unless otherwise noted)


Intermittent moderate gas, steam, and ash emissions; no ash seen after 15 June 2018

The current eruptive period at Klyuchevskoy began in late August 2015 (BGVN 39:10). Lava effusion ended in early November 2016 (BGVN 42:04), but explosive activity continued to be observed through February 2018 (BGVN 43:05). From mid-February through mid-August 2018 moderate to weak gas and steam plumes were observed (figure 29), but no ash plumes were reported after 15 June 2018 (figure 29). The Kamchatkan Volcanic Eruption Response Team (KVERT) is responsible for monitoring, and is the primary source of information. The Aviation Color Code was lowered from Orange to Yellow during this reporting period.

Figure (see Caption) Figure 29. Fumarolic plume rising from the summit of Klyuchevskoy, 15 April 2018. Courtesy of Yu. Demyanchuk (IVS FEB RAS, KVERT).

The Aviation Color Code (ACC) was lowered to Yellow by KVERT on 9 February. On 18 February an ash plume that rose to 5.2 km in altitude was reported by the Tokyo Volcanic Ash Advisory Center (VAAC). Moderate gas and steam activity was reported on 25 and 29 April, and 2 May 2018. During 7-8 and 10 May KVERT reported that gas, steam, and ash plumes rose to 5.0-5.5 km altitude and extended to 340 km SE; subsequently the ACC was raised back to Orange. Explosions were reported on 14 May with accompanying ash plumes that rose to 10.5 km in altitude. The ash clouds lingered around Klyuchevskoy and surrounding volcanoes for about eight hours before gradually dissipating. Nighttime summit incandescence and a hot avalanche was observed. A diffuse ash plume was reported by KVERT on 6 June that extended 12 km to the W. Another ash plume was visible on 15 June, but decreasing activity resulted in the ACC being lowered to Yellow again on 29 June. Only moderate gas and steam activity was noted through mid-August.

A thermal anomaly was reported over Klyuchevskoy approximately 16 times during this reporting period in February, April, May, June, and August 2018. The number of MIROVA thermal anomalies detected increased in the first half of January 2018, with decreasing and intermittent low-intensity detections in subsequent months (figure 30).

Figure (see Caption) Figure 30. MODIS thermal anomalies identified in the MIROVA system, plotted as log radiative power for the year ending 24 August 2018. Courtesy of MIROVA.

Geologic Background. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); 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/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/).


Ambae (Vanuatu) — July 2018 Citation iconCite this Report

Ambae

Vanuatu

15.389°S, 167.835°E; summit elev. 1496 m

All times are local (unless otherwise noted)


Major explosions during March-April 2018 cause heavy ashfall on island; significant lahar damages to infrastructure

Ambae (Aoba) is a large basaltic shield volcano in the New Hebrides arc that has generated periodic phreatic and pyroclastic explosions originating in the summit crater lakes Manaro Lakua and Voui during the last 25 years; the central edifice with the active summit craters is often referred to as Manaro Voui. A pyroclastic cone appeared in Lake Voui during November 2005-February 2006 (figure 30, BGVN 31:12). The volcano remained mostly quiet until an explosive eruption from a new pyroclastic cone in the lake began in mid-September 2017 and lasted through mid-November (BGVN 43:02). Activity included high-altitude ash emissions (9.1 km), lava flows, and Strombolian activity. After a quieter December, ash emissions resumed during January-April 2018. This report summarizes activity from January to June 2018, with information provided by the Vanuatu Geohazards Observatory of the Vanuatu Meteorology and Geo-Hazards Department (VMGD), the Wellington Volcanic Ash Advisory Center (VAAC), satellite data from several sources, and social media photographs.

Ongoing steam and intermittent ash emissions were observed during January and February 2018; incandescent ejecta continued from the pyroclastic cone at the summit. An increase in the frequency and volume of ash emissions in March led VMGD to raise the Alert Level to 3 (on a 0-5 level scale) by the middle of the month. Ash plume heights ranged from 3-5 km altitude. Heavy rains on 30 March caused a large lahar that significantly damaged a village on the N side of the island. A high-altitude plume on 31 March was measured at 13.7 km altitude. Significant ashfall around the island caused infrastructure damage and health hazards to humans, livestock, and plants. An explosion in early April produced another high-altitude ash plume observed in satellite imagery at 12.2 km altitude and one of the largest SO2 plumes measured in several years. A major ash plume on 11 April rose to 9.1 km altitude and enveloped much of the island in ash-laden meteoric clouds. The pyroclastic cone growing in Lake Voui had bisected the lake by March, and continued to fill it in. By late May, only two remnants of the lake remained, and a nearby smaller lake was dry. A low-level ash emission in late June signaled the beginning of a new, larger eruptive episode that began on 1 July 2018.

Activity during January-February 2018. The Wellington VAAC reported an ash plume at Ambae on 2 January 2018 drifting E at 3.1 km altitude that dissipated after a few hours. A plume on 8 January estimated at the same altitude resulted in reports of ashfall on the N and NE areas of the island; meteoric clouds prevented observations of the plume. Ongoing steam emissions were reported for the rest of January. On 7 February a continuous ash plume was observed in satellite data at 2.7 km altitude moving N. The following day, it was visible spreading E from the summit. A pilot confirmed observation of the plume continuing to spread to the E at 3.1 km altitude late on 8 February. Another low-level emission on 10 February extended NE at 2.1 km for a few hours. An ash plume on 13 February was clearly visible drifting N in satellite imagery; its altitude was estimated at 3.1 km.

A larger eruption on 16 February generated an ash plume that rose to 4.6 km altitude and initially drifted NE. Continuous ash emission extended as high as 5.5 km through 17 February and drifted SE and then S. By the next day, the constant emissions were still visible in satellite imagery, estimated at 4.6 km altitude; the main plume was drifting E with a remnant moving to the SW, finally dissipating on 19 February (figure 54). Ash emissions were visible in infrared imagery at about 3.9 km altitude on 23 February. Ongoing explosions were observed in the webcam on 23 and 24 February; ash was visible in satellite imagery until the end of the day on 24 February. A brief explosion observed in the webcam around sunrise on 27 February generated a small ash plume that rose to 3.1 km altitude and drifted SE. Moderate sulfur dioxide emissions were recorded a number of times during January and February (figure 55).

Figure (see Caption) Figure 54. On 18 February 2018, the pyroclastic cone at Ambae had grown significantly since 1 October 2017 (see figure 46 BGVN 43:02) (upper image) and actively ejected pyroclastic material along with magmatic gas and steam (lower image). Courtesy of pilot David Sarginson, Facebook.
Figure (see Caption) Figure 55. SO2 plumes from Vanuatu's Ambae, Ambrym, and Gaua volcanoes were all substantial enough sometime during January and February 2018 to be recorded by the OMI instrument on NASA's Aura satellite. Emissions on 2 January 2018 (top left) were drifting slowly SW from Ambae (upper plume) and Ambrym (lower plume); only Ambae had a plume drifting W on 11 January (top right); both Ambae and Ambrym SO2 plumes drifted NE on 17 February (bottom left); on 19 February (bottom right) Gaua (top plume) produced an emission that drifted E while Ambae and Ambrym generated SO2 that drifted SW. Courtesy of NASA Goddard Space Flight Center.

Activity during March 2018. The frequency and volume of ash emissions increased significantly during March 2018. Ash plumes were visible in satellite imagery during 3-6 March 2018. The initial plume rose to 3.7 km altitude and drifted NE, rising to 3.9 on 4 March and drifting N. The following day plumes rose to 4.6 km. By 6 March the plume was lower, drifting NW at 2.4 km altitude. A series of continuous low-level ash emissions were visible in satellite and webcam imagery every day from 11-19 March (figure 56). They initially drifted SE and SW and then moved to the W on 15 March at altitudes of generally 2.4-3.1 km, occasionally higher. The plumes drifted N and W during 17-19 March. This increase in ash emissions affecting local villages led VMGD to raise the alert level from 2 to 3 on 18 March 2018. They noted that activity was similar to the previous October but with more sustained ash emissions.

Figure (see Caption) Figure 56. Continuous ash emissions from Ambae beginning on 11 March 2018 (10 March UTC shown here) were visible in satellite imagery for over a week. Courtesy of European Space Agency, Copernicus EMS.

Local observers reported an explosion on 21 March that rose to 3.4 km altitude and drifted SW (figures 57-59). Continuous emissions through the end of the month were discernible in either satellite imagery or the webcam each day. Plume altitudes ranged from 3.1 to 4.9 km altitude, drifting in several directions. Significant ashfall began affecting local villages, destroying crops and livestock, and collapsing structures during the second half of March.

Figure (see Caption) Figure 57. A strong explosion on 21 March 2018 at Ambae produced an ash plume that rose several kilometers above the crater. Ashfall affected villagers in many communities on the island. Image courtesy VMGD Saratamata webcam located 22 km NE on the NE tip of Ambae Island, annotations by Cultur Volcan.
Figure (see Caption) Figure 58. A major ash plume rose from the crater of the pyroclastic cone in Lake Voui on Ambae on 21 March 2018. Photo courtesy of Robson S Tigona (VMGD), posted on Facebook.
Figure (see Caption) Figure 59. The dense ash plume from the explosion on 21 March 2018 at Ambae caused significant localized ashfall on the SW of the island as seen from Nduidui wharf in W Ambae. Courtesy of Dan McGarry, Vanuatu Daily Post.

Local news reports on 25 March noted that ejecta from the previous evening was visible over 70 km away to the SW by residents on Espiritu Santo Island, and small amounts of ash fell on Pentecost Island, 60 km SE (figure 60). According to the Vanuatu Independent, Virgin Australia cancelled flights to Vanuatu on 25 March. The New Zealand Defence Force did an aerial survey on 26 March and observed a large ash plume rising several kilometers (figure 61). Radio New Zealand reported on 30 March that large amounts of ashfall and acid rain had damaged crops, water supplies and buildings on Ambae (figures 62). A New Zealand GNS Science volcanologist reported that gardens were covered by ash and limbs on trees were broken. Some of the roofs over buildings and water supplies had collapsed due to the weight of the volcanic ash. Heavy ashfall in the S and NW parts of the island at the end of the month resulted in evacuations of several villages in the affected areas.

Figure (see Caption) Figure 60. Ashfall was observed on Pentecost Island, 60 km SE of Ambae after significant explosions overnight during 24-25 March 2018. Courtesy of Dan McGarry, Vanuatu Daily Post via twitter.
Figure (see Caption) Figure 61. The New Zealand Defence Force photographed this large ash plume rising from the summit of Ambae during an aerial survey on 26 March 2018. Courtesy of the New Zealand Defence Force (NZDF).
Figure (see Caption) Figure 62. Dense volcanic ash fell at the Penama Adventist College (PAC) in Red Cliff on Ambae in late March 2018. The upper image was taken on 14 April 2017, the lower image on 27 March 2018. Photos by John Metojoe, Vanuatu Police Force, and PAC. Courtesy of Philipson Bani (IRD/LMV).

The village of Waluebue on the N side of Ambae was badly damaged by a lahar during the night of 30-31 March. Homes and churches were destroyed from the mud and large boulders in the debris flow. All residents were safely evacuated (figures 63-67).

Figure (see Caption) Figure 63. A large lahar deposited boulders and damaged many buildings in the village of Waluebue on the N side of Ambae during the night of 30-31 March 2018. Photo courtesy of Clifford Tarisimbi.
Figure (see Caption) Figure 64. As seen in this example of a building undercut on one side and partially buried on the other, a large lahar damaged many buildings in the village of Waluebue on the N side of Ambae during the night of 30-31 March 2018. Photos courtesy of Clifford Tarisimbi.
Figure (see Caption) Figure 65. Mud and boulders buried some buildings to the roofline when a large lahar damaged passed through the village of Waluebue on the N side of Ambae during the night of 30-31 March 2018. Photos courtesy of Clifford Tarisimbi.
Figure (see Caption) Figure 66. Boulders a meter or more in diameter destroyed buildings when large lahar traveled through the village of Waluebue on the N side of Ambae during the night of 30-31 March 2018. Photo courtesy of Clifford Tarisimbi.
Figure (see Caption) Figure 67. Boulders a meter or more in diameter destroyed buildings when large lahar traveled through the village of Waluebue on the N side of Ambae during the night of 30-31 March 2018. Photo courtesy of Clifford Tarisimbi.

A new series of high-altitude ash emissions were reported by the Washington VAAC beginning on 30 March (figure 68). Early reports from satellite images and webcams indicated an ash plume at 6.1 km altitude. This was followed within the hour of confirmation from satellite imagery of the plume at 13.7 km altitude moving NW. By the following morning, two plumes were visible, one drifting S at 6.1 km and a second drifting NW at 13.7 km altitude. Meteoric clouds prevented observations later that day, but by 1 April, intermittent explosions were producing plumes moving E at an estimated altitude of 3.0 km, and SE estimated at 6.1 km altitude.

Figure (see Caption) Figure 68. A 13.7-km-high ash plume was visible from the VMGD Webcam at Ambae on 31 March 2018. Satellite imagery showed plumes drifting in multiple directions. Courtesy of VMGD.

Activity during April-June 2018. New eruptions occurred overnight during 5-6 April 2018 that generated an ash plume and a large distinct SO2 plume. Meteoric clouds and darkness prevented observation of the ash plume, but the SO2 signal was clearly visible on false-color satellite imagery. The plume initially rose to 7.3 km altitude and drifted W; a few hours later, it rose to 12.2 km. With a Dobson Unit measurement of 52.55 units, it was one of the strongest SO2 plumes measured on the planet since 2015, according to Simon Carn of Michigan Technological University (figure 69). An ongoing eruption was visible in the webcam on 6 April, but meteoric clouds again prevented observation in satellite data. A cluster of lightning strikes was detected by the World Wide Lightning Location Network (WWLLN) around the reported time of the eruption, according to Simon Carn. Intermittent low-level ash emissions were confirmed in the webcam on 8 April, estimated to be moving NE and E at 3.0-4.9 km altitude.

Figure (see Caption) Figure 69. The largest SO2 plume recorded since 2015 erupted from Ambae during 5-6 April 2018. Courtesy of NASA Goddard Space Flight Center.

Ash from a continuous low-level eruption during 9-10 April 2018 was clearly visible in the webcam and partly visible in satellite imagery drifting E and NE at 4.3-4.9 km altitude. The SO2 plume from the eruption stretched across most of the South Pacific (figure 70). Ashfall from the plume spread across a large area of the island causing substantial damage in local communities (figures 71 and 72).

Figure (see Caption) Figure 70. A sulfur dioxide plume from Ambae in Vanuatu stretched across the South Pacific in this 9 April 2018 image from the OMI instrument on the Aura satellite. Courtesy of NASA Goddard Space Science Center and Simon Carn.
Figure (see Caption) Figure 71. Ashfall from continuous emissions at Ambae during 9-10 April 2018 spread across much of the island, damaging local communities. Image posted on 10 April 2018. Courtesy of Wilfred Woodrow, Facebook.
Figure (see Caption) Figure 72. Ashfall from continuous emissions during 9-10 April 2018 at Ambae spread across much of the island, damaging local communities. Photo from Ghevin Banga, posted by Bani Philipson (IRD/LMV).

The ash plume height increased significantly on 11 April to 9.1 km altitude and drifted SE according to the Wellington VAAC. Planet Lab images showed the plume covering the N half of the island a short time later (figure 73). The following day, the plume altitude gradually lowered from 4.6 to 1.8 km and drifted N, then NW. Local communities reported intermittent low-level ash emissions and localized ashfall late on 12 April; this was the last report of ash emissions for April. Thick meteoric and ash clouds enveloped much of the island as seen in social media video on 12 April.

Figure (see Caption) Figure 73. Three satellite images from Planet Labs Inc. show the changes at Ambae between September 2017 and April 2018. On 30 September 2017 (top), the pyroclastic cone in Lake Voui was still an island within the lake. By 10 March 2018 (middle), the lake had been divided in two by the growth of the cone, the lake was discolored, and ashfall covered a large area several kilometers in diameter around the lake. A major ash emission on 11 April 2018 (bottom) rose to 9.1 km altitude and covered the N half of the island. Courtesy of Planet Labs Inc. posted on Twitter at Planet@planetlabs.

According to the Vanuatu Daily Post on 16 April 2018, the Council of Ministers for Vanuatu declared their intent to seek help from International Relief Organizations to evacuate the island's population after the latest episodes of extensive ashfall destroyed much of the infrastructure. Photographs from an overflight by VGMD on 21 April 2018 showed the increased size of the pyroclastic cone inside Lake Voui dividing the lake into two segments, one nearly consumed by the cone (figure 74). They reported small eruptions on 23 and 27 April; these were the last ash emissions until the end of June 2018.

Figure (see Caption) Figure 74. Aerial images of the active pyroclastic cone at Ambae were captured by VMGD during an overflight on 21 April 2018. Only dense steam emissions were observed in the view to the E across the summit, and the original Lake Voui was in two segments split by the pyroclastic cone. Courtesy of VMGD.

The thermal activity recorded by the MODVOLC and MIROVA systems corresponded with the observations of explosions and ash emissions. There were MODVOLC thermal alerts issued each month from January through 10 April 2018, with strong, multi-alert periods in February and March; these data were similar to the MIROVA signal for the period, which also showed increased activity during the same time (figure 75).

Figure (see Caption) Figure 75. Data from the MIROVA project show significant pulses of heat flow from Ambae during February-April 2018. Inset photo shows the large ash plume of 9 April as viewed from the VMGD webcam, which corresponds to the largest heat flow in April shown on the graph. Courtesy of MIROVA and VMGD.

By the end of May 2018, Manaro Ngoru, the small water body on the W side of the summit was dry; Lake Voui, divided into two segments by the pyroclastic cone, had a small amount of orange-brown water in the W half, and muddy brown water in the E half (figures 76 and 77). Steam plumes rose continuously from the cone, but no ash emissions were observed.

Figure (see Caption) Figure 76. The summit of Ambae on 22 May 2018 was covered with ash over a large area; former Lake Voui was divided in two by the pyroclastic cone, and only a modest steam plume rose from the top of the cone. Manaro Ngoru, the former lake on the W side of the summit, was completely dry. Courtesy of Planet Labs.
Figure (see Caption) Figure 77. The W side of Lake Voui on Ambae on 29 May 2018 was a small area of dark reddish brown water around the pyroclastic cone. View is to the S. Courtesy of Bani Philipson (IRD/LMV). =

VMGB issued a volcano alert on 7 June 2018, announcing that they had lowered the Alert Level from 3 to 2, due to the reduced activity at Ambae during late April and May. Radio New Zealand reported that on 9 June, the Vanuatu government announced plans to move its Penama Province capital due to the ongoing eruption. The Penama Council agreed to relocate its headquarters from Saatamaa in Eastern Ambae to Loltong in North Pentacost. The Penama Province is one of six in Vanuatu and includes the three islands of Ambae, Maewo, and Pentecost.

The Wellington VAAC issued an ash advisory from a low-level ash emission on 21 June 2018. It was clearly visible in satellite imagery, and rose to 3 km altitude, drifting SE. That was the last activity reported until a large new ash plume was recorded in the webcam on 1 July 2018.

Geologic Background. The island of Ambae, also known as Aoba, is a massive 2500 km3 basaltic shield that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone dotted with scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes (Manaro Ngoru, Voui, and Manaro Lakua) is located at the summit within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. That large central edifice is also called Manaro Voui or Lombenben volcano. Post-caldera explosive eruptions formed the summit craters about 360 years ago. A tuff cone was constructed within Lake Voui (or Vui) about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department (VMGD), 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/); 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); 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/); European Space Agency (ESA), Copernicus (URL: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus; 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/); New Zealand Defence Force (NZDF), Wellington, New Zealand (URL: http://www.nzdf.mil.nz/, Twitter: @NZDefenceForce); Vanuatu Daily Post (URL: http://dailypost.vu/news/flash-appeal/article_7c929c1e-dda3-5eab-925b-c814e04eeacb.html); Dan McGarry, Vanuatu Daily Post (Twitter: @dailypostdan); Vanuatu Independent News Magazine, Port Vila, Vanuatu (URL: https://vanuatuindependent.com/2018/03/26/flight-cancelled-due-to-volcanic-ash/); Simon Carn, Dept of Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931, USA (URL: http://www.volcarno.com/, http://so2.umbc.edu/omi/); Radio New Zealand, 155 The Terrace, Wellington 6011, New Zealand (URL: https://www.radionz.co.nz/international/pacific-news/359231/vanuatu-provincial-capital-moves-due-to-volcano); Bani Philipson, Observatoire de Physique du Globe de Clermont-Ferrand (OPGC) and Institut de Recherche pour le Developpement (IRD), Laboratoire Magmas et Volcans (LMV), University Campus of Cézeaux, 6 Blaise Pascal Avenue, TSA 60026 - CS 60026, 63178 AUBIERE Cedex, France (URL: http://lmv.univ-bpclermont.fr/bani-philipson/, Twitter: @philipsonbani); David Sarginson (Facebook: URL: https://www.facebook.com/david.sarginson.16); Clifford Tarisimbi (Facebook: https://www.facebook.com/profile.php?id=100009930510696); Wilfred Woodrow (Facebook: https://www.facebook.com/groups/558036627684741/permalink/974980079323725); Planet Labs Inc. (URL: http://www.planet.com/).


Kilauea (United States) — July 2018 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Overflows of lava lake in Halema'uma'u crater; Pu'u 'O'o crater floor collapses 30 April 2018; inflation and increased seismicity

Open lava lakes at the Kilauea summit caldera along with a lava lake and flows from the East Rift Zone (ERZ) have been almost continuous since the current eruption began in 1983, and the rift zone has been intermittently active for at least two thousand years. The period from January-April 2018 included the ending of activity in one part of the ERZ and the beginning of a new episode. March 2018 marked the tenth year of the active lava lake inside the Overlook vent at Halema'uma'u. Information for this report comes primarily from the US Geological Survey's (USGS) Hawaii Volcano Observatory (HVO) which provides daily reports, volcanic activity notices, and photo and video data.

At the end of 2017, the lava lake inside the Overlook vent at Halema'uma'u crater maintained the typical activity it had exhibited throughout the year, with a consistent lava circulation pattern, and occasional spattering events from hardened lava falling into the lake from the pit walls. The lake level rose and fell by a few meters over periods of hours to days, ending the year about 30 m below its level at the beginning of the year. Longer-term subsidence of the Pu'u 'O'o cone on the East Rift Zone was also apparent during 2017, although there was little change in the elevation of the lava pond inside the west pit area of the crater; occasional rockfalls triggered minor spattering. At the end of 2017 the East Rift Zone episode 61g surface lava flow activity persisted on the upper portions of the flow field near Pu'u 'O'o, on the pali, and in scattered areas along the coastal plain. Changes in the subsurface flow in lava tubes contributed to frequent changes to surface breakout locations. The lava flowing into the ocean at Kamokuna slowed and finally ended in November 2017.

During January-April 2018, the lava lake level inside the Overlook vent of Halema?uma?u crater rose and fell daily with alternating periods of inflation and deflation, with a gradual overall inflationary trend. Inflation intensified at the end of April, and the lake overflowed onto the floor of the crater during 21-27 April. The lake level had dropped several meters below the rim of the vent by the last day of the month. Activity of the episode 61g lava flow decreased gradually throughout the period. The flow remained active at the base of the pali and on the upper flow field through February, but activity tapered off on the coastal plain. By the end of March, only the upper flow field was still active. Notable inflationary tilt began at Pu'u 'O'o on 12 March 2018. Lava flowed out of vents on the main crater floor and also created a perched lava pond in the west pit. In mid-April HVO noted that the inflation resulted from increased pressurization of the magma under Pu'u 'O'o and in the past this had led to the formation of new vents and lava flows along the East Rift Zone. A marked increase in seismicity and ground deformation at Pu'u 'O'o on the afternoon of 30 April was followed by the collapse of the crater floor, dispersing red ash a significant distance around the cone. Following the collapse, HVO seismometers and tiltmeters recorded a substantial increase in seismic activity and deformation from Kilauea's summit to an area about 10-16 km downrift (east) of Pu'u 'O'o which propagated eastward overnight along the Lower East Rift Zone (LERZ), marking the beginning of a major new eruptive phase.

Activity during January 2018. Consistent activity continued into January 2018 with few notable changes. The lava lake inside the Overlook vent at Halema'uma'u crater rose and fell by a few meters over hours and days; on the East Rift Zone the lava pond persisted at Pu'u 'O'o cone, and scattered breakouts from the episode 61g lava flow continued. Early on 19 January two earthquakes of magnitude 2.4 and 2.5 occurred on the lower East Rift Zone near Leilani Estates. Also on 19 January, a rockfall from the wall of Halema?uma?u crater plunged into the lava lake producing a short-lived explosion of spatter and wallrock that blanketed an area around the former visitor overlook. Debris fell as far as the Halema?uma?u parking lot (figure 312).

Figure (see Caption) Figure 312. Spatter up to about 30 cm in size was thrown onto the rim of Halema'uma'u crater at Kilauea during explosive events on 19 January 2018. Some fragments were thrown or blown farther downwind, reaching as far as the closed section of Crater Rim Drive in Hawai'i Volcanoes National Park. The boot of an HVO scientist, who entered the area to check on HVO's webcameras, is shown here for scale. Courtesy of HVO.

HVO noted that spattering from the lava lake at Halema'uma'u was visible from the visitor overlook overnight during 25-26 January. Spatter appeared again briefly the next day, and overnight during 29-30 January. Four spattering sites were visible on a clear 30 January day (figure 313). Webcam views overnight on 30-31 January showed that incandescence persisted from the small lava pond on the W side of the Pu'u 'O'o crater. On the morning of 26 January a new breakout from the episode 61g flow appeared on the pali. By the end of January, most of the breakouts from the episode 61g flow field were concentrated at the base of the pali and on the upper flow field, with little activity on the coastal plain.

Figure (see Caption) Figure 313. Clear views at the summit of Kilauea on 30 January 2018 revealed four spattering sites visible on the surface of the Halema'uma'u lava lake inside the Overlook vent. Through the gas plume, a visible scar (light-colored wall rock) from the 19 January rockfall that triggered an explosive event, could be seen on the southern Overlook vent wall. Another, smaller scar on the northeastern lake wall (left), resulted from two small rock falls on 24 January. Courtesy of HVO.

Activity during February 2018. The lake level inside the Overlook vent continued with daily fluctuations of several meters, between 31 and 42 m below the Halema'uma'u crater floor, during February 2018. A small veneer collapse (rockfall) into the lava lake on 23 February was visible in lava lake webcam images. Throughout the month, persistent incandescence was observed in the webcam at the Pu'u 'O'o west pit lava pond (figure 314). On 10 February a large portion of the NE rim of the west pit collapsed. Prior to and during the rim collapse, the adjacent ground also subsided. The episode 61g flow remained active at the base of the pali (figure 315) and in the upper flow field. A new breakout on the upper flow field, 1-2 km from the vent, appeared early on 26 February. A small swarm of earthquakes occurred in the upper East Rift Zone on 21 February; the largest event was a M 2.3. Seismicity throughout the volcano was otherwise at normal rates throughout the month.

Figure (see Caption) Figure 314. Incandescence from the west pit at Kilauea's Pu'u 'O'o cone on 19 February 2018 was typical of that observed during clear weather throughout the month. Courtesy of HVO.
Figure (see Caption) Figure 315. 'A'a flows at the base of Pulama pali at Kilauea on 20 February 2018 produced shimmers of heat (top center) and incandescent fragments. Rubble from the flow rolled downhill, as the molten center slowly pushed forward. Courtesy of HVO.

Activity during March 2018. A brief swarm of small earthquakes occurred in the upper East Rift Zone on 2 March 2018. An ongoing long-period earthquake swarm at 5-10 km depth beneath the caldera began late on 6 March and continued into the next day. At the Halema'uma'u crater, the lava lake fluctuated daily, with levels ranging from a low of 40.5 m below the crater floor to a high of 20 m below it. Changes in levels of up to 10 m in a 24-hour period were common. Vigorous spattering was observed on 6 March (figure 316). On 16 March, the lava lake rose high enough (26 m below the crater floor) for active spattering to be visible in webcams mounted in the HVO tower, located across the crater from the vent. The 10th anniversary of the eruption within Halema'uma'u crater was marked on 19 March. When the vent first opened on 19 March 2008, it formed a small pit about 35 m wide. Over the following decade, the pit (informally called the "Overlook crater") grew to about 280 x 200 m in size (see figure 313).

Figure (see Caption) Figure 316. Within Kilauea volcano's summit lava lake at the Halema'uma'u crater, vigorous spattering on 6 March 2018 was occurring on the southern margin where a ledge of solidified lava had built out from the vent wall. Courtesy of HVO.

Notable inflationary tilt at Pu'u 'O'o cone began on 12 March 2018; GPS stations also started recording extension across the cone on that date. A small increase in seismic events was observed at Pu'u 'O'o on the evening of 21 March. Increased views of spattering from the west pit lava pond were visible beginning the following day, likely due to subsidence over the previous months as reported by HVO. During the evening of 25 March lava flowed out of a vent in the SE part of the crater floor and continued to expand for the rest of the month (figure 317). Inflationary tilt slowed significantly on 27 March. Cracks along the ridge between the main crater and the west pit continued to grow throughout the month as the ridge continued to subside (figure 318).

Figure (see Caption) Figure 317. On 25 March 2018 a small lava flow began erupting onto the Pu'u 'O'o crater floor at Kilauea for the first time since May 2016. In this thermal image, taken by the PTcam on 26 March 2018 at 1318, the flow (bright color) appears to be supplied by one of the small spatter cones in the crater's south embayment. The lava flow did not extend beyond the crater. This type of activity is not unusual for Pu'u 'O'o. Courtesy of HVO.
Figure (see Caption) Figure 318. At Pu'u 'O'o on Kilauea's East Rift Zone, the ridge separating the main crater (top) from the west pit (bottom) had been subsiding over the previous several months due to small rockfalls and unstable ground when this image was taken on 27 March 2018. As the ground shifted, cracks along the ridge and on both sides of it continued to open. The lava pond within the west pit rose several meters during March and produced overflows (darker lava) onto the floor of the pit as it rose. A small lava flow also erupted onto the floor of the main crater on 25 March and remained active through 27 March, visible as the lava darker in color in the foreground of the main crater floor. Courtesy of HVO.

By 20 March surface lava flow activity from the episode 61g flow near the base of the pali appeared to have diminished, and only sparse lava flow activity on the coastal plains was noted after 23 March. Activity on the upper flow field, closer to Pu'u 'O'o, continued (figure 319). A 30 March overflight by HVO confirmed no flow activity on the coastal plain or the pali.

Figure (see Caption) Figure 319. Active lava breakouts were scarce across the episode 61g flow field on Kilauea's East Rift Zone, with active flows confined to an area approximately 1-2 km from Pu'u 'O'o during March 2018. This breakout from the lava tube consisted of fluid pahoehoe and was photographed on 27 March 2018 during an overflight. The incandescent area is several meters across. Courtesy of HVO.

Activity during 1-16 April 2018. Constant spattering at the Overlook vent lava lake (figure 320) was intermittently visible from HVO and the Jagger Museum during April 2018 as the lake level rose and fell several meters on a daily basis. Its lowest level of the month was 32 m below the crater floor, and a general inflationary trend throughout the month resulted in significant overflows onto the floor of Halema?uma?u crater at the end of the month. A rockfall in the morning of 6 April triggered an explosion at the summit lava lake that damaged the power system to the Halema?uma?u crater rim webcams (figure 321). A moderate swarm of over 200 earthquakes occurred on 11 April at depths of 7-9 km below the summit; the largest event in the sequence was M 2.4. Seismicity returned to its background rate in the early morning of 12 April. Three minor ledge collapses, common while the lava lake level is lowering, occurred on 12 April.

Figure (see Caption) Figure 320. A clear view of Kilauea's summit lava lake in the Overlook vent on 4 April 2018 revealed spattering on the N side and center of the lake surface, a departure from its more common location on the SE side of the lake; this occasionally happened when the surface flow direction reversed. Spattering is caused by gas bubbles bursting within the lava lake. Courtesy of HVO.
Figure (see Caption) Figure 321. On 6 April 2018 at 1028 HST a partial collapse of the southern Overlook crater wall triggered an explosive event at Kilauea's summit lava lake. A large plume of gas, ash, and lava fragments rose from the lava lake and was visible from the Jaggar overlook. The explosion threw debris onto the Halema'uma'u crater rim at the old visitor overlook, which has been closed due to ongoing volcanic hazards such as this explosive event. Courtesy of HVO.

For the first half of April 2018, steady minor inflation continued at Pu'u 'O'o, interrupted by brief episodes of sharp deflation that appeared related to small lava flows on the crater floor. During an overflight on 13 April HVO geologists viewed a perched lava pond inside the west pit (figure 322). A slight increase in seismicity in the Upper East Rift Zone began overnight during 15-16 April; the largest event was a M 2.9 earthquake.

Figure (see Caption) Figure 322. During an overflight of Kilauea on 13 April 2018 geologists from HVO observed that lava within the west pit at Pu'u 'O'o had formed a perched lava pond (center) contained within a levee. This levee, formed by an accumulation of hardened lava, confined molten lava to the perched pond, which allowed the lava surface to rise higher than the west pit floor. If the pond rises high enough, lava can spill over the levee, forming small flows around the margin of the perched pond. Courtesy of HVO.

At the beginning of April 2018 the episode 61g lava flow was active only above the Pulama pali. The areas of the upper flow field with active lava flows were located within the Kahauale?a Natural Area Reserve, which has been closed to the public since 2007 due to volcanic hazards. On 13 April 2018, geologists observed scattered breakouts from the 61g flow within about 2.2 km from Pu'u 'O'o and another sluggish breakout about 5 km from Pu'u 'O'o (figure 323).

Figure (see Caption) Figure 323. An HVO geologist photographed an active pahoehoe breakout on 13 April 2018 at Kilauea after taking a lava sample nearby. This breakout was located approximately 0.4 km from the episode 61g vent. As the flow inflated, internal pressure cracked the rigid crust of the flow allowing molten lava to ooze out. Courtesy of HVO.

Activity during 17-30 April 2018. Beginning in mid-April 2018 seismometers recorded an increase in the number of small earthquakes beneath the summit and upper East Rift Zone reflecting increased pressurization. Kilauea's summit and East Rift Zone magma systems are connected, with changes at one sometimes leading to changes at the other. Tiltmeters, GPS, web cameras, and field observations, continued to record inflation at the Halema'uma'u crater, at Pu'u 'O'o, and at the upper portion of the episode 61g lava tube system. HVO noted that this inflation could lead to the opening of a new vent on or near Pu'u 'O'o that could cause a significant drop in the summit lake level.

At the Halema'uma'u crater, inflation significantly outpaced deflation for the second half of April. In the afternoon of 18 April the lake level was at 25 m below the crater floor. A lengthy episode of inflation brought the lava to within 6 m of the floor on the afternoon of 21 April. As the level continued to rise, a small overflow along the S crater rim occurred about midnight overnight on 21-22 April (figure 324). The lava lake was below the rim again the next morning but spilled out several times over the next several days to the N, S, and SW. The flows, similar to those produced during the last significant overflow event in April-May 2015, consisted of lobate sheets of shelly pahoehoe traveling as far as 375 m across the floor of Halema?uma?u. A small overflow had also occurred in October 2016.

Figure (see Caption) Figure 324. The rising summit lava lake levels first peaked overnight on 21-22 April 2018, producing small overflows onto the floor of Halema'uma'u Crater at Kilauea. The largest overflow, on the N side of the Overlook vent (shown here), reached about 80 m from the lake margin. Image taken on 22 April 2018, courtesy of HVO.

The summit lava lake spilled out of the Overlook crater rim multiple times during 22-27 April, caused by repeated inflation-deflation cycles (figures 325-327). Between overflows, the lava column receded below the crater rim. An overflight during the afternoon of 23 April showed that the overflows covered about 30% of the Halema?uma?u crater floor, approximately 16 ha. The height of the lava lake, on the floor of Halema'uma'u crater, was 79 m below the rim of the crater on 25 April. HVO estimated that only about one quarter of the floor of the crater remained uncovered by new flows as of 26 April. Summit tiltmeters continued to record an overall inflationary trend with brief periods of deflation until turning to more sustained deflation around midnight overnight on 26-27 April. A magnitude 3.2 earthquake occurred around 1308 HST on 26 April but did not cause any eruptive changes. Seismometers recorded a few small earthquakes in the upper East Rift Zone and south part of the caldera during 25-29 April.

Figure (see Caption) Figure 325. On 24 April 2018 between around 2030 and 2300, Kilauea's summit lava lake overflowed again. The large overflow spread W (to the right) from the lava lake onto the floor of Halema'uma'u around 2230 in this image. The bright (yellow-white) spot is spattering along the S margin of the lava lake. USGS photo by M. Patrick, courtesy of HVO.
Figure (see Caption) Figure 326. Beginning at approximately 0615 on 26 April 2018 a new overflow began covering about 36 hectares (90 acres) of Kilauea's Halema'uma'u crater floor with lava, continuing for about four hours and covering about two-thirds of crater floor. This was the largest overflow since the summit eruption began in 2008. In this view to the S taken later in the day, the gas plume was being produced by the lava lake in the SE crater floor (upper left). Courtesy of HVO.
Figure (see Caption) Figure 327. This thermal image (looking S) taken on 26 April 2018 at Kilauea shows the active overflows from the lava lake (upper left) onto the Halema'uma'u crater floor. View is toward the south. Courtesy of HVO.

The summit lake level dropped 16 m during 27-28 April, ending the period of inflation that produced the overflows onto the crater floor. The lake level remained about 15 m below the floor when skies cleared on 30 April and permitted a view from the webcam (figure 328). Slight inflation returned later in the day and the lake level rose to just beneath the vent rim.

Figure (see Caption) Figure 328. A break in the weather on the morning of 30 April 2018 allowed HVO's webcam to capture this image of the lava lake within Halema'uma'u at the summit of Kilauea. Following multiple overflows of the lava lake the previous week, the lake level dropped after summit deflation. Early that morning, the lava lake level was estimated to be about 15 m below the vent rim, but shortly thereafter, the summit switched to inflation, and the lake level rose to just below the vent rim. Courtesy of HVO.

HVO released a Volcanic Activity Notice, in addition to their regular daily report, midday on 17 April 2018. They noted that observations and measurements at Pu'u 'O'o during the previous month suggested that the magma system had become increasingly pressurized, raising the possibility that a new vent could form at any time, either on the Pu'u 'O'o cone or along adjacent areas. Since mid-March there had been uplift of the Pu'u 'O'o crater floor by several meters. Similar episodes of inflation and uplift at Pu'u 'O'o occurred in May-June 2014, prior to the start of the June 27th flow (active 2014-2016) and May 2016 before the start of the ongoing episode 61g flow.

When measured during a site visit on 18 April the pond level in the west pit at Pu'u 'O'o was 7 m higher than it had been in late March as a result of lava overflows building up the surrounding levee. An overflight on 23 April showed the perched lava pond with overflows slowly filling the pit (figure 329), and significant cracks on the NE part of the crater rim (figure 330). The pond had another overflow that remained in the pit on 24 April, and the floor continued to rise. Inflationary tilt continued at Pu'u 'O'o until it leveled off around midnight during 26-27 April, but the crater floor continued to rise for the next four days.

Figure (see Caption) Figure 329. On the East Rift Zone of Kilauea, the perched lava pond in Pu'u 'O'o's west pit persisted during the second half of April, seen here on 23 April 2018. Overflows of the pond levees were slowly filling the bottom of the west pit and raising the floor. Courtesy of HVO.
Figure (see Caption) Figure 330. Ongoing uplift of the crater floor of Pu'u 'O'o at Kilauea beginning in mid-March 2018 generated numerous cracks on the crater floor and around the rim. These cracks cut through both recent lava flows (darker color) and older flows on the crater floor. Image taken on 23 April 2018, courtesy of HVO.

Just after 1400 on 30 April 2018, a marked increase in seismicity and ground deformation began at Pu'u 'O'o. A few minutes later, a thermal webcam (PTcam) located on the crater rim showed the first of two episodes of floor collapse; the second collapse began at 1520 and lasted about an hour. Webcam views into the crater and surrounding area were frequently obscured by poor weather conditions. However, shortly after 1600 the PTcam recorded images that were likely the signature of small explosions from the western side of the crater as the floor collapsed.

Following the collapse there was an increase in seismicity and deformation from the summit to an area about 10-16 km downrift (east) of Pu'u 'O'o. Overnight, this activity continued to propagate eastward along the rift zone. The largest earthquake of this sequence was a magnitude 4.0 just offshore south of Pu'u 'O'o at 0239 on the morning of 1 May. HVO field crews were turned back the next morning by ash in the air above Pu'u 'O'o, likely due to continuing collapse within the crater and vigorous gas emissions. Reddish ash was also noted in abundance on the ground around Pu'u 'O'o.

Lava flow activity in the episode 61g flow continued on the upper flow field through the end of April 2018. Activity was focused above the pali and closer to Pu'u 'O'o, within 2 km of the vent. After the explosion and collapse of the crater floor at Pu'u 'O'o on 30 April, a large amount of red ash was deposited around the cone and covered over some of the active breakouts of the 61g flow (figure 331).

Figure (see Caption) Figure 331. The collapse of the Pu'u 'O'o crater floor at Kilauea on 30 April 2018 produced a large amount of red ash that was deposited around Pu'u 'O'o, as well as blown farther downwind, with a thin dusting of ash reaching uprift (west) as far as Mauna Ulu. On 1 May 2018, a layer of red ash covered active 61g lava flow surface breakouts in an area between 1-2 km from the 61g vent. Courtesy of HVO.

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/).


San Cristobal (Nicaragua) — June 2018 Citation iconCite this Report

San Cristobal

Nicaragua

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

All times are local (unless otherwise noted)


Moderate explosion on 22 April 2018

Activity at the San Cristobal volcano complex during 2017 was characterized by numerous weak ash-and-gas explosions, a succession of strong ash-and-gas explosion on 18 August, and thousands of degassing events (BGVN 43:03). This report covers January through July 2018.

According to the Instituto Nicaragüense de Estudios Territoriales (INETER), at 1320 on 22 April a moderate explosion generated an ash-and-gas plume that rose 500-800 m (figure 38), causing ashfall in the Comarca La Bolsa (8 km SW) and Hacienda Las Rojas (3 km WSW) and Loma Las Brujas (2 km W).

Figure (see Caption) Figure 38. Photo of the gas-and-ash explosion at San Cristobal on 22 April 2018.  Courtesy of Fausto Tijerino, INETER (Boletín mensual, Sismos y Volcanes de Nicaragua, Abril, 2018).

INETER's April bulletin reported that the monthly averages of sulfur dioxide levels at San Cristobal during January through March 2018 ranged from 305-449 metric tons per day. On 22 April, the day of the explosion, levels reached 1903 tons. During the reporting period, MODIS satellite instruments using the MODVOLC algorithm recorded only two questionable thermal anomalies at San Cristobal. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, recorded numerous hotspots, but only one within 5 km of the volcano during January through July 2018. The latter one occurred during late March.

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://webserver2.ineter.gob.ni/vol/dep-vol.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/).


San Miguel (El Salvador) — June 2018 Citation iconCite this Report

San Miguel

El Salvador

13.434°N, 88.269°W; summit elev. 2130 m

All times are local (unless otherwise noted)


Intermittent small ash emissions between 14 January and 30 May 2018

El Salvador's San Miguel, also known as Chaparrastique, had six small ash emission events during January 2015-June 2017 (BGVN 42:07). New activity consisting of intermittent ash emissions began on 14 January and continued until 30 May 2018, reported below based on information provided by El Salvador's Servicio Nacional de Estudios Territoriales (SNET) and special reports from the Ministero de Medio Ambiente y Recursos Naturales (MARN).

SNET and MARN reported that during 14-17 January 2018 there were four gas-and-ash emissions from San Miguel that rose no higher than 300 m above the crater rim, at least one of which dispersed SW. The reports noted that prior to each emission seismicity decreased and then suddenly increased. MARN reported that during 25-26 January seismic tremor levels fluctuated between 75 and 179 RSAM (Real-time Seismic Amplitude Measurement) units per hour on average, slightly above normal (50-150 units).

On 19 February, MARN reported the beginning of sustained gas emissions along with small ash emissions. The plume did not exceed 350 m above and was displaced by winds to the SW. This activity was similar to the activity on 14-15 January 2018.

SNET reported on 2 March that gas plumes rose as high as 400 m above the crater rim during the previous week. Ash appeared in "gas pulse" emissions on 24, 26, and 28 February, and 1 March. RSAM values fluctuated between 70 and 179 units during 1-2 March. At 2200 on 5 March seismic amplitude began to increase, with RSAM values rising to as high as 318 units by 0600 on 6 March. A webcam recorded minor gas emission during 5-6 March. MARN reported that RSAM values fluctuated between 68 and 248 units, with an average of 156 during 8-9 March. Continued volcanic tremor during 9-16 March was noted, along with persistent low-level degassing from the central crater. Volcanic tremor levels during 15-16 March fluctuated between 77 and 203 RSAM units per hour, with an average of 124.

By early April, MARN had noted a decrease in activity. On 3 April it reported that RSAM levels varied between 46 and 87 units, with an average of 55. Activity increased briefly during 7-13 April, and MARN reported that periodic microseisms combined with changes in seismic tremor and gas pulses had increased significantly, reaching maximum values of 400 RSAM units in an average hour (figure 25).

Figure (see Caption) Figure 25. RSAM values at San Miguel during 7-13 April 2018. Courtesy of Ministero de Medio Ambiente y Recursos Naturales (MARN).

Discrete earthquakes were detected between 13 and 17 April, and discontinuous volcanic tremor during 17-18 April was associated with weak, sporadic degassing from the central crater. Seismicity reached maximum values of 216 RSAM units in an average hour.

MARN reported that during 20-27 April volcanic tremor fluctuated between 37 and 106 RSAM units per average hour. Seismicity was low during 28 April-4 May, with RSAM between 39 and 61 units per hour.

In May MARN reported that the volcanic activity had declined compared to April. As of 18 May there was no change in volcanic activity, despite the seismic swarm that started on the night of 5 May felt in the municipalities of Chirilagua-Intipucá, 30 km SE. Average SO2 emission rates were variable during 1 January-6 May 2018 (figure 26).

Figure (see Caption) Figure 26. Sulfur dioxide emissions at San Miguel between from 1 January-6 May 2018. Courtesy of Ministero de Medio Ambiente y Recursos Naturales (MARN).

SNET reported a significant increase in the number of low- and high-frequency earthquakes beneath the crater beginning on 22 May. RSAM values fluctuated between 142 and 176 units during 30 May-1 June. Webcam images on 30 May showed a small gray gas emission.

Geologic Background. The symmetrical cone of San Miguel volcano, one of the most active in El Salvador, rises from near sea level to form one of the country's most prominent landmarks. The unvegetated summit rises above slopes draped with coffee plantations. A broad, deep crater complex that has been frequently modified by historical eruptions (recorded since the early 16th century) caps the truncated summit, also known locally as Chaparrastique. Radial fissures on the flanks of the basaltic-andesitic volcano have fed a series of historical lava flows, including several erupted during the 17th-19th centuries that reached beyond the base of the volcano on the N, NE, and SE sides. The SE-flank flows are the largest and form broad, sparsely vegetated lava fields crossed by highways and a railroad skirting the base of the volcano. The location of flank vents has migrated higher on the edifice during historical time, and the most recent activity has consisted of minor ash eruptions from the summit crater.

Information Contacts: Servicio Nacional de Estudios Territoriales (SNET), Ministero de Medio Ambiente y Recursos Naturales (MARN), Km. 5½ Carretera a Nueva San Salvador, Avenida las Mercedes, San Salvador, El Salvador (URL: http://www.snet.gob.sv/ver/vulcanologia, http://www.marn.gob.sv/category/avisos/vulcanologia/).


Kirishimayama (Japan) — June 2018 Citation iconCite this Report

Kirishimayama

Japan

31.934°N, 130.862°E; summit elev. 1700 m

All times are local (unless otherwise noted)


Ash plumes and lava flows at Shinmoedake starting in March 2018; explosion at Iwo-yama

Kirishimayama is a large group of more than 20 Quaternary volcanoes located N of Kagoshima Bay, Japan (figure 22). For the last 1,000 years, repeated eruptions have taken place at two locations in the complex: the Ohachi crater on the W flank of the Takachihomine stratovolcano, and the Shinmoedake stratovolcano 4 km NW of Ohachi. A single eruption was reported in 1768 from the Iwo-yama (Ebino Kogen) dome located on the NW flank of the Karakunidake stratovolcano, about 5 km NW of Shinmoedake.

Figure (see Caption) Figure 22. Subfeatures of the Kirishimayama volcanic complex showing the three areas with activity discussed in this report: Ohachi, Shinmoedake, and Iwo-yama (Ebino Kogen). View is to the SE. Image taken by the Japan Maritime Self Defense Force on 7 October 2014. Courtesy of JMA (Volcanic activity report on Kirishimayama, October, Heisei 26 [2014]).

The last confirmed eruption at the Ohachi crater was in July 1923. Intermittent steam plumes have been observed since then, including in December 2003 (BGVN 33:09), but the Japan Meteorological Agency (JMA) noted that it had been quiet since 1 December 2007. Shinmoedake has been the site of several short-lived eruptive events since 2008. Most of the events were single-day explosions with ash emissions (BGVN 35:12). A more protracted event from January to September 2011 included numerous explosions with ash plumes, which produced ashfall tens of kilometers away, the growth of a lava dome, ejecta of large blocks, and small pyroclastic flows (BGVN 36:07). Shinmoedake remained quiet until seismicity increased on 23 September 2017, followed by several explosions during October 2017 (BGVN 43:01). Seismic unrest was first reported from the area around Iwo-yama in December 2013, and it has been regularly monitored since that time. This report covers activity from November 2017 through May 2018 and includes new explosive events at Shinmoedake during March-May 2018, an explosive event at Iwo-yama in April 2018, and a brief increase in seismicity at Ohachi in February 2018. Information is provided primarily by the JMA and the Tokyo Volcanic Ash Advisory Center (VAAC), with additional satellite data and news media reports.

Summary of activity during November 2017-May 2018. After steam plumes disappeared at Ohachi in mid-2006, only minor intermittent seismicity was reported through 2017. A sudden increase in earthquakes and tremor activity on 9 February 2018 led JMA to raise the 5-level Alert Level system from 1 (potential for increased activity) to 2 (do not approach the crater) for about a month. Activity diminished after the middle of February and Ohachi remained quiet through May 2018, with only a continuing modest thermal anomaly at the crater.

The latest eruptive episode at Shinmoedake, during 11-17 October 2017, generated an SO2 plume recorded by NASA satellites, caused ashfall up to 100 km away, and created a new vent about 80 m in diameter on the E side of the crater. Intermittent earthquakes and tremors along with low-level steam plumes characterized activity during November 2017-February 2018. A new eruptive episode began on 1 March 2018 with near-constant explosive activity that lasted until 10 March. A new lava flow at the summit was first observed by JMA on 6 March and began to overflow the NW rim of the crater on 9 March. The Tokyo VAAC reported ash plumes over 6 km altitude on 10 March. An explosion on 5 April produced the largest ash plume of the period; it rose to 10.1 km altitude, was visible drifting E for 24 hours, and resulted in significant ashfall in the region. The lava flow had ceased advancing down the NW flank by the end of April. Another explosion on 14 May 2018 generated an ash plume that rose to 7.3 km altitude and caused ashfall 30 km S that covered the roadways.

An increase in seismicity at Iwo-yama in December 2013, followed by a 7-minute-period of tremor activity in August 2014 was the first recorded at the site since 1768. Thermal anomalies and weak fumarolic activity first appeared in December 2015. Seismicity, including intermittent tremor events and larger amplitude earthquakes, gradually increased during 2016 and 2017. Intermittent fumarolic activity and temperature anomalies began to increase measurably in mid-2017. Jets of sediment-laden hot water emerged from several vents early in 2017. A further increase in fumarolic activity and the temperature of the thermal anomalies in February 2018 led JMA to raise the Alert Level at Iwo-yama. Large amplitude earthquakes and a tremor event accompanied an ash-bearing explosion on 19 April 2018 from a vent on the S side of Iwo-yama. The following day, a vent opened 500 m to the W and produced vigorous steam emissions. On 26 April 2018 an explosion from the new vent sent ash 200 m high. Jets of hot water continued at the Iwo-yama vents through May 2018.

Activity at Ohachi during 2003-2018. JMA reported tremor activity with epicenters near Ohachi in mid-December 2003 (BGVN 33:09) that was followed by fumarolic activity for a few weeks. Intermittent steam plumes were observed during 2004; on 26 March 2004 a tremor event lasted for four hours and a steam plume rose 800 m above the crater (figure 23). A few periods of microtremor were recorded, and intermittent fumarolic activity was observed with webcams until March 2006, after which most activity ceased. JMA lowered the 5-level Alert Level from 2 (Do not approach the crater) to 1 (Potential for increased activity) on 22 May 2006. Fumarolic activity was not observed after July 2006, and no new thermal activity was reported during a field visit in October 2006. Minor seismicity was reported for a few days during July 2007, and small-amplitude, short-duration tremor activity was occasionally recorded during 2008-2014.

Figure (see Caption) Figure 23. Steam plumes were visible on the NW side of the Ohachi crater at Kirishimayama on 31 March 2004. Courtesy of JMA (JMA Kirishimayama annual report, Heisei 16 (2004)).

Although earthquake activity increased slightly in July 2015, the warning level was not raised, and no surface fumarolic activity was observed during field visits in August and September 2015 (figure 24). Seismic activity remained elevated at Ohachi through February 2016 and then gradually decreased during March. Although tremors were recorded in May and December 2016, there was no change in condition at the site and seismicity continued to decrease; no tremors were recorded during 2017.

Figure (see Caption) Figure 24. No fumarolic activity was visible at the Ohachi crater at Kirishimayama on 18 September 2015 during a site visit. View is to the NW. Courtesy of JMA (JMA Kirishimayama annual report, Heisei 27 (2015)).

Earthquake frequency on the SW side of Ohachi increased during 9-16 February 2018, resulting in 199 seismic events, and tremor activity was also recorded on 9 February. This activity led JMA to increase the Alert Level to 2 on 9 February 2018. In spite of the increased seismic activity, the thermal activity remained unchanged from previous months with continued minor thermal anomalies in the same areas as before (figure 25). Seismicity decreased significantly during March 2018 to only 13 volcanic earthquakes, and no microtremor activity was recorded. Inspections carried out on 11 and 14 March showed no surface changes (figure 26) and resulted in JMA lowering the Alert Level back to 1 on 15 March 2018. Ohachi remained quiet through May 2018.

Figure (see Caption) Figure 25. Thermal anomalies at the Ohachi crater of Kirishimayama were unchanged compared with previous months when measured on 9 February 2018 in this view to the NW. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, February, Heisei 30 (2018)).
Figure (see Caption) Figure 26. An overview looking W of the Ohachi crater at Kirishimayama on 2 March 2018 showed no surface activity after the increased seismicity of February. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, March, Heisei 30 (2018)).

Activity at Shinmoedake during August 2008-October 2017. An explosion on 22 August 2008 lasted for about six hours and produced ashfall in Kobayashi City (10 km NE) (BGVN 33:09). Seismicity had increased rapidly a few days prior to the explosion, and then decreased gradually for the remainder of 2008. Other than a brief increase in seismicity in May the following year, only steam plumes rising about 100 m from the crater were reported for 2009.

Seven small ash-bearing explosive events were reported during March-July 2010. Small-amplitude tremor activity on 30 March 2010 was accompanied by a plume that rose 400 m above the crater rim; a small amount of ash fell 400 m to the W of the fumarole within the crater. The webcam on the S rim of the crater captured a grayish plume rising 300 m after a small explosion on 17 April 2010. Another small explosion on 27 May produced a grayish-white plume that rose 100 m above the crater rim and resulted in minor ashfall NE in Kobayashi City. Officials noted a new fumarole on the W flank after this event. Two more explosions on 27 and 28 June 2010 resulted in a small amount of ash deposited 10 km E of Shinmoedake. A small explosion was reported on 5 July. On 10 July, a grayish-white plume, observed in the webcam, rose 100 m above the crater rim after an explosion, and a small low-temperature pyroclastic surge flowed 300 m down the SW slope. GPS instruments recorded minor inflation from December 2009 through September 2010.

A new, more substantial, eruption began at Shinmoedake on 19 January 2011. Activity increased on 26 January with an explosion that released a large volume of ash and pumice and included the growth of a new lava dome (BGVN 35:12, 36:07). Thirteen additional explosions occurred through 1 March 2011. Activity became more intermittent after mid-February, and the last emission was reported on 7 September 2011. Seismicity declined significantly in March 2012 and had returned to background levels by May 2012. With no surface changes and very low seismicity, JMA reduced the Alert Level from 3 to 2 on 22 October 2013, and the only reported activity was steam plumes rising 50-200 m above the crater rim during 2013. The lava dome in the crater remained about 600 m in diameter. Inflation had slowed and stopped after December 2011 but began again around December 2013. Shallow, low-level seismicity during 2014 with epicenters near Shinmoedake was distributed within a few kilometers below the summit; there were no surface changes observed at the crater during several overflights conducted by the Japan Maritime Self Defense Force throughout the year.

Occasional steam plumes rising 400 m above the crater rim were reported during 2015. Volcanic earthquakes were intermittent, with brief increases in activity during March-May and October- December with roughly the same number as the previous year. Inflationary deformation that began around December 2013 ceased in January 2015. A very brief tremor on 1 March 2015 was the first recorded since 1 February 2012. During 2016, occasional steam plumes rose 300 m above the crater. In spite of a seismic swarm on 23 February 2016, and a general increase in seismicity throughout the year, no eruptions occurred, and no surface changes were observed. JMA kept the Alert Level at 2 throughout the year. A small tremor event on 17 September was the only recorded during 2016. Very little activity was reported from January to September 2017; occasional steam plumes were reported rising 400 m above the crater rim. JMA lowered the Alert Level from 2 to 1 on 26 May 2017.

A minor increase in seismicity was observed beginning in July 2017, and was followed by a marked increase on 23 September. After a further increase in frequency and amplitude of earthquakes on 4 October, JMA raised the Alert Level to 2 for Shinmoedake on 5 October 2017. This was followed by an eruption that began on 11 October 2017. A new vent was observed on the E side of the crater during an overflight that same day, and ashfall was reported in numerous communities as far as 90 km NE (BGVN 43:01). A significant SO2 plume was measured by the OMI instrument on the Aura satellite the following day (figure 27). After raising the Alert Level to 3 on 11 October, JMA expanded the restricted area radius from 2-3 km during 15-31 October.

Figure (see Caption) Figure 27. A significant SO2 plume from the explosion at the Shinmoedake crater of Kirishimayama was measured on 12 October 2017 by NASA's OMI instrument on the Aura satellite. Courtesy of NASA Goddard Space Flight Center.

Explosions on 14 October 2017 resulted in confirmed ashfall in Kagoshima city (50 km SW), Takahara Town (15 km E), Kobayashi city (25 km NE), Saito city (55 km NE), Hyuga city (90 km NE), and Misato town (75 km NE). Ongoing explosions continued until 17 October, after which persistent steam plumes were observed rising as high as 600 m above the crater. In an overflight conducted on 23 October JMA scientists noted the new vent was about 80 m in diameter, and ejecta from the vent had formed a small cone around the vent. (figure 28).

Figure (see Caption) Figure 28. Two vents were visible on the E side of the crater in this view to the WNW taken on 23 October 2017 of Shinmoedake crater at Kirishimayama. The left vent (center front) had formed during the 2011 eruption, and the right vent formed during the 11-17 October 2017 eruption earlier in the month. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, October, Heisei 29 (2017)).

Activity at Shinmoedake during November 2017-March 2018. After the eruption of 11-17 October 2017 seismicity decreased significantly, and no morphological changes were observed for the remainder of the year. Steam plumes rose 300-500 m above the crater during November and December. Short-duration tremors were detected during 25-29 November, along with a slight increase in the number of volcanic earthquakes. A small earthquake swarm recorded during 2-4 December was the only significant seismic activity that month.

Infrequent, large-amplitude earthquakes were recorded during 15-17 January 2018, along with a few short-duration tremor events, the first since 29 November 2017. The earthquakes were located within a 1 km radius of Shinmoedake, around 2-4 km deep. Steam plumes at the crater rose no more than 100 m most days; occasional plumes rising as high as 200 m were noted. An earthquake swarm on 25 February was the first notable event of the month; the steam plumes remained under 100 m above the crater, except for a 500-m-high plume on 21 February. Thermal imaging surveys in late February indicated a modest increase in heat flow from fractures inside the crater and on the W slope compared with previous measurements.

Earthquakes with shallow epicenters below Shinmoedake increased in number early on 1 March 2018 and a new eruptive episode followed a few hours later, leading JMA to increase the restricted zone to 3 km around the crater (figure 29). SO2 emissions also increased sharply. By the afternoon of 1 March an ash plume rose 1,500 m above the crater, emerging from the vent on the E side and drifting SE. Ashfall was confirmed on 1 March in the area up to 18 km E of the crater. Large blocks of ejecta were observed within the crater on 5 March.

Figure (see Caption) Figure 29. A new eruptive episode at the Shinmoedake crater of Kirishimayama began around 1100 on 1 March 2018 with ash emissions emerging from the new vent on the E side of the crater. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, February, Heisei 30 (2018)).

During an overflight on 6 March 2018, JMA witnessed a new lava flow covering a large area on the E side of the crater floor (figure 30). Eighteen explosive eruptions occurred on 6 March and JMA reported that the ash plume rose 2,800 m above the crater (figure 31). Ashfall was confirmed SW of Shinmoedake in Shibushi city (50 km SSE), Tarumizu City (50 km SSW) and Aira City (30 km SW). NASA 's Aqua satellite captured a false color image of the eruption on 6 March showing the ash plume drifting SE and SW from Shinmoedake (figure 32). About 80 flights in and out of nearby Kagoshima airport were canceled.

Figure (see Caption) Figure 30. Lava emerged from the new vent on the E side of the Shinmoedake crater at Kirishimayama on 6 March 2018 in this view to the W. Plumes of both ash and steam rose from the center and N sides of the crater. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, February, Heisei 30 (2018)).
Figure (see Caption) Figure 31. Ash and steam rose from newly emergent lava inside the summit crater of Shinmoedake at Kirishimayama on 6 March 2018, and disrupted air traffic for most of the day. Courtesy of Kyodo News via AP.
Figure (see Caption) Figure 32. NASA 's Aqua satellite captured a false color image of the eruption from Shinmoedake crater at Kirishimayama on 6 March 2018 with an ash plume drifting SE and SW. Courtesy of NASA Earth Observatory.

Tremor events occurred continuously over 1-8 March; forty-seven explosions were recorded between 6 and 8 March; they decreased in frequency after the middle of the month. The OMI instrument on the NASA Aura satellite recorded a significant SO2 plume on 7 March 2018 (figure 33). Geospatial data that had shown a gradual inflation of the Kirishimayama complex since July 2017 showed a sharp deflation during 6-7 March 2018, after which inflation resumed.

Figure (see Caption) Figure 33. An SO2 plume with a density of almost ten Dobson Units (DU) was recorded by the OMI instrument on the Aura satellite on 7 March 2018. Courtesy of NASA Goddard Space Flight Institute.

During an overflight on 9 March 2018, a staff member from the Geographical Survey Institute observed the lava flow beginning to overflow the NW side of the crater (figure 34). Explosions resulted in ejecta traveling 800 m from the crater on 9 March and an ash plume rising 3,200 m. An increase in the intensity of activity the following day sent ejecta 1,800 m from the vent and generated an ash plume that rose 4,500 m (figure 35); this led JMA to increase the restricted area around the crater to 4 km between 10 and 15 March.

Figure (see Caption) Figure 34. The new lava flow began to overtop the NW side of Shinmoedake crater (left side of crater with steam) at Kirishimayama on 9 March 2018. Photographed by a staff member from the Geographical Survey Institute during a helicopter overflight by the Kyushu Regional Development Bureau. Courtesy of the Geographical Survey Institute (Correspondence on the eruption of Kirishimayama (Shinmoedake) in Heisei 30 (2018), 29 March 2018).
Figure (see Caption) Figure 35. An increase in explosive activity at the Shinmoedake crater of Kirishimayama on 10 March 2018 sent an ash plume 4,500 m above the crater (left), and incandescent ejecta 1,800 m from the vent (right). Courtesy of JMA (Volcanic activity commentary on Kirishimayama, March, Heisei 30 (2018)).

A thermal image taken on 11 March showed that the lava was moving very slowly down the NW flank, advancing only a few tens of meters since 9 March (figure 36). JMA confirmed during an overflight on 14 March that the lava flowing down the NW flank was about 200 m wide. Two explosions on 25 March produced plumes that rose 3,200 and 2,100 m, ejecta that traveled 800 m, and a small pyroclastic flow that advanced about 400 m down the W flank (figure 37). Although analysis of satellite data by Japan's Geographical Survey Institute suggested that the eruption of lava into the crater had ceased by 9 March, it continued to flow slowly down the NW flank for several weeks. The diameter of the flow inside the crater was about 700 m, and it had traveled about 85 m down the NW flank by 28 March (figure 38).

Figure (see Caption) Figure 36. A thermal image taken on 11 March 2018 of the new lava flow in the Shinmoedake crater at Kirishimayama showed the slow movement of the flow over the NW rim and down the flank a few tens of meters in two days. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, March, Heisei 30 (2018)).
Figure (see Caption) Figure 37. Two explosions on 25 March 2018 from Shinmoedake crater at Kirishimayama produced plumes that rose 3,200 and 2,100 m, ejecta that traveled 800 m, and a small pyroclastic flow that advanced about 400 m down the W flank (foreground). Courtesy of JMA (Volcanic activity commentary on Kirishimayama, March, Heisei 30 (2018)).
Figure (see Caption) Figure 38. Lava was still slowly moving down the NW flank of the Shinmoedake crater at Kirishimayama on 26 March 2018, and gray ash covered much of the adjacent flank, possibly from a pyroclastic flow the previous day. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, March, Heisei 30 (2018)).

The Tokyo VAAC issued multiple daily reports from 1-15 March 2018, and a few intermittent reports during the rest of the month. JMA usually reports plume heights in meters above the crater and the Tokyo VAAC reports them as altitudes above sea level; conversions are noted where the height or altitude of a plume is exceptional. They reported an ash plume drifting SE on 1 March at 1.5 km altitude; the plume had risen to 2.4 km by the end of the day. The following day a plume was visible in satellite images at 2.1 km altitude drifting E. Continuous emissions drifting NE above 2.4 km altitude were reported on 3 and 4 March. Several explosions generated plumes that were visible in satellite imagery during 5-7 March drifting S, SW, and W at altitudes between 3.0 and 4.6 km. Plumes from larger explosions during 9 and 10 March rose to altitudes between 4.3 and 6.1 km and drifted SE, finally dissipating after about 24 hours. Explosions on 12 and 13 March drifted NE and E at 3.4-4.9 km altitude, with continuous emissions visible in satellite imagery during those days. Two explosions on 24 March produced plumes that drifted SE at 3.7 and 4.9 km altitude, and were visible in satellite imagery until they dissipated the next day.

A strong MIROVA thermal anomaly signal appeared at the beginning of March and slowly tapered off into April. The signal is consistent with the reports of the eruption of lava from the summit of Shinmoedake and its gradual cooling (figure 39). The MODVOLC thermal alert signals also closely match the reports of the eruption of the lava. The first six alerts were issued on 6 March, four each on 9 and 10 March, three each on 11 and 12 March, and one each on 13, 14, 16, 23, and 30 March, matching a gradual cooling pattern for the lava after the main eruptive event.

Figure (see Caption) Figure 39. A strong MIROVA thermal anomaly signal appeared at Kirishimayama at the beginning of March and slowly tapered off into April 2018. The signal is consistent with the reports of the eruption of lava from the summit of Shinmoedake, and its gradual cooling. A thermal image of the lava flow at Shinmoedake from 28 March 2018 (inset) shows significant cooling from two weeks earlier (see figure 36). Courtesy of MIROVA and JMA (Volcanic activity commentary on Kirishimayama, March, Heisei 30 (2018)).

Activity at Shinmoedake during April and May 2018. A new explosion on 5 April 2018 generated a large ash plume that rose 5,000 m above the crater; a small pyroclastic flow traveled 400 m down the SE flank, and ejecta was thrown 1,100 m from the vent (figure 40). The Tokyo VAAC reported an explosion, and an ash plume at 6.7 km altitude drifting E visible in satellite imagery early in the day. A few hours later, the plume was visible at 10.1 km altitude, or more than 8,000 m above the crater. Incandescent tephra was ejected hundreds of meters high, and lightning was observed within the large ash plume (figures 41 and 42). The plume was observed continuously in satellite images for almost 24 hours before dissipating; a significant SO2 plume was also recorded (figure 43).

Figure (see Caption) Figure 40. Ejecta was thrown 1,100 m from the vent in an explosion at the Shinmoedake crater of Kirishimayma on 5 April 2018 (farthest right incandescence). A large ash plume (to the right of the main incandescence) eventually rose to over 8,000 m above the crater. View is to the N from the Inogishi webcam. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, April, Heisei 30 (2018)).
Figure (see Caption) Figure 41. An explosion on 5 April 2018 from the Shinmoedake crater at Kirishimayama sent incandescent ejecta several hundred meters above the crater. Courtesy of Kyodo News via Reuters.
Figure (see Caption) Figure 42. Significant lightning was reported in the large ash plume from the 5 April 2018 explosion at the Shinmoedake summit crater at Kirishimayama. Courtesy of Kyodo News via Reuters.
Figure (see Caption) Figure 43. The OMPS instrument on the Suomi NPP satellite recorded an SO2 plume drifting SE after the 5 April 2018 explosion at the Shinmoedake crater of Kirishimayama. Courtesy of NASA Goddard Space Flight Center.

A large amount of ashfall was reported in parts of Kobayashi city and Takaharu (15 km E) (figures 44 and 45) on 5 April 2018. Ashfall reports also indicated that a wide area to the N of Shinmoedake including Hitoyoshi City (30 km N), to the NE including Kadogawa Town (95 km NE), and to the E including Miyazaki City (50 km E) were also affected. Another eruption took place the following day, on 6 April, but weather clouds obscured views of the summit. No eruptions were recorded after 6 April for the remainder of the month.

Figure (see Caption) Figure 44. Ashfall was measured and sampled on 5 April 2018 in Kobayashi City (25 km NE) after an explosion with a large ash plume rose from the Shinmoedake crater at Kirishimayama. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, March, Heisei 30 (2018)).
Figure (see Caption) Figure 45. Ashfall covered major roadways and buildings in Takaharu, 15 km E of Kirishimayama, after an explosion from the Shinmoedake crater on 5 April 2018. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, March, Heisei 30 (2018)).

In multiple flyovers, on 19, 20, and 21 April 2018, authorities observed lava continuing to flow down the NW flank (figure 46), along with residual high temperatures in the central part of the lava flow (figure 47). Additionally, fumarolic areas around the fractures on the W slope persisted. By the end of April, the flow on the NW flank of the crater was 150 m long. Seismicity had declined at the end of March, but increased again during the explosive period in early April. Occasional tremors were recorded during 5-14 April. Intermittent spikes of around 100 small earthquakes were also recorded on 14 and 21 April.

Figure (see Caption) Figure 46. The lava flow down the NW flank of Shinmoedake crater at Kirishimayama was nearly stagnant by 21 April 2018, as seen in this view to the SW taken that same day by the Miyazaki Prefecture Disaster Preparedness Emergency Air Corps. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, April, Heisei 30 (2018)).
Figure (see Caption) Figure 47. Residual high heat flow was still visible near the center of the Shinmoedake crater of Kirishimayama on 21 April 2018 but the lava flow had cooled significantly since March (compare with figure 36). Courtesy of JMA (Volcanic activity commentary on Kirishimayama, April, Heisei 30 (2018)).

Another spike in earthquakes with epicenters within 2 km of Shinmoedake occurred on 2 May 2018 with over 700 events recorded. A substantial explosion on 14 May generated an ash plume that rose 4.5 km above the crater according JMA (figure 48). The Tokyo VAAC reported the ash plume initially at 4.9 km altitude drifting SE based on webcam reports; when the plume appeared in satellite data a short time later it was drifting SE at 7.3 km altitude and was continuously visible in satellite imagery for about 24 hours before dissipating. Ashfall was confirmed in numerous areas of the Miyazaki prefecture to the E, and the Kagoshima prefecture to the S and W. Seismicity increased briefly after the explosion. Enough ash fell in Miyakonojo City (30 km S) that it covered the white lines on the roadways (figure 49). A thermal image taken on 15 May showed a new high-heat flow area on the E side of the new lava flow inside the crater that JMA concluded was likely the result of the explosive event of the previous day (figure 50).

Figure (see Caption) Figure 48. A large explosion at the Shinmoedake crater of Kirishimayama on 14 May 2018 sent an ash plume to 4,500 m above the crater as seen in this view to the NE from the Inogishi webcam. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, May, Heisei 30 (2018)).
Figure (see Caption) Figure 49. Enough ash fell in Miyakonojo City (30 km S) after an explosion at Shinmoedake crater of Kirishimayama on 14 May 2018, that it covered the white lines on the roadways. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, May, Heisei 30 (2018)).
Figure (see Caption) Figure 50. The thermal signature at Shinmoedake crater at Kirishimayama on 15 May 2018 revealed a high-heat flow area that JMA concluded likely resulted from the explosion the previous day. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, May, Heisei 30 (2018)).

Activity at Iwo-yama during 2014-2017. An increase in seismicity around Iwo-yama, on the NW flank of the Karakunidake stratovolcano (figure 22) beginning in December 2013 was noted by JMA. The epicenters were distributed from 1-6 km below Iwo-yama. Satellite measurements suggested minor inflation in the area around Karakunidake beginning in December 2013, which lasted until January 2015. A 7-minute-long tremor event occurred near Iwo-yama on 20 August 2014. Although inspections of the area by JMA revealed no thermal or fumarolic activity, they listed the Iwo-yama area with an unofficial Alert Level of "Danger around the crater" on 24 October 2014, equivalent to the official Alert Level 2. They modified the warning during May 2015 to "Normal, keep in mind, it is an active volcano," the same as the official Alert Level 1. During the second half of 2015 there were occasional earthquakes and tremors reported in the area, but no surface or thermal activity was recorded (figure 51) until December. Thermal anomalies appeared in the area for the first time during the first week of December 2015; weak fumarolic activity accompanied by H2S odors were first reported during 15-17 December 2015 on the SW side of the Iwo-yama crater (figure 52).

Figure (see Caption) Figure 51. No surface activity, and very little thermal activity was present at the Iwo-yama (Ebino Kogen) area of Kirishimayama on 2 November 2015. View is to the N, taken from the N flank of Karakunidake. Courtesy of JMA (JMA Kirishimayama annual report, Heisei 27 (2015)).
Figure (see Caption) Figure 52. Steam plumes and a thermal anomaly at the Iwo-yama area of Kirishimayama first appeared during December 2015 (images from 28 December 2015, view to the S). Courtesy of JMA (JMA Kirishimayama annual report, Heisei 27 (2015)).

Periods of intermittent microtremor activity occurred once in January, four times in February, and twice in December during 2016, with durations ranging from 40 seconds to 5 minutes. A seismic swarm on 28 February led JMA to raise the unofficial Alert Level to "danger around the crater" for the month of March (equivalent to the official Alert Level 2). A new thermal area with fumarolic activity appeared on 24 March 2016 on the SE side of the crater. Intermittent steam plumes were observed throughout 2016; the highest rose 200 m on 11 October. Thermal anomalies also persisted throughout the year on the S and SW areas of the crater. Alert Level 1 (Note that it is an active volcano) was formally assigned to Iwo-yama on 6 December 2016. The Alert Level was raised to 2 on 12 December after a seismic swarm, tremor, and the observation of inflation in the inclination data in the previous days.

Fumarolic activity decreased in January 2017 after a brief increase at the end of December 2016; JMA lowered the Alert Level back to 1 on 13 January and steam plumes generally rose only 30 m high during the month. The thermal anomalies persisted in the same areas of the SW and W portions of the crater as before, though new fumarolic activity appeared in those areas during February 2017. During March field surveys, observers identified hot water emerging from the fumaroles in the SW and S areas of the crater. The inclinometer detected inflation beginning on 25 April 2017, but it leveled off during August. An increase in the number of fumaroles in the area of the thermal anomaly at the SW side of the crater was confirmed by a JMA field inspection in late April. When the University of Tokyo Earthquake Research Institute visited the site on 8 May 2017, they observed sediment-laden water deposits that had been dispersed on the SW side within the crater, and ejecta around the SW edge. This led JMA to increase the Alert Level to 2.

Fumarolic activity increased during mid-to-late July 2017 and steam plumes were reported at 300 m above the crater for a brief period. On 27 July visitors confirmed dead and discolored plants on the NE side of the crater, and audible fumarolic activity. A new thermal anomaly zone with fumaroles was visible on the SW flank outside the crater during a site visit on 31 August. Low levels of seismicity were intermittent throughout 2017, but no tremor events were recorded. A large amplitude earthquake with its epicenter under Iwo-yama occurred on 5 September 2017; no sudden changes were observed at the site a few days later, although thermal images taken on 9 September revealed an increase in temperature from two years prior (figure 53, compared with figure 52). JMA lowered the warning level to 1 at the end of October. During November and December 2017, steam plumes generally rose 100-200 m above the crater.

Figure (see Caption) Figure 53. Steam plumes and a thermal anomaly persisted into September 2017 at the Iwo-yama crater of Kirishimayama. Emissions of the plume on the left were audible during the July visit. Compare with the lower temperatures measured in December 2015, figure 52. Image taken on 9 September 2017 from the Iwomayama South webcam on the S side of the area. Courtesy of JMA (JMA Kirishimayama annual report, Heisei 29 (2017)).

Activity at Iwo-yama during January-May 2018. An analysis of nearby hot-spring waters indicated a significant jump in Cl/SO4 ratios characteristic of high-temperature volcanic gas beginning in November 2017. The first tremor since 12 December 2016 was recorded on 19 January 2018 and coincided with a brief period of inflation in the vicinity of Iwo-yama. Regional inflation of the area had begun again in July 2017 and continued into 2018. Low-frequency, small-amplitude earthquakes were intermittent during January 2018 and steam plumes rose 100-200 m. Increases in seismicity, fumarolic activity, and the temperatures of the thermal anomalies during mid-February 2018 prompted JMA to raise the Alert Level on 20 February 2018 at Iwo-yama to 2. Steam plume heights increased to 200-300 m after 20 February. Seismicity decreased during March 2018, however observations from the webcam revealed an increase in fumarolic and thermal activity (figure 54).

Figure (see Caption) Figure 54. Fumarolic activity and heatflow increased at the Iwo-yama crater of Kirishimayama during March 2018, with steam plumes at the central vent rising several hundred meters. Images taken on 23 March 2018. View is to the N from the Iwo-yama south webcam. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, March, Heisei 30 (2018)).

The infrared imaging webcam recorded a burst of heat from a vent on the SW side of the crater on 7 April; the amplitude of seismic vibrations also increased. A field visit on 9 April revealed a hot water pool several meters in diameter on the SW side of the crater with sediment-laden water flowing from it and a 10-m-high steam plume. Local inflation recorded at Iwo-yama turned to deflation on 19 April; large-amplitude earthquakes were also reported. A tremor that day was followed by an explosion a few minutes later from a new vent on the S side of Iwo-yama. The plume rose 500 m and ejecta was scattered 200-300 m from the vent to the SE. During an overflight on 19 April JMA noted ash deposits around the vent; ash emission from the vent continued until the following morning (figure 55). The Tokyo VAAC reported a small ash emission on 19 April from Kirishimayama that rose to 1.8 km altitude and drifted E, but it was not visible in satellite imagery. On the evening of 20 April, another new vent with a vigorous steam plume appeared 500 m W of Iwo-yama (figure 56). Sediment-laden water was observed around the vent the following day. Increased seismicity at Iwo-yama lasted for about 20 days; additional tremor activity was reported on 20 and 24 April.

Figure (see Caption) Figure 55. An explosion sent steam and ash 500 m high, and ejecta 200-300 m SE from a new vent on the S side of Iwo-yama on 19 April 2018 at Kirishimayama. Ash emission continued until the following morning. N is to the left, fresh ash deposits cover the area SE of the new vent (upper right). Courtesy of JMA (Volcanic activity commentary on Kirishimayama, April, Heisei 30 (2018)).
Figure (see Caption) Figure 56. A new fumarole with a vigorous steam plume appeared about 500 m W of Iwo-yama during the evening of 20 April 2018. N is to the left. Miyazaki Prefecture Disaster Preparedness Emergency Air Corps Photograph taken from a helicopter on 21 April 2018. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, April, Heisei 30 (2018)).

A brief explosion that lasted about ten minutes occurred from this new vent around 1815 on 26 April 2018 sending a plume of ash about 200 m above the vent (figure 57). A small ash emission from Kirishimayama was reported by the Tokyo VAAC on 26 April that rose to 1.5 km altitude. In a site visit on 30 April, JMA noted active fumaroles and small explosions around both vent areas (figure 58). After the explosion of 19 April, steam plumes rose as high as 700 m from the vent on the S side of the crater, and intermittent spouts a few meters high of sediment-laden water were also observed. Steam plumes rose as high as 500 m from the vent located 500 m to the W.

Figure (see Caption) Figure 57. An explosion from the new vent located 500 m W of Iwo-yama at Kirishimayama on 26 April 2018 sent ash 200 m above the vent. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, April, Heisei 30 (2018)).
Figure (see Caption) Figure 58. Vigorous steam plumes rose from both the S side vent at Iwo-yama (background) and the new vent 500 m W (foreground) on 30 April 2018 at the Kirishimayama complex. North is to the left. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, April, Heisei 30 (2018)).

Fumarolic activity continued at Iwo-yama during May 2018, but no new explosions nor ash emissions were reported. Shallow seismic events were intermittent, but significantly decreased from April. No tremors were recorded. JMA lowered the Alert Level on 1 May 2018 from 3 to 2. Steam plumes rose 300-500 m from the vents, and thermal anomalies persisted at the crater and the adjacent new vent to the W throughout the month. Jets of sediment-laden hot water rising several meters continued from the vent on the S side of Iwo-yama (figure 59).

Figure (see Caption) Figure 59. Jets of sediment-laden hot water (gray spout at center) rose several meters from the S vent at Iwo-Yama at Kirishimayama during May 2018. Image taken on 15 May 2018. Courtesy of JMA (Volcanic activity commentary on Kirishimayama, April, Heisei 30 (2018)).

Geologic Background. Kirishimayama is a large group of more than 20 Quaternary volcanoes located north of Kagoshima Bay. The late-Pleistocene to Holocene dominantly andesitic group consists of stratovolcanoes, pyroclastic cones, maars, and underlying shield volcanoes located over an area of 20 x 30 km. The larger stratovolcanoes are scattered throughout the field, with the centrally located Karakunidake being the highest. Onamiike and Miike, the two largest maars, are located SW of Karakunidake and at its far eastern end, respectively. Holocene eruptions have been concentrated along an E-W line of vents from Miike to Ohachi, and at Shinmoedake to the NE. Frequent small-to-moderate explosive eruptions have been recorded since the 8th century.

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); 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/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.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/); Geographical Survey Institute, Geospatial Information Authority of Japan, Ministry of Land, Infrastructure, Transport and Tourism, No. 1 North Town, Tsukuba city, Ibaraki Prefecture 305-0811 Japan Tel: 029-864-1111 (Representative) Fax: 029-864-1807 (URL: http://www.gsi.go.jp/index.html); Kyodo News (URL: https://www.kyodonews.jp/english/); Associated Press (URL: http://www.ap.org/ ); Reuters (http://www.reuters.com/).


Sabancaya (Peru) — June 2018 Citation iconCite this Report

Sabancaya

Peru

15.787°S, 71.857°W; summit elev. 5960 m

All times are local (unless otherwise noted)


Strong, sporadic explosions with ash plumes throughout December 2017-May 2018

Although tephrochronology has dated activity at Sabancaya back several thousand years, renewed activity that began in 1986 was the first recorded in over 200 years. Intermittent activity since then has produced significant ashfall deposits, seismic unrest, and fumarolic emissions. A renewed period of explosive activity began in early November 2016 and continued through 2017. It was characterized by continuing pulses of ash emissions with plume heights exceeding 10 km altitude, thermal anomalies, and numerous significant SO2 plumes (BGVN 42:12). Details of the continuing eruptive activity from December 2017 to May 2018 in this report come from the two Peruvian observatories that monitor the volcano: Instituto Geofisico del Peru - Observatoria Vulcanologico del Sur (IGP-OVS), and Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico) (OVI-INGEMMET). Aviation notices come from the Buenos Aires Volcanic Ash Advisory Center (VAAC), and satellite data is reported from several sources.

Sabancaya continued with its explosive eruption that began on 6 November 2016 during December 2017-May 2018. Around 100 aviation notices were issued each month by the Buenos Aires VAAC; tens of daily explosions were reported, fluctuating from highs in the 60s per day in December 2017 to lows in the teens per day during February-April 2018. Ash plumes heights varied at 3-5 km above the summit; altitudes mentioned in the VAAC reports were between 7.3 and 8.5 km altitude most days, although plume heights over 9.1 km were observed a number of times. MIROVA thermal anomalies were recorded every week; MODVOLC thermal alerts occurred every month. A significant number of SO2 anomalies greater than two Dobson Units were measured by NASA's Goddard Space Flight Center each month (table 2).

Table 2. Eruptive Activity at Sabancaya, December 2017-May 2018. Compiled using data from IGP-OVS, OVI-INGEMMET, Buenos Aires VAAC, HIGP - MODVOLC Thermal Alerts System, and NASA Goddard Space Flight Center.

Month VAAC Reports Avg Daily Explosions by week Max Plume Heights (m above crater) Plume Drift MODVOLC Alerts Min Days with SO2 over 2 DU
Dec 2017 120 69, 63, 55, 67, 42 2,500-3,300 40-50 km, SW, NE, NW, W, N 2 7
Jan 2018 101 41, 57, 57, 33 2,500-3,300 50 km, SW, W, NW, N 2 13
Feb 2018 94 22, 18, 19, 17 2,500-4,500 30-50 km, SE, S, SW, NW 1 12
Mar 2018 115 12, 10, 17, 17, 18 2,000-5,350 30-50 km, S, SW, W, NW, N 3 13
Apr 2018 114 15, 15, 19, 22 2,000-3,200 30-40 km, All 3 12
May 2018 132 25, 27, 30, 35, 28 1,900-4,300 30-40 km, NW, N, NE, E, SE, S 4 7

Activity during December 2017-February 2018. The Buenos Aires VAAC issued 120 aviation alerts during December 2017; webcam and satellite imagery revealed continuous emissions of water vapor and gas, accompanied by sporadic puffs of ash, throughout the month. When visible in satellite imagery, plumes rose to 7.3-8.2 km altitude (figure 46); a few plumes were reported to 9.1 km altitude. According to OVI-INGEMMET, about 1,800 explosions took place in December. During the third week, ashfall was reported in Huambo (28 km WNW). There were two MODVOLC thermal alerts issued, on 3 and 10 December.

Figure (see Caption) Figure 46. Webcam photo of an ash plume at Sabancaya on 16 December 2017. The Buenos Aires VAAC reported a plume that day to 8.2 km altitude. Courtesy of OVI-INGEMMET (RSSAB-51-2017/OVI-INGEMMET & IGP Semana del 11 al 17 de diciembre de 2017).

The number of explosions reported by OVI-INGEMMET dropped slightly to about 1,400 during January 2018. The number of VAAC reports was similar to December; when weather clouds prevented observations of emissions, seismic activity showed intermittent peaks that suggested puffs of ash. Plume descriptions by the Buenos Aires VAAC ranged from intermittent plumes that rose to 7.0-7.6 km altitude early in the month to persistent puffs of ash that rose to 7.9-8.2 km altitude during the last two weeks of January. The prevailing winds were directed SW and NW, and ash plumes often drifted as far as 50 km. NASA Goddard Space Flight Center recorded at least 13 days with SO2 emissions greater than two Dobson Units (DU) (figure 47). HIGP issued two MODVOLC thermal alerts on 4 and 20 January.

Figure (see Caption) Figure 47. SO2 emissions at Sabancaya were significant throughout the report period. Most months, NASA-GSFC measured 10 or more days where the Dobson Unit (DU) values exceeded two. Dobson Units are a measure of the molecular density of SO2 in the atmosphere. The larger plumes shown here are from 6 January 2018 (top left), 23 February 2018 (top right), 18 March 2018 (bottom left), and 28 April 2018 (bottom right). Courtesy of NASA Goddard Space Flight Center.

OVI-INGEMMET reported ash plume heights during February 2018 at 2,500-4,500 m above the summit. They also noted that deflation was measured during the middle two weeks of the month. The number of daily explosions decreased significantly from the previous few months, with about 500 total explosions recorded in February. The Buenos Aires VAAC noted that the webcam showed continuous emissions of gases with sporadic puffs of ash every day that the summit was visible. Ash plumes were only visible in satellite imagery a few times during the month; during 8-10 February, intermittent emissions were seen moving SE between 7.9 and 8.5 km altitude. During 17-24 February, weak, thin ash plumes drifted several different directions at 7.3-7.9 km altitude (figure 48), and on 28 February a plume was visible drifting NW at 7.6 km altitude. Only a single MODVOLC thermal alert was issued on 18 February.

Figure (see Caption) Figure 48. A strong pulse of ash rose from the summit of Sabancaya early in the morning of 21 February 2018. Courtesy of OVI-INGEMMET (RSSAB-08-2018/OVI-INGEMMET & IGP Semana del 19 al 25 de febrero de 2018).

Activity during March-May 2018. Three MODVOLC thermal alerts were issued in March 2018, two on 14 March and one on 27 March. Sporadic ash explosions continued, but with the lowest number per day of the reporting period. About 450 explosions were recorded during March. In spite of the smaller number of explosions, some of the tallest ash plumes of the period occurred this month. The Buenos Aires VAAC reported a diffuse ash plume drifting NW in satellite imagery on 2 March at 8.8 km altitude. The following week, several ash plumes were spotted in satellite imagery at altitudes of 7.3-8.2 km drifting either SW or NW. On 11 March, cloudy weather prevented visual satellite imagery observations, but multispectral imagery and the webcam revealed intermittent pulses of ash moving SW at 7.6 km altitude. The following day sporadic strong pulses of ash were observed in the webcam, and there was a pilot report of an ash plume at 9.1 km altitude. During the second half of March, ash plumes were noted in satellite imagery most days at altitudes of 6.4-8.2 km; a few pulses produced short-lived ash plumes that rose over 9.1 km, including on 14, 22, 24, and during 27-30 March (figure 49). The highest plume was observed in visible imagery drifting E on 28 March at 10.1 km altitude. A lahar was also reported on 28 March descending the SE flank, towards the Sallalli River; no damage was reported.

Figure (see Caption) Figure 49. An ash plume at Sabancaya on 30 March 2018 can be seen rising from the summit and above the meteorological cloud in this webcam image. The Buenos Aires VAAC reported ash plumes on 30 March that rose to 9.1 and 9.5 km and drifted NE. Courtesy of OVI-INGEMMET (RSSAB-13-2018/OVI-INGEMMET & IGP Semana del 26 de marzo al 01 de abril de 2018).

The number of explosions during April 2018 increased slightly from March to about 540. The maximum plume heights ranged from 2,000 to 3,200 m above the summit according to OVI-INGEMMET. The webcam showed continuous emissions of water vapor and gas and sporadic pulses of ash throughout the month. Ashfall was reported during the first week in Achoma (23 km NE), Chivay (33 km NE), and Huanca. During the second week, the prevailing winds brought ashfall to the W and NW to Huambo (28 km W) and Cabanaconde (22 km NW). The Buenos Aires VAAC reported faint ash plumes visible in satellite imagery nearly every day; plume heights consistently ranged from 7.0 to 8.2 km altitude. Three MODVOLC thermal alerts were issued during the month, one on 13 April and two on 17 April.

Activity increased in many ways during May 2018. The Buenos Aires VAAC issued 132 aviation alerts, the most of any month during the period. The numbers of daily explosions increased compared to April, resulting in a monthly total of around 900. OVI-INGEMMET reported plume heights up to 4,300 m above the summit. MODVOLC thermal alerts were issued on 8, 19, 24, and 26 May. In addition to ash plumes visible in satellite imagery every day at altitudes of 7.3-8.2 km altitude (figure 50), a significant number of ash plumes were reported to altitudes greater than 9.1 km during the month, resulting in more VONA's (Volcanic Observatory Notice to Aviation) issued than in previous months. Sporadic strong puffs of ash were observed in the webcam on the days that satellite imagery measurements of ash plume heights exceeded 9.1 km including on 4, 5, 10, 14, 19, 21, 22, 25, 28, and 31 May. The highest plumes reached 10.4 km altitude on 19 May and 10.1 km altitude on 25 May. Hotspots were also reported on 20, 24, and 27 May. As in previous months, the webcam showed constant emissions of steam and gas, with intermittent pulses of volcanic ash throughout the month.

Figure (see Caption) Figure 50. An IGP webcam at Sabancaya recorded the plume height above the summit at 2,800 m on 27 May 2018. Courtesy of OVI-INGEMMET (RSSAB-22-2018/OVI-INGEMMET & IGP Semana del 28 de mayo al 3 de junio del 2018).

Geologic Background. Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Information Contacts: Observatorio Volcanologico del INGEMMET, (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa, Peru (URL: http://ovi.ingemmet.gob.pe); Instituto Geofisico del Peru, Observatoria Vulcanologico del Sur (IGP-OVS), Arequipa Regional Office, Urb La Marina B-19, Cayma, Arequipa, Peru (URL: http://ovs.igp.gob.pe/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); 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/).


Masaya (Nicaragua) — June 2018 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 persists during July 2017-April 2018

Nicaragua's Volcan Masaya has an intermittent lava lake that has attracted visitors since the time of the Spanish Conquistadores; tephrochronology has dated eruptions back several thousand years. The unusual basaltic caldera has had historical explosive eruptions in addition to lava flows and actively circulating magma at the lava lake. An explosion in 2012 ejected ash to several hundred meters above the volcano, bombs as large as 60 cm fell around the crater, and ash fell to a thickness of 2 mm in some areas of the park. Brief incandescence and thermal anomalies of uncertain origin in April 2013 were followed by very little activity until the reemergence of the lava lake inside Santiago crater was reported in December 2015. By late March 2016 the lava lake had grown and intensified enough to generate a significant thermal anomaly signature (BGVN 41:08, figure 49) which persisted at a constant power level through April 2017 (BGVN 42:09, figure 53) with an increase in the number of thermal anomalies from November 2016 through April 2017. Although the MIROVA thermal anomaly signal decreased slightly in intensity during May 2017, INETER scientists reported continued strong convection at the lava lake. Similar activity continued throughout July 2017-April 2018 and is covered in this report with information provided by the Instituto Nicareguense de Estudios Territoriales (INETER) and satellite thermal data.

A persistent thermal signature in the MIROVA data during July 2017-April 2018 supported the visual observations of the active lava lake at the summit throughout this period (figure 58). MODVOLC thermal alerts were also issued every month, with the number of alerts ranging from a high of 17 in November 2017 to a low of six in April 2018.

Figure (see Caption) Figure 58. MIROVA thermal data for Masaya for the year ending on 11 May 2018 showed a persistent and steady level of heat flow consistent with the observations of the active lava lake inside Santiago crater. Courtesy of MIROVA.

INETER made regular visits to the summit most months in coordination with specialists from several universities to gather SO2 data; CO2, H2S and gravity measurements were also taken during specific site visits. Thermal measurements around the lava lake inside Santiago crater taken on 24 February 2018 indicated temperatures ranging from 210-389°C. Seismicity remained very low throughout the period. The lava lake was actively convecting each time it was visited, and Pele's hair was abundant around the summit area (figures 59-64).

Figure (see Caption) Figure 59. The lava lake at Masaya was actively convecting on 22 August 2017 when observed by INETER scientists. Courtesy of INETER (Boletín Sismos y Volcanes de Nicaragua. Agosto, 2017).
Figure (see Caption) Figure 60. Pele's hair near the summit of Masaya on 22 August 2017. Scale is likely a few tens of centimeters. Courtesy of INETER (Boletín Sismos y Volcanes de Nicaragua. Agosto, 2017).
Figure (see Caption) Figure 61. The summit crater (Santiago) of Masaya with an active lava lake and fumarole plume (white circle) during 8-16 January 2018. Courtesy of INETER (Boletín Sismos y Volcanes de Nicaragua. Enero, 2018).
Figure (see Caption) Figure 62. Thermal measurements of the lava lake inside Santiago crater at the summit of Masaya on 24 February 2018 indicated temperatures in the 210-389°C range. Courtesy of INETER (Boletín Sismos y Volcanes de Nicaragua. Febrero, 2018).
Figure (see Caption) Figure 63. Nindiri plateau, the broad, flat area inside the summit crater of Masaya, was covered with Pele's hair and basaltic tephra on 6 March 2018. Courtesy of Carsten ten Brink.
Figure (see Caption) Figure 64. The lava lake inside Santiago crater at Masaya was actively convecting on 1 April 2018. Courtesy of Alexander Schimmeck.

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: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); 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/); Alexander Schimmeck, flickr (URL: https://www.flickr.com/photos/alschim/), photo used under Creative Commons license Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) (URL: https://creativecommons.org/licenses/by-nc-nd/2.0/); Carsten ten Brink, flickr (URL: https://www.flickr.com/photos/carsten_tb/), photo used under Creative Commons license Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) (URL: https://creativecommons.org/licenses/by-nc-nd/2.0/).


Nevados de Chillan (Chile) — June 2018 Citation iconCite this Report

Nevados de Chillan

Chile

36.868°S, 71.378°W; summit elev. 3180 m

All times are local (unless otherwise noted)


Hundreds of ash-bearing explosions; dome appears in crater in mid-December 2017

Nevados de Chillán is a complex of late-Pleistocene to Holocene stratovolcanoes constructed in the Chilean Central Andes. The Nuevo and Arrau craters are adjacent vents on the NW flank of the cone of the large stratovolcano referred to as Volcán Viejo. An eruption started with a phreatic explosion and ash emission on 8 January 2016 from a new crater on the E flank of Nuevo. Explosions continued through September 2017 with ash plumes rising several kilometers and Strombolian activity sending ejecta hundreds of meters (BGVN 42:10). This report covers continuing activity from September 2017-May 2018. Information for this report is provided by Chile's Servicio Nacional de Geología y Minería (SERNAGEOMIN)-Observatorio Volcanológico de Los Andes del Sur (OVDAS), Oficina Nacional de Emergencia-Ministerio del Interior (ONEMI), and by the Buenos Aires Volcanic Ash Advisory Center (VAAC).

About 150 ash-bearing explosions were recorded during September and October 2017, with plumes rising almost 2 km above the summit. Activity decreased during the second half of October, and no ash plumes were recorded during November. A significant increase in activity in early December led to over 200 explosions with ash emissions. An overflight on 21 December 2017 produced images of a fissure at the bottom of the new crater. The presence of a growing lava dome in the crater was confirmed in early January 2018. Frequent Strombolian explosions produced nighttime incandescence at the summit and down the flanks. Hundreds of ash-bearing explosions occurred during February 2018; the largest plume rose 2.5 km above the summit, and many smaller pulses produced ash and steam that rose 1.5 km. Sporadic incandescence at night and continued explosions of magmatic gases were typical during March 2018. A large explosion on 31 March coincided with the first appearance of a low-level MODIS thermal anomaly in the MIROVA data, and incandescence from explosions at night indicated that the dome continued to grow during April and May. SERNAGEOMIN reported that the top of the lava dome was visible from the E flank for the first time at the end of May 2018.

Activity during September-December 2017. SERNAGEOMIN reported 117 ash-bearing explosions between 16 and 30 September 2017 (figure 17). The one that released the most energy occurred on 19 September. The plumes of steam and ash rose up to 1,800 m above the crater. The Buenos Aires VAAC observed a narrow plume of ash in satellite imagery moving N at 3.9 km altitude and dissipating rapidly on 15 September, and a similar plume moving SE near the summit on 26 September 2017.

Figure (see Caption) Figure 17. Over 100 ash-bearing explosions were reported at Nevados de Chillán during late September 2017, including ones on 15 September (upper left), 20 September (upper right), 23 September (lower left) and 24 September (lower right). Courtesy of SERNAGEOMIN.

During the first two weeks of October 2017 there were 30 ash-bearing explosions recorded. The Buenos Aires VAAC reported small sporadic puffs of ash on 6 October 2017 that were visible in the webcam (figure 18), but not in satellite data, and a similar dense but short-lived plume on 14 October. SERNAGEOMIN reported a series of pulsating low-energy explosions visible in the webcam that drifted SW on 11 and 12 October 2017, and rose no more than 1 km above the summit.. Only two ash-bearing explosions were recorded during the second half of the month. The volcano was much quieter during November; plumes of steam were observed rising only 100 m above the summit throughout the month, with no ash-bearing plumes reported.

Figure (see Caption) Figure 18. Ash plumes at Nevados de Chillán on 6 (left) and 11 (right) October 2017 were two of the 30 plumes recorded during the first half of October. Courtesy of SERNAGEOMIN.

A significant increase in activity in early December 2017 resulted in 245 explosions associated with ash emissions during the first two weeks, some rising as high as 3,000 m above the summit. The Buenos Aires VAAC reported a puff of ash on 1 December that rose to 3.7 km altitude and drifted S, dissipating rapidly. The next day another plume rose slightly higher, to 4.3 km. A dense emission on 4 December rose to 4.9 km and drifted SE before dissipating in a few hours and was not visible in satellite data. On 11 and 14 December, short-lived emissions rose to 4.3 km (figure 19). A yellow cloud of sulfur formed on 11 December within 300 m of the active crater. The webcams also recorded sporadic nighttime incandescence during increased explosions in the early morning of 14 December. Continuous steam emissions with pulses of minor ash were first noted on 16 December; they were visible in satellite imagery the next day at 3.9-4.3 km altitude drifting NE, and by 18 December, consisted only of water vapor.

Figure (see Caption) Figure 19. An increase in explosive activity at Nevados de Chillán in December 2017 resulted in numerous explosions with ash plumes including on 1 December (upper left), 2 December (upper right), 4 December (lower left), and 11 December (lower right). Courtesy of SERNAGEOMIN.

In a special report released on 19 December, OVDAS-SERNAGEOMIN reported an increase in surface activity over the previous three days, recording minor explosions averaging four per hour, and seismic pulses lasting 5-10 minutes; they also noted harmonic tremor with the increase in explosion frequency. A detailed review of images taken during an overflight on 21 December revealed a fissure 30-40 m long trending NW at the bottom of the crater. Incandescence at night was regularly observed after 20 December (figure 20), and ash emissions rose to 3,000 m above the summit during the second half of the month.

Figure (see Caption) Figure 20. Phreatic explosions with steam and minor ash were common at Nevados de Chillán during the last two weeks of December 2017. Ash emissions and pyroclastic flows (top image) were noted during 12-19 December, and numerous incandescent blocks accompanied the explosions on 28 December (bottom image). Courtesy of SERNAGEOMIN.

Activity during January-April 2018. SERNAGEOMIN volcanologists identified a growing lava dome within the new crater during two overflights on 9 and 12 January 2018 (figures 21); it was emerging from the fissure first identified on 21 December. During the first two weeks of January SERNAGEOMIN reported 1,027 pulsating explosions associated primarily with magmatic gases, and very little ash that rose up to 1,000 m above the summit. Confirmed ash emissions were reported on 11 January at 4.3 km altitude faintly visible moving SE in satellite imagery, according to the Buenos Aires VAAC. Nighttime incandescence from the growing dome was periodically observed (figure 22). Based on the overflight data and satellite imagery, they calculated a growth rate for the dome of 1,360 m3 per day. They estimated the size at 37,000 m3 by mid-month.

Figure (see Caption) Figure 21. During an overflight at Nevados de Chillán on 9 January 2018, SERNAGEOMIN scientists observed the growing dome within the crater. Courtesy of SERNAGEOMIN.
Figure (see Caption) Figure 22. Incandescence at night increased from the growing dome at Nevados de Chillán on 13 January 2018. Courtesy of SERNAGEOMIN.

Overflights on 23 and 31 January measured temperatures of 305-480°C over the surface of the dome, with the highest values at the fissure. The growth rate calculated after these overflights was 2,540 m3 per day. The webcam revealed emissions of ash and water vapor during the second half of the month that rose less than 1,000 m above the summit crater.

An explosion on 2 February 2018 sent an ash plume to 2,500 m above the summit (figure 23). Vibrations from the explosion were reported in Las Trancas (10 km) and at the Gran Hotel Termas de Chillan (5 km). SERNAGEOMIN began referring to the active crater as Nicanor, and the dome was named Gil-Cruz. During the first two weeks of February, 840 explosions associated with plumes of magmatic gases were reported. The plumes generally rose as high as 1,500 m above the summit and were often accompanied by incandescence at night. Two overflights on 7 and 14 February recorded temperatures of 500 and 550°C. SERNAGEOMIN determined a dome growth rate of 1,389 m3 per day, and a total volume of 82,500 m3 by mid-month. At least four explosions on 14 February were characterized by two simultaneous plumes, one of white steam and the other darker with a higher ash content according to SERNAGEOMIN. The highest plume that day reached 1,200 m above the summit crater. The Buenos Aires VAAC also reported a small pulse of ash on 14 February that rose to 4.6 km altitude and drifted SE. The dome continued to grow slowly during the rest of February, with a small increase in size noted during a 22 February flyover. Plumes of mostly water vapor with minor ash rose a maximum of 1,080 m above the summit during the hundreds of small explosions that took place.

Figure (see Caption) Figure 23. A substantial explosion on 2 February 2018 at Nevados de Chillán sent an ash plume 2,500 m above the summit and generated vibrations that were felt 10 km from the summit. Courtesy of SERNAGEOMIN.

Sporadic incandescence at night and continued explosions of magmatic gases were typical during March 2018, with plume heights reaching 2,000 m over the Nicanor crater. During an overflight on 11 March, a temperature of 330°C was measured around the Gil-Cruz dome, which had grown to a volume of about 100,000 m3 but still remained below the crater rim. Morphological changes in the still-slowly growing dome included fracture lines and unstable large vertical blocks. A significant decrease in seismic energy was noted beginning on 24 March that ended when two larger explosions occurred on 30 and 31 March (figure 24).

Figure (see Caption) Figure 24. A substantial explosion on 31 March 2018 at Nevados de Chillán generated distinct ash and steam plumes (top) and sent several large blocks down the flanks (bottom). Courtesy of SERNAGEOMIN.

During an overflight on 3 April 2018, scientists observed energetic pulses of steam and minor ash from the central NW-SE trending fissure inside the crater. They noted that lapilli from explosions had been ejected as far as 1 km from the fissure, and that the Gil-Cruz dome had increased in volume since 11 March; they also observed an area of subsidence on the top of the growing dome (figure 25). The dome was expanding toward the E side of the crater, and the top of the dome rose above the crater rim. They measured a maximum temperature of 670°C on the surface of the dome. The decrease in daily seismicity, the larger explosions of the previous days, and the increased size of the dome with greater risk of collapse, pyroclastic flows, and lahars, all led SERNAGEOMIN to raise the alert level at Chillan to Orange on 5 April 2018.

Figure (see Caption) Figure 25. The growing lava dome at Nevados de Chillán, referred to as Gil-Cruz, had an active steam plume at the center when photographed by SERNAGEOMIN during an overflight on 3 April 2018. Courtesy of SERNAGEOMIN.

The Buenos Aires VAAC reported continuous emissions of steam and gas with minor ash along with a small pulse of ash on 2 April 2018. Low-altitude plumes of mostly water vapor were common throughout April 2018. Incandescence from explosions was visible on clear nights during the month, and ejecta rose as high as 250 m above the crater and was scattered around the crater rim. Seismicity remained constant at moderate levels related to the repeated explosions and the growth of the dome. A faint ash plume could be seen in visible satellite imagery on 18 April at 3.7 km altitude drifting E.

Observations reported on 1 May 2018 from the previous flyover indicated that the rate of growth of the dome had slowed to about 690 m3 per day, and the estimated volume had grown to about 150,000 m3. Activity remained at similar levels throughout May 2018. Seismic instruments recorded long-period seismicity and tremor episodes similar to previous months that corresponded with surface explosions and the extrusion of the lava dome. Seismic energy levels were moderate but fluctuated at times. Plumes of predominantly water vapor with minor gas rose a few hundred meters above the summit drifting generally S or SE before dissipating. Incandescence was often observed on clear nights, accompanied by ejection of incandescent blocks that were observed generally 100 to 150 m above the active crater. A larger explosive event took place on 7 May. Occasional plumes with minor ash were reported on 11 May. SERNAGEOMIN reported on 24 May 2018 that the top of the lava dome was visible from the E flank.

Geologic Background. The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, Cerro Blanco (Volcán Nevado), is located at the NW end of the group. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in elevation. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986 and eventually exceeded its height.

Information Contacts: Servicio Nacional de Geología y Minería, (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI), Beaucheff 1637/1671, Santiago, Chile (URL: http://www.onemi.cl/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); 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/).


Marapi (Indonesia) — June 2018 Citation iconCite this Report

Marapi

Indonesia

0.38°S, 100.474°E; summit elev. 2885 m

All times are local (unless otherwise noted)


Two explosions during April-May 2018 cause ashfall to the southeast

The Marapi volcano on Sumatra (not to be confused with the better known Merapi volcano on Java) previously erupted on 4 June 2017, generating dense ash-and-steam plumes that rose as high as 700 m above the crater and caused minor ashfall in a nearby district (BGVN 42:10). The volcano is monitored by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Centre for Volcanology and Geological Hazard Mitigation or CVGHM).

On 27 April 2018, a phreatic explosion produced an ash plume that rose 300 m above the crater rim (figure 8); a thin ash deposit was reported in the Cubadak area (Tanah Datar Regency), about 12 km SE. Another explosion at 0703 on 2 May 2018 (figure 9) produced a voluminous dense gray ash plume that rose 4 km above the crater rim and drifted SE; seismic data recorded by PVMBG indicated that the event lasted just over 8 minutes (485 seconds).

The Alert Level has remained at 2 (on a scale of 1-4), where it has been since August 2011. Residents and visitors have been advised not to enter an area within 3 km of the summit.

Figure (see Caption) Figure 8. Ash plume from a phreatic explosion at Marapi on 27 April 2018. Courtesy of Sutopo Purwo Nugroho (BNPB).
Figure (see Caption) Figure 9. An explosion from Marapi on 2 May 2018 sent an ash plume to a height of 4 km. Courtesy of PVMBG.

Geologic Background. Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2000 m above the Bukittinggi plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

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/).


Nyiragongo (DR Congo) — June 2018 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Thermal anomalies show that lava lake remains active through May 2018

As has been the case since at least 1971, the active lava lake in the summit crater of Nyiragongo was present during a tourist visit in June 2017, and seismicity was recorded in the crater in October 2017 (BGVN 42:11). Thermal data from satellite-based instruments shows that an open lava lake remained through 23 May 2018. MIROVA analysis of MODIS satellite thermal data (figure 64) shows nearly daily strong thermal anomalies. Similarly, MODVOLC alerts for the same time period shows a consistently frequent number of anomalies (figure 65).

Figure (see Caption) Figure 64. Thermal anomaly MIROVA plot of log radiative power at Nyiragongo for the year ending 23 May 2018. Courtesy of MIROVA.
Figure (see Caption) Figure 65. Map showing MODVOLC alert pixels at Nyiragongo, reflecting MODIS satellite thermal data, for the year ending 23 May 2018. Each pixel shows a thermal alert for a ground area of about 1.5 km2. Nyiragongo (many pixels) is in the center of the map, and Nyamuragira volcano (fewer pixels) is about 13 km to the NNW. Courtesy of HIGP - MODVOLC Thermal Alerts System.

Geologic Background. One of Africa's most notable volcanoes, Nyiragongo contained a lava lake in its deep summit crater that was active for half a century before draining catastrophically through its outer flanks in 1977. In contrast to the low profile of its neighboring shield volcano, Nyamuragira, 3470-m-high Nyiragongo displays the steep slopes of a stratovolcano. Benches in the steep-walled, 1.2-km-wide summit crater mark levels of former lava lakes, which have been observed since the late-19th century. Two older stratovolcanoes, Baruta and Shaheru, are partially overlapped by Nyiragongo on the north and south. About 100 parasitic cones are located primarily along radial fissures south of Shaheru, east of the summit, and along a NE-SW zone extending as far as Lake Kivu. Many cones are buried by voluminous lava flows that extend long distances down the flanks, which is characterized by the eruption of foiditic rocks. The extremely fluid 1977 lava flows caused many fatalities, as did lava flows that inundated portions of the major city of Goma in January 2002.

Information Contacts: 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/).


Ebeko (Russia) — June 2018 Citation iconCite this Report

Ebeko

Russia

50.686°N, 156.014°E; summit elev. 1103 m

All times are local (unless otherwise noted)


Ash explosions remained frequent through May 2018, with plumes typically rising more than 1 km

The most recent eruption at Ebeko, a remote volcano in the Kuril Islands, began in October 2016 (BGVN 42:08) with explosive eruptions accompanied by ashfall. Frequent ash explosions were observed through November 2017 and the eruption remained ongoing at that time (BGVN 43:03). Activity consisting of explosive eruptions, ash plumes, and ashfalls continued during December 2017 through May 2018 (table 6). Eruptions were observed by residents in Severo-Kurilsk (about 7 km E), by volcanologists, and based on satellite imagery. The Kamchatkan Volcanic Eruption Response Team (KVERT) is responsible for monitoring Ebeko, and is the primary source of information. The Aviation Color Code (ACC) remained at Orange throughout this reporting period. This color is the second highest level of the four color scale.

Table 6. Summary of activity at Ebeko volcano from December 2017 to May 2018. Aviation Color Code (ACC) is a 4-color scale. Data courtesy of KVERT

Date Plume Altitude Plume Distance Plume Direction Other observations
1-4 and 7 Dec 2017 2 km -- -- ACC at Orange. Ashfall reported in Severo-Kurilisk. Explosions on 2-4 and 7 Dec.
8, 9, 11 Dec 2017 2.3 km -- -- Explosions.
16, 18-19, and 21-22 Dec 2017 3.5 km 16 km SSW Explosions. Ash plume and weak thermal anomaly on 16 Dec.
25 Dec 2017 1.5 km -- -- Explosion.
01-05 Jan 2018 -- -- -- No activity noted.
08-10 Jan 2018 2.5 km -- -- Explosions.
11-12, 14-16, and 18 Jan 2018 3.1 km -- -- Explosion. Minor ashfall reported in Severo-Kurilsk on 15,16, and 18 Jan.
22-23 Jan 2018 2 km -- -- Explosions.
26-27 and 29-31 Jan 2018 2.5 km -- -- Explosions. Ashfall reported in Severo-Kurilsk on 29 Jan.
05-08 Feb 2018 2.4 km -- -- Explosions. Ashfall reported in Severo-Kurilisk on 8 Feb.
09-10 and 14 Feb 2018 2.2 km -- -- Explosions.
17-18 and 20-21 Feb 2018 2.4 km -- -- Explosions. Ashfall reported in Severo-Kurilisk on 17-18 Feb.
23-25 and 27-28 Feb 2018 3.3 km -- -- Explosions.
06 Mar 2018 1.7 km -- -- Explosions.
12-13 Mar 2018 2.7 km -- -- Explosions.
18 and 21-22 Mar 2018 1.8 km -- -- Explosions. Ashfall reported in Severo-Kurilisk on 17 and 21 Mar.
23-25 and 28-29 Mar 2018 2.3 km -- -- Explosions.
31 Mar-06 Apr 2018 2.7 km -- -- Explosions.
07 and 11-12 Apr 2018 1.8 km -- -- Explosions. Ashfall reported in Severo-Kurilisk on 6 Apr.
15 and 17-19 Apr 2018 2.6 km -- -- Explosions.
21 and 25 Apr 2018 2.5 km -- -- Explosions.
01-03 May 2018 2.8 km -- -- Explosions.
04 and 06-10 May 2018 2.4 km -- -- Explosions.
12-14 May 2018 2.8 km 21 km SW Explosions. Ash plume drifted SW on 13 May.

Minor ash explosions were reported throughout the period from December 2017 through May 2018 (figure 17). Minor amounts of ash fell in Severo-Kurilisk at the end of 2017 and into 2018. Ash was reported on 2-4, and 7 December 2017; 15, 16, 18, and 29 January 2018; 8, 17, and18 February; 17 and 21 March; and 6 April. Ash plume altitudes during this reporting period ranged from 1.5 to 3.5 km (table 6); the summit is at 1.1 km.

Figure (see Caption) Figure 17. Explosions from Ebeko sent ash up to an altitude of 1.5 km, or about 400 m above the summit, on 6 February 2018. Courtesy of T. Kotenko (IVS FEB RAS).

Geologic Background. The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/).

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Scientific Event Alert Network Bulletin - Volume 10, Number 05 (May 1985)

Managing Editor: Lindsay McClelland

Concepcion (Nicaragua)

Small ash eruptions

Etna (Italy)

Lava flows toward SW and SE; strong gas and vapor emissions

Fournaise, Piton de la (France)

Eruption with premonitory seismicity

Kilauea (United States)

Summit inflation and low-level harmonic tremor continue; episode 33 of 1983-85 eruption

Masaya (Nicaragua)

Small ash eruptions

Momotombo (Nicaragua)

Continued high fumarole temperatures

Ruapehu (New Zealand)

Hydrothermal eruptions accompany seismic activity

Ruiz, Nevado del (Colombia)

Increased seismicity and abnormal fumarolic activity

Soputan (Indonesia)

Seven-hour tephra eruption; jumbo jet flies through plume

St. Helens (United States)

Strong seismicity accompanies major dome-building episode

Tecapa (El Salvador)

Earthquake swarm at historically inactive volcano



Concepcion (Nicaragua) — May 1985 Citation iconCite this Report

Concepcion

Nicaragua

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

All times are local (unless otherwise noted)


Small ash eruptions

A series of small ash eruptions occurred in December 1984.

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: D. Fajardo B., INETER.


Etna (Italy) — May 1985 Citation iconCite this Report

Etna

Italy

37.748°N, 14.999°E; summit elev. 3295 m

All times are local (unless otherwise noted)


Lava flows toward SW and SE; strong gas and vapor emissions

"The eruption continued through May without significant changes from last month. The main lava channel has been transformed into a lava tube, between 2,510 and 2,320 m elevation, that has at least four windows through which it was possible to see the lava flow. The lava has maintained a constant velocity during the last few weeks. On 23 May another lava overflow occurred as a result of roof collapse along the upper portions of the lava tube (2,485 m elevation), generating small lava flows of brief duration.

"The numerous short-lived vents inside the lava field (from 2,320 to 2,150 m elevation) were variable, as usual, in number and position. The lava flows that originated from these short-lived vents have increased the size of the lava field on both the W and E sides to a maximum width of ~1.5 km.

"Beginning 10 May the lava moved mainly toward the SW (Monte Rinatura and Monte Nero). Around the beginning of June there were numerous lava flows toward the SE (1910 craters area). Lava continued to flow toward the south (Monte Castellazzi area), but these flows were not strongly fed. None of the lava flows descended below 2,000 m elevation.

"The more or less intense emission of gas and vapor from both vents of the central crater and from the Northeast Crater continue. Emissions of ash are rare and inconsistent. Gas under pressure emerged from a small opening at the southern base of the 1984 cone inside the Southeast Crater (P. Briole, personal communication). R. Clocchiatti conducted temperature measurements with a thermocouple; the temperature ranged between 1053°C and 1,088°C (CEN-SACLAY).

"M. Cosentino and G. Lombardo reported that no particular seismic activity was recorded. Instead, an increase in the average amplitude of harmonic tremor was noticed, probably connected to the degassing of the central and Northeast craters.

"The Etna guides and rescue volunteers from the Italian Alpine Club (A. Cristaudo and A. Nicotra) helped with information on the activity."

Geologic Background. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Information Contacts: R. Romano, IIV.


Piton de la Fournaise (France) — May 1985 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)


Eruption with premonitory seismicity

"Since the last eruption, seismicity and deformation measured at the four summit stations had remained at very low levels (0-5 earthquakes and 1-7 µrad of tilt per month). The pattern of tilt vectors implied a progressive deflation of the area that had undergone large deformation during the last eruption.

"Beginning on 15 May, several small earthquakes (M <1) were recorded at depths of 1.5-2.5 km beneath the summit. Simultaneously, the summit dry tilt stations began to show an inflationary pattern. The number of seismic events progressively increased. Seismic activity peaked on 8 June with 13 events, and decreased to a low level on the 13th. No significant migration of the earthquakes was observed. Inflation appeared to have been almost continuous except during two episodes when deformation slowed (3 June) or reversed (8 June) corresponding to the periods of largest seismic energy release.

"This activity differed from the 1983 pre-eruptive crisis. The late 1983-early 1984 eruption was preceded by two weeks of seismic activity (48 events) with no associated deformation. The most recent activity lasted for at least four weeks. The earthquakes are located in the same area as before, but summit tilt stations show inflation of 15-40 µrads."

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: J. Lenat, OVPDLF; M. Kasser, Inst. Geographique National (IGN), Paris; A. Nercessian, IPG, Paris; R. Vie le Sage, Délégation aux Risques Majeurs (DRM), Paris; P. Bachelery, Univ. de la Réunion; A. Bonneville, Univ. du Languedoc; G. Boudon, Obs. Volc. de la Mt. Pelée; M. Halbwaks, Univ. de Chambéry.


Kilauea (United States) — May 1985 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Summit inflation and low-level harmonic tremor continue; episode 33 of 1983-85 eruption

"For the first time since October 1984, Kilauea did not erupt during a calendar month. Mapping of episode 32 (21-22 April) eruptive products was completed in May and showed that 16.1 x 106 m3 of lava and 0.25 x 106 m3 of tephra (dense rock equivalent) were produced. Lava from the 1983-85 eruption covered 40 km2 of the middle E rift zone.

"Following episode 32, magma was first visible in the conduit on 9 May, at approximately 50 m depth. By the end of May, the magma column had risen to within 30 m of the Pu`u `O`o crater floor and remained mostly crusted over.

Deformation. "The summit of Kilauea continued to inflate during May. However, a period of significant summit subsidence occurred from 22 May at 1800 to 27 May at 0900. During this interval, the Uwekahuna tiltmeter recorded 2.8 µrad of summit deflation. The net inflation during May was 5.7 µrad.

Seismicity. "Harmonic tremor continued at a fluctuating low level in the middle E rift zone near Pu`u `O`o following episode 32. The number of shallow microearthquakes in the E rift zone and summit region varied from several tens to a few hundreds per day. Short-period summit earthquakes increased gradually in response to the slow rate of inflation. Frequent bursts of long-period events and harmonic tremor were recorded from intermediate to deep sources beneath Kilauea."

Addendum: Episode 33 of the middle E rift zone eruption occurred on 1213 June. Discontinuous low level fountaining and spillover from the Pu`u `O`o vent began at 0430 on the 12th. By 2306, fountaining had become vigorous and continuous. Lava flowed about 3.5 km to the SE over older lavas from Pu`u `O`o before the episode ended at [0453] on the 13th.

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, G. Ulrich, R. Hanatani, R. Koyanagi, and R. Okamura, HVO.


Masaya (Nicaragua) — May 1985 Citation iconCite this Report

Masaya

Nicaragua

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

All times are local (unless otherwise noted)


Small ash eruptions

In December 1983, 4,993 microearthquakes were recorded at Masaya. Early that month, a very large gas column was continuing to emerge from Santiago Crater. A series of small ash eruptions occurred in April 1984. There was a small gas explosion on 23 January 1985, and another ash eruption occurred in April 1985.

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: D. Fajardo B., INETER.


Momotombo (Nicaragua) — May 1985 Citation iconCite this Report

Momotombo

Nicaragua

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

All times are local (unless otherwise noted)


Continued high fumarole temperatures

Summit fumarole temperatures have remained high, with small fluctuations probably related to seasonal rainfall variations. The maximum temperature in 1984 was 895°C in August; the same fumarole had a temperature of 875°C when measured in 1985.

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: D. Fajardo B., INETER.


Ruapehu (New Zealand) — May 1985 Citation iconCite this Report

Ruapehu

New Zealand

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

All times are local (unless otherwise noted)


Hydrothermal eruptions accompany seismic activity

After 3 years of quiescience, small hydrothermal eruptions began on or shortly before 21 May. On 16 May, major overflow of Crater Lake into the Whangaehu River began, as shown by pH and conductivity measurements downstream (at Tangiwai). Seismic activity, characterized by increased high-frequency tremor and local earthquakes, began [in early May, with some minor tremor on the 5th and small volcanic earthquakes on the 11th]. Eruptions were first observed in Crater Lake on 21 May and were also seen on 25 May.

On 28 May NZGS personnel noted 15 small hydrothermal eruptions during a 10-hour period. All the eruptions occurred in the lake center, where resumption of weak upwelling had first been observed on 26 April. The eruptions were characterized by updoming of the central lake surface, noisy ejection of water and mud jetting to 10 m above the lake surface, and waves radiating from the lake center. Clouds limited deformation measurements across the crater but a pair of horizontal angle observations indicated no major change in crater diameter.

The lake was battleship-gray in color, with clean snow around the water margin about 1 m above lake level. The lake temperature had increased to 45°C from the 20-25°C range of recent months. Interim analyses of the lake water show a progressive dilution throughout the summer months. Chlorine and magnesium contents have increased since activity began, but the Mg/Cl ratio has not changed significantly.

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: I. Nairn and B. Scott, NZGS, Rotorua; P. Otway, NZGS, Wairakei.


Nevado del Ruiz (Colombia) — May 1985 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)


Increased seismicity and abnormal fumarolic activity

"Since late November 1984, local earthquakes have been felt near the summit. On 22 December, stronger earthquakes were detected, followed by a half hour of apparent harmonic tremor. During a visit to the crater in early January 1985, increased fumarolic activity, evidence of phreatic explosions, and the wide deposition of sulfur salts over the adjacent snowcap were noted. At times, a thin layer of ash had been ejected, which was analyzed by J. Tomblin and found to consist of alteration products and sulfur.

"Seismic activity continued, with 17 felt earthquakes in March and 18 in April. There are no operating seismographs in the region. Abnormal fumarolic activity also continued. The one hot spring with frequent temperature monitoring, NW of the crater, had not shown any variation in temperature.

"Ruiz is a glacier-clad stratovolcano (bordering Tolima and Caldas Departments). . . . Colombian officials have begun the necessary studies."

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: M. Hall, Escuela Politécnica, Ecuador; J. Tomblin, UNDRO; O. Gómez, Civil Defense Coordinator, Manizales.


Soputan (Indonesia) — May 1985 Citation iconCite this Report

Soputan

Indonesia

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

All times are local (unless otherwise noted)


Seven-hour tephra eruption; jumbo jet flies through plume

An ash eruption from Soputan's main crater occurred 19-20 May from 1815 to 0130. The eruption column rose to 4 km altitude, and ~2 cm of ash (fine to coarse) accumulated at villages (Kawangkoan, Langoan, Noongan, and Ratahan) 9-12 km from the crater. There were no casualties and no evacuations were necessary. The volcano has remained quiet since 22 May.

On 20 May at 0058, a jumbo jet en route from Hong Kong to Sydney, Australia, with 267 passengers and 16 crew members encountered the ash cloud ~80 km SSE of the volcano (approximately 0.5°N, 124.54°E). An orange glow discharged from the nose of the aircraft and orange sparks passed over the windshield. Engine inlets were illuminated by a white light. A light haze that smelled like burnt dust filled the cabin, and ash accumulated on flat surfaces. These effects continued for 7-8 minutes, while the aircraft remained on course at 0.85x the speed of sound, for a distance of roughly 120-135 km. The aircraft continued to Sydney, arriving 4 hours after exiting the ash cloud, and landed uneventfully. Because of damage caused by the ash cloud, it was necessary to replace all four of the aircraft's engines, other navigational components, and more than a dozen windows.

The TOMS instrument on the NIMBUS 7 polar orbiting satellite detected an area of SO2 enhancement SE of Soputan during its pass at local noon on 20 May. The area of enhancement extended from about 124.5°E to 126°E near the equator and from about 125°E to 127°E at 1.5°S with the maximum at about 1°S, 126°E.

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: VSI; Boeing, Seattle, WA; A. Krueger, NASA/GSFC.


St. Helens (United States) — May 1985 Citation iconCite this Report

St. Helens

United States

46.2°N, 122.18°W; summit elev. 2549 m

All times are local (unless otherwise noted)


Strong seismicity accompanies major dome-building episode

During mid-May, seismicity and rates of displacement began to increase from background levels. After 8 months of quiescence, a new lobe was extruded onto the composite lava dome, and a major intrusive event further enlarged the dome.

On 13 May, the number of medium- to high-frequency events recorded from the crater seismic station began to increase. Measurements on 16 May indicated that displacement rates on the dome had increased slightly while seismicity continued to build gradually. Several vigorous gas emissions, the first since 24 September 1984, occurred on 17 May from a vent in the NE part of the dome's summit area. No tephra was ejected, and the largest plume rose to just above the crater rim. Seismicity and displacement rates continued to increase, and on 20 May the USGS and University of Washington issued a volcano advisory notice stating that recent changes at the volcano suggested "renewed eruptive activity will begin within the next 2 weeks, possibly within the next few days."

By the 23rd, seismicity had reached high levels. On the 24th, very low-frequency events increased in size and number, although medium- to high-frequency events decreased. Observations made during a night overflight on the 25th at 0030 indicated increased glow from cracks on the dome. Later that morning, the low-frequency earthquakes that typically immediately precede and accompany extrusions had become more numerous, and deformation patterns suggested to USGS scientists that magma had nearly reached the surface of the dome. Observations during the next week were few because of poor weather conditions.

Between 21 and 23 May, a trough-like fracture system began to develop on top of the dome. By 27 May, this graben was 30-50 m wide and had cut across the entire S portion of the dome. Sometime between the 27th and 30th, a new lobe of gas-poor lava was extruded on the SE flank of the dome, near the E end of the newly formed graben. The 80-m-wide lobe extended out of the graben about 100 m down to the crater floor (figure 28). By the 30th, the graben was 400 m long, 30 m deep, and averaged 90-100 m wide. The dome flank S of the graben had been displaced outward.

Figure (see Caption) Figure 28. Sketch of Mt. St. Helens, by Bobbie Myers, looking NW, showing the composite lava dome after formation of the graben and extrusion of the new lobe in May 1985.

Seismicity continued at very high levels; on the 29th, M 2.5-2.8 events were recorded every few minutes as deep as 1 km below the dome. During past extrusion episodes, seismicity typically decreased sharply when lava reached the surface, but on the 31st, seismicity remained vigorous. Late on 31 May or early on 1 June, a slow decrease in the number of seismic events began. By 5 June seismicity had decreased to moderate levels and had reached background levels by the 17th.

Measurements by USGS scientists on 16 June indicated that the S flank of the dome had moved outward about 70-100 m during the eruption, but that the current displacement rate had by then decreased to about a centimeter per day. A station on the crater floor S of the dome moved 46 m outward and 18 m upward between 17 May and 8 June, but had moved only a few centimeters more by the 16th. These measurements suggested to USGS scientists that about 6-8 x 106 m3 of magma were intruded into the dome during this eruption, the largest single dome-building event since 12 June 1980.

After the vigorous gas emission events of 17 May, vapor emission continued from the same vent during the eruption. However, SO2 emission rates averaged about 40 t/d during May, about the same as the average April rate of 30 ± 5 t/d. On 30 May, the rate increased from background levels to 90 ± 10 t/d, by 2 June to 160 ± 25, and by the 8th to 220 ± 10 t/d. SO2 emission decreased to 165 ± 10 t/d on June 10th and to 60 ± 10 t/d on the 12th.

Equipment to measure H2 emission was installed on top of the dome in January. After 3 months of very low measurements, ambient H2 around the top of the dome began to increase dramatically on 24 May, continued to rise over the next few days, and reached a very high value before the station was destroyed early on the 29th. Because the instrument was not yet calibrated, the measurements cannot be quantified.

Geologic Background. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fuji-san of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome. Mount St. Helens was formed during nine eruptive periods beginning about 40-50,000 years ago and has been the most active volcano in the Cascade Range during the Holocene. Prior to 2200 years ago, tephra, lava domes, and pyroclastic flows were erupted, forming the older St. Helens edifice, but few lava flows extended beyond the base of the volcano. The modern edifice was constructed during the last 2200 years, when the volcano produced basaltic as well as andesitic and dacitic products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the north flank, and were witnessed by early settlers.

Information Contacts: D. Swanson, C. Newhall, S. Brantley, K. McGee, J. Sutton, B. Myers, USGS CVO, Vancouver, WA; C. Jonientz-Trisler, University of Washington.


Tecapa (El Salvador) — May 1985 Citation iconCite this Report

Tecapa

El Salvador

13.494°N, 88.502°W; summit elev. 1593 m

All times are local (unless otherwise noted)


Earthquake swarm at historically inactive volcano

"An earthquake swarm occurred by surface faulting on 21 April in the Chinameca Complex, near Tecapa, a volcano with no known historic eruption. A magnitude 4.7 (mb) earthquake, the largest so far, occurred on 23 April . . . . Four days later, 27 April, during the peak activity (in terms of numbers of recorded and felt events per day), an 8 km-long graben formed on the NW flank of the volcano. The N40°W-striking graben is 0.8-1 km wide, with a vertical offset of 30 cm. Through 6 June, 170 earthquakes were felt in the area. A very preliminary analysis of the earthquake location data implies that activity began on a tectonic fault some 15 km NW of the volcanic summit, and moved nearer to the volcano at the time the graben formed. Since 3 June, 5-20 earthquakes per day were recorded by a high-gain seismograph station 50 km from the volcano, down from 300 events per day on 26, 27, and 28 April, and 21 and 23 May."

Geologic Background. Tecapa is a complex basaltic-to-andesitic stratovolcano at the NW end of a cluster of volcanoes E of the Río Lempa between San Vicente and San Miguel volcanoes. The Berlín caldera, whose rim is visible on the W side of the complex, was formed during the eruption of the Blanca-Rosa dacitic pumice in the late Pleistocene. Following caldera formation, the cones of Cerro Las Palmas, Cerro Pelón, Tecapa-Laguna de Alegria, and Cerro Alegria were constructed along a WSW-ENE line. The crater of Tecapa-Laguna de Alegria contains a deep notch on the eastern rim and is filled by Laguna de Alegria crater lake. The volcanic complex currently displays fumarolic activity, and a producing geothermal plant is located at the Berlín geothermal field.

Information Contacts: J. González, Centro de Investigaciones Geotécnicas, San Salvador; D. Harlow, USGS.

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/).