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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

Tengger Caldera (Indonesia) Ash emissions on 19 and 28 July 2019; lahar on the SW flank of Bromo

Unnamed (Tonga) Submarine eruption in early August creates pumice rafts that drifted west to Fiji

Popocatepetl (Mexico) Frequent explosions continue during March-August 2019

Semeru (Indonesia) Intermittent activity continues during March-August 2019; ash plumes and thermal anomalies

Saunders (United Kingdom) Intermittent activity most months, October 2018-June 2019; photographs during February and May 2019

Pacaya (Guatemala) Lava flows and Strombolian explosions continued during February-July 2019

Colima (Mexico) Renewed volcanism after two years of quiet; explosion on 11 May 2019

Masaya (Nicaragua) Lava lake activity declined during March-July 2019

Rincon de la Vieja (Costa Rica) Occasional weak phreatic explosions during March-July 2019

Aira (Japan) Explosions with ejecta and ash plumes continue weekly during January-June 2019

Agung (Indonesia) Continued explosions with ash plumes and incandescent ejecta, February-May 2019

Kerinci (Indonesia) Intermittent explosions with ash plumes, February-May 2019



Tengger Caldera (Indonesia) — August 2019 Citation iconCite this Report

Tengger Caldera

Indonesia

7.942°S, 112.95°E; summit elev. 2329 m

All times are local (unless otherwise noted)


Ash emissions on 19 and 28 July 2019; lahar on the SW flank of Bromo

The Mount Bromo pyroclastic cone within the Tengger Caldera erupts frequently, typically producing gas-and-steam plumes, ash plumes, and explosions (BGVN 44:05). Information compiled for the reporting period of May-July 2019 is from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) and the Darwin Volcanic Ash Advisory Centre (VAAC).

The eruptive activity at Tengger Caldera that began in mid-February continued through late July 2019, including white-and-brown ash plumes, ash emissions, and tremors. During the months of May through June 2019, white plumes rose between 50 to 600 m above the summit. Satellite imagery captured a small gas-and-steam plume from Bromo on 5 June (figure 18). Low-frequency tremors were recorded by a seismograph from May through July 2019.

Figure (see Caption) Figure 18. Sentinel-2 satellite image showing a small gas-and-steam plume rising from the Bromo cone (center) in the Tengger Caldera on 5 June 2019. Thermal (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

According to PVMBG and a Volcano Observatory Notice for Aviation (VONA), an ash eruption occurred on 19 July 2019; however, no ash column was observed due to weather conditions. A seismograph recorded five earthquakes and three shallow volcanic tremors the same day. In addition, rainfall triggered a lahar on the SW flank of Bromo.

On 28 July the Darwin VAAC reported that ash plumes originating from Bromo rose to a maximum altitude of about 3.9 km and drifted NW from the summit, based on webcam images and pilot reports. PVMBG reported that lower altitude ash plumes (2.4 km) on the same day were also recorded by webcam images, satellite imagery (Himawari-8), and weather models.

Geologic Background. The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most active and most frequently visited volcanoes.

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/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/).


Unnamed (Tonga) — November 2019 Citation iconCite this Report

Unnamed

Tonga

18.325°S, 174.365°W; summit elev. -40 m

All times are local (unless otherwise noted)


Submarine eruption in early August creates pumice rafts that drifted west to Fiji

Large areas of floating pumice, termed rafts, were encountered by sailors in the northern Tonga region approximately 80 km NW of Vava'u starting around 9 August 2019; the pumice reached the western islands of Fiji by 9 October (figure 7). Pumice rafts are floating masses of individual clasts ranging from millimeters to meters in diameter. The pumice clasts form when silicic magma is degassing, forming bubbles as it rises to the surface, which then rapidly cools to form solid rock. The isolated vesicles formed by the bubbles provide buoyancy to the rock and in turn, the entire pumice raft. These rafts are spread and carried by currents across the ocean; rafts originating in the Tonga area can eventually reach Australia. This report summarizes the pumice raft eruption from early August 2019 using witness accounts and satellite images (acquisition dates are given in UTC). Pending further research, the presumed source is the unnamed Tongan seamount (volcano number 243091) about 45 km NW of Vava'u, the origin of an earlier pumice raft produced during an eruption in 2001.

Figure (see Caption) Figure 7. The path of the pumice from the unnamed Tongan seamount from 9 August to 9 October 2019 based on eye-witness accounts and satellite data discussed below, as well as additional Aqua/MODIS satellite images from NASA Worldview. Blue Marble MODIS/NASA Earth Observatory base map courtesy of NASA Worldview.

The first sighting of pumice was around 1430 on 9 August NW of Vava'u in Tonga (18° 22.068' S, 174° 50.800' W), when Shannon Lenz and Tom Whitehead on board SV Finely Finished initially encountered isolated rocks and smaller streaks of pumice clasts. The area covered by rock increasing to a raft with an estimated thickness of at least 15 cm that extended to the horizon in different directions, and which took 6-8 hours to cross (figure 8). There was no sulfur smell and the sound was described as a "cement mixer, especially below deck." There was also no plume or incandescence observed. Their video, posted to YouTube on 17 August, showed a thin surface layer of cohesive interconnected irregular streaks of pumice with the ocean surface still visible between them. Later footage showed a continuous, undulating mass of pumice entirely covering the ocean surface. Larger clasts are visible scattered throughout the raft. The pumice raft was visible in satellite imagery on this day NW of Late Island (figure 9). By 11 August the raft had evolved into a largely linear feature with smaller rafts to the SW (figure 10). Approximately four hours later, about 15 km to the WSW, Rachel Mackie encountered the pumice. Initially the pumice was "ribbons several hundred meters long and up to 20m wide. It was quite fine and like a slick across the surface of the water." By 2130 they were surrounded by the pumice, and around 25 km away the smell of sulfur was noted.

Figure (see Caption) Figure 8. The pumice raft from the unnamed Tongan seamount on 9 August 2019 taken by Shannon Lenz and Tom Whitehead on board SV Finely Finished. The photos show the pumice raft extending to the horizon in different directions. Scattered larger clasts protrude from the relatively smooth surface that entirely obscures the ocean surface. Courtesy of Shannon Lenz and Tom Whitehead via noonsite.
Figure (see Caption) Figure 9. The pumice raft from the unnamed Tongan seamount on 9 August 2019 (UTC) can be seen NW of Late Island of Tonga in this Aqua/MODIS satellite image. The dashed white line encompasses the visible pumice. The location of the pumice in this image is shown in figure 7. Courtesy of NASA WorldView.
Figure (see Caption) Figure 10. The Sentinel-2 satellite first imaged the pumice from the unnamed Tongan seamount on 11 August 2019 (UTC). This image indicates the pumice distribution with the main raft towards the W and the easternmost area of pumice approximately 45 km away. The eastern tip of the pumice area is located approximately 30 km WNW of Lake islands in Tonga. The location of the pumice in this image is shown in figure 7. Natural color (bands 4, 3, 2) Sentinel-2 satellite image courtesy of Sentinel Hub Playground.

Michael and Larissa Hoult aboard the catamaran ROAM encountered the raft on 15 August (figure 11). They initially saw isolated clasts ranging from marble to tennis ball size (15-70 mm) at 18° 46′S, 174° 55'W. At around 0700 UTC (1900 local time) they noted the smell of sulfur at 18° 55′S, 175° 21′W, and by 0800 UTC they were immersed in the raft with visible clasts ranging from marble to basketball (25 cm) sizes. At this point the raft was entirely obscuring the ocean surface. On 16 and 21 August the pumice continued to disperse and drift NW (figures 12 and 13). On 20 August Scott Bryan calculated an average drift rate of around 13 km/day, with the pumice on this date about 164 km W of the unnamed seamount.

Figure (see Caption) Figure 11. Images of pumice from the unnamed Tongan seamount encountered by Michael and Larissa Hoult aboard the catamaran Roam on 15 August. Left: Larissa takes photographs with scale of pumice clasts; top right: a closeup of a pumice clast showing the vesicle network preserving the degassing structures of the magma; bottom left: Michael holding several larger pumice clasts. The location of their encounter with the pumice is shown in figure 7. Courtesy of SailSurfROAM.
Figure (see Caption) Figure 12. The pumice from the unnamed Tongan seamount (volcano number 243091) on 16 August 2019 UTC. The location of the pumice in this image is shown in figure 7. Natural color (bands 4, 3, 2) Sentinel-2 satellite image courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 13. On 21 August 2019 (UTC) the pumice from the unnamed Tongan seamount (volcano number 243091) had drifted at least 120 km WNW of Late Island in Tonga. The location of the pumice in this image is shown in figure 7. Natural color (bands 4, 3, 2) Sentinel-2 satellite image courtesy of Sentinel Hub Playground.

An online article published by Brad Scott at GeoNet on 9 September reported the preliminary size of the raft to be 60 km2, significantly smaller than the 2012 Havre seamount pumice raft that was 400 km2. Satellite identification of pumice-covered areas by GNS scientists showed the material moving SSW through 14 August (figure 14).

Figure (see Caption) Figure 14. A compilation of mapped pumice raft extents from 9 August (red line) through to 14 August (dark blue) from Suomi NPP, Terra, Aqua, and Sentinel-2 satellite images. The progression of the pumice raft is towards the SW. Courtesy of Salman Ashraf, GNS Science.

On 5 September the Maritime Safety Authority of Fiji (MSAF) issued a notice to mariners stating that the pumice was sighted in the vicinity of Lakeba, Oneata, and Aiwa Islands and was moving to the W. On 6 September a Planet Labs satellite image shows pumice encompassing the Fijian island of Lakeba over 450 km W of the Tongan islands (figure 15). The pumice entered the lagoon within the barrier reef and drifted around the island to continue towards the W. The pumice was imaged by the Landsat 8 satellite on 26 September as it moved through the Fijian islands, approximately 760 km away from its source (figure 16). The pumice is segmented into numerous smaller rafts of varying sizes that stretch over at least 140 km. On 12 September the Fiji Sun reported that the pumice had reached some of the Lau islands and was thick enough near the shore for people to stand on it.

Figure (see Caption) Figure 15. Planet Labs satellite images show Lakeba Island to the E of the larger Viti Levu Island in the Fiji archipelago. The top image shows the island on 7 July 2019 prior to the pumice raft from the unnamed Tongan seamount. The bottom image shows pumice on the sea surface almost entirely encompassing the island on 6 September. The location of the pumice in this image is shown in figure 7. Courtesy of Planet Labs.
Figure (see Caption) Figure 16. Landsat 8 satellite images show the visible extent of the unnamed seamount pumice on 26 September 2019 (UTC), up to approximately 760 km from the Tongan islands. The pumice seen here extends over a distance of 140 km. The top image shows the locations of the other three images in the white boxes, with a, b, and c indicating the locations. White arrows point to examples of the light brown pumice rafts in these images, seen through light cloud cover. The island in the lower right is Koro Island, the island to the lower left is Viti Levu, and the island to the top right is Vanua Levu. The location of the pumice in this image is shown in figure 7. Landsat 8 true color-pansharpened satellite images courtesy of Sentinel Hub.

Pumice had reached the Yasawa islands in western Fiji by 29 September and was beginning to fill the eastern bays (figure 17). By 9 October bays had been filled out to 500-600 m from the shore, and pumice had also passed through the islands to continue towards the W (figure 18). At this point the pumice beyond the islands had broken up into linear segments that continued towards the NW.

Figure (see Caption) Figure 17. These Sentinel-2 satellite images show the pumice from the unnamed Tongan seamount drifting towards the Yasawa islands of Fiji. The 24 September 2019 (UTC) image shows the beaches without the pumice, the 29 September image shows pumice drifting westward towards the islands, and the 9 October image shows the bays partly filled with pumice out to a maximum of 500-600 m from the shore. These islands are approximately 850 km from the Tongan islands. The Yasawa islands coastline impacted by the pumice shown in these images stretches approximately 48 km. The location of the pumice in this image is shown in figure 7. Sentinel-2 natural color (bands 4, 3, 2) satellite images courtesy of Sentinel Hub.
Figure (see Caption) Figure 18. This Sentinel-2 satellite image acquired on 9 October 2019 (UTC) shows expanses of pumice from the unnamed Tongan seamount that passed through the Yasawa islands of Fiji and was continuing NWW, seen in the center of the image. The location of the pumice in this image is shown in figure 7. Sentinel-2 natural color (bands 4, 3, 2) satellite images courtesy of Sentinel Hub.

Geologic Background. A submarine volcano along the Tofua volcanic arc was first observed in September 2001. The newly discovered volcano lies NW of the island of Vava'u about 35 km S of Fonualei and 60 km NE of Late volcano. The site of the eruption is along a NNE-SSW-trending submarine plateau with an approximate bathymetric depth of 300 m. T-phase waves were recorded on 27-28 September 2001, and on the 27th local fishermen observed an ash-rich eruption column that rose above the sea surface. No eruptive activity was reported after the 28th, but water discoloration was documented during the following month. In early November rafts and strandings of dacitic pumice were reported along the coast of Kadavu and Viti Levu in the Fiji Islands. The depth of the summit of the submarine cone following the eruption determined to be 40 m during a 2007 survey; the crater of the 2001 eruption was breached to the E.

Information Contacts: GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.gns.cri.nz/); Salman Ashraf, GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.gns.cri.nz/, https://www.geonet.org.nz/news/8RnSKdhaWOEABBIh0bHDj); Brad Scott, New Zealand GeoNet Project, a collaboration between the Earthquake Commission and GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.geonet.org.nz/, https://www.geonet.org.nz/news/8RnSKdhaWOEABBIh0bHDj); Scott Bryan, School of Earth, Environmental & Biological Sciences, Science and Engineering Faculty, Queensland University of Technology, R Block Level 2, 204, Gardens Point (URL: https://staff.qut.edu.au/staff/scott.bryan); Shannon Lenz and Tom Whitehead, SV Finely Finished (URL: https://www.noonsite.com/news/south-pacific-tonga-to-fiji-navigation-alert-dangerous-slick-of-volcanic-rubble/, YouTube: https://www.youtube.com/watch?v=PEsHLSFFQhQ); Michael and Larissa Hoult, Sail Surf ROAM (URL: https://www.facebook.com/sailsurfroam/); Rachel Mackie, OLIVE (URL: http://www.oliveocean.com/, https://www.facebook.com/rachel.mackie.718); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Planet Labs, Inc. (URL: https://www.planet.com/); Fiji Sun (URL: https://fijisun.com.fj/2019/09/12/pumice-menace-hits-parts-of-lau-group/).


Popocatepetl (Mexico) — September 2019 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


Frequent explosions continue during March-August 2019

The current eruptive period of Popocatépetl began on 9 January 2005 and it has since been producing frequent explosions accompanied by ash plumes, gas emissions, and ballistic ejecta that can impact several kilometers away from the crater, as well as dome growth and destruction. This activity continued through March-August 2019 with an increase in volcano alert level during 28 March-6 May. This report summarizes activity during this period and is based on information from Centro Nacional de Prevención de Desastres (CENAPRED), Universidad Nacional Autónoma de México (UNAM), and various webcam and remote sensing data.

An overflight on 28 February confirmed that dome 82, which was first observed on 14 February, was still present and was 200 m in diameter. During March there were 3,291 observed low-intensity emissions, and 33 larger explosions that produced ash plumes to a maximum height of 5 km, accompanied by near-continuous emission of water vapor and volcanic gases. Explosions ejected blocks that fell on the flanks out to 1.2-2 km on 1, 10, 13, 17, 26, 27, and 29 March. The events on the 17th and 27th resulted in vegetation fires. Frequent sulfur dioxide (SO2) plumes were detected by TropOMI (figure 130). An overflight on 7 March showed intense degassing and an ash plume at 1142, preventing visibility into the crater (figure 131). On 13 March Strombolian activity was observed for approximately 15 minutes at 0500, accompanied by incandescent ejecta that deposited mainly on the ESE flank.

An overflight on 15 March was taken by CENAPRED and UNAM personnel to observe changes to the crater after explosions on the 13th and 14th. They reported that dome 82 had been destroyed and the crater maintained its previous dimensions of 300 m in diameter and 130 m deep. An explosion on the 27th ejected incandescent rocks out to 2 km from the crater and produced a 3-km-high ash plume that dispersed to the NE. Ashfall was reported in Santa Cruz, Atlixco, San Pedro, San Andrés, Santa Isabel Cholula, San Pedro Benito Juárez, and in the municipalities of Puebla, Hueyapan, Tetela del Volcán, and Morelos.

On 28 March an explosion at 0650 generated a 2.5-km-high ash plume and ejecta out to 1 km from the crater, and a 130-minute-long event produced gas and ah plumes (figure 132). On this day the volcano alert level was increased from Yellow Phase 2 to Yellow Phase 3. On the 29th an ash plume rose to 3 km and was accompanied by ejecta that reached 2 km away from the crater. Later that day a 20-minute-long event produced ash and gas. During a surveillance flight on 30 March a view into the crater showed no dome present, and the crater size had increased to 350 m in width and 250-300 m in depth after recent explosions (figure 131). On this day Strombolian activity was also observed lasting for 14 minutes, producing an ash plume to 800 m and ejecta out to 300 m from the crater. Incandescence at the crater was often seen during nighttime throughout the month.

Figure (see Caption) Figure 130. Significant SO2 plumes at Popocatépetl detected by the TROPOMI instrument on the Sentinel-5P satellite during 3-11 March 2019. SO2 plumes are frequently observed and these images show examples of plume drift directions on 3 March 2019 (top left), 6 March 2019 (top right), 7 March 2019 (bottom left), and 11 March 2019 (bottom right). Date, time, and measurements are provided at the top of each image. Courtesy of NASA Goddard Flight Center.
Figure (see Caption) Figure 131. Activity at Popocatépetl and views of the crater during surveillance flights in March 2019. The top images show an ash plume (left) and a gas-and-steam plume (right) on 7 March. On 30 March (bottom left and right) no lava dome was observed in the crater, which was measured to be 350 m in diameter and 250-300 m deep. Courtesy of CENAPRED and Geophysics Institute of UNAM.
Figure (see Caption) Figure 132. Explosive activity at Popocatépetl on 28 March 2019 producing ash plumes (top and bottom left) and ejecting incandescent ejecta out to 2 km from the crater at 1948. Courtesy of Carlos Sanchez/AFP (top), CENAPRED (bottom left and right), and Webcams de Mexico (bottom left).

There was a decrease in events during the next two months with 1,119 recorded low-intensity emissions and no larger ash explosions throughout April, followed by 1,210 low-intensity emissions and seven larger ash explosions through May (figure 133). Water vapor and volcanic gas emissions were frequently observed through this time and incandescence was observed some nights. A surveillance overflight on 26 April noted no new dome within the crater. On 6 May the alert level was lowered back to Yellow Phase 2. Another overflight on 9 May showed no change in the crater. An explosion at 1910 on 22 May produced an ash plume to 3.5 km above the crater with ashfall reported in Ozumba, Temamatla, Atlautla, Cocotitlán, Ayapango, Ecatzingo, Tenango del Aire and Tepetlixpa.

Figure (see Caption) Figure 133. Graph showing the number of daily ash explosions and low-intensity emissions at Popocatépetl during March-August 2019. There was a decrease in the number of events during April and March, with an increase from March onwards. Data courtesy of CENAPRED.

Through the month of June there were 2,820 low-intensity emissions and 21 larger ash explosions recorded. Gas emissions were observed throughout the month. Two explosions on 3 June produced ash plumes up to 3.5 and 2.8 km, with ejecta out to 2 km S during the first explosion. On 11 June an explosion produced an ash plume to 1 km above the crater and ballistic ejecta out to 1 km E. Observers on a surveillance overflight on the 12th reported no changes within the crater

Explosions with estimated plume heights of 5 km occurred on the 14th and 15th, with the latter producing ashfall in the municipalities of San Pablo del Monte, Tenancingo, Papantla, San Cosme Mazatencocho, San Luis Teolocholco, Acuamanala, Nativitas, Tepetitla, Santa Apolonia Teacalco, Santa Isabel Tetlatlahuaca, and Huamantla, in the state of Tlaxcala, as well as in Nealtican, San Nicolás de los Ranchos, Calpan, San Pedro Cholula, Juan C. Bonilla, Coronango, Atoyatempan, and Coatzingo, in the state of Puebla.

On 17 June an explosion produced an ash plume that reached 8 km above the crater and dispersed towards the SW. An ash plume rising 2.5 km high was accompanied by incandescent ejecta impacting a short distance from the crater on the 21st, and another ash plume reached 2.5 km on the 22nd. Explosions on 26, 29, and 30 June resulted in ash plumes reaching 1.5 km above the crater and ballistic ejecta impacting on the flanks out to 1 km.

For the month of July there was an increased total of 5,637 recorded low-intensity emissions, and 173 larger ash explosions (figure 134). On 8 July an explosion produced ballistic ejecta out to 1.5 km and an ash plume up to 1 km above the crater. An ash plume up to 2.6 km was produced on the 12th. On 19 July a surveillance overflight observed a new dome (dome 83) with a diameter of 70 m and a thickness of 15 m (figure 135). Explosions on 20 July produced ashfall, and minor explosions that ejected incandescent ballistics onto the slopes. An event on the 24th produced an ash plume that reached 1.2 km, and ash plumes the following day reached 1 km. An overflight on 27 July confirmed that these explosions destroyed dome 83, and the crater dimensions remained the same (figure 136). The following day, ash plumes reached up to 1.6 km above the crater, and up to 2 km on the 29th. Minor ashfall was reported in the municipality of Ozumba on 30 June.

Figure (see Caption) Figure 134. Examples of ash plumes at Popocatépetl on 1 July (top left), 18 July (top right and bottom left), and 30 July (bottom right) 2019. In the night time image taken on 18 July hot rocks are visible on the flank. Webcam images courtesy of CENAPRED and Webcams de Mexico.
Figure (see Caption) Figure 135. A surveillance overflight at Popocatépetl on 19 July 2019 confirmed a new dome, dome number 83, with a width of 70 m and a thickness of 15 m. Courtesy of CENAPRED and Geophysics Institute of UNAM.
Figure (see Caption) Figure 136. Photos of the summit crater of Popocatépetl taken during a surveillance flight on 27 July 2019 confirmed that the 83rd lava dome was destroyed by recent explosions and the crater maintained the same dimensions as previously measured. Courtesy of CENAPRED and Geophysics Institute of UNAM.

Throughout August the number of recorded events was higher than previous months, with 5,091 low-intensity emissions and 204 larger ash explosions (figure 137). Two explosions generated ash plumes and incandescent ejecta on 2 August, the first with a plume up to 1.5 km with ejecta impacting the slopes, and the second with an 800 m plume and ejecta landing back in the crater. Ashfall from the events was reported in in the municipalities of Tenango del Aire, Ayapango and Amecameca. On the 14th ashfall was reported in Juchitepec, Ayapango, and Ozumba. Explosions on 16 August produced ash plumes up to 2 km that dispersed to the WSW. Over the following two days ash plumes reached 1.2 km and resulted in ashfall in Cuernavaca, Tepoztlán, Tlalnepantla, Morelos, Ozumba, and Ecatzingo. Over 30-31 August ash plumes reached between 1-2 km above the crater and ashfall was reported in Amecameca, Atlautla, Ozumba, and Tlalmanalco. Incandescence was sometimes observed at the crater through the month.

Figure (see Caption) Figure 137. Ash plumes at Popocatépetl on 7 August (top) and 26 August 2019 (bottom). Courtesy of CENAPRED and Webcams de Mexico.

The MODVOLC algorithm for MODIS thermal anomalies registered thermal alerts through this period, with 22 in March, three in May, five in July, and one in August. The MIROVA system showed that the frequency of thermal anomalies at Popocatépetl was higher in March, sporadic in April and May, low in June, and had increased again in July and August (figure 138). Elevated temperatures were frequently visible in Sentinel-2 thermal satellite data when clouds and plumes were not covering the crater (figure 139).

Figure (see Caption) Figure 138. Thermal activity at Popocatépetl detected by the MIROVA system showed frequent anomalies in March, intermittent anomalies through April-May, low activity in June, and an increase in July-August 2019. Courtesy of MIROVA.
Figure (see Caption) Figure 139. Sentinel-2 thermal satellite images frequently showed elevated temperatures in the crater of Popocatépetl during March-August 2019, as seen in this representative image from 7 May 2019. Sentinel2- atmospheric penetration (bands 12, 11, 8A) scene courtesy of Sentinel Hub Playground.

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

Information Contacts: Centro Nacional de Prevención de Desastres (CENAPRED), Av. Delfín Madrigal No.665. Coyoacan, México D.F. 04360, México (URL: http://www.cenapred.unam.mx/); Universidad Nacional Autónoma de México (UNAM), University City, 04510 Mexico City, Mexico (URL: https://www.unam.mx/); 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/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://SO2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Webcams de Mexico (URL: http://www.webcamsdemexico.com/); Agence France-Presse (URL: http://www.afp.com/).


Semeru (Indonesia) — September 2019 Citation iconCite this Report

Semeru

Indonesia

8.108°S, 112.922°E; summit elev. 3657 m

All times are local (unless otherwise noted)


Intermittent activity continues during March-August 2019; ash plumes and thermal anomalies

The ongoing eruption at Semeru weakened in intensity during 2018, with occasional ash plumes and thermal anomalies (BGVN 44:04); this reduced but ongoing level of activity continued through August 2019. The volcano is monitored by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM) and the Darwin Volcanic Ash Advisory Centre (VAAC). The current report summarizes activity from 1 March to 31 August 2019. The Alert Level remained at 2 (on a scale from 1-4); the public was warned to stay 1 km away from the active crater and 4 km away on the SSE flank.

Based on analysis of satellite images, the Darwin VAAC reported that ash plumes rose to an altitude of 4-4.3 km on 19 April, 20 June, 10 July, and 13 July, drifting in various directions. In addition, PVMBG reported that at 0830 on 26 June an explosion produced an ash plume that rose around 600 m above the summit and drifted SW. A news article (Tempo.com) dated 12 August cited PVMBG as stating that the volcano had erupted 17 times since 8 August.

During March-August 2019 thermal anomalies were detected with the MODIS satellite instruments analyzed using the MODVOLC algorithm only on 5 July and 22 August. No explosions were recorded on those two days. Scattered thermal anomalies within 5 km of the volcano were detected by the MIROVA (Middle InfraRed Observation of Volcanic Activity) system, also based on analysis of MODIS data: one at the end of March and 3-6 hotspots over the following months, almost all of low radiative power. Satellite imagery intermittently showed thermal activity in the Jonggring-Seloko crater (figure 37), sometimes with material moving down the SE-flank ravine.

Figure (see Caption) Figure 37. Sentinel-2 satellite images showing the persistent elevated thermal anomaly in the Jonggring-Seloko crater of Semeru were common through August 2019, as seen in this view on 20 July. Hot material could sometimes be identified in the SE-flank ravine. Atmospheric penetration rendering (bands 12, 11, 8A) courtesy of Sentinel Hub Playground.

Geologic Background. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

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/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Tempo.com (URL: https://www.tempo.com/).


Saunders (United Kingdom) — August 2019 Citation iconCite this Report

Saunders

United Kingdom

57.8°S, 26.483°W; summit elev. 843 m

All times are local (unless otherwise noted)


Intermittent activity most months, October 2018-June 2019; photographs during February and May 2019

Historical observations of eruptive activity from the glacier-covered Mount Michael stratovolcano on Saunders Island in the South Sandwich Islands were not recorded until the early 19th century at this remote site in the southernmost Atlantic Ocean, and remain extremely rare. With the advent of satellite observation technology, indications of more frequent eruptive activity have become apparent. Vapor emission is frequently reported from the summit crater, and AVHRR and MODIS satellite imagery has revealed evidence for lava lake activity in the summit crater (Lachlan-Cope and others, 2001). Limited thermal anomaly data and satellite imagery indicated at least intermittent activity during May 2000-November 2013, and from November 2014 through April 2018 (Gray and others, 2019). Ongoing observations, including photographs from two site visits in February and May 2019 suggest continued activity at the summit during most months through May 2019, the period covered in this report. Information, in addition to on-site photographs, comes from MIROVA thermal anomaly data, NASA SO2 instruments, and Sentinel-2 and Landsat satellite imagery.

Near-constant cloud coverage for much of the year makes satellite data intermittent and creates difficulty in interpreting the ongoing nature of the activity. Gray and others (2019) concluded recently after a detailed study of shortwave and infrared satellite images that there was continued evidence for the previously identified lava lake on Mount Michael since January 1989. MIROVA thermal anomaly data suggest intermittent pulses of thermal energy in September, November, and December 2018, and April 2019 (figure 17). Satellite imagery confirmed some type of activity, either a dense steam plume, evidence of ash, or a thermal anomaly, each month during December 2018-March 2019. Sulfur dioxide anomalies were recorded in January, February, and March 2019. Photographic evidence of fresh ash was captured in February 2019, and images from May 2019 showed dense steam rising from the summit crater.

Figure (see Caption) Figure 17. MIROVA thermal anomaly data from 19 September 2018 through June 2019 showed sporadic, low-level pulses of thermal energy in late September, November, and December 2018, and April 2019. Courtesy of MIROVA.

After satellite imagery and thermal anomaly data in late September 2018 showed evidence for eruptive activity (BGVN 43:10, figure 16), a single thermal anomaly in MIROVA data was recorded in mid-November 2018 (figure 17). A rare, clear Sentinel-2 image on 2 December revealed a dense steam plume over the active summit crater; the steam obscured the presence of any possible thermal anomalies beneath (figure 18).

Figure (see Caption) Figure 18. Sentinel-2 images of Mount Michael on Saunders Island on 2 December 2018 revealed a dense steam plume over the summit crater that was difficult to distinguish from the surrounding snow in Natural Color rendering (bands 4,3,2) (left), but was clearly visible in Atmospheric Penetration rendering (bands 12,11, 8a) (right). Courtesy of Sentinel Hub Playground.

Clear evidence of recent activity appeared on 1 January 2019 with both a thermal anomaly at the summit crater and a streak of ash on the snow (figure 19). Steam was also present within the summit crater. A distinct SO2 anomaly appeared in data from the TROPOMI instrument on 14 January (figure 20).

Figure (see Caption) Figure 19. A thermal anomaly and dense steam were recorded at the summit of Mount Michael on Saunders Island on 1 January 2019 in Sentinel-2 Satellite imagery with Atmospheric Penetration rendering (bands 12, 11, 8a) (left). The same image shown with Natural Color rendering (bands 4,3,2) (right) shows a recent streak of brown particulates drifting SE from the summit crater. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 20. A distinct SO2 plume was recorded drifting NW from Saunders Island by the TROPOMI instrument on the Sentinel 5-P satellite on 14 January 2019. Courtesy of NASA Goddard Space Flight Center.

Multiple sources of satellite data and sea-based visual observation confirmed activity during February 2019. SO2 emissions were recorded with the TROPOMI instrument on 10, 11, 15, and 16 February (figure 21). A Landsat image from 10 February showed a dense steam plume drifting NW from the summit crater, with the dark rim of the summit crater well exposed (figure 22). Sentinel-2 images in natural color and atmospheric penetration renderings identified a dense steam plume drifting S and a thermal anomaly within the summit crater on 15 February (figure 23). An expedition to the South Sandwich Islands between 15 February and 8 March 2019 sponsored by the UK government sailed by Saunders in late February and observed a stream of ash on the NNE flank beneath the cloud cover (figure 24).

Figure (see Caption) Figure 21. Faint but distinct SO2 plumes were recorded drifting away from Saunders Island in various directions on 10, 11, 15, and 16 February 2019. Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 22. The dark summit crater of Mount Michael on Saunders Island was visible in Landsat imagery on 10 February 2019. A dense steam plume drifted NW and cast a dark shadow on the underlying cloud cover. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 23. At the summit of Mount Michael on Saunders Island, Sentinel-2 images in Natural Color (bands 4,3,2) (left) and Atmospheric Penetration (bands 12, 11, 8a) (right) renderings identified a dense steam plume drifting S and a thermal anomaly within the summit crater on 15 February 2019. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 24. Recent ash covered the NNE flank of Mount Michael on Saunders Island in late February 2019 when observed by an expedition to the South Sandwich Islands sponsored by the UK government. Courtesy of Chris Darby.

Faint SO2 emissions were recorded twice during March 2019 (figure 25), and a dense steam plume near the summit crater was visible in Landsat imagery on 23 March (figure 26). Two thermal anomalies were captured in the MIROVA data during April 2019 (figure 17).

Figure (see Caption) Figure 25. Faint SO2 plumes were recorded on 1 and 11 March 2019 emerging from Saunders Island. Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 26. A dense steam plume drifted E from the summit crater of Mount Michael at Saunders Island on 25 March 2019. Landsat-8 image courtesy of Sentinel Hub Playground.

A volcano-related research project "SSIVOLC" explored the South Sandwich Islands volcanoes during 15 April-31 May 2019. A major aim of SSIVOLC was to collect photogrammetric data of the glacier-covered Mount Michael (Derrien and others, 2019). A number of still images were acquired on 17 and 22 May 2019 showing various features of the island (figures 27-30). The researchers visually observed brief, recurrent, and very weak glow at the summit of Mount Michael after dark on 17 May, which they interpreted as reflecting light from an active lava lake within the summit crater.

Figure (see Caption) Figure 27. The steep slopes of an older eroded crater on the E end of Saunders island in the 'Ashen Hills' shows layers of volcanic deposits dipping away from the open half crater. In the background, steam and gas flow out of the summit crater of Mount Michael and drift down the far slope. Drone image PA-IS-03 taken during 17-22 May 2019, courtesy of Derrien and others (2019) used under Creative Commons Attribution 4.0 International (CC-BY 4.0) License.
Figure (see Caption) Figure 28. A dense steam plume drifts away from the summit of Mount Michael on Saunders Island in this drone image taken during 17-22 May 2019. The older summit crater is to the left of the dark patch in the middle of the summit. North is to the right. Image SU-3 courtesy of Derrien and others (2019) used under Creative Commons Attribution 4.0 International (CC-BY 4.0) License.
Figure (see Caption) Figure 29. This close-up image of the summit of Mount Michael on Saunders Island shows steam plumes billowing from the summit crater, and large crevasses in the glacier covered flank, taken during 17-22 May 2019. The old crater is to the left. Image TL-SU-1 courtesy of Derrien and others (2019) used under Creative Commons Attribution 4.0 International (CC-BY 4.0) License.
Figure (see Caption) Figure 30. A dense plume of steam rises from the summit crater of Mount Michael on Saunders Island and drifts over mounds of frozen material during 17-22 May 2019. The older crater is to the left, and part of the Ashen Hills is in the foreground. Image TL-SU-2 courtesy of Derrien and others (2019) used under Creative Commons Attribution 4.0 International (CC-BY 4.0) License.

References: Lachlan-Cope T, Smellie J L, Ladkin R, 2001. Discovery of a recurrent lava lake on Saunders Island (South Sandwich Islands) using AVHRR imagery. J. Volcanol. Geotherm. Res., 112: 105-116.

Gray D M, Burton-Johnson A, Fretwell P T, 2019. Evidence for a lava lake on Mt. Michael volcano, Saunders Island (South Sandwich Islands) from Landsat, Sentinel-2 and ASTER satellite imagery. J. Volcanol. Geotherm. Res., 379:60-71. https://doi.org/10.1016/j.volgeores.2019.05.002.

Derrien A, Richter N, Meschede M, Walter T, 2019. Optical DSLR camera- and UAV footage of the remote Mount Michael Volcano, Saunders Island (South Sandwich Islands), acquired in May 2019. GFZ Data Services. http://doi.org/10.5880/GFZ.2.1..2019.003

Geologic Background. Saunders Island is a volcanic structure consisting of a large central edifice intersected by two seamount chains, as shown by bathymetric mapping (Leat et al., 2013). The young constructional Mount Michael stratovolcano dominates the glacier-covered island, while two submarine plateaus, Harpers Bank and Saunders Bank, extend north. The symmetrical Michael has a 500-m-wide summit crater and a remnant of a somma rim to the SE. Tephra layers visible in ice cliffs surrounding the island are evidence of recent eruptions. Ash clouds were reported from the summit crater in 1819, and an effusive eruption was inferred to have occurred from a N-flank fissure around the end of the 19th century and beginning of the 20th century. A low ice-free lava platform, Blackstone Plain, is located on the north coast, surrounding a group of former sea stacks. A cluster of parasitic cones on the SE flank, the Ashen Hills, appear to have been modified since 1820 (LeMasurier and Thomson, 1990). Vapor emission is frequently reported from the summit crater. Recent AVHRR and MODIS satellite imagery has revealed evidence for lava lake activity in the summit crater.

Information Contacts: 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/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Chris Darby (URL: https://twitter.com/ChrisDDarby, image at https://twitter.com/ChrisDDarby/status/1100686838568812544).


Pacaya (Guatemala) — August 2019 Citation iconCite this Report

Pacaya

Guatemala

14.382°N, 90.601°W; summit elev. 2569 m

All times are local (unless otherwise noted)


Lava flows and Strombolian explosions continued during February-July 2019

Pacaya is one of the most active volcanoes in Guatemala, with activity largely consisting of frequent lava flows and Strombolian activity at the Mackenney crater. This report summarizes continued activity during February through July 2019 based on reports by Guatemala's Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH) and Sistema de la Coordinadora Nacional para la Reducción de Desastres (CONRED), visiting scientists, and satellite data.

At the beginning of February activity included Strombolian explosions ejecting material up to 5 to 30 m above the Mackenney crater and a degassing plume up to 300 m. Multiple lava flows were observed throughout the month on the N, NW, and W flanks, reaching 350 m from the crater and resulting in avalanches from the flow fronts. Strombolian activity continued with sporadic to continuous explosions ejecting material 5-75 m above the Mackenney crater. Degassing produced plumes up to 300 m above the crater, and incandescence from the crater and lava flows were seen at night. Daniel Sturgess of Bristol University observed activity on the 24th, noting a 70-m-long lava flow with individual blocks from the front of the flow rolling down the flanks (figure 108). He reported that mild Strombolian explosions occurred every 10-20 minutes and ejected blocks, up to approximately 4 m in diameter, as high as 5-30 m above the crater and towards the northern flank.

Figure (see Caption) Figure 108. An active lava flow on the NW flank of Pacaya on 24 February 2019 with incandescence visible in lower light conditions. Courtesy of Daniel Sturgess, University of Bristol.

Similar activity continued through March with multiple lava flows reaching a maximum of 200 m N and NW, and avalanches descending from the flow fronts. Ongoing Strombolian explosions expelled material up to 75 m above the Mackenney crater. Degassing produced a white-blue plume to a maximum of 900 m above the crater (figure 109) and incandescence was noted some nights.

Figure (see Caption) Figure 109. A degassing plume at Pacaya reaching 350 m above the crater and dispersing to the S on 19 March 2019. Courtesy of CONRED.

During April lava flows continued on the N and NW flanks, reaching a maximum length of 300 m, with avalanches forming from the flow fronts. Degassing formed plumes up to 600 m above the crater that dispersed with various wind directions. Strombolian activity continued with explosions ejecting material up to 40 m above the crater. On the 2nd and 3rd weak rumbles were heard at distances of 4-5 km. Similar activity continued through May with lava flows reaching 300 m to the N, degassing producing plumes up to 600 m above the crater, and Strombolian explosions ejecting material up to 15 m above the crater.

Lava flows continued out to 300 m in length to the N and NW during June (figures 110 and 111). Strombolian activity ejected material up to 30 m above the crater and degassing resulted in plumes that reached 300 m. During July there were multiple active lava flows that reached a maximum of 300 m in length on the N and NW flanks (figure 112). Avalanches generated by the collapse of material at the front of the lava flows were accompanied by explosions ejecting material up to 30 m above the crater.

Figure (see Caption) Figure 110. An active lava flow on Pacaya on 9 June 2019 with incandescent blocks rolling down the flank from the flow front. Courtesy of Paul Wallace, University of Liverpool.
Figure (see Caption) Figure 111. Activity at Pacaya on 22 June 2019 with a degassing plume dispersed to the W and a 300-m-long lava flow. Photos by Miguel Morales, courtesy of CONRED.
Figure (see Caption) Figure 112. Two lava flows were active to the N and NW at Pacaya on 20 July 2019. Photos courtesy of CONRED.

During February through July multiple lava flows and crater activity were detected in Sentinel-2 satellite thermal images (figures 113 and 114) and relatively constant thermal energy was detected by the MIROVA system with a slight decrease in the energy and frequency of anomalies during June (figure 115). The thermal anomalies detected by the MODVOLC system for each month from February through July spanned 6-30, with six during June and 30 during April.

Figure (see Caption) Figure 113. Sentinel-2 thermal satellite images of Pacaya show lava flows to the N and NW during February through April 2019. There was a reduction in visible activity in early March. False color (urban) satellite images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 114. Sentinel-2 thermal satellite images of Pacaya showing lava flow and hot avalanche activity during June and July 2019. False color (urban) satellite images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 115. MIROVA log radiative power plot of MODIS thermal infrared at Pacaya during October 2018 through July 2019. Detected thermal energy is relatively stable with a decrease through June and subsequent increase during July. Courtesy of MIROVA.

Geologic Background. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); Coordinadora Nacional para la Reducción de Desastres (CONRED), Av. Hincapié 21-72, Zona 13, Guatemala City, Guatemala (URL: http://conred.gob.gt/www/index.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/); 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/); Daniel Sturgess, School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, United Kingdom (URL: http://www.bristol.ac.uk/earthsciences/); Paul Wallace, Department of Earth, Ocean and Ecological Sciences, University of Liverpool, 4 Brownlow Street, Liverpool L69 3GP, United Kingdom (URL: https://www.liverpool.ac.uk/environmental-sciences/staff/paul-wallace/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Colima (Mexico) — August 2019 Citation iconCite this Report

Colima

Mexico

19.514°N, 103.62°W; summit elev. 3850 m

All times are local (unless otherwise noted)


Renewed volcanism after two years of quiet; explosion on 11 May 2019

Frequent historical eruptions at Volcán de Colima date back to the 16th century and include explosive activity, lava flows, and large debris avalanches. The most recent eruptive episode began in January 2013 and continued through March 2017. Previous reports have covered activity involving ash plumes with extensive ashfall, lava flows, lahars, and pyroclastic flows (BGVN 41:01 and 42:08). In late April 2019, increased seismicity related to volcanic activity began again. This report covers activity through July 2019. The primary source of information was the Centro Universitario de Estudios e Investigaciones de Vulcanologia, Universidad de Colima (CUEIV-UdC).

On 11 May 2019, CUEIV-UdC reported an explosion that was recorded by several monitoring stations. A thermal camera located south of Colima captured thermal anomalies associated with the explosion as well as intermittent degassing, which mainly consisted of water vapor (figure 131). A report from the Unidad Estatal de Protección Civil de Colima (UEPCC), and seismic and infrasound network data from CUEIV-UdC, recorded about 60 high-frequency events, 16 landslides, and 14 low-magnitude explosions occurring on the NE side of the crater during 11-24 May. Drone imagery showed fumarolic activity occurring on the inner wall of this crater on 22 May (figure 132).

Figure (see Caption) Figure 131. Gas emissions from Colima during the 11 May 2019 eruption as seen from the Naranjal station. Courtesy of CUEIV-UdC (Boletin Seminal de la Actividad del Volcan de Colima 17 mayo 2019 no 121).
Figure (see Caption) Figure 132. A drone photo showing fumarolic activity occurring within the NE wall of the crater at Colima on 22 May 2019. Courtesy of CUEIV-UdC (Boletin Seminal de la Actividad del Volcan de Colima 24 mayo 2019 no 122).

Small explosions and gas-and-steam emissions continued intermittently through mid-July 2019 concentrated on the NE side of the crater. An overflight on 9 July 2019 revealed that subsidence from the consistent activity slightly increased the diameter of the vent; other areas within the crater also showed evidence of subsidence and some collapsed material on the outer W wall (figure 133). During the weeks of 19 and 26 July 2019, monitoring cameras and seismic data recorded eight lahars.

Figure (see Caption) Figure 133. A drone photo of the crater at Colima on 8 July 2019 shows continuing fumarolic activity and evidence of a collapsed wall on the W exterior side. Courtesy of CUEIV-UdC (Boletin Seminal de la Actividad del Volcan de Colima 12 julio 2019 no 129).

Geologic Background. The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Information Contacts: Centro Universitario de Estudios e Investigaciones de Vulcanologia, Universidad de Colima (CUEIV-UdC), Colima, Col. 28045, Mexico; Centro Universitario de Estudios Vulcanologicos y Facultad de Ciencias de la Universidad de Colima, Avenida Universidad 333, Colima, Col. 28045, Mexico (URL: http://portal.ucol.mx/cueiv/); Unidad Estatal de Protección Civil, Colima, Roberto Esperón No. 1170 Col. de los Trabajadores, C.P. 28020, Mexico (URL: http://www.proteccioncivil.col.gob.mx/).


Masaya (Nicaragua) — August 2019 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 activity declined during March-July 2019

Masaya, in Nicaragua, contains a lava lake found in the Santiago Crater which has remained active since its return in December 2015 (BGVN 41:08). In addition to this lava lake, previous volcanism included explosive eruptions, lava flows, and gas emissions. Activity generally decreased during March-July 2019, including the number and frequency of thermal anomalies, lava lake levels, and gas emissions. The primary source of information for this report comes from the Instituto Nicareguense de Estudios Territoriales (INETER).

On 21 July 2019 a small explosion in the Santiago Crater resulted in some gas emissions and an ash cloud drifting WNW. In addition to the active lava lake (figure 77), monthly reports from INETER noted that thermal activity and gas emissions (figure 78) were decreasing.

Figure (see Caption) Figure 77. Active lava lake visible in the Santiago Crater at Masaya on 27 June 2019. Photo by Sheila DeForest (Creative Commons BY-SA license).
Figure (see Caption) Figure 78. Gas emissions coming from the Santiago Crater at Masaya on 29 June 2019. Photo by Sheila DeForest (Creative Commons BY-SA license).

On 15 May and 22 July 2019, INETER scientists used a FLIR SC620 thermal infrared camera to measure temperatures of fumaroles on the Santiago Crater. In May 2019 the temperature of fumaroles had decreased by 48°C since the previous month. Between May and July 2019 fumarole temperatures continued to decline; temperatures ranged from 90° to 136°C (figure 79). Compared to May 2019 these temperatures are 3°C lower. INETER reports that the level of the lava lake has been slowly dropping during this reporting period.

Figure (see Caption) Figure 79. FLIR (forward-looking infrared) and visible images of the Santiago Crater at Masaya showing fumarole temperatures ranging from 90° to 136°C. The scale in the center shows the range of temperatures in the FLIR image. Courtesy of INETER (March 2019 report).

According to MIROVA (Middle InfraRed Observation of Volcanic Activity) data from MODIS satellite instruments, frequent thermal anomalies were recorded from mid-March through early May 2019, with little to no activity from mid-May to July 2019 (figure 80). Sentinel-2 thermal images show high temperatures in the active lava lake on 10 March 2019 (figure 81). Thermal energy detected by the MODVOLC algorithm showed 14 hotspot pixels with the most number of hotspots (7) occurring in March 2019.

Figure (see Caption) Figure 80. Thermal anomalies were relatively constant at Masaya from early September 2018 through early May 2019 and then abruptly decreased until mid-June 2019 as recorded by MIROVA. Courtesy of MIROVA.
Figure (see Caption) Figure 81. Sentinel-2 thermal satellite image showing a detected heat signature from the active lava lake at Masaya on 10 March 2019. The lava lake is visible (bright yellow-orange). Approximate diameter of the crater containing the lava lake is 500 m. Thermal (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Sheila DeForest (URL: https://www.facebook.com/sheila.deforest).


Rincon de la Vieja (Costa Rica) — August 2019 Citation iconCite this Report

Rincon de la Vieja

Costa Rica

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

All times are local (unless otherwise noted)


Occasional weak phreatic explosions during March-July 2019

The acid lake of Rincón de la Vieja's active crater has generated intermittent weak phreatic explosions regularly since 2011, continuing during the past year through at least August 2019. The volcano is monitored by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), and the information below comes from its weekly bulletins between 4 March and 2 September 2019. Clouds often prevented webcam and satellite views. The current report describes activity from March through July 2019.

OVSICORI-UNA reported that weak events occurred on 19 March at 1851 and on 29 March 2019 at 2043. A two-minute-long phreatic explosion on 1 April at 0802 produced a plume that rose 600 m above the crater rim. Continuous emissions were visible during 3-4 April, rising 200 m above the crater rim. On 3 April, at 1437, a small explosion was detected. An explosion on 10 April at 0617 produced a gas-and-steam plume that rose 1 km above the crater rim and drifted SE. On 12 April at 0643, a plume rose 500 m. Another event took place at 0700 on 13 April, although poor weather conditions prevented visual observations. On 14 April, OVSICORI-UNA noted that aerial photographs showed a milky-gray acid lake at a relatively low water level with convection cells of several tens meters of diameter in the center and eastern parts of the lake.

According to an OVSICORI-UNA bulletin, a small phreatic explosion occurred on 1 May. Another explosion on 11 May at 0720 produced a white gas-and-steam plume that rose 600 m above the crater rim. Phreatic explosions were recorded on 14 May at 1703 and on 17 May at 0357, though dense fog prevented visual confirmation of both events with webcams. On 15 May a local observer noted a diffuse plume of steam and gas, material rising from the crater, and photographed milky-gray deposits on the N part of the crater rim ejected from the event the day before. A major explosion occurred on 24 May.

OVSICORI-UNA recorded a significant phreatic 10-minute-long explosion that began on 11 June at 0343, but plumes were not visible due to weather conditions. No further phreatic events were reported in July.

Seismic activity was very low during the reporting period, and there was no significant deformation. Short tremors were frequent toward the end of April, but were only periodic in May and June; tremor almost disappeared in July. A few long-period earthquakes were recorded, and volcano-tectonic earthquakes were even less frequent.

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

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/, https://www.facebook.com/OVSICORI/).


Aira (Japan) — July 2019 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


Explosions with ejecta and ash plumes continue weekly during January-June 2019

Sakurajima rises from Kagoshima Bay, which fills the Aira Caldera near the southern tip of Japan's Kyushu Island. Frequent explosive and occasional effusive activity has been ongoing for centuries. The Minamidake summit cone has been the location of persistent activity since 1955; the Showa crater on its E flank has also been intermittently active since 2006. Numerous explosions and ash-bearing emissions have been occurring each month at either Minamidake or Showa crater since the latest eruptive episode began in late March 2017. This report covers ongoing activity from January through June 2019; the Japan Meteorological Agency (JMA) provides regular reports on activity, and the Tokyo VAAC (Volcanic Ash Advisory Center) issues tens of reports each month about the frequent ash plumes.

From January to June 2019, ash plumes and explosions were usually reported multiple times each week. The quietest month was June with only five eruptive events; the most active was March with 29 (table 21). Ash plumes rose from a few hundred meters to 3,500 m above the summit during the period. Large blocks of incandescent ejecta traveled as far as 1,700 m from the Minamidake crater during explosions in February and April. All the activity originated in the Minamidake crater; the adjacent Showa crater only had a mild thermal anomaly and fumarole throughout the period. Satellite imagery identified thermal anomalies inside the Minamidake crater several times each month.

Table 21. Monthly summary of eruptive events recorded at Sakurajima's Minamidake crater in Aira caldera, January-June 2019. The number of events that were explosive in nature are in parentheses. No events were recorded at the Showa crater during this time. Data courtesy of JMA (January to June 2019 monthly reports).

Month Ash emissions (explosive) Max. plume height above crater Max. ejecta distance from crater
Jan 2019 8 (6) 2.1 km 1.1 km
Feb 2019 15 (11) 2.3 km 1.7 km
Mar 2019 29 (12) 3.5 km 1.3 km
Apr 2019 10 (5) 2.2 km 1.7 km
May 2019 15 (9) 2.9 km 1.3 km
Jun 2019 5 (2) 2.2 km 1.3 km

There were eight eruptive events reported by JMA during January 2019 at the Minamidake summit crater of Sakurajima. They occurred on 3, 6, 7, 9, 17, and 19 January (figure 76). Ash plume heights ranged from 600 to 2,100 m above the summit. The largest explosion, on 9 January, generated an ash plume that rose 2,100 m above the summit crater and drifted E. In addition, incandescent ejecta was sent 800-1,100 m from the summit. Incandescence was visible at the summit on most clear nights. During an overflight on 18 January no significant changes were noted at the crater (figure 77). Infrared thermal imaging done on 29 January indicated a weak thermal anomaly in the vicinity of the Showa crater on the SE side of Minamidake crater. The Kagoshima Regional Meteorological Observatory (KRMO) (11 km WSW) recorded ashfall there during four days of the month. Satellite imagery indicated thermal anomalies inside Minamidake on 7 and 27 January (figure 77).

Figure (see Caption) Figure 76. Incandescent ejecta and ash emissions characterized activity from Sakurajima volcano at Aira during January 2019. Left: A webcam image showed incandescent ejecta on the flanks on 9 January 2019, courtesy of JMA (Explanation of volcanic activity in Sakurajima, January 2019). Right: An ash plume rose hundreds of meters above the summit, likely also on 9 January, posted on 10 January 2019, courtesy of Mike Day.
Figure (see Caption) Figure 77. The summit of Sakurajima consists of the larger Minamidake crater and the smaller Showa crater on the E flank. Left: The Minamidake crater at the summit of Sakurajima volcano at Aira on 18 January 2019 seen in an overflight courtesy of JMA (Explanation of volcanic activity in Sakurajima, March 2019). Right: Two areas of thermal anomaly were visible in Sentinel-2 satellite imagery on 27 January 2019. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

Activity increased during February 2019, with 15 eruptive events reported on days 1, 3, 7, 8, 10, 13, 14, 17, 22, 24, and 27. Ash plume heights ranged from 600-2,300 m above the summit, and ejecta was reported 300 to 1,700 m from the crater in various events (figure 78). KRMO reported two days of ashfall during February. Satellite imagery identified thermal anomalies at the crater on 6 and 26 February, and ash plumes on 21 and 26 February (figure 79).

Figure (see Caption) Figure 78. An explosion from Sakurajima at Aira on 7 February 2019 sent ejecta up to 1,700 m from the Minamidake summit crater. Courtesy of JMA (Explanation of volcanic activity in Sakurajima, February 2019).
Figure (see Caption) Figure 79. Thermal anomalies and ash emissions were captured in Sentinel-2 satellite imagery on 6, 21, and 26 February 2019 originating from Sakurajima volcano at Aira. Top: Thermal anomalies within the summit crater were visible underneath steam and ash plumes on 6 and 26 February (closeup of bottom right photo). Bottom: Ash emissions on 21 and 26 February drifted SE from the volcano. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

The number of eruptive events continued to increase during March 2019; there were 29 events reported on numerous days (figures 80 and 81). An explosion on 14 March produced an ash plume that rose 3,500 m above the summit and drifted E. It also produced ejecta that landed 800-1,100 m from the crater. During an overflight on 26 March a fumarole was the only activity in Showa crater. KRMO reported 14 days of ashfall during the month. Satellite imagery identified an ash plume on 13 March and a thermal anomaly on 18 March (figure 82).

Figure (see Caption) Figure 80. A large ash emission from Sakurajima volcano at Aira was photographed by a tourist on the W flank and posted on 1 March 2019. Courtesy of Kratü.
Figure (see Caption) Figure 81. An ash plume from Sakurajima volcano at Aira on 18 March 2019 produced enough ashfall to disrupt the trains in the nearby city of Kagoshima according to the photographer. Image taken from about 20 km away. Courtesy of Tim Board.
Figure (see Caption) Figure 82. An ash plume drifted SE from the summit of Sakurajima volcano at Aira on 13 March (left) and a thermal anomaly was visible inside the Minamidake crater on 18 March 2019 (right). "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

A decline in activity to only ten eruptive events on days 7, 13, 17, 22, and 25 was reported by JMA for April 2019. An explosion on 7 April sent ejecta up to 1,700 m from the crater. Another explosion on 13 April produced an ash plume that rose 2,200 m above the summit. Most of the eruptive events at Sakurajima last for less than 30 minutes; on 22 April two events lasted for almost an hour each producing ash plumes that rose 1,400 m above the summit. Ashfall at KRMO was reported during seven days in April. Two distinct thermal anomalies were visible inside the Minamidake crater on both 12 and 27 April (figure 83).

Figure (see Caption) Figure 83. Two thermal anomalies were present inside Minamidake crater at the summit of Sakurajima volcano at Aira on 12 (left) and 27 (right) April 2019. "Geology" rendering (bands 12, 4, and 2) courtesy of Sentinel Hub Playground.

There were 15 eruptive events during May 2019. An event that lasted for two hours on 12 May produced an ash plume that rose 2,900 m from the summit and drifted NE (figure 84). The Meteorological Observatory reported 14 days with ashfall during the month. Two thermal anomalies were present in satellite imagery in the Minamidake crater on both 17 and 22 May.

Figure (see Caption) Figure 84. An ash plume rose 2,900 m above the summit of Sakurajima at Aira on 12 May 2019 (left); incandescent ejecta went 1,300 m from the summit crater on 13 May. Courtesy of JMA (Explanation of volcanic activity in Sakurajima, May 2019).

During June 2019 five eruptive events were reported, on 11, 13, and 24 June; the event on 11 June lasted for almost two hours, sent ash 2,200 m above the summit, and produced ejecta that landed up to 1,100 m from the crater (figure 85). Five days of ashfall were reported by KRMO.

Figure (see Caption) Figure 85. A large ash plume on 11 June 2019 rose 2,200 m above the summit of Sakurajima volcano at Aira. Courtesy of Aone Wakatsuki.

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

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Mike Day, Minnesota, Twitter (URL: https://twitter.com/MikeDaySMM, photo at https://twitter.com/MikeDaySMM/status/1083489400451989505/photo/1); Kratü, Twitter (URL: https://twitter.com/TalesOfKratue, photo at https://twitter.com/TalesOfKratue/status/1101469595414589441/photo/1); Tim Board, Japan, Twitter (URL: https://twitter.com/Hawkworld_, photo at https://twitter.com/Hawkworld_/status/1107789108754038789); Aone Wakatsuke, Twitter (URL: https://twitter.com/AoneWakatsuki, photo at https://twitter.com/AoneWakatsuki/status/1138420031258210305/photo/3).


Agung (Indonesia) — June 2019 Citation iconCite this Report

Agung

Indonesia

8.343°S, 115.508°E; summit elev. 2997 m

All times are local (unless otherwise noted)


Continued explosions with ash plumes and incandescent ejecta, February-May 2019

After a large, deadly explosive and effusive eruption during 1963-64, Indonesia's Mount Agung on Bali remained quiet until a new eruption began in November 2017 (BGVN 43:01). Lava emerged into the summit crater at the end of November and intermittent ash plumes rose as high as 3 km above the summit through the end of the year. Activity continued throughout 2018 with explosions that produced ash plumes rising multiple kilometers above the summit, and the slow effusion of the lava within the summit crater (BGVN 43:08, 44:02). Information about the ongoing eruptive episode comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Center (VAAC), and multiple sources of satellite data. This report covers the ongoing eruption from February through May 2019.

Intermittent but increasingly frequent and intense explosions with ash emissions and incandescent ejecta characterized activity at Agung during February through May 2019. During February, explosions were reported three times; events on seven days in March were documented with ash plumes and ashfall in surrounding villages. Five significant events occurred during April; two involved incandescent ejecta that traveled several kilometers from the summit, and ashfall tens of kilometers from the volcano. Most of the five significant events reported in May involved incandescent ejecta and ashfall in adjacent villages; air traffic was disrupted during the 24 May event. Ash plumes in May reached altitudes over 7 km multiple times. Thermal activity increased steadily during the period, according to both the MIROVA project (figure 44) and MODVOLC thermal alert data. MAGMA Indonesia reported at the end of May 2019 that the volume of lava within the summit crater remained at about 25 million m3; satellite information indicated continued thermal activity within the crater. Alert Level III (of four levels) remained in effect throughout the period with a 4 km exclusion radius around the volcano.

Figure (see Caption) Figure 44. Thermal activity at Agung from 4 September 2018 through May 2019 was variable. The increasing frequency and intensity of thermal events was apparent from February-May. Courtesy of MIROVA.

Steam plumes rose 30-300 m high daily during February 2019. The Agung Volcano Observatory (AVO) and PVMBG issued a VONA on 7 February (UTC) reporting an ash plume, although it was not visible due to meteoric cloud cover. Incandescence, however, was observed at the summit from webcams in both Rendang and Karangasem City (16 km SE). The seismic event associated with the explosion lasted for 97 seconds. A similar event on 13 February was also obscured by clouds but produced a seismic event that lasted for 3 minutes and 40 seconds, and ashfall was reported in the village of Bugbug, about 20 km SE. On 22 February a gray ash plume rose 700 m from the summit during a seismic event that lasted for 6 minutes and 20 seconds (figure 45). The Darwin VAAC reported the plume visible in satellite imagery moving W at 4.3 km altitude. It dissipated after a few hours, but a hotspot remained visible about 10 hours later.

Figure (see Caption) Figure 45. An ash plume rose from the summit of Agung on 22 February 2019, viewed from the Besakih temple, 7 km SW of the summit. Courtesy of PunapiBali.

Persistent steam plumes rose 50-500 m from the summit during March 2019. An explosion on 4 March was recorded for just under three minutes and produced ashfall in Besakih (7 km SW); no ash plume was observed due to fog. A short-lived ash plume rose to 3.7 km altitude and drifted SE on 8 March (UTC) 2019. The seismic event lasted for just under 4 minutes. Ash emissions were reported on 15 and 17 March to 4.3 and 3.7 km altitude, respectively, drifting W (figure 46). Ashfall from the 15 March event spread NNW and was reported in the villages of Kubu (6 km N), Tianyar (14 km NNW), Ban, Kadundung, and Sukadana. MAGMA Indonesia noted that two explosions on the morning of 17 March (local time) produced gray plumes; the first sent a plume to 500 m above the summit drifting E and lasted for about 40 seconds, while the second plume a few hours later rose 600 m above the crater and lasted for 1 minute and 16 seconds. On 18 March an ash plume rose 1 km and drifted W and NW. An event on 20 March was measured only seismically by PVMBG because fog prevented observations. An eruption on 28 March produced an ash plume 2 km high that drifted W and NW. The seismic signal for this event lasted for about two and a half minutes. The Darwin VAAC reported the ash plume at 5.5 km altitude, dissipating quickly to the NW. No ash was visible four hours later, but a thermal anomaly remained at the summit (figure 47). Ashfall was reported in nearby villages.

Figure (see Caption) Figure 46. Ash plumes from Agung on 15 (left) and 17 (right) March 2019 resulted in ashfall in communities 10-20 km from the volcano. Courtesy of PVMBG and MAGMA Indonesia (Information on G. Agung Eruption, 15 March 2019 and Gunung Agung Eruption Press Release March 17, 2019).
Figure (see Caption) Figure 47. A thermal anomaly was visible through thick cloud cover at the summit of Agung on 29 March 2019 less than 24 hours after a gray ash plume was reported 2,000 m above the summit. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

The first explosion of April 2019 occurred on the 3rd (UTC); PVMBG reported the dense gray ash plume 2 km above the summit drifting W. A few hours later the Darwin VAAC raised the altitude to 6.1 km based on infrared temperatures in satellite imagery. The seismic signal lasted for three and a half minutes and the explosion was heard at the PGA Post in Rendang (12 km SW). Incandescent material fell within a radius of 2-3 km, mainly on the S flank (figure 48). Ashfall was reported in the villages of Telungbuana, Badeg, Besakih, Pempatan, Teges, and Puregai on the W and S flanks (figure 49). An explosion on 11 April also produced a dense gray ash plume that rose 2 km above the summit and drifted W. A hotspot remained about six hours later after the ash dissipated.

Figure (see Caption) Figure 48. Incandescent ejecta appeared on the flanks of Agung after an eruption on 4 April 2019 (local time) as viewed from the observation post in Rendang (8 km SW). Courtesy of Jamie Sincioco.
Figure (see Caption) Figure 49. Ashfall in a nearby town dusted mustard plants on 4 April 2019 from an explosion at Agung the previous day. Courtesy of Pantau.com (Photo: Antara / Nyoman Hendra).

PVMBG reported an eruption visible in the webcam early on 21 April (local time) that rose to 5.5 km altitude and drifted SW. The ash spread W and S and ash fell around Besakih (7 km SW), Rendang (8 km SW), Klungkung (25 km S), Gianyar (20 km WSW), Bangli (17 km WNW), Tabanan (50 km WSW), and at the Ngurah Rai-Denpasar Airport (60 km SW). About 15 hours later a new explosion produced a dense gray ash plume that rose to 3 km above the summit and produced incandescent ejecta in all directions as far as 3 km away (figure 50). The ash spread to the S and ashfall was reported in Besakih, Rendang, Sebudi (6 km SW), and Selat (12 km SSW). Both of the explosions were heard in Rendang and Batulompeh. The incandescent ejecta from the explosions remained within the 4-km exclusion zone. A satellite image on 23 April showed multiple thermal anomalies within the summit crater (figure 51). A dense gray plume drifted E from Agung on 29 April (30 April local time) at 4.6 km altitude. It was initially reported by ground observers, but was also visible in multispectral satellite imagery for about six hours before dissipating.

Figure (see Caption) Figure 50. An explosion at Agung on 21 April 2019 sent incandescent eject 3,000 m from the summit. Courtesy of MAGMA Indonesia (Gunung Agung Eruption Press Release April 21, 2019).
Figure (see Caption) Figure 51. Multiple thermal anomalies were still present within the summit crater of Agung on 23 April 2019 after two substantial explosions produced ash and incandescent ejecta around the summit two days earlier. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

PVMBG reported an eruption on 3 May 2019 that was recorded on a seismogram with a signal that lasted for about a minute. Satellite imagery reported by the Darwin VAAC showed a growing hotspot and possible ash near the summit at 4.3 km altitude moving NE. A few days later, on 6 May, a gray ash plume rose to 5.2 km altitude and drifted slowly W before dissipating; it was accompanied by a seismic signal that lasted for about two minutes. Explosions on 12 and 18 May produced significant amounts of incandescent ejecta (figure 52). The seismic signal for the 12 May event lasted for about two minutes; no plume was observed due to fog, but incandescent ejecta was visible on the flanks and the explosion was heard at Rendang. The Darwin VAAC reported an ash plume from the explosion on 17 May (18 May local time) at 6.1 km altitude in satellite imagery moving E. They revised the altitude a short while later to 7.6 km based on IR temperature and movement; the plume drifted N, NE, and E in light and variable winds. A few hours after that it was moving NE at 7.6 km altitude and SE at 5.5 km altitude; this lasted for about 12 hours until it dissipated. Ashfall was reported in villages downwind including Cutcut, Tongtongan, Bonyoh (20 km WNW), and Temakung.

Figure (see Caption) Figure 52. Explosions on 12 (left) and 18 (right) May (local time) 2019 produced substantial ejecta on the flanks of Agung visible from a distance of 10 km or more in PVMBG webcams. The ash plume from the 18 May event resulted in ashfall in numerous communities downwind. Courtesy of PVMBG (Information Eruption G. Agung, May 13, 2019, Information Eruption G. Agung, May 18, 2019).

The initial explosion on 18 May was captured by a webcam at a nearby resort and sent incandescent ejecta hundreds of meters down the NE flank within 20 seconds (figure 53). Satellite imagery on 3, 8, 13, and 18 May indicated multiple thermal anomalies growing stronger at the summit. All of the images were captured within 24 hours of an explosive event reported by PVMBG (figure 54).

Figure (see Caption) Figure 53. The 18 May 2019 explosion at Agung produced an ash plume that rose to over 7 km altitude and large bombs of incandescent material that traveled hundreds of meters down the NE flank within the first 20 seconds of the explosion. Images taken from a private webcam located 12 km NE. Courtesy of Volcanoverse, used with permission.
Figure (see Caption) Figure 54. Satellite images from 3, 8, 13, and 18 May 2019 at Agung showed persistent and increasing thermal anomalies within the summit crater. All images were captured within 24 hours of explosions reported by PVMBG. "Atmospheric Penetration" rendering (bands 12, 11, and 8A) courtesy of Sentinel Hub Playground.

PVMBG issued a VONA on 24 May 2019 reporting a new ash emission. They indicated that incandescent fragments were ejected 2.5-3 km in all directions from the summit, and the seismic signal lasted for four and a half minutes (figure 55). A dense gray ash plume was observed from Tulamben on the NE flank rising 2 km above the summit. Satellite imagery indicated that the plume drifted SW and ashfall was reported in the villages of Besakih, Pempatan, Menanga, Sebudi, Muncan, Amerta Bhuana, Nongan, Rendang, and at the Ngurah Rai Airport in Denpassar. Additionally, ashfall was reported in the districts of Tembuku, Bangli, and Susut (20 km SW). The Darwin VAAC reported an ash plume visible in satellite imagery at 4.6 km altitude along with a thermal anomaly and incandescent lava visible in webcam imagery. The remains of the ash plume were about 170 km S of the airport in Denpasar (60 km SW) and had nearly dissipated 18 hours after the event. According to a news article several flights to and from Australia were cancelled or diverted, though the International Gusti Ngurah Rai (IGNR) airport was not closed. On 31 May another large explosion produced the largest ash plume of the report period, rising more than 2 km above the summit (figure 56). The Darwin VAAC reported its altitude as 8.2 km drifting ESE visible in satellite data. It split into two plumes, one drifted E at 8.2 km and the other ESE at 6.1 km altitude, dissipating after about 20 hours.

Figure (see Caption) Figure 55. A large explosion at Agung on 24 May 2019 produced incandescent ejecta that covered all the flanks and dispersed ash to many communities to the SW. Courtesy of PVMBG (Gunung Agung Eruption Press Release 24 May 2019 20:38 WIB, Kasbani, Ir., M.Sc.).
Figure (see Caption) Figure 56. An explosion at Agung on 31 May 2019 sent an ash plume to 8.2 km altitude, the highest for the report period. Courtesy of Sutopo Purwo Nugroho, BNPB.

Geologic Background. Symmetrical Agung stratovolcano, Bali's highest and most sacred mountain, towers over the eastern end of the island. The volcano, whose name means "Paramount," rises above the SE caldera rim of neighboring Batur volcano, and the northern and southern flanks extend to the coast. The summit area extends 1.5 km E-W, with the high point on the W and a steep-walled 800-m-wide crater on the E. The Pawon cone is located low on the SE flank. Only a few eruptions dating back to the early 19th century have been recorded in historical time. The 1963-64 eruption, one of the largest in the 20th century, produced voluminous ashfall along with devastating pyroclastic flows and lahars that caused extensive damage and many fatalities.

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/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); The Jakarta Post, Mount Agung eruption disrupts Australian flights, (URL: https://www.thejakartapost.com/news/2019/05/25/mount-agung-eruption-disrupts-australian-flights.html); PunapiBali (URL: http://punapibali.com/, Twitter: https://twitter.com/punapibali, image at https://twitter.com/punapibali/status/1098869352588288000/photo/1); Jamie S. Sincioco, Phillipines (URL: Twitter: https://twitter.com/jaimessincioco. Image at https://twitter.com/jaimessincioco/status/1113765842557104130/photo/1); Pantau.com (URL: https://www.pantau.com/berita/erupsi-gunung-agung-sebagian-wilayah-bali-terpapar-hujan-abu?utm_source=dlvr.it&utm_medium=twitter); Volcanoverse (URL: https://www.youtube.com/channel/UCi3T_esus8Sr9I-3W5teVQQ); Sutopo Purwo Nugroho, BNPB (Twitter: @Sutopo_PN, URL: https://twitter.com/Sutopo_PN ).


Kerinci (Indonesia) — June 2019 Citation iconCite this Report

Kerinci

Indonesia

1.697°S, 101.264°E; summit elev. 3800 m

All times are local (unless otherwise noted)


Intermittent explosions with ash plumes, February-May 2019

Frequently active, Indonesia's Mount Kerinci on Sumatra has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838. Intermittent explosions with ash plumes, usually multiple times per month, have characterized activity since April 2018. Similar activity continued during February-May 2019, the period covered in this report with information provided primarily by the Indonesian volcano monitoring agency, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), MAGMA Indonesia, notices from the Darwin Volcano Ash Advisory Center (Darwin VAAC), and satellite data. PVMBG has maintained an Alert Level II (of 4) at Kerinci for several years.

On 13 February 2019 the Kerinci Volcano Observatory (KVO), part of PVMBG, noted a brownish-white ash emission that was drifting NE about 400 m above the summit. The seismicity during the event was dominated by continuous volcanic tremor. A brown ash emission was reported on 7 March 2019 that rose to 3.9 km altitude and drifted NE. Ash also drifted 1,300 m down the SE flank. Another ash plume the next morning drifted W at 4.5 km altitude, according to KVO. On 10, 11, and 13 March KVO reported brown ash plumes drifting NE from the summit at about 4.0-4.3 km altitude. The Darwin VAAC observed continuous ash emissions in satellite imagery on 15 March drifting W at 4.3 m altitude that dissipated after about 3 hours (figure 10). A gray ash emission was reported on 19 March about 600 m above the summit drifting NE; local news media noted that residents of Kayo Aro reported emissions on both 18 and 19 March (figure 11). An ash emission appeared in satellite imagery on 25 March (figure 10). On 30 March the observatory reported two ash plumes; a brown emission at 0351 UTC and a gray emission at 0746 UTC that both drifted NE at about 4.4 km altitude and dissipated within a few hours. PVMBG reported another gray ash plume the following day at a similar altitude.

Figure (see Caption) Figure 10. Sentinel-2 satellite imagery of Kerinci from 15 (left) and 25 (right) March 2019 showed evidence of ash plumes rising from the summit. Kerinci's summit crater is about 500 m wide. "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 11. Dense ash plumes from Kerinci were reported by local news media on 18 and 19 March 2019. Courtesy of Nusana Jambi.

Activity continued during April with a brown ash emission reported on 3 April by several different agencies; the Darwin VAAC and PVMBG daily reports noted that the plume was about 500 m above the summit (4.3 km altitude) drifting NE. KVO observed two brown ash emissions on 13 April (UTC) that rose to 4.2 km altitude and drifted NE. Satellite imagery showed minor ash emissions from the summit on 14 April; steam plumes 100-500 m above the summit characterized activity for the remainder of April (figure 12).

Figure (see Caption) Figure 12. A dilute ash emission rose from the summit of Kerinci on 14 April 2019 (left); only steam emissions were present on a clear 29 April in Sentinel-2 imagery (right). "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.

Ashfall on the NE and S flanks within 7 km of the volcano was reported on 2 May 2019. According to a news article, at least five villages were affected late on 2 May, including Tanjung Bungo, Sangir, Sangir Tengah, Sungai Rumpun, and Bendung Air (figures 13 and 14). The smell of sulfur was apparent in the villages. Brown ash emissions were observed on 3 and 4 May that rose to 4.6 and 4.1 km altitude and drifted SE. The Darwin VAAC reported an emission on 5 May, based on a pilot report, that rose to 6.7 km altitude and drifted NE for about an hour before dissipating. A brown ash emission on 10 May rose 700 m above the summit and drifted SE. Satellite imagery captured ash emissions from the summit on 14 and 24 May (figure 15). For the remainder of the month, 300-700-m-high dense steam plumes were noted daily until PVMBG reported white and brown plumes on 26 and 27 May rising 500-1,000 m above the summit. Although thermal anomalies were not reported during the period, persistent weak SO2 emissions were identified in TROPOMI instrument satellite data multiple times per month (figure 16).

Figure (see Caption) Figure 13. Ashfall was reported from five villages on the flanks of Kerinci on 2 May 2019. Courtesy of Uzone.
Figure (see Caption) Figure 14. An ash plume at Kerinci rose hundreds of meters on 2 May 2019; ashfall was reported in several nearby villages. Courtesy of Kerinci Time.
Figure (see Caption) Figure 15. Ash emissions from Kerinci were captured in Sentinel-2 satellite imagery on 14 (left) and 24 (right) May 2019. The summit crater is about 500 m wide. "Geology" rendering (bands 12, 4, 2), courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 16. Weak SO2 anomalies from Kerinci emissions were captured by the TROPOMI instrument on the Sentinel-5P satellite multiple times each month from February to May 2019. Courtesy of NASA Goddard Space Flight Center.

Geologic Background. Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

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/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Nuansa Jambi, Informasi Utama Jambi: (URL: https://nuansajambi.com/2019/03/20/gunung-kerinci-semburkan-asap-tebal/); Kerinci Time (URL: https://kerincitime.co.id/gunung-kerinci-semburkan-abu-vulkanik.html); Uzone.id (URL: https://news.uzone.id/gunung-kerinci-erupsi-5-desa-tertutup-abu-tebal).

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Bulletin of the Global Volcanism Network - Volume 31, Number 05 (May 2006)

Managing Editor: Richard Wunderman

Ambae (Vanuatu)

During May-June 2006, Lake Voui's water rapidly turns from blue to red

Anatahan (United States)

Eruptions restarted in 2005 and continued until at least June 2006

Bagana (Papua New Guinea)

Lava flows and ash emission throughout March 2006

Bulusan (Philippines)

Explosive activity continues

Daikoku (United States)

Discovery of agitated pool of molten sulfur at 420 m ocean depth

Heard (Australia)

2006 imagery indicates renewed volcanism

Krummel-Garbuna-Welcker (Papua New Guinea)

Earthquakes continue while vents remain calm through April 2006

Lamington (Papua New Guinea)

Mild vapor emission and earthquakes through March 2006

Langila (Papua New Guinea)

Moderate activity steady through March 2006

Merapi (Indonesia)

Mid-2006 brings multiple pyroclastic flows that kill two, and travel up to 7 km

NW Rota-1 (United States)

Views of submarine volcano ejecting lava and bombs

Popocatepetl (Mexico)

During first half of 2006, several ash plumes rose to ~ 7-8 km altitude

Rabaul (Papua New Guinea)

Gas emissions and earthquakes during March-April 2006

Soufriere Hills (United Kingdom)

Big dome collapse and tall plume on 20 May 2006 leave a W-leaning crater

St. Helens (United States)

Intracrater lava dome continues to grow through at least May 2006

Ubinas (Peru)

Ash and steam emissions stir hazard and environmental concerns

Villarrica (Chile)

Unusual seismicity, minor pyroclastic, and gas explosions, January-April 2005



Ambae (Vanuatu) — May 2006 Citation iconCite this Report

Ambae

Vanuatu

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

All times are local (unless otherwise noted)


During May-June 2006, Lake Voui's water rapidly turns from blue to red

Alain Bernard reported that Lake Voui in Aoba-Ambae volcano (BGVN 31:01) was undergoing a spectacular change in its color?the previously aqua-colored lake was turning red (figure 27).

Figure (see Caption) Figure 27. Lake Voui at Aoba as seen from the air on 28 May (top) and 3 June 2006 (bottom). Images courtesy of Esline Garaebiti (top) and Philippe Métois (bottom).

Images of a pale reddish Lake Voui were obtained by Esline Garaebiti, who flew over the volcano 28 May 2006. Philippe Métois, who flew over on 3 June 2006, photographed a blood-red lake. These photos were are posted on the CVL website along with recent ASTER temperature data. This color change was tentatively attributed to a rapid shift in the lake water's redox state. The change might be linked to the ratio of SO2/H2S in the hydrothermal fluids.

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: Alain Bernard, IAVCEI Commission on Volcanic Lakes (CVL), Université Libre de Bruxelles (ULB), CP160/02, avenue F.D. Roosevelt 50, Brussels, Belgium (URL: http://www.ulb.ac.be/sciences/cvl/aoba/Ambae1.html, http://www.ulb.ac.be/sciences/cvl/multispectral/multispectral2.htm); Esline Garaebiti, Department of Geology, Mines, and Water Resources (DGMWR), Port-Vila, Vanuatu; Philippe Métois, World of Wonders.


Anatahan (United States) — May 2006 Citation iconCite this Report

Anatahan

United States

16.35°N, 145.67°E; summit elev. 790 m

All times are local (unless otherwise noted)


Eruptions restarted in 2005 and continued until at least June 2006

Anatahan erupted almost continuously from 5 January 2005 until 3 September 2005 when eruptions suddenly ceased (BGVN 30:07, 30:08). Observations through 16 September indicated relative quiet. Indications from later reports (discussed below) are that this lull continued through at least mid- to late-February 2006. Eruptions resumed after that, although the observations suggest chiefly or entirely gas-rich plumes. Jenifer Piatt suggested that plumes after early September 2005 and through May 2006 rose only to low altitude, perhaps 2,500 m.

This report covers the period through early June 2006 and includes both field observations as well as several satellite-based SO2 measurements, and extensive satellite images of thin plumes assessed as vog (volcanic smog; table 5). Some of those plumes extended W to SW from Anatahan and had overall atmospheric SO2 masses on the order of up to 4 kilotons (kt).

Table 5. AURA/OMI SO2 from Anatahan plumes at stated dates in 2006 (the two indicated with asterisks ("**") shown as figures). The last column displays the plume's overall estimated SO2 mass. The second and third columns indicate, respectively, the area of the sulfurous plume, and the estimated maximum SO2 concentration (in DU) and its latitude and longitude. Courtesy of Simon Carn.

Date Time (UTC) Orbit Area of plume (km2) Highest concentration in Dobson Units (DU) Coordinates Atmospheric SO2 (kilotons)
15 Mar 2006 0400-0420** 08852 -- -- -- 1-2
12 Apr 2006 0249-0428** -- 9.1 x 104 1.9 DU 13.16°N, 137.26°E 2.2
16 Apr 2006 0401-0404 09318 9.8 x 104 6.7 DU 16.28°N, 145.39°E 3.9
23 Apr 2006 0407-0410 09420 11.0 x 104 4.6 DU 17.42°N, 143.06°E 3.5
31 May 2006 0331-0334 09979 4.8 x 104 3.0 DU 16.07°N, 145.24°E 1.4

During the week ending 19 September 2005, there were three periods of elevated tremor. On 13 September, technicians from the Emergency Management Office of the Commonwealth of the Northern Mariana Islands (EMO-CNMI) who were reinstalling seismic station ANA2 on Anatahan reported that the plume was gray, small, and moving to the NW. They heard no explosions and saw no craters or large ballistics in vicinity of ANA2.

CMNI-USGS reports for 3 September until at least 26 December 2005 noted an absence of erupted ash. At least as late as 27 February 2006, Anatahan lacked reported ash emissions. Also as late as the 27th, seismicity was at background levels, amounting to a few percent of the late June 2005 maximum, with occasional long-period earthquakes. On 27 February 2006, the Alert level was reduced to Normal and the Aviation Color Code to Green because of the continuing low levels of activity.

By the date of the next USGS update, on 20 March 2006, activity had increased somewhat and the Alert level was raised to Advisory and the Aviation Color Code to Yellow. A faint, thin plume of gas that was occasionally observable during January and February became continuous and slightly more dense on satellite imagery during the first three weeks of March.

Using the Ozone Monitoring Instrument (OMI) on NASA's EOS/Aura satellite, Simon Carn imaged Anatahan's plume of 15 March 2006 (figure 27). Anatahan lies at the solid triangle; the plume blew largely SW. Carn found that the atmospheric SO2 mass was 1-2 kilotons. He noted that there had been an upsurge in satellite-detected SO2 output that began in mid-February 2006. The highest concentrations of several OMI analyses (table 6 and figure 28) were measured on 16 and 23 April (3.9 and 3.5 kilotons of SO2, respectively).

Table 6. A summary of Anatahan plume data based on US AFWA satellite observations during 15 March to 31 May 2006. DMSP stands for Defense Meteorological Satellite Program. Courtesy of Charles Holliday and Jenifer E. Piatt, AFWA.

Date Time (UTC) Satellite (resolution or wavelength) Observation
15 Mar 2006 0354 Aqua Modis (500 m res.) Faint vog plume seen drifting generally SSW
16 Mar 2006 0125 Terra Modis (500 m res.) Vog seen drifting generally to the SW
17 Mar 2006 0330 Aqua Modis (1 km res.) Cloud cover obscured visibility
18 Mar 2006 0415 Aqua Modis (500 m res.) Vog plume appears longer and more dense, drifting generally SW
19 Mar 2006 0320 Aqua Modis (500 m res.) Moderately dense vog plume, extending over 370 km SW. No signature has been visible on MTSAT split window IR imagery nor NOAA channel differencing images, suggesting minimal ash content in the plume.
19 Mar 2006 1606 NOAA-18 Shortwave IR (3.55-3.93 µm) Hot spot visible at island
19 Mar 2006 2221 DMSP F-16 Visible (566 m res.) A very faint plume discernable out to 230 km SW from source
20 Mar 2006 0400 Aqua Modis (500 m res.) Vog plume drifting S and SW
20 Mar 2006 2209 DMSP F-16 Visible (556 m res.) Very light vog drifting SSW
21 Mar 2006 0305 Aqua Modis (500 m res.) Distinct vog plume drifting SSW
21 Mar 2006 1546 NOAA-18 Shortwave IR (3.55-3.93 µm) Hot spot indicated at island
24 Mar 2006 0035 Terra Modis (500 m res.) Vog plume drifting W then NW
24 Mar 2006 0804 DMSP F-13 Visible (1.11 km res.) Plume extended at least 833 km W before curling N. Using shadows, the plume is estimated at below ~1.2 km (4,000 ft).
29 Mar 2006 1604 NOAA - 18 Shortwave IR (3.55-3.93 µm) Hot spot indicated at island
29 Mar 2006 2110 DMSP F-13 Visual (1.11 km res.) Steam measures 37 km W and vog measures ~320 km SW and ~670 km NNE of the summit. Tops are estimated below ~1.5 km (5,000 ft).
29 Mar 2006 2110 DSMP F-13 Visual (556 m res.) Steam and vog visible at island; greater detail of vog trending ~320 km to SW
30 Mar 2006 0820 DMSP F-13 Visual (1.11 km res.) Steam measured 56 km NW; vog measured ~600 km SW and ~670 km NNE of the summit. Tops are estimated below ~1.5 km (5,000 ft).
30 Mar 2006 1554 NOAA 18 Shortwave IR (3.55-3.93 µm) Hot spot detected at the island
02 Apr 2006 1953 NOAA18 Shortwaave IR (3.55-3.93 µm) Hot spot detected
04 Apr 2006 0320 Aqua Modis (500 m res.) Cloud formation along the vog plume with tops estimated at below ~3 km (10,000 ft)
04 Apr 2006 0559 DMSP-F-12 Visual (556 m res.) Vog measures 210 km SSW of the summit
14 Apr 2006 0355 Aqua Modis (500 m res.) Vog drifting over ~390 km SW
14 Apr 2006 0808 DMSP F-13 Visual (556 m res.) Vog seen drifting over ~ 500 km SW, expanding extensively as it spreads
17 Apr 2006 0125 Terra Modis (500 m res.) Light vog plume blown over 400 km WSW to W
17 Apr 2006 1612 NOAA-18 Shortwave IR (3.55-3.93 µm) Hot spot visible
17 Apr 2006 2143 DMSP F-13 Visual (556 m res.) Vog measures over 490 km WSW
22 Apr 2006 2153 DMSP F-16 Visual (556 m res.) Faint vog plume trended ~40 km NW
23 Apr 2006 0045 Terra Modis (250 m res.) Possible gray steam/ash plume extending under 28 km NW and vog extending over 155 km NW
23 Apr 2006 1954 NOAA-17 Shortwave IR (3.55-3.93 µm) Hot spot detected at island
24 Apr 2006 0130 Terra Modis (500 m res.) Visible vog trended ~325 km W then curved ~130 km NE and dissipated
23 May 2006 0430 Aqua Modis (500 m res.) Vog seen drifting generally W, then curving S and SW
23 May 2006 0710 NOAA 15 Visual (1.85 km res.) Vog trending generally SW then W for ~390 km
26 May 2006 0130 Terra Modis (500 m res.) Vog trending WNW(?)
26 May 2006 0800 DMSP F-16 Visual (2.78 km res.) Vog seen drifting WSW for up to 1,250 km
26 May 2006 1234 NOAA 17 Shortwave IR (3.55-3.93 µm) Hot spot detected at the island
30 May 2006 2120 DMSP F-14 Visible (2.77 km res.) Plume extends over 1,480 km to the WSW
30 May 2006 2120 DMSP F-14 Visible (556 m res.) Plume extends over 1,480 to the WSW. NASA Aura/OMI estimated the columnar SO2 concentration associated with the plume.
31 May 2006 0315 Aqua Modis (500 m res.) Vog seen drifting generally to the SW, with great dispersion
Figure (see Caption) Figure 27. AURA/OMI image of SO2 from Anatahan at 0400-0420 UTC on 15 March 2006 (orbit 08852). The overall estimated SO2 mass in the 15 March plume was 1-2 kilotons. Concentration path-lengths for the atmospheric column are scaled in Dobson Units (DU). This is an example of a comparatively short plume, with greatest SO2 concentrations nearest the source, and blown somewhat more southerly than some of the later ones. Courtesy of Simon Carn.
Figure (see Caption) Figure 28. AURA/OMI image of SO2 from Anatahan at 0249-0428 UTC on 12 April 2006. The overall estimated SO2 mass in the 12 April plume was 2.2 kilotons (for other parameters and comparisons, see table 6). This is an example of a comparatively elongate plume, with highest SO2 registered in areas ~1,000 km ESE of the source. Courtesy of Simon Carn.

OMI is a Dutch-Finnish imaging spectrometer that measures ozone and other atmospheric trace gases such as SO2. OMI is a nadir-viewing imaging spectrometer that covers the ultraviolet and visible spectral range (270-500 nm). Its high spatial resolution increases the chance of observing cloud-free pixels, thereby enhancing the accuracy of the data products. OMI observes a strip of the Earth's surface about 2,600-2,800 km wide in one shot. The satellite's own movement along with Earth's rotation enables OMI to scan the entire globe. A two-dimensional CCD detector records both the complete swath and the spectrum of every ground pixel in the swath. The spatial information is imaged on one dimension of the CCD detector while the spectrum is projected along the other dimension of the CCD detector. OMI detects the total column amount of SO2 between the sensor and the Earth's surface and maps this quantity as it orbits.

On 17 March around 2200 UTC, the level of seismicity nearly doubled and continued at that level for 2 hours. On the 18th around 1400 UTC, the level of seismicity again nearly doubled and continued at that level for about 8 hours before returning to the baseline level prior to 17 March. The increased seismicity consisted of small (M 0-1) long-period earthquakes occurring approximately every minute, sometimes reaching two per minute. A total of about 600 such events were detected during 17 and 18 March. Volcanic Ash Advisories were issued by the Washington VAAC; plumes appeared to contain gas and only insignificant amounts of ash.

According to the Air Force Weather Agency (AFWA), on 19 March a hot spot at Anatahan was visible on satellite imagery. Vog (volcanic smog) extended 200 km from the island (figure 29).

Figure (see Caption) Figure 29. Anatahan's SW-drifting plume at 0320 UTC on 19 March as seen in a satellite image (AQUA MODIS, 500 m resolution) The US Air Force Weather Agency (AFWA) analysts interpreted this plume as vog. Courtesy of AFWA and NASA.

On 24 March around 1330, seismicity at Anatahan abruptly increased to about twice the background level. The seismicity consisted of low-amplitude tremor and small, long-period earthquakes, similar to the seismicity on 17 and 18 March. On 24 March, vog from Anatahan was visible on satellite imagery extending W, then curling N. The plume was estimated to be below 1.2 km altitude, and no ash or hot spots were visible. Anatahan remained at Alert level Advisory; Aviation Color Code Yellow (Volcanic activity has increased somewhat, but remains fairly low and is being closely monitored).

From 28 March to 4 April, seismic levels fluctuated. Seismicity again jumped up to about double the background level for a few hours on 29 and 31 March and 2 April. Anatahan continued to produce a gas-and-steam plume visible in satellite imagery. On 4 April, Saipan residents reported smog and the smell of sulphur.

On 8 April a team from EMO-CNMI visited Anatahan and found steam and gas discharging from the E crater along the SW crater wall above a discolored lake. Testing confirmed the presence of SO2 and H2S in the plume. The plume rose to an altitude of less than 2 km and drifted to the NW as brownish vog. No ash fell from the plume onto the island. Based on these results and satellite surveillance, Anatahan was inferred to be emitting steam, gas, and vog.

Three long-period earthquakes occurred on 14 and 15 April. Each was preceded by several minutes of significantly reduced seismicity. AFWA reported that a hot spot was visible on NOAA shortwave IR imagery on 17 April at 1612 UTC, and vog extended over 490 km WSW in F-13 imagery on 17 April at 2143 UTC. SO2 mass values for 23 April were the second highest in this reporting interval. On 24 April 2006 AFWA reported that hot spots were occasionally visible and that vog was nearly always visible in satellite images.

Throughout May 2006, Anatahan's E crater continued to emit vog that was visible in MODIS imagery. Seismicity levels were low throughout April and May. A few to several microearthquakes occurred each day, all with magnitudes M 1 or smaller.

Ash may have erupted in late May. Although ash was indicated on radar on 27 May, and in a pilot's report for 29 May, those events took place during intervals of such low seismicity that people watching that data felt eruptions were unlikely to have occurred then.

On the other hand, based on a pilot report, the Washington VAAC declared that an ash plume from Anatahan reached an altitude of 3 km on 29 May and drifted W. Vog issuing from the E crater was visible on satellite imagery at about 1333 on 29 May 2006, and increased prior to emission of an ash plume. A report issued from the Washington VAAC on 30 May at 0535 indicated a faint, low-level gas-and-ash plume extending from the summit. At 2120 UTC on 30 May the plume extended over 1,480 km WSW.

By 19 June continued gas and steam emissions remained visible in satellite imagery. Seismicity dropped from recent levels and occasional microearthquakes were recorded locally.

Geologic Background. The elongate, 9-km-long island of Anatahan in the central Mariana Islands consists of a large stratovolcano with a 2.3 x 5 km compound summit caldera. The larger western portion of the caldera is 2.3 x 3 km wide, and its western rim forms the island's high point. Ponded lava flows overlain by pyroclastic deposits fill the floor of the western caldera, whose SW side is cut by a fresh-looking smaller crater. The 2-km-wide eastern portion of the caldera contained a steep-walled inner crater whose floor prior to the 2003 eruption was only 68 m above sea level. A submarine cone, named NE Anatahan, rises to within 460 m of the sea surface on the NE flank, and numerous other submarine vents are found on the NE-to-SE flanks. Sparseness of vegetation on the most recent lava flows had indicated that they were of Holocene age, but the first historical eruption did not occur until May 2003, when a large explosive eruption took place forming a new crater inside the eastern caldera.

Information Contacts: Juan Takai Camacho and Ramon Chong, Emergency Management Office of the Commonwealth of the Northern Mariana Islands (EMO-CNMI), PO Box 100007, Saipan, MP 96950, USA (URL: http://www.cnmihsem.gov.mp/); Simon Carn, Joint Center for Earth Systems Technology (JCET), University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA; Charles Holliday and Jenifer E. Piatt, U.S. Air Force Weather Agency (AFWA)/XOGM, Offutt Air Force Base, NE 68113, USA.


Bagana (Papua New Guinea) — May 2006 Citation iconCite this Report

Bagana

Papua New Guinea

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

All times are local (unless otherwise noted)


Lava flows and ash emission throughout March 2006

Little activity had been recorded at Bagana since 18 September 2005, when forceful emissions of whitish-brown ash occurred, accompanied by ash fall in downwind areas and large booming noises. From the end of January to mid-April 2006 there were brief periods of effusive activity. The summit crater released moderate to dense white vapor throughout this time.

Emissions were forceful on 27 February, and on 3, 5, 7, 13, 22, 24, and 29 March. Denser emissions of pale gray ash clouds were reported on 27 March. Rumbling and roaring noises were heard on 15-16, 22, and 26-28 March. Moderate to bright glow was accompanied by projections of lava fragments and the advance of a lava flow down the S-SW flank, which was visible from 15 March until the end of the month. During April, the summit crater continued to release white vapor. A forceful emission was recorded on 8 April. A weak glow was visible on 9 April. Occasional weak rumbling noises were heard on 12-13 and 15 April. On 4 May, there was an ash plume visible on satellite imagery at a height of ~ 3 km (10,000 ft) altitude that extended 4 km W. On 18 June there was an ash-and-steam plume drifting SW; the height of the plume was not recorded.

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

Information Contacts: Ima Itikarai and Herman Patia, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Bulusan (Philippines) — May 2006 Citation iconCite this Report

Bulusan

Philippines

12.769°N, 124.056°E; summit elev. 1535 m

All times are local (unless otherwise noted)


Explosive activity continues

Bulusan erupted at 2258 on 21 March 2006, continuing into April 2006 (BGVN 31:04). Figure 2 shows the location of Bulusan volcano on the SE tip of Luzon. Figure 3 gives satellite measurements of SO2 one day after the eruption.

Figure (see Caption) Figure 2. Map of the Philippines showing the PHIVOLCS earthquake and volcano monitoring network, and Bulusan's location. Smaller inset focuses on the Bulusan region and indicates some settlements. The smaller map is from Encarta Maps; the larger map, courtesy of PHIVOLCS.
Figure (see Caption) Figure 3. Sulfur dioxide (SO2) emissions at 1345-1347 (local) on 22 March 2006 from Bulusan. The eruption was measured by the Ozone Monitoring Instrument (OMI) on NASA's EOS/Aura satellite [OMI detects the total column amount of SO2 between the sensor and the Earth's surface]. This cloud appeared quite significant (estimated total mass ~ 1,000 metric tons) considering that the event was reported as phreatic and that the image was collected about 15 hours after the eruption. Courtesy of Simon Carn.

An ash eruption on 29 April did not cause any damage, but authorities asked people to avoid the region near the crater (figure 4). The current report stems in large part from information coming from The Philippine Institute of Volcanology and Seismology (PHIVOLCS). Table 2 provides a brief summary of 2006 activity and resulting plumes.

Figure (see Caption) Figure 4. Image of a light ash plume snaking W from Bulusan acquired at 1250 on 29 April 2006. The image was made by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the U.S. National Aeronautics and Space Administration (NASA) Terra satellite. Courtesy of NASA Earth Observatory.

Table 2. Bulusan explosive plumes recorded during 2006. Courtesy of PHIVOLCS.

Date Local Time Plume character Plume height above summit Direction(s) of plume drift
21 Mar 2006 2258 ash 1.5 km N, W, SW
29 Apr 2006 1044 ash 1.5 km WSW, NW
25 May 2006 2117 ash -- W, SW
31 May 2006 1617 ash/steam 1.5 km W, WNW
07 Jun 2006 2017 ash/steam 2.0 km N, W, SW
10 Jun 2006 0018 ash/steam 1.0 km N, NE
13 Jun 2006 1904 ash/steam 1.5 km NW
18 Jun 2006 1556 ash/steam 1.5 km W
20 Jun 2006 2013 cloud-covered summit -- --
28 Jun 2006 0206 cloud-covered summit -- --

A phreatic ash explosion was recorded by the seismograph network at Bulusan between 2117 and 2130 on 25 May 2006. Light ashfall ranging from trace amounts to deposits 2 mm thick was reported from the W and SW villages of Bacolod, Sankayon, Puting Sapa, Rangas, Mapili, Caladgao, and Buraburan in the municipality of Juban, and Bolos in the municipality of Irosin, province of Sorsogon. PHIVOLCS reported that the ash explosion was more-or-less typical of activity at Bulusan during its current eruptive phase, and they expect more explosions to occur. Bulusan was at Alert Level 1, with a Permanent Danger Zone of 4 kilometers around the summit. The PHIVOLCS volcano alert signals range from Alert Level 1 (low-level unrest, no eruption imminent) through Alert Level 5 (hazardous explosive eruption in progress).

An ash-and-steam cloud emitted from the volcano on 31 May 2006 (figure 5) resulted in light ashfall, from trace amounts to 1.5 mm thickness, in areas W and NW of the volcano. An ash-and-steam cloud from Bulusan on 7 June 2006 resulted in light ashfall 5 km N and trace amounts as far as 20 km N. The Alert Level was raised to 2, which means restricted entry within 4 km of the summit. On 10 June, an ash-and-steam cloud reached a height of ~ 1 km above the summit and drifted N and NE. The Manila Standard Today reported one death caused by an asthma condition aggravated by exposure to ash.

Figure (see Caption) Figure 5. A Bulusan ash explosion seen at 1617 on 31 May 2006. The event was photographed from the foot of the volcano, 5- 6 km from the summit, in the town of Irosin. Courtesy of PHIVOLCS.

On 13 June 2006 at 1904, an explosion lasting ~13 minutes issued from a fissure W of the summit vent of Bulusan. It produced an ash-and-steam cloud (table 2). Ashfall up to 7 mm thick accumulated at the foot of the volcano in neighborhoods in the municipality of Juban.

On 18 June at 1556 , an explosion lasted ~11 minutes; it produced an ash-and-steam cloud (figure 6). This was the 8th explosion since Bulusan reactivated in March. Ash up to 5 mm thick fell on a W-flank village.

Figure (see Caption) Figure 6. Mount Bulusan spews ash on 18 June 2006. Courtesy of Associated Press.

On 20 June, a mild ash-and-steam explosion lasted approximately 17 minutes. The seismic network around the volcano recorded only one high frequency volcanic earthquake prior to the explosion. The ash and steam emission coincided with heavy rains that generated some lahars and torrential flows. The sulfur dioxide (SO2) emission rate that morning was 469 tons per day (t/d).

At 0800 on 26 June 2006, PHIVOLCS reported that the Bulusan seismic network had recorded four volcanic earthquakes during the past 24 hours. Steaming activity was wispy to moderate and reached an approximate height of 50 m above the summit before drifting WNW. On 28 June 2006, PHIVOLCS reported at 0800 that continuous seismic observation at Bulusan disclosed one small explosion-type earthquake and two volcanic earthquakes for the past 24 hours. The explosion occurred at 0206 on 28 June and lasted for about 4 minutes. However, the event was not observed because the summit was cloud covered all of 27 June until early in the morning of 28 June. No ashfall was reported following the explosion, and no lahar occurred at Gulang-gulang River in Cogon, Irosin. Sulfur dioxide (SO2) emission rates of the volcanic plume measured on 27 June decreased slightly, to 597 tons per day (t/d) in comparison to the 26 June 2006 rate of 942 t/d.

PHIVOLCS summarized the current 2006 activity as follows. In general, the character of explosions evolved only slightly, apparently becoming a little stronger later. The explosions in June were also somewhat longer in duration than earlier ash ejections, based on instrumental records and general visual monitoring. However, the absence of earthquakes, tremor, and generally low SO2 emission rates prior to each explosion suggested an absence of a large or active magmatic intrusion into shallow depths. Instead, they interpreted the sequence of explosions since March 2006 as pointing to interaction of small volumes of magma with an overlying water-saturated zone beneath the summit. These were thought to develop overpressures released during each explosion. It remains to be seen if the recent explosions would provide an "uncorking effect" and induce a major hazardous eruption. The very low earthquake activity was taken to suggests otherwise.

Geologic Background. Luzon's southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. It lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded since the mid-19th century.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), PHIVOLCS Building, C.P. Garcia Avenue, U.P. Campus, Diliman, Quezon City, PHILIPPINES (URL: http://www.phivolcs.dost.gov.ph/); Earth Observatory, National Aeronautics and Space Administration (NASA) (URL: http://earthobservatory.nasa.gov/NaturalHarards/); The Manila Standard Today (URL: http://manilastandard.net/); Simon Carn, Joint Center for Earth Systems Technology (JCET), University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250.


Daikoku (United States) — May 2006 Citation iconCite this Report

Daikoku

United States

21.324°N, 144.194°E; summit elev. -323 m

All times are local (unless otherwise noted)


Discovery of agitated pool of molten sulfur at 420 m ocean depth

Submarine exploration at Daikoku seamount has discovered a small pit or cauldron containing a pool of molten sulfur. During the period of 18 April-13 May 2006, scientists from the National Oceanic and Atmospheric Agency (NOAA), aboard the research vessel Melville completed the 2006 Submarine Ring of Fire Expedition. This expedition was the third in a series exploring of the submarine volcanoes lying along the Mariana arc (figure 1). The arc extends from S of the island of Guam northward more than 1,450 km. Daily logs of the 2006 expedition, including photographs and video clips, can be viewed on the NOAA Ocean Explorer website (see Information Contacts below).

Figure (see Caption) Figure 1. Bathymetric tectonic map of the Marianas arc showing islands and seamounts (with respective labels on backgrounds of dark and white). Reports in this issue discuss (from N to S), Diakoku, Anatahan, and NW Rotoa-1. Courtesy of Submarine Ring of Fire 2006 Expedition, NOAA Vents Program.

William Chadwick reported on the 2006 expedition (Oregon State University press release, 25 May 2006) that ". . . on another volcano called Daikoku, in the northern part of the Mariana volcanic arc, the researchers discovered a pool of molten sulfur at a depth of 420 m. It was measured at 187°C. It was a sulfur pond with a flexible 'crust' that was moving in a wavelike motion. The movement was triggered by continuous gases being emitted from beneath the pool and passing through the sulfur." (figure 2).

Figure (see Caption) Figure 2. On 4 May 2006 scientists piloting the submersible Remotely Operated Vehicle (ROV) Jason at Daikoku observed and photographed a convecting, black pool of liquid sulfur (inset, and upper image) with a partly solidified sulfur crust (bottom image). Gases, particulate with the appearance of smoke, and liquid sulfur were bubbling up from the back edge of the sulfur pool. The top image shows a zoomed-in view of the liquid sulfur extruding from a fracture in the solid crust. Image courtesy of Submarine Ring of Fire 2006 Expedition, NOAA Vents Program.

In another pit on the summit of Daikoku, over 100 m deep and ~ 80 m in diameter, the scientists observed a large plume of slowly rising white fluid.

References. Embley, R.W., Baker, E.T., Chadwick, W.W., Jr., Lipton, J.E., Resing, J.A., Massoth, G.J., and Nakamura, K., 2004, Explorations of Mariana Arc volcanoes reveal new hydrothermal systems: EOS, Transactions, American Geophysical Union, v. 85, no. 2, p. 37, 40.

Embley, R.W., Chadwick, W.W., Jr, Baker, E.T., Butterfield, D.A., Resing, J.A., de Ronde, C. E.J., Tunnicliffe, V., Lupton, J.E., Juniper, S.K., Rubin, K.H., Stern, R.J., Lebon, G.T., Nakamura, K., Merle, S.G., Hein, J.R., Wiens, D.A., and Tamura, Y., 2006, Long-term eruptive activity at a submarine arc volcano: Nature, v. 441, no. 7092, p. 494-497.

Oregon State University, 25 May 2006, Press Release: Nature paper details eruption activity at submarine volcano: College of Oceanic and Atmospheric Science (COAS), 104 COAS Admininstration Building, Corvallis, OR 97331.

Geologic Background. The conical summit of Daikoku seamount lies along an elongated E-W ridge SE of Eifuku submarine volcano and rises to within 323 m of the sea surface. It is one of about a dozen displaying hydrothermal activity in the southern part of the Izu-Marianas chain. A steep-walled, 50-m-wide cylindrical crater on the north flank, about 75 m below the summit, is at least 135 m deep and was observed to emit cloudy hydrothermal fluid. During a NOAA expedition in 2006, scientists observed a convecting, black pool of liquid sulfur with a partly solidified, undulating sulfur crust at a depth of 420 m below the summit. Gases, particulate with the appearance of smoke, and liquid sulfur were bubbling up from the back edge of the sulfur pool.

Information Contacts: William W. Chadwick, Jr., Cooperative Institute for Marine Resources Studies (CIMRS), NOAA Pacific Marine Environmental Laboratory (PMEL), 2115 SE OSU Drive, Newport, OR 97365 USA; NOAA Ocean Explorer (URL: http://oceanexplorer.noaa.gov/explorations/06fire/welcome.html).


Heard (Australia) — May 2006 Citation iconCite this Report

Heard

Australia

53.106°S, 73.513°E; summit elev. 2745 m

All times are local (unless otherwise noted)


2006 imagery indicates renewed volcanism

Matt Patrick observed from MODIS (Moderate Resolution Imaging Spectroradiometer) images analyzed by the HIGP MODVOLC algorithm that relatively new activity began in March 2006 at Heard Island. Two isolated alerts occurred on 11-12 March 2006, and sustained alerts occurred from 7-18 May, 28 May-5 June, and 13-20 June (table 1). Alerts were 1-3 pixels in size. The pixel locations all appeared to be clustered generally near the summit of Big Ben, suggesting central vent (lava lake?) activity rather than lava flows. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images over the last several months have all been cloudy and therefore unable to reinforce or support the MODVOLC results. However, a nighttime ASTER image on 29 May 2006 at 0110 showed the new activity (figure 9).

Table 1. MODVOLC alerts for 2006 through 21 June. Courtesy of Hawai'i Institute of Geophysical and Planetology (HIGP) Thermal Alerts Team.

Date Time (local) Pixels Satellite
11 Mar 2006 2315 1 Terra
12 Mar 2006 0100 2 Aqua
07 May 2006 0100 1 Terra
07 May 2006 2305 1 Terra
08 May 2006 0150 1 Aqua
09 May 2006 2255 1 Terra
10 May 2006 0140 1 Aqua
11 May 2006 2335 1 Terra
18 May 2006 2250 2 Terra
28 May 2006 2325 1 Terra
29 May 2006 0110 2 Aqua
02 Jun 2006 2345 3 Terra
03 Jun 2006 0130 2 Aqua
05 Jun 2006 0115 1 Aqua
13 Jun 2006 2325 2 Terra
14 Jun 2006 0110 4 Aqua
15 Jun 2006 0010 2 Terra
16 Jun 2006 0100 1 Aqua
20 Jun 2006 2330 1 Terra
Figure (see Caption) Figure 9. ASTER image of Heard Island taken at 0110 on 29 May 2006. The main image is the thermal infrared Band 14 (90 m pixel size), with the inserts showing the shortwave infrared (SWIR Band 9; 30 m pixel size) and thermal infrared (TIR Band 14) closeups. This a nighttime image with no visible bands with 15 m pixel size was difficult to interpret. The N-most segment of the summit anomaly, seen clearly in the Band 9 image, may be the vent, with the remainder of the anomaly possibly representing a ~ 900-m-long lava flow to the S. Alternatively, the segmentation of the anomaly may reflect different vents. Courtesy Matt Patrick, HIGP Thermal Alert Team.

The previous phases of activity spanned May 2000-February 2001 and June 2003-June 2004 (BGVN 29:12).

Geologic Background. Heard Island on the Kerguelen Plateau in the southern Indian Ocean consists primarily of the emergent portion of two volcanic structures. The large glacier-covered composite basaltic-to-trachytic cone of Big Ben comprises most of the island, and the smaller Mt. Dixon lies at the NW tip of the island across a narrow isthmus. Little is known about the structure of Big Ben because of its extensive ice cover. The historically active Mawson Peak forms the island's high point and lies within a 5-6 km wide caldera breached to the SW side of Big Ben. Small satellitic scoria cones are mostly located on the northern coast. Several subglacial eruptions have been reported at this isolated volcano, but observations are infrequent and additional activity may have occurred.

Information Contacts: Matt Patrick, HIGP Thermal Alerts Team, Hawai'i Institute of Geophysics and Planetology (HIGP) / School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Andrew Tupper, Darwin Volcanic Ash Advisory Centre, Bureau of Meteorology, Australia.


Krummel-Garbuna-Welcker (Papua New Guinea) — May 2006 Citation iconCite this Report

Krummel-Garbuna-Welcker

Papua New Guinea

5.416°S, 150.027°E; summit elev. 564 m

All times are local (unless otherwise noted)


Earthquakes continue while vents remain calm through April 2006

Garbuna remained relatively quiet between mid-February and mid-April 2006. The two vents at the summit released weak to moderate volumes of white vapor during this time, but no glow was observed. There was a weak rumbling noise on 14 April. Seismic activity remained at a low level. Few earthquakes were recorded during February and March; the daily average number of high-frequency events was 3 and of low-frequency events between 0 and 5. In April, a few earthquake swarms were recorded with individual events every 1-2 minutes. These episodes lasted less than 20 minutes. Low-frequency earthquakes occurred at the rate of 3-5 times per day and the Real-time Seismic Amplitude Measurement (RSAM) data was at background level fluctuating between 8 and 51 units.

Geologic Background. The basaltic-to-dacitic Krummel-Garbuna-Welcker Volcanic Complex consists of three volcanic peaks located along a 7-km N-S line above a shield-like foundation at the southern end of the Willaumez Peninsula. The central and lower peaks of the centrally located Garbuna contain a large vegetation-free area that is probably the most extensive thermal field in Papua New Guinea. A prominent lava dome and blocky lava flow in the center of thermal area have resisted destruction by thermal activity, and may be of Holocene age. Krummel volcano at the south end of the group contains a summit crater, breached to the NW. The highest peak of the group is Welcker volcano, which has fed blocky lava flows that extend to the eastern coast of the peninsula. The last major eruption from both it and Garbuna volcanoes took place about 1800 years ago. The first historical eruption took place at Garbuna in October 2005.

Information Contacts: Ima Itikarai and Herman Patia, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Lamington (Papua New Guinea) — May 2006 Citation iconCite this Report

Lamington

Papua New Guinea

8.95°S, 148.15°E; summit elev. 1680 m

All times are local (unless otherwise noted)


Mild vapor emission and earthquakes through March 2006

Lamington has continued the trend of relative quiet during mid-January to the end of March 2006. Consistent reporting has been difficult due to overcast weather. Small volumes of thin white vapor were released during this time. No audible noises or glow were recorded. High frequency earthquakes continued to be recorded. The highest total was 25 recorded on 18 February.

Geologic Background. Lamington is an andesitic stratovolcano with a 1.3-km-wide breached summit crater containing a lava dome. Prior to its renowned devastating eruption in 1951, the forested peak had not been recognized as a volcano. Mount Lamington rises above the coastal plain north of the Owen Stanley Range. A summit complex of lava domes and crater remnants tops a low-angle base of volcaniclastic deposits dissected by radial valleys. A prominent broad "avalanche valley" extends northward from the breached crater. Ash layers from two early Holocene eruptions have been identified. After a long quiescent period, the volcano suddenly became active in 1951, producing a powerful explosive eruption during which devastating pyroclastic flows and surges swept all sides of the volcano, killing nearly 3000 people. The eruption concluded with growth of a 560-m-high lava dome in the summit crater.

Information Contacts: Ima Itikarai and Herman Patia, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Langila (Papua New Guinea) — May 2006 Citation iconCite this Report

Langila

Papua New Guinea

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

All times are local (unless otherwise noted)


Moderate activity steady through March 2006

Moderate activity took place at Langila during January 2006, including continuous ash fall, rumbling, and weak emissions of lava fragments. During 20 January to 7 February eruptive activity was characterized by thin, pale gray ash clouds. Minimal noises were heard on 26-27 February. A changing weak-to-bright glow accompanied by projections of glowing lava fragments were visible on the nights of 22-23 and 28 February, and 1-2, and 6 March. Moderate-to-thick dark gray ash clouds were reported on 1-2, 6-7, and 9 March. Ash plumes rose less than 2 km above the summit crater before drifting SW-W of the volcano. Crater 3 remained quiet.

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

Information Contacts: Ima Itikarai and Herman Patia, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Merapi (Indonesia) — May 2006 Citation iconCite this Report

Merapi

Indonesia

7.54°S, 110.446°E; summit elev. 2910 m

All times are local (unless otherwise noted)


Mid-2006 brings multiple pyroclastic flows that kill two, and travel up to 7 km

Seismic activity at Merapi began to increase on 19 March 2006, leading the Center of Volcanology and Geological Hazard Mitigation (CVGHM) to raise the Alert Level from 1 to 2 (on a scale of 1-4). Ten thousand residents were warned to prepare for possible evacuation.

On 10 April, authorities banned mountain climbing due to reports of increased tremor. Unverified preliminary reports indicated "lava" reportedly flowing near Pasar Bubar village, ~ 350 m from the volcano's crater. At 1500 on 12 April, CVGHM raised the Alert Level from 2 to 3. No one was permitted within 8 km of the summit.

During 21-25 April, seismicity remained elevated; several seismic signals associated with rockfalls were recorded. The SO2 flux measured from Merapi was 175 metric tons on 22 April. On 22 and 23 April, fumarolic emissions rose 400 m above the summit. On 25 April, two rockslides from lava-flow fronts were heard from nearby observatories. According to news reports, about 600 of the approximately 14,000 people living near the volcano had been evacuated by 24 April.

According to news reports, on 27 April nearly 2,000 villagers were evacuated from Sidorejo and Tegalmulyo villages. That day, small amounts of ash fell in Gemer village about 5 km from the summit.

On 28 April, CVGHM reported volcanic material traveling ~ 1.5 km SW to the Lamat River. Seismicity that day was dominated by multi-phase earthquakes; but signals from landslides, rockfalls, and low-frequency events were also recorded.

On 6 May, gas plumes rose to 800 m above the summit and eighteen incandescent avalanches of volcanic material were observed. On 7 May, 26 incandescent avalanches that extended ~ 100 m were seen during the morning. On 6 and 7 May, the lava dome continued to grow and seismicity was dominated by multi-phase earthquakes. Shallow volcanic earthquakes and signals from landslides and rockfalls were also recorded. On 8 May, the Darwin VAAC reported that CVGHM warned of a plume rising to ~ 3.7 km, but no ash was visible on satellite imagery.

According to the Darwin VAAC, gas plumes that rose ~ 600 m above the summit were visible on satellite imagery on 11 May. Avalanches of incandescent material extended 200 m SE towards the Gendol River, and 1.5 km SW towards the Krasak River. Several small incandescent avalanches of volcanic material were visible from observatory posts. The new lava dome at the volcano's summit had grown to fill the gap between the 1997 and 2001 lava flows on the W side of the summit, and had reached a height about the same as the 1997 lava flows. Seismicity was dominated by multi-phase earthquakes and signals associated with avalanches.

At 0940 on 13 May, the Alert Level was raised from 3 to 4, the highest level, and ~ 4,500 people living near the volcano were evacuated.

On 15 May pyroclastic flows traveled as far as 4 km to the W. By 16 May, more than 22,000 people had been evacuated, according to figures posted at the district disaster center; about 16,870 people were evacuated from three districts in Central Java Province, and more than 5,600 others were evacuated from the Slemen district. On 17 May, pyroclastic flows traveled as far as 3 km. Local volcanologists reported that the lava dome continued to grow, but at a slower rate than during previous days.

Pyroclastic flows to the SW and SE reached 4 km on 19 May and 3 km on 20 May. On 22 May, the lava dome volume was estimated at ~ 2.3 million cubic meters. The Darwin VAAC reported that low-level emissions continued during 18-19 and 23 May. CVGHM recommended that residents who lived in valleys on the NNW flanks near Sat, Lamat, Senowo, Trising, and Apu Rivers and on the SE flank near Woro River be allowed to return to their homes. Residents remained evacuated from villages within a 7 km radius from the volcano's summit and within 300 m of the banks of the Krasak/Bebeng, Bedog, and Boyong Rivers to the SW, and the Gendol River to the SE.

According to news reports, an eruption produced a cloud of hot gas and ash on 17 May. Witnesses said the size of the plume was smaller than ash-and-gas plumes seen on 15 May. On 18 May, a representative for Merapi from the Center for Volcanological Research and Technology Development (part of CVGHM), reported new ashfall.

On 24-25 May, lava flows were observed moving SW towards the Krasak River and SE towards the Gendol River. News reports indicated that on 27 May a M 6.3 earthquake that killed about 5,400 people resulted in a three-fold increase in activity at Merapi. A M 5.9 earthquake coincided with pyroclastic flows of unknown origin that extended 3.8 km SW. During 28-30 May, multiple pyroclastic flows reached 3 km SE and 4 km SW. Gas plumes reached 500 m above the summit on 25 May, 1,200 m on 26 May, 100 m on 29 May, and 900 m on 30 May.

From 31 May to 6 June, SO2-bearing plumes were observed daily; on 1 June they reached 1.3 km above the summit. According to the Darwin VAAC, low-level emissions were visible on satellite imagery on 1 and 6 June. Multiple pyroclastic flows reached ~ 4 km SE toward the Gendol River and 3.5 km SW toward the Krasak and Boyong Rivers. CVGHM reported on 31 May that lava avalanches moved W for the first time during the recent eruption.

According to a volcanologist in Yogyakarta, lava-flow distances and dome volume had both approximately doubled since the 27 May M 6.2 earthquake. On 6 June, people living near the base of the volcano began to move into temporary shelters. Activities remain restricted within a 7 km radius from the volcano's summit and within 300 m of the banks of Krasak/Bebeng, Bedog, and Boyong Rivers to the SW, and Gendol River to the SE.

On 8 June, the lava-dome growth rate at Merapi was an estimated 100,000 cubic meters per day and the estimated volume was then ~ 4 million cubic meters. An estimated volume loss of 400,000 cubic meters on 4 June had been due to a partial collapse of the S part of the Geger Buaya crater wall, which was constructed from 1910 lava flows.

On 8 June, a pyroclastic flow, lasting 12 minutes, reached a distance of ~ 5 km SE toward the Gendol River, the predominant travel direction since the M 6.2 earthquake on 27 May. According to a news report, this event prompted approximately 15,500 people to evacuate from the Sleman district to the S and the Magelang district to the W. On 13 June, the Alert Level was lowered from 4 to 3 but renewed pyroclastic-flow activity the next day prompted a return to Alert Level 4.

Gas plumes were observed almost daily during 7-13 June and reached ~ 1.2 km above the summit on 10 June. The Darwin VAAC reported small ash plumes visible on satellite imagery; minor ashfall was reported to the S at an observatory outpost, and in Yogyakarta, about 32 km away.

Gas plumes emitted on 14 and 15 June reached 900 m above the summit. On 14 June a dome collapse lasting ~ 3.5 hours produced pyroclastic flows that reached 7 km SE. Two volunteers on a search-and-rescue team assisting with evacuation efforts were trapped in an underground refuge in Kaliadem village and died, the first fatalities of the current eruption. Stone (2006) wrote that the volunteers had ". . . sought refuge in a bunker, one of several on the mountain built for that contingency. The blast door was slightly ajar when rescuers dug down to the bunker the next day. The men had burned to death."

On 15 June, pyroclastic flows reached a distance of 4.5 km SE along the Gendol River. Pyroclastic flows continued during 16-19 June as a new dome grew. The Alert Level remained at 4.

During 21-25 June, seismic signals at Merapi indicated almost daily occurrences of rockfalls and pyroclastic flows. Due to inclement weather, pyroclastic flows were only observed on 24 June and reached a distance of 4 km SE along the Gendol River and 2.5 km SW along the Krasak River. Gas plumes were observed during 22-25 June and reached 1.5 km above the summit on 24 June.

Reference. Stone, Richard, 2006, Volcanology?Scientists steal a daring look at Merapi's explosive potential; Science, American Association for the Advancement of Science (AAAS), v. 312, pp. 1724-6.

Geologic Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities during historical time.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Associated Press (URL: http://news.yahoo.com/s/ap/indonesia_volcano); Reuters (URL: http://news.yahoo.com/s/nm/20060418/wl_nm/indonesia_volcano_dc_2).


NW Rota-1 (United States) — May 2006 Citation iconCite this Report

NW Rota-1

United States

14.601°N, 144.775°E; summit elev. -517 m

All times are local (unless otherwise noted)


Views of submarine volcano ejecting lava and bombs

During 18 April-13 May 2006, scientists from the National Oceanic and Atmospheric Agency (NOAA) and Oregon State University completed the 2006 Submarine Ring of Fire Expedition aboard the research vessel Melville. This expedition was the third in a series of explorations of the submarine volcanoes lying along the Mariana intra-ocean volcanic arc. That arc extends from S of the island of Guam northward more than 1,450 km through the Commonwealth of the Northern Mariana Islands (see map in above report on Daikoku). A previous expedition to Northwest Rota-1 in 2004 discovered and named this volcano and found it erupting (BGVN 29:03). Daily logs of the 2006 expedition, including photographs and video clips, can be viewed on the NOAA Ocean Explorer web site noted below, from which much of this report was taken.

On 23 and 24 April 2006, the unmanned (remotely operated vessel, ROV) submersible Jason 2 revisited Brimstone Pit, a spot on the volcano where an ash-and-gas plume was discovered in 2004 and observed again in 2005 (Embley and others, 2004 and 2006). The changes were striking. According to Robert Embley (Oregon State University press release, 25 May 2006), "we saw features of submarine volcanic activity never before directly observed, including explosions of lava from a crater accompanied by a red glow and voluminous volcanic gases and ejected rocks." A degassing event at Brimstone Pit began releasing bubbles that formed a growing submarine plume cloud. The Pit, at a depth of 560 m, was significantly deeper (by ~ 20 m) than it was in the previous visits and there appeared to have been a recent collapse of the summit area. The Pit exuded a sluggish pulsating cloud of white color along with some gas bubbles. Some time later, the pit was almost filled with the white cloud, which appeared to come from the lavas themselves. The observers concluded that they witnessed lava extruding on the seafloor.

Particle plumes were mapped using a light-scattering sensor (LSS), part of the CTD (conductivity-temperature-depth) instrument package towed over the summit and flanks of the volcano. The CTD revealed layers of turbid (cloudy) water extending as far as 8 km down the S flank, and to depths up to 2,900 m. The turbid layers may arise from periodic collapse of the unstable slopes of volcanic fallout material similar to that found in the white cloud observed at the summit.

Submersible dives on 25 April 2006 to the Brimstone Pit revealed a lava flow forming there. The initial approach to the Pit revealed a line of bubbles (mainly CO2) escaping from a fracture in the underlying rock. However, in place of the previously flat ground that described the Pit on 24 April, a small ash cone had formed. It was ~ 6 m in diameter with walls about 1 m high, made up entirely of fine-grained ash. As the submersible approached, observers saw a plume discharging out of the cone's center and, on closer inspection, it appeared that ash was raining out of the bottom of the plume and falling onto the flanks of the small cone.

Near Brimstone Pit, the submersible collected a piece of newly erupted andesite lava containing elemental sulfur filling vesicles. The lava flow advanced but slowly, traveling forward bit by bit, chunk by chunk. As the lava advanced, the flow's toe vigorously degassed. The emitted gas and the associated plume took on a yellow hue. Scientists interpreted the escaping gases as mainly sulfur-rich (SO2 and H2S), which can mix with and make the surrounding seawater strongly acidic and precipitate elemental sulfur, the source of the plume's yellow hue. Liquid native sulfur inside the plume was seen raining on the seafloor as small droplets and filled in the numerous holes in the lava where the gases escaped. Locally, carbon dioxide formed bubbles in front of the advancing lava. These different gases provided the force behind the vigorous 'mini-explosions' within the lava flow.

Finishing the last of six dives at Northwest Rota-1 on 29 April 2006, and combining observations from the two previous expeditions, scientists developed some conclusions about processes at this extremely dynamic site. Prior to arrival in 2006, a major landslide must have originated near Brimstone Pit. During the first day of 2006 submersible observations, a turbid layer generated by the slide surrounded the lower flanks. The next day, when the water had cleared, half of Brimstone Pit had fallen away and the seafloor around the vent was swept clean of recent lava. Over the next week, eruptive activity gradually increased in intensity and vigor. By the end of the week, a 5-m-high cone made of ash and lava blocks had built up over the vent, and the turbid layer on the flanks was almost gone. On the last dive, scientists saw glowing lava jetting from the vent (figure 5).

Figure (see Caption) Figure 5. Glowing red lava jetting out of the vent at Northwest Rota-1 Brimstone Pit at depth of 560 m. Photo taken from the submersible Jason II, 29 April 2006. Image courtesy of Submarine Ring of Fire 2006 Exploration, NOAA Vents Program.

The scientists concluded that observing explosive volcanic activity at a submarine volcano was easier and more revealing in many ways than on land, perhaps because the eruptive activity, although violent at times, is usually limited to a small area due to the dampening effect of the surrounding water (figure 6). For example, at Brimstone Pit the pressure of 560 m of water over the site reduced the power of the explosive bursts. Also, the water quickly slows down the rocks and ash violently thrown out of the vent. The scientists viewed the release of volcanic gases from the erupting lava with new clarity, with the help of the streams of bubbles and multicolored plumes as they were emitted. In addition, the scientists recorded the activity using a portable underwater microphone (hydrophone).

Figure (see Caption) Figure 6. Eruption at Brimstone Pit in Northwest Rota-1 at a depth of 560 m. Photo taken by the submersible Jason II, 29 April 2006. Image courtesy of Submarine Ring of Fire 2006 Exploration, NOAA Vents Program.

Chadwick and his associates at NOAA have identified and named 56 seamounts in the Mariana Arc, 11 of which show hydrothermal activity, based primarily on CTD instrument tows (table 1; see figure 5 for map showing locations).

Table 1. Seamounts in the Mariana arc that are active volcanos based on submersible observations and/or that registered signs of hydrothermal activity on CTD tows. Brief comments on noteworthy observations from several of those visited in 2006 are included. Courtesy of William Chadwick, NOAA, June 2006.

Seamounts (listed S to N) Shallowest summit depth Longitude Latitude Comments
[Seamount X] 1,230 m 144.0167°E 13.2500°N --
Northwest Rota-1 517 m 144.7750°E 14.6000°N --
Esmeralda Bank 54 m 145.2458°E 14.9583°N --
E. Diamante 127 m 145.6583°E 15.9167°N Active, metal-rich, ephemeral 'black smokers' shallowest yet discovered.
Zealandia Bank 144 m 145.8000°E 16.8833°N --
Maug 54 m 145.2217°E 20.0208°N --
NW Uracas 703 m 144.8400°E 20.5833°N --
Daikoku 323 m 144.1942°E 21.3242°N See report in this issue.
NW Eifuku 1,551 m 144.0433°E 21.4875°N Liquid CO2 venting from 'white smokers.'
Kasuga 297 m 143.6417°E 21.6100°N --
Nikko 392 m 142.3255°E 23.0784°N Sulfur chimneys, boiling pots of molten sulfur surrounded by a thin crust on a larger lava lake.

References. Embley, R.W., Baker, E.T., Chadwick, W.W., Jr., Lipton, J.E., Resing, J.A., Massoth, G.J., and Nakamura, K., 2004, Explorations of Mariana Arc volcanoes reveal new hydrothermal systems: EOS, Transactions, American Geophysical Union, v. 85, no. 2, p. 37, 40.

Embley, R.W., Chadwick, W.W., Jr, Baker, E.T., Butterfield, D.A., Resing, J.A., de Ronde, C. E.J., Tunnicliffe, V., Lupton, J.E., Juniper, S.K., Rubin, K.H., Stern, R.J., Lebon, G.T., Nakamura, K., Merle, S.G., Hein, J.R., Wiens, D.A., and Tamura, Y., 2006, Long-term eruptive activity at a submarine arc volcano: Nature, v. 441, no. 7092, p. 494-497.

Oregon State University, 25 May 2006, Press Release: Nature paper details eruption activity at submarine volcano: College of Oceanic and Atmospheric Science (COAS), 104 COAS Admininstration Building, Corvallis, OR 97331.

Geologic Background. A submarine volcano detected during a 2003 NOAA bathymetric survey of the Mariana Island arc was found to be hydrothermally active and named NW Rota-1. The basaltic to basaltic-andesite seamount rises to within 517 m of the sea surface SW of Esmeralda Bank and lies 64 km NW of Rota Island and about 100 km north of Guam. When Northwest Rota-1 was revisited in 2004, a minor submarine eruption from a vent named Brimstone Pit on the upper south flank about 40 m below the summit intermittently ejected a plume several hundred meters high containing ash, rock particles, and molten sulfur droplets that adhered to the surface of the remotely operated submersible vehicle. The active vent was funnel-shaped, about 20 m wide and 12 m deep. NW Rota-1 is a large submarine volcano with prominent structural lineaments about a kilometer apart cutting across the summit of the edifice and down the NE and SW flanks.

Information Contacts: William W. Chadwick, Jr., Cooperative Institute for Marine Resources Studies (CIMRS), NOAA Pacific Marine Environmental Laboratory (PMEL), 2115 SE OSU Drive, Newport, OR 97365 USA; NOAA Ocean Explorer (URL: http://oceanexplorer.noaa.gov/explorations/06fire/welcome.html).


Popocatepetl (Mexico) — May 2006 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


During first half of 2006, several ash plumes rose to ~ 7-8 km altitude

The last report on Popocatépetl covered February-December 2005 (BGVN 30:12). This report covers January-June 2006. Throughout this reporting interval, the warning level remained at Yellow. Seismicity is summarized on table 18.

Table 18. Recorded earthquakes near Popocatépetl during April-June 2006. Courtesy of CENAPRED.

Date Local Time Depth (km) Magnitude
04 Apr 2006 1426 5.4 2.2
05 Apr 2006 0416 5.4 2.3
05 Apr 2006 1557 8.0 2.4
06 Apr 2006 0921 1.0 2.3
07 Apr 2006 0339 6.3 1.9
12 Apr 2006 0457 5 2.8
18 Apr 2006 0101 6.4 2.6
27 Apr 2006 1024 4.3 2.2
25 May 2006 2019 4.9 2.3
29 May 2006 1548 5.6 2.1
30 May 2006 1224 7.7 2.2
31 May 2006 0238 9.3 2.4
31 May 2006 1253 4.2 2.0
02 Jun 2006 0502 5.4 2.2
08 Jun 2006 0637 4.7 3.0

On 6 January 2006, a small explosion occurred at Popocatépetl around 0042. According to the Washington VAAC, the resultant ash plume was visible on satellite imagery and its top reached ~ 5.8 km altitude, extending NE. Centro Nacional de Prevención de Desastres (CENAPRED) reported that after the explosion overall activity decreased to previous levels. During 24-30 January, several emissions of gas, steam, and small amounts of ash occurred. A moderate explosion on 26 January at 0957 produced an ash plume that rose to ~ 8.4 km altitude and drifted NE.

Throughout the month of February, several small-to-moderate emissions of steam, gas, and ash occurred. On the 4th, an explosion produced a plume that rose to ~ 6.7 km altitude. Aerial photos taken on 10 February showed a 130-m-diameter lava dome at the bottom of the crater. At 0528 on 24 February an M 2.3 earthquake was detected and was located 0.5 km to the N of the crater at a depth of 4.1 km.

During April-June, the volcano issued several small emissions of steam, gas, and ash; reports also noted several small coincident earthquakes. At 1807 on 23 May, an ash emission was observed that reached a height of ~ 7.4 km altitude. The ash column was dispersed towards the SE and was followed by a high-frequency, low-amplitude tremor signal that lasted 90 minutes and then returned to previous low levels.

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

Information Contacts: Centro Nacional de Prevención de Desastres (CENAPRED), Av. Delfín Madrigal No.665. Coyoacan, México D.F. 04360, México (URL: https://www.gob.mx/cenapred/).


Rabaul (Papua New Guinea) — May 2006 Citation iconCite this Report

Rabaul

Papua New Guinea

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

All times are local (unless otherwise noted)


Gas emissions and earthquakes during March-April 2006

Despite minor inflationary movements that began in mid-February 2006, Tavurvur remained relatively quiet from the end of March to mid-April 2006. Variable amounts of white vapor were released from the summit area and from an active fumarole on the upper W flank during this period. Vapor emissions became denser during and after rainfall. There were no noises heard or visible glow detected at night. Seismic activity remained at a low level. A high-frequency earthquake that originated NE of the caldera was recorded on 22 March. No other distinct high-frequency events were recorded, but 53 low-frequency earthquakes were recorded during 1-14 April.

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

Information Contacts: Ima Itikarai and Herman Patia, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Soufriere Hills (United Kingdom) — May 2006 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


Big dome collapse and tall plume on 20 May 2006 leave a W-leaning crater

Activity at Soufrière Hills remained at elevated levels (table 63), similar to that previously reported (BGVN 30:12), a state that culminated with a dome collapse on 20 May 2006. Although that event took away considerable portions of the dome (and caused a small tsunami), photographs revealed post-collapse dome growth focused over a broad SE sector extending from the SW around to the NE. Numerous rockfalls continued from the S, E, and NE flanks of the lava dome. The NE-side rockfalls added talus to the upper reaches of the Tar River valley and were visible at night.

Table 63. Soufrière Hills seismicity during 28 December 2005 to 12 May 2006. * Due to weather conditions, gas measurements were not made. ** As a result of the collapse, instrumentation was lost and gas measurements were not able to be measured. Courtesy of MVO.

Date Hybrid EQ's Volcano-tectonic EQ's Long-period EQ's Rockfall signals SO2 flux (metric tons/day)
28 Dec-06 Jan 2006 -- -- 11 37 522
06 Jan-13 Jan 2006 -- 1 30 116 724
13 Jan-20 Jan 2006 -- -- 17 61 767
20 Jan-27 Jan 2006 -- -- 11 60 470
27 Jan-03 Feb 2006 1 3 11 92 594
03 Feb-10 Feb 2006 2 39 61 84 465
10 Feb-17 Feb 2006 2 9 121 10 568
17 Feb-24 Feb 2006 1 3 26 30 286
22 Feb-03 Mar 2006 1 7 157 18 388
03 Mar-10 Mar 2006 2 2 148 282 454
10 Mar-17 Mar 2006 -- 4 115 319 480
17 Mar-24 Mar 2006 13 3 231 336 1,034
24 Mar-31 Mar 2006 12 1 230 316 523
31 Mar-07 Apr 2006 -- 3 38 507 578
07 Apr-14 Apr 2006 -- 3 99 620 540
14 Apr-21 Apr 2006 3 -- 80 100 *
21 Apr-28 Apr 2006 -- -- 30 589 521
28 Apr-05 May 2006 -- -- 109 279 310
05 May-12 May 2006 -- -- 74 571 702
12 May-19 May 2006 7 1 130 753 674
19 May-26 May 2006 89 11 229 373 **
26 May-02 Jun 2006 62 4 172 195 **
02 Jun-09 Jun 2006 20 -- 28 163 **

A central spine was first observed on 17 January 2006 when clouds briefly cleared from the dome. On 22 January, two new relatively thin, vertical planar spines were seen on the SE flank of the lava dome and collapsed on 29 January. Helicopter and field observations indicated continued dome growth, particularly in the SE (figure 64).

Figure (see Caption) Figure 64. A photo showing the growing dome on SoufriPre Hills as viewed from Tar River at the seaward (E) end of the delta. Photo taken 23 January 2006 along the SW coastline. Courtesy of Montserrat Volcano Observatory (MVO).

On 10 February, MVO reported increased activity to the Washington VAAC. Satellite imagery showed a prominent hotspot at the volcano and a NW-drifting ash plume at an altitude of ~3 km. A small dark lobe of lava was observed on the western side of the lava dome in the crater. Steaming and venting were observed throughout the day. A photo appears as figure 65.

Figure (see Caption) Figure 65. A 10 February 2006 photo taken at Soufriere Hills showing ash and steam venting from the dome. This view is from the SE; the ash cloud drifted N. Courtesy of MVO. Courtesy of MVO.

By early 11 February, this lobe had advanced rapidly towards the NE side of the dome and was visible as a steep-sided plateau of lava from inhabited areas around Salem. Photographs from fixed cameras showed continued changes to this lava lobe over the next few days, and the NE margin could be seen glowing at night and shedding rockfalls into the NE part of the crater. Ash-and-gas emissions continued through 15 February, producing plumes to an altitude of ~2.7 km. The initial growth rate of this lobe surpassed 5 cubic meters per second, but the rate declined around 17 February. The new lava lobe began to fill the gap between the lava dome and the N and W crater walls, raising the possibility that small rockfalls could spill over those areas in coming weeks. After 22 February, incandescent rockfalls were visible at night, coursing down the N, E, and SW sides of the dome and into the Tar River Valley (figure 66).

Figure (see Caption) Figure 66. A Soufriere Hills photo showing the incandescent rockfalls at night taken from Perches Mountain, SE of the volcano. This photo was taken on 22 February 2006. Courtesy of MVO.

On 26 February, rapid vertical growth of the lava dome at Soufrière Hills was visible on camera images, and by 27 February a large spine about 30 m wide and at least 30 m high had developed at the dome's summit. By 28 February this spine had split into two parts and was leaning precariously to the NE. At about 2115 on 28 February the overhanging parts of the spine disintegrated and generated pyroclastic flows that traveled down the Tar River Valley almost as far as the coast. A low-level ash cloud drifted W. Additional changes to the shape of the spines and the upper NE flank of the volcano were noted in the following days as they disintegrated further. Rockfalls were visible on the N, NE, and E flanks of the volcano. Some fumaroles were observed on the upper outside part of Gages Wall (W of the lava dome) on 27 February, suggesting movement of fluids in this area.

During 3-17 March, lava-dome growth continued and the dome reached an altitude of ~950 m. The active lava lobe shed rockfalls and small pyroclastic flows to the W, N, and E. A vigorous gas vent was seen on the W side of the lava dome on 8 March, above Gages valley. Small fumaroles were visible at the top of Gages valley and below the lava dome remnant that stands at the top of Gages Valley.

Observations during 17 March-7 April revealed that lava-dome growth was focused in the summit area and towards the E and NE (figure 67). The N side of the lava dome showed little change. Rockfalls and pyroclastic flows were restricted to the Tar River Valley and were numerous on 19-20 March. The largest pyroclastic flows traveled as far as 2 km.

Figure (see Caption) Figure 67. A Soufriere Hills photo of the growing lava dome taken on 30 March 2006. The photographer stood on Jack Boy Hill and looked NE. Courtesy of MVO.

Lava extrusion continued during 7-21 April. Growth occurred to the E and N, and an eastward-facing lobe developed on the NE side of the dome. Numerous small rockfalls continued from the active eastern flanks of the dome, adding to the talus in the upper reaches of the Tar River valley. Rockfalls were accompanied by minor ash venting. Due to unusual wind conditions, plumes were predominately transported N and NW, shifting to the E on 20 April. As a result of this process, light ashfall occurred over much of Montserrat. Thermal images taken on 27 April indicated some very hot areas on the E flank of the dome.

Deposits from a series of pyroclastic flows occurring on 4 May extended as far as the Tar River delta. Northerly directed winds during the reporting period resulted in light ashfall in areas north of the Belham valley. The dome volume was approximately 80 million cubic meters and the average growth rate through April was about 8 cubic meters per second.

On 18 May, a survey conducted on the southern half of the dome was carried out using a terrestrial laser scanner and showed that the summit of the dome had reached a height of 1,006 m, this is 83 m higher than Chance's Peak (figure 68).

Figure (see Caption) Figure 68. The SE side of the Soufriere Hills lava dome as viewed from Galways Mountain on 11 May 2006. A new shear lobe forms the highest point of the dome and is growing toward the S. Chance's Peak is in the back left and Centre Hills in the back right. Courtesy of MVO.

20 May collapse. A major lava dome collapse took place on the morning of 20 May (figure 69). A helicopter flight in the afternoon confirmed that most of the lava dome had gone, together with some remnants of the 2003 lava dome, leaving a broad, deep, eastward-sloping crater at the summit of the volcano. The volume of the lava dome was believed to be about 90 million cubic meters and most of this collapsed over a period of less than three hours. Views of the W part of the crater where ash venting is continuing were not possible but it is unlikely that there is significant dome material remaining there.

Figure (see Caption) Figure 69. A set of photos taken 1600 on 20 May 2006 after the lava dome collapse. (A) A shot taken from the E showing an overview of the delta, Tar River Valley, and dome complex. (B) The crater as viewed from the NE above the Tar River Valley. Ash emission continued from a vent on the W side of the crater and rose to an altitude of 1.8 km. (C) A photo taken from E of the steaming summit crater showing most of the lava dome, including parts of the remaining 2003 dome. (D) A photo shot from MVO showing the towns of Flemings, Hope, and Salem in the early afternoon as the ash-and-gas cloud dissipated. Belham River Valley, Old Towne, and Garibaldi Hill remained obscured by the cloud of ash and gas. Courtesy of MVO.

At 0222 on 20 May there was a single precursor, a long-period seismic event located 3 km below the dome. A brief episode of heightened seismic amplitude corresponding to ash venting occurred during 0300-0330. During heavy rain, another episode of increased seismic amplitude, interpreted as ash venting, began at 0552, and it developed into a high-amplitude seismic signal. The heavy rain caused mudflows in Belham River valley. By 0632 low-level ash clouds were drifting to the NW of the volcano from the crater area and a steam plume was rising to 6,000 ft (~1800 m). Unconfirmed reports suggested that pyroclastic flows first reached the sea at about 0645. Regular pulses of pyroclastic flows were reaching the sea down the Tar River valley by 0720 with major pulses recorded in seismic amplitude at 0736, 0743, and between 0801 and 0804. Also between 0730 and 0810 a number of long-period seismic events were detected. At 0740 an ash cloud was reported at nearly 17 km, altitude the highest reported ash cloud during the ten years of the eruption. At 0743, pyroclastic surges were observed spreading across the NE flanks of the volcano reaching the Spanish Point area. It was also estimated at this time that surges had spread 3 km offshore from Tar River valley, across the surface of the ocean.

By 0750, lithics were falling in areas NW of the volcano; most were less than 3.5 cm across, and the largest found in the inhabited area was 6 cm across. Six car windscreens were reported broken. The deepest ash fall in inhabited areas was about 3 cm. Activity began to reduce in intensity after 0815 and a high-amplitude seismic signal remained until 0900. At this time, residents in the Old Towne and Salem area were subjected to high levels of volcanic gases particularly hydrogen chloride causing some to move N (figure 69). Widespread and noisy mudflows were reported in the Trants area to the NE of the volcano. Ash venting from the W of the crater continued until about 1700 when it began to decline.

A 1-m-high tsunami was reported from Deshaies beach in Guadeloupe and swells were detected in Little Bay, Montserrat, and at Jolly and English Harbour, Antigua. Relatively light but continuous ash-and-steam venting followed the collapse.

The weeks after the 20 May collapse. Wind direction shifted towards the N late on 21 May causing ash fall and raining mud in most parts of the island. Scientists remained alert to the possibility of further explosive activity but seismic activity was at low levels after the event on 20 May.

Since the May collapse, the lava dome continued to grow. As of 9 June it was approximately 20 million cubic meters in size. This is similar to the size of the dome in early January 2006. The average growth rate since the dome collapsed on 20 May was close to 10 cubic meters per second, well above the average growth rate of 6 cubic meters per second noted between January and April 2006.

By the end of the report period the dome was broad and flat-topped with a growing talus slope extending E. The lava on the summit of the dome is blocky, which is typical of lava extruded at a high rate. Vigorous ash and gas emitted by a vent W of the lava dome occurred during the week of 2 June. The venting is accompanied by a roaring sound that is sometimes audible in the Salem area. Prevailing winds have taken most of this ash and gas to the west over Plymouth. Satellite imagery on 4 June showed a thin area of ash out to St. Croix. In addition, there were multiple SFC and pilot reports of ash over the E portion of Puerto Rico and the Virgin Islands. Mudflows were reported on the 11 and 13 June during heavy rainfall.

Geologic Background. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. The volcano is flanked by Pleistocene complexes to the north and south. English's Crater, a 1-km-wide crater breached widely to the east by edifice collapse, was formed about 2000 years ago as a result of the youngest of several collapse events producing submarine debris-avalanche deposits. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits, including those from an eruption that likely preceded the 1632 CE settlement of the island, allowing cultivation on recently devegetated land to near the summit. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but no historical eruptions were recorded until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.

Information Contacts: Montserrat Volcano Observatory (MVO), Fleming, Montserrat, West Indies (URL: http://www.mvo.ms/).


St. Helens (United States) — May 2006 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)


Intracrater lava dome continues to grow through at least May 2006

From August to December 2005, the lava dome inside the crater of Mount St. Helens continued to grow, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash (BGVN 30:12). The hazard status was at Volcano Advisory (Alert Level 2); aviation color code Orange.

Based on the online reports of the Cascades Volcano Observatory (CVO) of the U.S. Geological Survey (USGS), this pattern of activity continued in January and February 2006 and suggests that the slow extrusion of dacite onto the crater floor at Mount St. Helens continued. Slight decreases in seismicity occurred on two occasions after larger than normal earthquakes. By mid-January the new dome was noticeably taller and broader than in December. Rockfalls from its summit generated small ash plumes that slowly rose above the crater rim and dissipated as they drifted E.

On 24 January a shallow M 2.7 earthquake triggered a rockfall from the new lava dome, which in turn produced an ash plume that filled the crater before dissipating and drifting N over the pumice plain. Analysis of recent photographs from cameras in the crater showed that the top of the new lava dome was at an elevation of ~ 2,240 m, about 90 m higher than it was in early November 2005.

In February, occasional clear views of the volcano revealed incandescence on the currently growing lava lobe and a few incandescent rockfalls. Comparison of photos taken between 17 December and 7 February showed that the base of the active lobe of the lava dome enlarged by about 100 m. Photographs taken during the week of 5 February showed that the active part of the new lava dome continued to extrude, with points on the surface of the dome moving a couple of meters per day (figure 61).

Figure (see Caption) Figure 61. High-angle view of Mount St. Helens new dome from the NNW, taken on 5 February 2006 by John Pallister. Photograph courtesy of USGS.

Gas measurements made on 15 February suggested that the volcanic-gas flux remained unchanged from recent measurements. Observations made on 17 February revealed that the active NE part of the new lava dome was developing a steeply inclined jagged spine. At its top, temperatures as high as 580°C were measured using a thermal sensor.

Growth of the new lava dome inside the crater of Mount St. Helens continued during March, April, and May 2006, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash. Small earthquakes occurred every several minutes, punctuated by occasional larger earthquakes. The Global Positioning System (GPS) receiver on the new lava dome showed that lava emerging from the vent was still advancing WNW at about a meter per day. Small rockfalls produced small ash clouds that rose from the dome's NW flank. The eruption of lava into the crater continued, shown by ongoing rockfalls and continuous GPS measurements made on the growing lava lobe.

Analysis of photographs revealed that a slab of rock approximately 50,000 cubic meters in volume was shed from the N margin of the growing spine during 6-7 May. This probably coincided with a large seismic signal recorded on the night of 7 May. Rock-avalanche deposits extended a few hundred meters to the NE. The avalanche was accompanied by an ash cloud. The spine continued to grow during 10-15 May, producing rockfalls that intensified on the evening of 14 May. Incandescence was visible on satellite imagery. On 17 May night-time incandescence from rockfalls was observed.

During 24-25 May, seismicity was at levels typical of the continuing lava-dome extrusion at Mount St. Helens. On 29 May, a M 3.1 earthquake and simultaneous large rockfall occurred. An ash plume produced at 0810 reached an altitude of 4.9 km - 6.1 km according to ground observations and pilot reports (figure 62). One pilot report suggested that the plume reached an altitude of 7.3 km. By 1308, ash from the event was no longer visible on satellite imagery. The rockfall originated primarily from the N side of the growing fin (figures 63 and 64).

Figure (see Caption) Figure 62. At Mt. St. Helens, a view from the Brutus camera at 0914 on 29 May 2006. Vapor with light ash obscures most of the extruding lava spine. The light gray swath in the center of the photograph shows the path of the rock avalanche as it flowed downhill. The dark areas adjacent to the rock-avalanche path shows the ash cloud (finer material) that accompanied the avalanche. Photograph courtesy USGS.
Figure (see Caption) Figure 63. Mount St. Helens crater and dome showing aftermath of rockfall event of 29 May 2006, seen from the N. Taken on 30 May 2006 by Willie Scott and Jim Vallance. Photograph courtesy USGS.
Figure (see Caption) Figure 64. Aerial view showing Mount St. Helens crater and dome as seen from the SW. Spirit Lake can just be seen in the upper right corner. Taken on 30 May 2006 by Willie Scott and Jim Vallance. Photograph courtesy USGS.

During June 2006, seismicity indicated that the lava spine continued to grow inside the crater of Mount St. Helens and occasionally produced minor rockfalls. On 9 June, pilots reported that an ash-and-steam plume, generated after a rockfall following a M 3.2 earthquake, reached an altitude of 4.6 km. According to seismic data, a medium-sized rockfall occurred on 13 June. Incandescence was observed on satellite imagery. A small steam plume from the lava dome and dust from minor rockfalls were visible from the US Forest Service's web camera at the Johnston Ridge Observatory on 25 and 26 June. On 26 June, a pilot reported that dust and ash reached an altitude of ~ 2.4 km and drifted W.

From January through June 2006, St Helens remained at Volcano Advisory (Alert Level 2); aviation color code Orange.

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: Cascades Volcano Observatory (CVO), U.S. Geological Survey, 1300 SE Cardinal Court, Building 10, Suite 100, Vancouver, WA 98683-9589, USA (URL: https://volcanoes.usgs.gov/observatories/cvo/).


Ubinas (Peru) — May 2006 Citation iconCite this Report

Ubinas

Peru

16.355°S, 70.903°W; summit elev. 5672 m

All times are local (unless otherwise noted)


Ash and steam emissions stir hazard and environmental concerns

Ubinas began erupting ash on 25 March 2006 (BGVN 31:03). Randall White from the U.S. Geological Survey (USGS) reported on 1 April that increased fumarolic activity occurred during the end of March. Victor Aguilar from the Universidad de San Agustint, visited the volcano on 31 March. He found strong steam-and-ash emissions occurring. Also, leaves of nearby crops were burned and a sound similar to a jet engine emanated from the vent area. Table 1 gives a summary of some recent plumes. Figure 3 contains an ASTER image of the volcano and surroundings on 8 May 2006.

Table 1. Summary of some recent plume activity from Ubinas. Courtesy of the Buenos Aires VAAC and INGEMMET; satellite imagery courtesy of NASA Earth Observatory.

Date (time) Altitude Drift direction Comments
06 Apr (1220) 6.1-9.1 km -- Ash absent on satellite imagery
06 Apr (1900) 6.1-7.3 km NE --
08 Apr -- -- Volcanic activity ceased
09 Apr 6.1-7.3 km SW --
11 Apr -- -- Volcanic activity ceased
13 Apr -- -- Ash emissions increased, ashfall reached 7 km from volcano
15 Apr 6.1-9.1 km -- Ash cloud
16 Apr -- -- Volcanic activity ceased
18 Apr (0715-1600) 1-3 km -- Continuous emissions of ash and gas
19 Apr ~3 km -- Plume containing ash/lava fragments lasted 6-7 hours
20 Apr-22 Apr -- NW, W, SW Plume reached 60 km from the volcano; traces of ash reached the Arequipa airport.
25 Apr-26 Apr 0.2-0.7 km -- --
04 May-08 May ~6.7 km -- See fig. 15
9-11, 13-14 May 7.3 km (max) -- --
20 May-25 May 7.3 km (max) -- --
24 May 6.7 km E Plume reported by pilot
25 May 7 km NW --
30 May 7.9 km E Ash plume seen on satellite imagery
31 May-05 Jun 7.9 km N, NE, SE, S --
09 Jun-11 Jun 6.7 km E, SW Ash clouds reported by pilots
Figure (see Caption) Figure 3. A faint white plume rose from the summit of Ubinas on 8 May 2006, when the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite captured this image. Courtesy NASA Earth Observatory.

The Perú Instituto Geológico Minero y Metalúrgico (INGEMMET) reported that gas and ash were emitted from Ubinas from 27 March to at least 19 April. On 13 April, ash emissions increased noticeably in comparison to the previous days, with ashfall in the villages of Ubinas, Querapi, and Sacuaya, and as far as 7 km from the volcano. Acid rain was also noted in these villages, particularly between 1400 and 1600 hours on 14 April. Explosions on 13 and 14 April were heard in nearby villages. According to a news report on 18 April, however, officials urged residents of the town of Querapi ~ 5 km from the volcano to evacuate.

On 19 April, a lava dome was observed on the crater floor for the first time. It was incandescent, 60 m in diameter, and 4 m high. Explosions were heard as far as 6 km from the volcano and a plume composed of ash and lava fragments rose ~ 3 km above the volcano. Plumes lasted for 6-7 hours and hazard statements suggested significant danger within 4 km of the crater. The Buenos Aires Volcanic Ash Advisory Center (VAAC) released volcanic ash advisory statements during the report period.

According to news reports, as of 19 April at least 1,000 people living N of the volcano suffered respiratory problems, dozens of livestock died and many more were ill after eating ash-covered grass, and water sources were polluted with ash. Dozens of people from Querapi, the town closest to the volcano, began to evacuate on 21 April. On 22 April, officials declared a state of emergency for the area near the volcano and sent aid for evacuees.

During 25 and 26 April, the volume of ash emitted from the volcano decreased significantly. Gas plumes rose between 200 and 700 m above the volcano's caldera. Seismicity during 22-26 April was higher than normal. The Buenos Aires VAAC posted volcanic ash advisories during the report period.

Several thermal anomalies were observed by MODIS/MODVOLC in 2006 at the following local times: 0105 hours, 27 May; 2220 hours, 31 May; 2225 hours, 7 June; 2210 hours, 18 June; and 2235 hours, 30 June. On 3 June, the Alert Level for Ubinas was increased to Orange due to heightened explosive activity. According to a news report, on 5 June, officials in S Perú prepared to evacuate approximately 480 families; approximately 550 families were evacuated on 10 and 11 June. Ubinas emitted a plume of ash and/or steam on 24 June 2006. The Moderate Resolution Imaging Spectroradiometer (MODIS) flying onboard NASA's Aqua satellite showed the plume moving E.

Geologic Background. A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Perú. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Information Contacts: Randall A. White, USGS/OFDA Volcano Disaster Assistance Program; Victor Aguilar, Universidad de San Agustin, Perú; Buenos Aires Volcanic Ash Advisory Center; Instituto Geológico Minero y Metalúrgico (INGEMMET ? Institution of Mining and Metallurgical Geology); National Aeronautics and Space Administration (NASA) Earth Observer (URL: http://earthobservatory.nasa.gov/NaturalHarards/).


Villarrica (Chile) — May 2006 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Unusual seismicity, minor pyroclastic, and gas explosions, January-April 2005

Our last report on Villarrica, through January 2005, described plumes, the growth of a lava lake in the crater, and some night-time Strombolian explosions (BGVN 29:12). This report covers January to April 2005.

According to the March 2005 newsletter of the Multinational Andean Project: Geoscience for Andean Communities (MAP-GAC) produced by the Geological Survey of Canada, both seismic activity and degassing from the permanent fumarole increased in January. One of the early January explosions described above sent pyroclastic material (ash and scoriaceous lapilli) onto the flanks of the snow-and-ice covered volcano, covering an area 1 km wide and 3 km long. Subsequent minor explosions have sent pyroclastic material to estimated heights of 300 m above the crater. Onlookers have reported incandescent material within the gas-and-pyroclastic column.

On 19 January 2005, volcanologists Hugo Moreno and Edmundo Polanco of OVDAS–SERNAGEOMIN observed the lava lake actively spattering at a distance of 30 m below the edge of the principal crater; the crater interior and perimeter were covered in spatter. The glacier covering the cone had developed new fractures and crevasses. Activity in February 2005 lessened.

During 29 March to 3 April 2005, the lava lake inside Villarrica's crater remained active, with Strombolian explosions occurring. Some gas explosions were observed to hurl volcanic bombs as far as ~ 300 m. According to a news report on 12 April 2005, the Oficina Nacional de Emergencia reported that unusual seismicity was recorded at Villarrica during early April. Fresh ash deposits were seen outside of the volcano's crater. Visitors were banned from climbing the volcano.

Geologic Background. Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.

Information Contacts: Werner Keller, Proyecto de Observacion Villarrica (POVI), Wiesenstrasse 8, 86438 Kissing, Germany (URL: http://www.povi.cl/); Hugo Moreno and Edmundo Polanco, Observatorio Volcanológico de los Andes del Sur (OVDAS), Servicio Nacional de Geología y Minería, Casilla 23D, Temuco, Chile (URL: http://www.sernageomin.cl/); MAP:GAC Newsletter, Geological Survey of Canada, 101-605 Robson Street, Vancouver, BC,V6B 5J3, Canada.

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.

Atmospheric Effects (1980-1989)  Atmospheric Effects (1995-2001)

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements

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 (BGVN 22:08) False Report of Mount Pinokis Eruption

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 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/).