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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 42, Number 12 (December 2017)

Managing Editor: Edward Venzke

Bogoslof (United States)

Explosions in July and August 2017; new lava dome visible 20-22 August destroyed by explosions that end on 30 August

Cleveland (United States)

Dome growth and destruction multiple times during January-November 2017

Dempo (Indonesia)

Phreatic explosion from the crater lake generates a dense ash plume in November 2017

Pacaya (Guatemala)

Pyroclastic cone in MacKenney crater grows above crater rim, January-September 2017

Sabancaya (Peru)

Continuous pulses of ash emissions for ten months, February-November 2017

Santa Maria (Guatemala)

Slow growth of new lava dome, persistent ash plumes, and nearby ashfall, January-October 2017

Sinabung (Indonesia)

Constant activity through September 2017, with ash plumes, block avalanches, and pyroclastic flows

Tungurahua (Ecuador)

Nearly constant ash emissions and frequent lahars during July-December 2015

Ulawun (Papua New Guinea)

Intermittent ash plumes during June-November 2017

Villarrica (Chile)

Lava lake level fluctuates and Strombolian activity persists during October 2016-November 2017



Bogoslof (United States) — December 2017 Citation iconCite this Report

Bogoslof

United States

53.93°N, 168.03°W; summit elev. 150 m

All times are local (unless otherwise noted)


Explosions in July and August 2017; new lava dome visible 20-22 August destroyed by explosions that end on 30 August

Intermittent eruptions from Bogoslof, 40 km N of the main Aleutian arc (BGVN 42:09, figure 2), have created and destroyed several distinct islands at the summit of this submarine volcano. Previous eruptions in 1927 and 1992 created lava domes that were subsequently heavily eroded, before the most recent eruption began in December 2016 (figure 16). Numerous explosions with ash plumes significantly changed the morphology of the island between December 2016 and March 2017. Ash plumes rose to over 10 km altitude during May-July 2017 multiple times. A lava dome briefly emerged in early June before it was destroyed by subsequent explosions. This report continues with an account of activity between July and December 2017. Eruptive activity ended on 30 August. Information comes primarily from the Alaska Volcano Observatory (AVO) and the Anchorage Volcanic Ash Advisory Center (VAAC).

Figure (see Caption) Figure 16. Worldview satellite image of Bogoslof collected at 2313 UTC on 12 June 2017, two days after a lava dome that appeared in the lagoon was destroyed. The circular embayments were formed by a series of more than 40 explosions that began in mid-December 2016. These explosions greatly reshaped the island as material was removed and redeposited as air fall. Vigorous steaming was visible from a region S of the most active vent areas in the lagoon. Lava extrusion produced a circular dome that first rose above the water on 5 June and grew to a diameter of ~160 m before being destroyed by an explosion early in the day on 10 June. Courtesy of AVO.

New explosions during 2, 4, 8, and 9-10 July 2017 produced ash plumes that rose from 6.1 to 11 km altitude. Although significant ash clouds were produced, there were no reports of ashfall in nearby communities. After almost a month of quiet, an eruption on 7 August created new tephra deposits, and extended the N shore of the island. This eruption created a significant SO2 plume that was recorded by satellite instruments. Intermittent pulses of tremor were recorded during mid-August. A new lava dome grew between 20 and 22 August to 160 m in diameter before it was destroyed in a series of explosions during 26-30 August. Thermal anomalies were observed in satellite data several times during September, and they tapered off into early October. Steam emissions were still visible in early November when the last weak thermal anomaly was reported. By early December, significant erosion had begun to change the island's shape, and only minor steam emissions were visible in clear satellite images.

Beginning at 1248 local time (AKDT) on 2 July 2017, a significant explosive event was detected in seismic and infrasound data, and observed in satellite imagery. The event lasted about 16 minutes, and produced an ash plume that rose to 11 km altitude and drifted E, passing N of Dutch Harbor. No explosions were reported the following day, but two events were detected in seismic, infrasound, and satellite data on 4 July. The first, at 1651, lasted 13 minutes and produced an eruption cloud that rose to 8.5 km altitude and drifted SE; the second 11-minute-long eruption began at 1907, and produced a small cloud that rose to 9.8 km altitude and drifted SE.

On the morning of 8 July 2017, an eruption with a total duration of 19 minutes began at 1015 AKDT and produced a volcanic cloud reaching an altitude of 9.1 km that drifted N. Overnight during 9-10 July Bogoslof erupted several times; the first two explosions during the 3-hour-long eruption produced a small ash cloud that rose to 6.1 km altitude and drifted SE, dissipating rapidly. Later on 10 July, an 8-minute-long eruption began at 1000 AKDT and a 15-minute-long eruption began at 1706 AKDT; neither produced a significant plume. None of the eruptions on 8, 9, or 10 July caused ashfall in local communities. Weakly elevated surface temperatures were observed in clear satellite images on 12 and 16 July.

Following almost a month of quiet, Bogoslof erupted again on 7 August 2017. The eruption was detected in seismic, infrasound, satellite, and lightning data. The eruption began at 1000 AKDT and lasted for about three hours, producing an ash plume that rose to 9.7 km altitude according to AVO, and drifted S over Umnak Island, then out over the Pacific Ocean. The Anchorage VAAC initially reported the plume at 10.4 km altitude moving S. A later pilot report noted an altitude of 12.2 km. Satellite measurements of sulfur dioxide (SO2) in the eruption cloud indicated the second highest mass of SO2 erupted since the onset of activity in December 2016 (figure 17). Satellite images of the island taken on 8 August showed new tephra deposits had surrounded the vent area, forming a new crater lake, and extending the N shore of the island by 250 m (figure 18).

Figure (see Caption) Figure 17. Although the data is coarsely pixelated, it is clear that a substantial SO2 plume emerged from Bogoslof during the 7 August eruption, as recorded by the OMPS instrument on the Suomio NPP satellite. Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 18. Worldview true-color satellite image of Bogoslof acquired on 8 August 2017, one day after a 3-hour-long explosive eruption. Ashfall deposits have expanded the island towards the N as the result of the eruption and formed an enclosed crater lake. At the time of this satellite overpass, the level of the crater lake was below sea level. Previous events such as these (that formed a shallow crater lake) formed a deep crater that was subsequently filled by an influx of ocean water. Vigorous steaming was apparent from the likely site of the initial explosive event in mid-December 2016. Sediment coming from erosion of the island is seen offshore surrounding most of the island. A comparison with figure 16, above, shows the extent of new material added on 7 August. Data provided under the Digital Globe NextView License. Courtesy of AVO.

Several short-duration seismic and infrasound signals were detected at the stations on nearby islands on 9 August 2017. Weakly elevated surface temperatures and a minor steam plume were observed in satellite images. Two short pulses of tremor were seen in seismic data on 14 August, one lasting five minutes and the other lasting three minutes. Seismicity returned to background levels following the pulses and remained quiet until a series of small earthquakes the next morning. Seismicity again returned to background levels by the following afternoon, 16 August, and remained quiet through the rest of that week. Photographs taken during an overflight on 15 August indicated that the vent region, which had dried out during the 7 August eruption, had refilled with water (figure 19).

Figure (see Caption) Figure 19. An overflight of Bogoslof on 15 August 2017 showed the increase in area of the crater lake after the eruption of 7 August (see figure 18). View is to the SE. Courtesy of AVO.

Unrest continued during mid-August 2017, and available data suggested that a lava dome had formed within the intra-island lake just W of the 1992 lava dome. The new dome was first observed on 18 August, and during 20-22 August grew to about 160 m in diameter. Two small explosions were detected in infrasound data at 0410 AKDT on 22 August. These explosions did not produce any volcanic plumes recognizable in satellite data. Elevated surface temperatures were observed on 24 August along with a steam plume extending S about 17 km from the island. Satellite images showed elevated surface temperatures and a robust steam plume the next day drifting 70 km SE. A photo from a nearby low-altitude airplane on 26 August, taken shortly before the next explosion, confirmed the intense steam plume (figure 20) likely caused by the interaction of the new dome with seawater. Two MODVOLC thermal alerts were issued on 25 August, the first two since January 2017, and the last two for the year.

Figure (see Caption) Figure 20. Bogoslof volcano with a vigorous steam plume likely caused by interaction of the new, hot lava dome with seawater. Photo by Dave Withrow (NOAA/Fisheries), taken at about 1300 AKDT on 26 August aboard a NOAA twin otter (N56RF) aircraft while surveying harbor seals west of Dutch Harbor. They were 13 nautical miles (24 km) from Bogoslof when photo was taken looking E with a 400 mm lens. Courtesy of AVO.

An explosive eruption at 1629 AKDT on 26 August 2017 lasted for about four minutes and produced a cloud that was observed in satellite images drifting SE over southern Unalaska Island. Cloud-top temperatures seen in satellite data indicated that it rose as high as 7.3 km altitude. The Anchorage VAAC reported the plume at 8.2 km altitude several hours later. The eruption was observed in seismic, infrasound, and satellite data, and one lightning stroke was detected. Elevated surface temperatures persisted, suggesting to AVO scientists that the lava dome was possibly still present within the crater lake. Three short-duration eruptive events occurred during 27-28 August. On 27 August at 1508 AKDT a brief explosive event lasting about two minutes produced a volcanic cloud that reached about 7.9 km altitude and drifted SE. Another explosive eruption occurred at 0323 AKDT on 28 August and lasted about 25 minutes. Satellite imagery showed only a very small eruption cloud drifting ESE that dissipated quickly. The third event occurred at 1117 AKDT that morning and produced a small ash cloud that likely reached 9 km altitude before dissipating over the North Pacific Ocean. Modeling of ash fallout from the cloud indicated trace to minor ash fall over the Southern Bering Sea in the area just S of the volcano.

Elevated surface temperatures were noted in satellite data on 29 August, along with a steam plume drifting SSE, suggesting to AVO the presence of lava at the surface. An explosive eruption began the next morning at 0405 AKDT and continued intermittently for almost two hours. It produced an ash cloud that reached to about 6 km altitude and drifted SSE, dissipating over the southern Bering Sea and North Pacific Ocean area. A vapor plume extended about 65 km SSE later that day.

AVO reported on 8 September 2017 that available data suggested that the most recent lava dome, first observed on 18 August, was removed by the explosive eruptions of 27-30 August. In addition, a narrow isthmus of new land extended across the crater, bisecting it and creating two lakes. Elevated surface temperatures were recorded in a satellite images on 11, 14, 17, 19, and 23 September. Discolored water was visible in satellite images on 17 September and may have represented outflow from the crater. Elevated surface temperatures continued to be observed in satellite data during periods of clear weather into the first two weeks of October, and again briefly at the beginning of November. Several areas of steam emissions were visible in satellite imagery on 9 October (figure 21).

Figure (see Caption) Figure 21. Worldview-3 satellite image of Bogoslof Island acquired on 9 October 2017. The areas that exhibited active steam emission are highlighted with yellow and black dashed lines. Image data acquired with the Digital Globe NextView License. Courtesy of AVO.

A clear, high-resolution satellite image taken on 2 November showed continued steaming of the ground on the S side of the smaller crater lake. Weakly elevated surface temperatures consistent with a hot crater lake were last observed in clear nighttime satellite images on 10 November 2017. Imagery from 20 November showed warm regions in the crater lagoon and at the site of the steaming that had persisted for several months (see figure 21). AVO scientists noted that this was consistent with a slowly cooling, post-eruptive system, and was likely responsible for the occasional observation of slightly elevated surface temperatures in satellite data. The MIROVA graph of thermal anomalies supported the slow cooling trend observed by AVO after the last explosions on 30 August 2017 (figure 22).

Figure (see Caption) Figure 22. The last series of explosive events recorded at Bogoslof during 26-30 August 2017 coincided with the last significant thermal anomalies on the MIROVA graph (infrared MODIS data) that covers the year ending on 19 January 2018. Gradual tapering of thermal anomalies is consistent with AVO satellite observations of a cooling trend during September through early November. Courtesy of MIROVA.

More than sixty explosive events occurred between 20 December 2016 and 30 August 2017. The most energetic of these sent water-rich, volcanic ash clouds to altitudes exceeding 10.7 km. The resulting dispersed volcanic clouds impacted local and international aviation operations over portions of the North Pacific and Alaska. Although most of the volcanic ash fell into the ocean, trace amounts were twice deposited on the community of Unalaska and the Port of Dutch Harbor. The 2016-17 eruption greatly changed the morphology of Bogoslof Island. At its greatest extent, the area of the island increased to about three times its pre-eruption size. Nearly all of the new material on the island is unconsolidated pyroclastic fall and flow (surge) deposits. The deposits are highly susceptible to wave erosion and additional changes in the configuration of the island are likely. A satellite image from 3 December 2017 shows significant erosion of the island with the vent lagoon opened to the ocean on the north shore of the island (figure 23).

Figure (see Caption) Figure 23. Worldview-3 satellite image of Bogoslof Island on 3 December 2017. Erosion of the island by waves had removed substantial material, and no new eruptive material had been added to the island since the end of August 2017. The approximate area of the island in this image was 1.3 square kilometers. Image data acquired with the Digital Globe NextView License. Courtesy of AVO.

Geologic Background. Bogoslof is the emergent summit of a submarine volcano that lies 40 km north of the main Aleutian arc. It rises 1500 m above the Bering Sea floor. Repeated construction and destruction of lava domes at different locations during historical time has greatly modified the appearance of this "Jack-in-the-Box" volcano and has introduced a confusing nomenclature applied during frequent visits of exploring expeditions. The present triangular-shaped, 0.75 x 2 km island consists of remnants of lava domes emplaced from 1796 to 1992. Castle Rock (Old Bogoslof) is a steep-sided pinnacle that is a remnant of a spine from the 1796 eruption. Fire Island (New Bogoslof), a small island located about 600 m NW of Bogoslof Island, is a remnant of a lava dome that was formed in 1883.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: http://www.avo.alaska.edu/ ), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.dggs.alaska.gov/); Anchorage Volcanic Ash Advisory Center (VAAC), Alaska Aviation Weather Unit, NWS NOAA US Dept of Commerce, 6930 Sand Lake Road, Anchorage, AK 99502-1845(URL: http://vaac.arh.noaa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Cleveland (United States) — December 2017 Citation iconCite this Report

Cleveland

United States

52.825°N, 169.944°W; summit elev. 1730 m

All times are local (unless otherwise noted)


Dome growth and destruction multiple times during January-November 2017

Dome growth and destruction accompanied by small ash explosions has been typical behavior at Alaska's Cleveland volcano in recent years (figures 20, 21, and 22). Located on Chuginadak Island in the Aleutians, slightly over 1,500 km SW of Anchorage, it has historical activity, including three large (VEI 3) eruptions, recorded back to 1893. The Alaska Volcano Observatory (AVO) and the Anchorage Volcanic Ash Advisory Center (VAAC) are responsible for monitoring activity and notifying air traffic of aviation hazards associated with Cleveland. This report provides a summary table of dome growth and destruction since 2013 (table 8), and details of continued activity from January through November 2017.

Figure (see Caption) Figure 20. A lava dome was growing at the summit of Cleveland on 4 August 2015. Concentric rings and radial fractures in the dome surface surrounded an elevated hot dome. Photo taken during the 2015 field season of the Islands of Four Mountains multidisciplinary project, work funded by the National Science Foundation, the USGS/AVO, and the Keck Geology Consortium. Courtesy of AVO.
Figure (see Caption) Figure 21. A 60-m-diameter lava dome was seen in this WorldView-1 satellite image from 25 May 2016 of Cleveland's summit crater. Image created by Rick Wessels, USGS. Image data copyright 2016 Digital Globe, NextView License. Courtesy of AVO.
Figure (see Caption) Figure 22. Thermal and photographic images of the lava dome that was growing in the summit crater of Cleveland on 26 July 2016. Top image is from a FLIR (Forward Looking InfraRed) camera, where warmer colors indicate hotter temperatures (scale is in Celsius); bottom image is a photograph of the summit crater, lava dome, and active fumaroles. AVO crew observed incandescence from the summit crater vent during this overflight. Courtesy of AVO.

Table 8. Observations of dome growth and other crater activity at Cleveland, 2013-2017. Data extracted from AVO reports.

Date Dome Observations
Jan-Feb 2013 New lava flow observed multiple times, 100 m across
4-6 May 2013 Explosions, ash cloud
 
Jun-Jul 2013 Elevated temperatures, satellite imagery
2-5 Oct 2013 Explosions
 
13 Nov 2013 Elevated surface temperatures near summit
25 Nov 2013 Explosion
 
28 Dec 2013 Strongly elevated surface temperature near summit
30 Dec 2013, 2 Jan 2014 Small ash cloud visible; explosion with ash plume
 
Jan-25 Feb 2014 Elevated surface temperatures near summit multiple times
25 Feb 2014 Two small explosions and ash clouds
 
7 Mar-4 Jun 2014 No detected activity
5 Jun 2014 Explosion
 
7 Jul 2014-Aug 2014 Intermittent weakly elevated surface temperatures at summit, vigorous steam plume, incandescence at summit during field visit
Late Aug-early Sep 2014 Elevated surface temperatures in satellite data
14, 24 Nov 2014 Vigorous steaming observed in webcam; Satellite image shows small lava dome in summit crater
5 Dec 2014-9 Jan 2015 Minor steaming and weakly elevated surface temperatures at summit
25, 28 Feb 2015 Weakly elevated surface temperatures at summit, low level steam plume observed
26 Mar 2015 Small steam plume, no further activity until 14 June
14 Jun 2015 Ash cover on upper flanks
 
17 Jun-21 Jul 2015 Elevated surface temperatures at summit
21 Jul 2015 Explosion
 
31 Jul, 4 Aug 2015 Strongly elevated surface temperatures at summit, photograph (figure 20) of lava dome in summit crater
6 Aug 2015 Small explosion
 
Aug-Oct 2015 Intermittent elevated surface temperatures at summit
29 Aug 2015 Seismic swarm
Sep-Nov 2015 No Reported Activity
Dec 2015 Elevated surface temperatures at summit
22-23 Dec 2015 Increased frequency of small VT events
 
Jan 2016 Elevated surface temperatures at summit
28 Feb 2016 Brief burst of small local earthquakes
 
Mar-1 April 2016 Elevated surface temperatures at summit
16 April 2016 Explosion
 
6 and 10 May 2016 Explosions
 
17-25 May 2016 Small lava dome observed (figure 21)
Jun-Jul 2016 Elevated surface temperatures at summit
26 Jul 2016 Lava dome observed (figure 22)
Aug-21 Oct 2016 Intermittent degassing, steam plumes, and elevated surface temperatures at summit
24, 28 Oct 2016 Explosion, ashfall observed
 
5 Nov 2016-23 Mar 2017 Elevated surface temperatures and intermittent steam emissions at summit. 3 Feb 2017 Satellite observation of lava dome
24 Mar 2017 Small explosion
 
Late Mar -15 May 2017 Elevated surface temperatures at summit crater; Dome observed 15 April
16 May 2017 Explosion
 
6-29 Jun 2017 Small, low-frequency earthquakes on 6 Jun, elevated surface temperatures at summit crater several times during June
4 Jul 2017 Explosion
 
7 Jul-21 Aug 2017 Elevated surface temperatures at summit crater; satellite (July 14-21) and photographic (July 25-26) observations of lava dome at summit (figure 23)
22 Aug 2017 Explosion
 
Late Aug-24 Sep 2017 Sporadic observations of elevated surface temperatures at summit crater
26, 28 Sep 2017 Explosions
 
28 Sep-Oct 2017 Elevated surface temperature at crater; lava effusion observed throughout October
28, 30 Oct 2017 Explosions
 
Early Nov 2017 Elevated surface temperatures at crater
14, 16 Nov 2017 Explosions

Lava dome extrusion may have been ongoing since early December 2016, when weakly elevated surface temperatures reappeared after the 24 October 2016 explosion. The lava dome was first observed in satellite imagery on 3 February 2017. Elevated surface temperatures were recorded throughout February and March 2017, and there was a small explosion on 24 March. Growth of a new dome was first observed on 15 April; it continued until being destroyed by an explosion on 16 May. Seismic data on 6 June and elevated temperatures on 7 June indicated growth of another dome, which continued until an explosion on 4 July 2017. There were multiple satellite and photographic observations of the growing dome during July and August; it was destroyed in an explosion on 22 August. Elevated surface temperatures were sporadically observed in early September. The next explosion took place on 26 September followed by two weaker ones on 28 September. Lava effusion was observed in satellite imagery throughout October. Small explosions on 28 and 30 October partly destroyed the lava dome. Elevated surface temperatures were recorded in early November along with small explosions on 14 and 16 November.

Activity during January-April 2017. While no activity was detected in infrasound or seismic data during January 2017, weakly elevated surface temperatures continued to be observed in infrequent clear satellite views (8 and 9 January), just as they were during 8-10 December and in infrared thermal data at the end of December (BGVN 42:04, figure 19). Low-level steam plumes were seen in clear views of the summit from the webcam during 15-19 and 21 January. Moderately elevated surface temperatures were observed in satellite data on 31 January 2017.

Satellite observations on 3 February 2017 confirmed the presence of a new lava dome at the bottom of the summit crater. The dome was about 70 m in diameter at that time, similar in size to previous domes. Observations in satellite imagery of weakly elevated surface temperatures at the summit continued during 7-9 February and during the last few days of the month. Minor steaming was seen in clear webcam images on 8 February. AVO noted that these observations were consistent with the presence of an active lava dome.

Minor steaming from the summit visible in clear webcam views, and slightly elevated surface temperatures in nighttime infrared satellite images, were present on several days during the first half of March. By the third week, surface temperatures were weakly to moderately elevated. At 0815 AKST (1615 UTC) on 24 March, a small explosion was detected in both seismic and infrasound (pressure sensor) data. This event was short-lived and similar to, if not smaller than, recent explosions. Cloud cover obscured observations by satellite. Slightly elevated surface temperatures were observed at the summit again during the last week of March.

No significant activity was detected in seismic, infrasound, or satellite data during the first two weeks of April 2017. A satellite image on 15 April, however, showed the presence of a small (less than 10-m-diameter) mound deep in the crater; the previous 75-m-diameter lava dome had been destroyed by the 24 March explosion. Satellite observations over the next several days indicated continued dome growth. Slightly elevated surface temperatures again appeared in a satellite view on 18 April. A satellite image on 23 April showed the dome partially filling the crater.

Activity during May-August 2017. Satellite images on 2 May showed that the lava dome was still active and had grown from about 15 m to more than 20 m in diameter. No further surface changes were evident on 8 May, indicating a pause or termination to the lava effusion. A short explosive eruption on 16 May at 1917 AKDT (17 May at 0317 UTC) was detected by local seismic instruments and lasted about 11 minutes. The resulting ash cloud rose to around 3.7-4.6 km altitude and was seen in satellite images to drift SW for about 5 hours. Satellite observations in the following days showed that the lava dome, built after the 24 March explosion, had been completely destroyed. Occasional clear webcam views showed steam emissions in the week following the 16 May explosion. Satellite imagery from 25 May suggested possible elevated surface temperatures at the summit while images from 26 May showed no change in the crater morphology since 16 May. No significant activity was detected in seismic or infrasound data for the remainder of May.

Evidence of possible lava effusion within the summit crater next appeared during the first week of June 2017. Small low-frequency earthquakes were detected on 6 June and elevated surface temperatures were observed in night-time satellite images on 7 June. Weakly elevated surface temperatures were observed in satellite images on 13, 19-23, and 29 June, and occasional clear webcam views of the summit showed light steaming. No activity was observed in seismic or infrasound data during the remainder of June.

A moderate explosive eruption lasting about ten minutes occurred early on the morning of 4 July at 0319 AKDT (1119 UTC). Elevated surface temperatures at the summit were visible after that on 7 and 14 July in satellite images, and occasional clear webcam views of the summit showed minor steaming. Satellite observations during 14-21 July revealed that a new dome, about 30 m in diameter and 10 m in height, had appeared at the bottom of the summit crater. Elevated surface temperatures were again observed on 22-24 July. New satellite observations between 21 and 28 July showed that the lava dome had reached about 42 m in diameter, with a slight inflation of its approximate height of 10 m. Minor steaming from the crater was seen in the webcam on 25 and 29-30 July; elevated surface temperatures were identified in satellite data on 30 July and 1 August. No activity was observed in seismic or infrasound data after the 4 July explosion for the remainder of the month.

Slow growth of the lava dome in the summit crater continued during the first few days of August 2017. Satellite observations showed that the dome surface area increased by about 75%, and covered an area of approximately 2,100 m2 (45 x 50 m) by 4 August. The height of the dome also increased due to intrusion of new lava. Elevated surface temperatures were observed in satellite data along with steam emissions from the summit crater seen in webcam images during periods of clear weather for the first few days of August, and again during 7-8 August. The small lava dome was observed during an overflight on 17 August (figure 23).

Figure (see Caption) Figure 23. A small lava dome grew inside the summit crater of Cleveland on 17 August 2017. Photo by Janet Schaefer, courtesy of AVO/ADGGS (Alaska Volcano Observatory/Alaska Division of Geological & Geophysical Surveys).

Minor degassing from the summit was seen in satellite and webcam images during 20-21 August. No explosive (ash-producing) activity was detected in seismic, infrasound, or webcam data in August until a 1-minute-long explosion on 22 August 2017 at 1043 AKDT (1843 UTC). Satellite data from 24 August indicated that the explosion destroyed the lava flow on the crater floor that had effused during July-August 2017. Explosion debris was evident on the crater floor, but no other changes to the summit area or flanks were noted. The 22 August explosion was detected by seismic and infrasound (air pressure) sensors, but no ash clouds were seen in satellite data. Nothing unusual was detected in seismic, infrasound, or satellite data for the remainder of August, except that elevated surface temperatures were observed sporadically in satellite data, suggesting that lava was present within the crater. A weak vapor plume was also sometimes visible at the summit in webcam images.

Activity during September-November 2017. Weakly elevated surface temperatures were observed in satellite data on 5 and 14 September 2017, along with minor steaming reported on 11, 17-19, and 22-24 September. These observations suggested to AVO the continued presence of lava in the crater. A small, short (three-minute-long) explosion was detected on local seismic and infrasound sensors at 1747 AKDT on 25 September (0147 on 26 September UTC) that produced a small volcanic cloud visible in satellite data about 30 minutes later with a height estimated at below 4.6 km altitude. Two weaker explosions were subsequently detected in infrasound and seismic data on 28 September (0516 and 0558 AKDT, 1319 and 1358 UTC), although no visible ash clouds were associated with these events. Weakly elevated surface temperatures during 28-30 September suggested that lava was present in the summit crater; a weak plume emanating from the crater could be seen when the summit was cloud-free.

Lava effusion in the crater was again noted in satellite data beginning on 30 September, forming a low dome that covered an area of about 4,200 m2 by 1 October 2017. Low-resolution satellite data from 6 October showed highly elevated surface temperatures, suggesting that slow growth of the dome continued. The dome doubled in size between 1 and 11 October when it appeared to cover an area of about 8,300 m2 and had approximate dimensions of 95 x 115 m. The number and intensity of elevated surface temperatures seen in satellite imagery declined during 7-13 October.

Satellite data from 15 October showed that the lava dome covered an area of about 9,500 m2 with dimensions of 100 x 125 m. There was no significant change in the size of the lava dome between 15 and 19 October based on satellite image analysis. On 16 October, satellite imagery revealed moderately elevated surface temperatures, and the webcam provided views of a small steam plume. Satellite data showed that the lava dome had grown further to about 110 x 140 m by 23 October and that surface temperatures were moderately elevated on 22 and 24 October. Small steam plumes were seen in webcam views during 22- 24 October. Small explosions on 28 and 30 October partly destroyed the dome within the summit crater. This was followed by slightly to moderately elevated surface temperatures occasionally observed in satellite imagery through the end of the month.

Moderately elevated surface temperatures were consistently observed in satellite imagery throughout the first half of November, suggesting new lava at or near the surface. Seismic and infrasound sensors detected a signal associated with low-level emissions shortly after midnight on 12 November. Two small explosions were also detected by the sensors on 14 and 16 November. These events were less energetic than those seen previously, and no volcanic cloud was observed following either explosion. A number of small earthquakes were detected on 14 November. Satellite observations of the summit indicated that a dome remained in the crater, and that the explosions were sourced from a vent in the middle of the dome. The satellite data showed no significant changes for the second half of November; although the volcano was obscured by cloud cover much of the time.

The infrared MIROVA thermal data for 2017 provided evidence that generally coincided with the satellite thermal observations of persistent heat production from dome growth throughout the year (figure 24).

Figure (see Caption) Figure 24. Infrared MODIS satellite data plotted with the MIROVA system shows intermittent thermal pulses from Cleveland for the year ending on 18 January 2018. Many of the spikes in thermal energy correspond to periods of satellite and photographic observation of dome growth. Courtesy of MIROVA.

Geologic Background. The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.dggs.alaska.gov/); Anchorage Volcanic Ash Advisory Center (VAAC), Alaska Aviation Weather Unit, NWS NOAA US Dept of Commerce, 6930 Sand Lake Road, Anchorage, AK 99502-1845 USA (URL: http://vaac.arh.noaa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


Dempo (Indonesia) — December 2017 Citation iconCite this Report

Dempo

Indonesia

4.016°S, 103.121°E; summit elev. 3142 m

All times are local (unless otherwise noted)


Phreatic explosion from the crater lake generates a dense ash plume in November 2017

Activity at Dempo on Sumatra in recent years has consisted of brief phreatic eruptions, most recently single-day events on 25 September 2006 (BGVN 34:03) and 1 January 2009 (BGVN 34:01). There were no additional reports from the Center of Volcanology and Geological Hazard Mitigation (CVGHM), also known as Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), until a brief episode of unrest in late April 2015, Another typically short phreatic explosion took place on 9 November 2017.

Activity during 2015. On 29 April the Alert Level was raised to 2 (on a scale of 1-4) by PVMBG following observations of diffuse white-gray plumes on 27 April rising to 50 m above the crater. Seismicity had increased during April compared to the previous month (figure 5). A Detik news report on 30 April quoted the PVMBG Head of the Western Volcano Field of Observation and Investigation, Hendra Gunawan, as saying that there had been tremor recorded over the previous four days. No ashfall was reported by PVMBG, and a phreatic eruption was only mentioned in the 29 April notice as a potential danger.

Figure (see Caption) Figure 5. Seismicity recorded at Dempo from 1 January to 29 April 2015. The types of earthquakes reported are HBS (Hembusan, puff or emission events), Trm (tremor), VB (shallow volcanic type B), VA (volcanic type A), TL (local tectonic), and TJ (distant tectonic). Courtesy of PVMBG.

Observers reported that during 1 June-9 September 2015 no plumes were seen and seismicity was low. On 10 September PVMBG lowered the Alert Level to 1.

Activity during 2017. Staff at the PVMBG Dempo observation post reported that no plumes rose from the crater during January and February 2017, but some diffuse white plumes during 1 March-4 April rose no higher than 50 m. Seismicity increased significantly above background levels from 21 March to 4 April (figure 5). On 5 April PVMBG raised the Alert Level to 2 based on visual and seismic data, but did not report any phreatic eruptions.

Figure (see Caption) Figure 6. Seismicity recorded at Dempo from 31 December 2016 to 6 April 2017. The types of earthquakes reported are HBS (Hembusan, puff or emission events), TRE (tremor), VB (shallow volcanic type B), VA (volcanic type A), TL (local tectonic), and TJ (distant tectonic). Courtesy of PVMBG.

According to PVMBG a three-minute-long phreatic eruption began at 1651 on 9 November 2017 and generated a dense ash plume that rose to 4.2 km altitude, about 1 km above the crater rim, and drifted S. Ashfall and sulfur gases were reported in villages on the S flanks, but there was no damage to property or injuries. The Alert Level remained at 2, with a 3-km-diameter exclusion zone; the Aviation Color Code was at Yellow.

Geologic Background. Dempo is a prominent stratovolcano that rises above the Pasumah Plain of SE Sumatra. The andesitic volcanic complex has two main peaks, Gunung Dempo and Gunung Marapi, constructed near the SE rim of a 3 x 5 km caldera breached to the north. The Dempo peak is slightly lower, and lies at the SE end of the summit complex. The taller Marapi cone was constructed within a crater cutting the older Gunung Dempo edifice. Remnants of seven craters are found at or near the summit, with volcanism migrating WNW over time. The large, 800 x 1100 m wide historically active crater cuts the NW side of the Marapi cone and contains a 400-m-wide lake located at the far NW end of the crater complex. Historical eruptions have been restricted to small-to-moderate explosive activity that produced ashfall near 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/); Detiknews (URL: https://news.detik.com/).


Pacaya (Guatemala) — December 2017 Citation iconCite this Report

Pacaya

Guatemala

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

All times are local (unless otherwise noted)


Pyroclastic cone in MacKenney crater grows above crater rim, January-September 2017

Activity since 1961 at Pacaya has been characterized by extensive lava flows, bomb-laden Strombolian explosions, and ash plumes emerging from MacKenney crater and several vent fissures, impacting communities in the vicinity; several million people live within 50 km. After a few months of quiet, intermittent ash plumes and incandescence in early June 2015 marked the beginning of the latest eruptive episode, which has been ongoing since that time. Observations of incandescence increased during the second half of 2015, and the presence of a new pyroclastic cone, about 15 m in diameter at the center of MacKenney crater, was confirmed in mid-December 2015.

Strombolian activity from the cone continued throughout 2016. It was most active during June and July, depositing new ejecta onto the flanks. Although it had quieted down by the end of the year, persistent degassing, steam plumes, and occasional incandescence were still observed from the new cone. It had filled much of the crater by December 2016. This report describes the continued growth of the pyroclastic cone during January-September 2017, as well as new lava flows that emerged during February and March. Information was provided primarily by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH) and satellite thermal data.

The pyroclastic cone inside MacKenney crater continued to grow sporadically during January-September 2017. Weak explosions in January produced ejecta 15 m above the top of the cone as steam and gas emissions rose about 400 m above the crater rim. By early February the top of the cone had risen to 10 m above the crater rim. Ejecta ranging in size from millimeters to 50 cm rose up to 25 m above the cone. Three small lava flows emerged from the crater in early February and flowed down the NW flank a few hundred meters before cooling. Growth of the cone continued more slowly during March-August, but incandescence was still observed, and weak explosions deposited tephra around the sides of the cone. Increased explosive activity during August reduced the height of the cone to slightly below the crater rim, but renewed explosions during September built it back up again to 10 m above the rim a few weeks later.

During January 2017, activity increased slightly compared with December 2016, and included degassing, tremors, incandescence, and weak explosions from MacKenney crater. Steam-and-gas plumes rose to around 400 m above the crater rim and generally drifted about 5 km before dissipating. Incandescence in the crater grew more visible towards the end of the month; ejecta from the pyroclastic cone within crater rose as much as 15 m above the crater rim. Seismic RSAM values also increased from a maximum of 2,500 to 3,500 units. The first MODVOLC thermal alert since 10 April 2016 appeared on 10 January 2017. Eight more alerts appeared during January, every few days for the rest of the month.

Degassing during February 2017 sent plumes slightly higher to 500 m above the crater . The top of the pyroclastic cone had risen to about 10 m above the crater rim by early February, as compared to about 10 m below the crater rim a year earlier in February 2016 (figure 78). Ejecta from the cone ranged in size from millimeters to 50 cm, and rose to heights of 10-25 m above the top of the cone with constant activity (figure 79).

Figure (see Caption) Figure 78. The pyroclastic cone inside MacKenney Crater at Pacaya grew substantially between February 2016 (upper photo) and 2 February 2017 (lower photo). View is to the NW with the 2010 fissure at the back, right side of the crater. Courtesy of INSIVUMEH (Reporte mensual, febrero 2017; Informe mensual de la actividad del Volcán Pacaya, junio 2017).
Figure (see Caption) Figure 79. Ejecta from the top of the pyroclastic cone inside MacKenney crater at Pacaya ranged in size from millimeters to approximately 50 cm, and was thrown tens of meters from the summit on 2 February 2017. Courtesy of INSIVUMEH (Reporte mensual, febrero 2017).

Three small lava flows were reported during February 2017, first emerging from the NW side of the crater from the fissure created during 2010 on 9 February 2017 and flowing NW towards Cerro Chino. Incandescent material was ejected 30-50 m above the crater rim and filled much of the crater. Lava travelled as far as 300 m down the NW flank. The dimensions of the flows were variable, but by the end of the month they were about 50 m long and 20 m wide. Ten MODVOLC thermal alerts were issued during February, indicating that activity was high inside and around the summit crater.

Steam plumes during March and April 2017 rose as high as 600 m above the crater rim. Lava flowed tens of meters outside the crater rim a few times at the end of March. The growth of the pyroclastic cone continued with Strombolian explosions of 10-25 m above the top of the cone during this time, and incandescence visible on clear nights. It was possible to see the new cone above the crater rim from the NW and W flanks (figure 80). Rumblings from the explosive activity were reported within 5 km of the cone. Although the three MODVOLC thermal alerts issued during the first week of March were the last through at least September 2017, weak explosions and nighttime incandescence continued during May as the pyroclastic cone continued to grow.

Figure (see Caption) Figure 80. The top of the new pyroclastic cone inside MacKenney crater at Pacaya was visible from the edge of nearby Cerro Chino crater, about 1 km NW, beginning in February 2017. Courtesy of INSIVUMEH (Reporte mensual, febrero 2017).

By June 2017, the steam plumes were rising about 800 m above the crater rim. The height of the pyroclastic cone remained at about 10 m above the crater rim, but continued to grow in volume and produce abundant steam and gas (figure 81). Similar emissions were reported during July, however, incandescence was only occasionally observed at night.

Figure (see Caption) Figure 81. Abundant steam and gas emerged from the upper part of the pyroclastic cone inside MacKenney crater at Pacaya on 17 June 2017. The dome rose height remained at about 10 m above the crater rim, shown in the lower left foreground. Courtesy of INSIVUMEH (Informe mensual de la actividad del Volcán Pacaya, junio 2017).

INSIVUMEH reported increased activity during August 2017 with the frequency of Strombolian explosions increasing to 5-7 per hour, and higher RSAM units recorded to 4,000; some material was ejected as high as 75 m above the crater rim, generating block avalanches as far as 100 m down the W flank. Explosions during 11 August reduced the height of the pyroclastic cone inside the crater such that it was no longer visible from the flank. Moderate to strong explosions were recorded a number of times during the month (figure 82).

Figure (see Caption) Figure 82. A thermal image of MacKenney crater at Pacaya on 18 August 2017 shows Strombolian activity at the summit. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Pacaya, Semana del 19-25 de Agosto de 2017).

Seismic and explosive activity remained high during September 2017. Two significant events were recorded. On 5 September RSAM values peaked at 5,000 units and remained elevated for about six hours before dropping back to average values around 2,000. This corresponded with a period of rebuilding of the pyroclastic cone within the crater. INSIVUMEH reported Strombolian explosions ejecting material as high as 100 m above the crater rim during 21-22 September. The second event lasted for about three days during 23 and 26 September when there was an increase in the rate of explosions, registering up to 40 per hour. After destruction of part of the cone during August, it was rebuilt to a level about 10 m above the crater rim again during this time.

Infrared thermal data generally agrees well with observations of increased activity and lava flows during January-March 2017 (figure 83). However, reports from INSIVUMEH indicate that explosive activity continued at the pyroclastic cone during April-September, although only the largest events during August and September created thermal signals that were captured in the MIROVA data.

Figure (see Caption) Figure 83. MIROVA graph of infrared MODIS data for the year ending on 15 October 2017 at Pacaya shows the thermal signature associated with lava flows and explosive activity during January through March 2017. Although increased explosive activity was reported in August and September, the thermal signal was much smaller. 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/); 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/).


Sabancaya (Peru) — December 2017 Citation iconCite this Report

Sabancaya

Peru

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

All times are local (unless otherwise noted)


Continuous pulses of ash emissions for ten months, February-November 2017

Activity that began in 1986 at Sabancaya was the first recorded in over 200 years. During the last period of substantial ash eruptions between 1990 and 1998 ashfall deposits up to 4 cm thick were reported 8 km E of the volcano. Intermittent seismic unrest and fumarolic emissions characterized activity from late 2012 through October 2016, with a few possible minor ash emissions unconfirmed during this period, and probable SO2 plumes.

Hybrid seismic events, related to the movement of magma, and SO2 emissions increased noticeably during September and October 2016. An explosive eruption period with numerous ash plumes began on 6 November 2016 and has continued throughout 2017. Continuous ash emissions with plume heights exceeding 10 km altitude were often recorded through February 2017. Thermal anomalies were first measured in satellite data in early November 2016, along with numerous significant SO2 plumes (BGVN 42:05). Details of the continuing eruptive activity at Sabancaya from February-November 2017 are discussed in this report with information from the two Peruvian observatories that monitor the volcano: Instituto Geofisico del Peru - Observatoria Vulcanologico del Sur (IGP-OVS), and Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico) (OVI-INGEMMET). Aviation reports and notices come from the Buenos Aires Volcanic Ash Advisory Center (VAAC), and satellite data is reported from several sources.

Images from December 2016. An expedition to Sabancaya during 9-18 December 2016 by photographer Martin Rietze recorded numerous ash emissions and the impacts of the ongoing eruption on the region (figures 31-36). Similar activity continued throughout 2017.

Figure (see Caption) Figure 31. Gas and a dense ash plume rose above Sabancaya during 12-15 December 2016 in this view taken 6.5 km NNE of the volcano. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 32. A column of ash drifted E from Sabancaya during 12-15 December 2016 while a cloud cap condensed on top of the plume. Image taken from 6.5 km NNE of the summit. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 33. An ash plume fanned out to the E from Sabancaya during 12-15 December 2016. Image taken from 15 km E. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 34. Sabancaya lies in the saddle between the older volcanic complexes of Ampato to the S (left) and Hualca Hualca to the N (right) in this view taken from 15 km E. It is the only one of the three to have erupted during the Holocene. An ash plume rose from Sabancaya during 12-15 December 2016, while ash from an earlier pulse is visible drifting S over Ampato. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 35. Trace amounts of ashfall from Sabancaya covered the region 10 km W of the volcano during 12-15 December 2016. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 36. An ash-and-steam plume rose vertically from Sabancaya during 12-15 December 2016 while a meteor streaked across the nighttime sky in this image taken 6.5 km NNE of the summit. Photo copyright by Martin Rietze, used with permission.

Summary of activity, February-November 2017. The persistent eruptive activity during February-November 2017 can be visualized by the continuous MIROVA plot of Log Radiative Power during this time (figure 37). The Buenos Aires VAAC issued 1,174 VAAC reports for Sabancaya during February-November 2017, with over 100 recorded each month (table 1). Tens of explosions were reported daily by OVI-INGEMMET and IGP-OVS throughout the period. Ash plumes usually rose to the 9-11 km altitude range (3,000-5,000 m above the summit), and drifted 30-50 km in many directions before dissipating. MODVOLC thermal alerts were reported between 2 and 16 times every month, and satellite data registered SO2 plumes with values greater than two Dobson Units multiple days each month (figure 38).

Figure (see Caption) Figure 37. MODIS infrared satellite data plotted by MIROVA for the 12 months ending 19 January 2018 show the continuous signature of thermal activity from Sabancaya during that time. Courtesy of MIROVA.

Table 1. Eruptive activity at Sabancaya, February-November 2017. Compiled using data from IGP-OVS/OVI-INGEMMET reports, the Buenos Aires VAAC, HIGP, and NASA GSFC.

Month VAAC Reports Avg Daily Explosions by week Max Plume Heights (m above crater) Plume Drift MODVOLC Alerts Days with SO2 over 2 DU
Feb 2017 108 58, 23, 19, 42 3,000-4,300 40 km, NW, N, S, SE, SW 6 12
Mar 2017 122 44, 36, 36, 37, 41 2,500-4,800 30-40 km, S, NW, SW, N 4 8
Apr 2017 113 27, 37, 36, 33 3,000-3,200 40 km NW, NE, SE, W, N 16 11
May 2017 117 41, 38, 39, 41 2,800-4,200 30-40 km NE, E, SE 4 3
Jun 2017 104 47, 31, 26, 15, 5 1,500-3,700 30-40 km E, SE, SW, S 4 5
Jul 2017 127 10, 19, 24, 40 3,500-5,500 40-50 km NW, S, E, N, SE 2 13
Aug 2017 124 65, 41, 46, 44 3,200-4,200 30-50 km N, SE, NW, S 12 10
Sep 2017 118 38, 29, 45, 45 2,500-3,500 30-40 km SE, E, NE 6 5
Oct 2017 120 42, 41, 47, 43 3,100-3,900 35-60 N, NW, W, S, SE, NE, E 9 8
Nov 2017 121 57, 66, 82, 78, 69 3,300-4,200 40-50 km N, NE, E, SE, NW, SW 11 10
Figure (see Caption) Figure 38. Numerous significant SO2 plumes were captured by the OMI instrument on the Aura satellite for Sabancaya during February-November 2017. Plumes drifted SSE on 4 March, 22 March, 30 July, and 6 August 2017 (top four images), and SW and W on 9 October and 10 November 2017 (bottom two images). The red pixels indicate values of Dobson Units (DU) greater than 2. Courtesy of NASA Goddard Space Flight Center.

Activity during February-November 2017. IGP-OVS and OVI-INGEMMET monitor seismicity, inflation and deflation, SO2 emissions, and visual activity with webcams from several locations around Sabancaya (figure 39). Ash plumes during February 2017 rose to heights of 3,000-4,300 m above the summit (figure 40). The average number of daily explosions decreased from 53 the first week to 19 the third week, and then increased to 42 during the last week. Ash plumes drifted up to 40 km in numerous directions.

Figure (see Caption) Figure 39. Stations where IGP-OVS and OVI-INGEMMET monitor seismicity (red), inflation and deflation (green), SO2 emissions (orange), and their webcam locations (yellow) for Sabancaya. Courtesy of IGP-OVS and OVI-INGEMMET weekly reports.
Figure (see Caption) Figure 40. Ash emission from Sabancaya, 12 February 2017. View from the OVI-INGEMMET webcam located near Coporaque, about 30 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 06 al 12 de febrero de 2017).

During March 2017 the number of daily explosions was very consistent averaging each week between 36 and 44 events. Maximum ash plume heights ranged from 2,500 to 4,800 m and drifted 30-40 km to either the NW or SW (figure 41). Ash fell in Pinchollo (20 km N) and Cabanaconde (22 km NW) during the last few days of the month.

Figure (see Caption) Figure 41. Ash emission from Sabancaya, 12 March 2017. Taken from OVI-INGEMMET webcam located about 4 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 06 al 12 de marzo de 2017).

Ash fell during the first week of April in Pinchollo, Maca (20 km NE) and Chivay (32 km NE). Plume heights during the month were slightly lower, ranging from 3,000-3,200 m and drifted 40 km in several directions. The frequency of daily explosions decreased slightly from March to an average each week ranging from 27 to37. The Buenos Aires VAAC reported that diffuse ash plumes drifted 100 km E on 9 April.

The frequency of daily explosions increased slightly during May; weekly averages ranged from 38 to 41. Plume heights were somewhat higher, at 2,800-4,200 m, and drifted 30-40 km in many directions (figure 42). There was a notable decrease during June 2017 in the number of daily explosions from an average during the first week of 47 to an average of only five at the end of the month. Deflation was observed in the GPS data after 21 June. Plume heights ranged from 1,500 to 3,700 m.

Figure (see Caption) Figure 42. On 20 May 2017 the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image of repeated puffs of ash rising from Sabancaya and drifting E. Courtesy of NASA Earth Observatory.

Activity increased steadily during July 2017. Daily explosions rose from an average of 10 during the first week to 40 the last week; ash plume heights were up to 5,000 m during those weeks (figures 43, 44) and drifted 50 km or more generally NW and SE. Ash plumes during the third week affected communities N of the volcano, including the villages of Cabanaconde, Pinchollo, Lari (20 km NE), Madrigal (20 km NE), Ichupampa (23 km NE), Maca and Achoma (21 km NE). Winds changed to the S on 22 July, so ashfall then affected Lluta (30 km SW), Huanca (75 km SSE), and some parts of Arequipa (80 km SSE).

Figure (see Caption) Figure 43. Ash and gas emission from Sabancaya rose several kilometers above the summit on 9 July 2017 in this OVI-INGEMMET image from their webcam located near Coporaque, about 30 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 03 al 09 de julio de 2017).
Figure (see Caption) Figure 44. On 26 July 2017, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite captured this natural-color image of an ash plume drifting E from Sabancaya. The rising ash cast a shadow on the ground below. Courtesy of NASA Earth Observatory.

After averaging 65 explosions per day during the first week of August 2017, activity declined slightly to weekly averages of 41-46 explosions per day for the rest of the month. Plume heights ranged from 3,200 to 4,200 m and drifted generally 30-50 km NW or SE. During September 2017 activity was much the same. Plume heights ranged from 2,500-3,500 m, and drifted 30-40 km SE or NE. The weekly averages of daily explosion frequency varied between 29 and 45 events.

A noteworthy difference in activity occurred during October 2017, when there were tremors with ash emissions lasting for more than three hours per day during the last two weeks of the month. Daily explosion frequency averaged from 41 to 47 each week, and plume heights ranged from 3,100 to 3,900 m (figure 45). A few plumes drifted as far as 60 km during the third week of the month.

Figure (see Caption) Figure 45. A large ash and gas plume rose from Sabancaya on 21 October 2017 in this view from the OVI-INGEMMET webcam located near Coporaque, about 30 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 16 al 22 de octubre de 2017).

During November 2017 the number of daily explosions increased from an average of 57 the first week to 82 by the third week, decreasing to 69 at the end of the month. Plume heights remained at 3,300-4,200 m, drifting 40-50 km in several directions. Tremors with ash emissions lasted 1-2 hours most days.

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

Information Contacts: Observatorio Volcanologico del INGEMMET, (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa (URL: http://ovi.ingemmet.gob.pe); Instituto Geofisico del Peru, Observatoria Vulcanologico del Sur (IGP-OVS), Arequipa Regional Office, Urb La Marina B-19, Cayma, Arequipa, Peru (URL: http://ovs.igp.gob.pe/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Martin Rietze (URL: http://www.mrietze.com/).


Santa Maria (Guatemala) — December 2017 Citation iconCite this Report

Santa Maria

Guatemala

14.757°N, 91.552°W; summit elev. 3745 m

All times are local (unless otherwise noted)


Slow growth of new lava dome, persistent ash plumes, and nearby ashfall, January-October 2017

The dacitic Santiaguito lava-dome complex on the W flank of Guatemala's Santa María volcano has been growing since 1922. The youngest of the four vents in the complex, Caliente, has been actively erupting with ash explosions, pyroclastic, and lava flows for more than 40 years. During July-September 2016, daily weak ash emissions were punctuated weekly by stronger emissions that sent ash plumes to altitudes of 3.3-6 km, and numerous pyroclastic flows were reported (BGVN 42:07). A new lava dome appeared in October and had filled half of the crater by years end; the frequency of explosions increased to 25-35 per day by December 2016. Guatemala's INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meterologia e Hidrologia) and the Washington VAAC (Volcanic Ash Advisory Center) provided regular updates on the continuing activity during the time period of this report from January-October 2017.

Activity at the Caliente dome was very consistent from January through October 2017. A lava dome that began growing during October 2016 continued to slowly increase in size. Its growth generated constant steam and gas emissions that rose 100-500 m above the dome, and daily explosions with ash that generally rose to 2.8-3.3 km altitude (200-800 m above the dome). Ashfall was reported almost daily in villages and farms within 5-12 km S and SW, including San Marcos Palajunoj, Loma Linda, Monte Bello, El Patrocinio, La Florida, El Faro, Patzulin, and others. There were 15-35 explosions per day throughout this time. As the lava dome within the Caliente summit crater increased in size, more block avalanches were observed traveling tens of meters down the flanks of Caliente, outside the crater rim. Several lahars affected the major drainages during May-October.

Fifteen to twenty small to moderate daily explosions with ash emissions were typical for the Caliente dome complex during most of January 2017, in addition to constant blue and white gas emissions from the top of the lava dome. This same pattern continued throughout February, when the new dome inside the summit crater continued to grow (figure 63). By March, the dome was large enough that occasional block avalanches of fresh lava reached outside the summit crater, and descended a few tens of meters onto the flanks; the lava dome, growing since October 2016, had not quite filled the crater (figure 64).

Figure (see Caption) Figure 63. The lava dome inside the summit crater of Caliente grew noticeably between 17 January and 28 February 2017 at Santa María in this view to the S. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA FEBRERO 2017).
Figure (see Caption) Figure 64. Ash and steam rises during an explosion from the new lava dome inside the summit crater of the Caliente dome of Santa María. Recently ejected blocks are steaming on the flanks close to the webcam on 19 March 2017. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA MARZO 2017).

By April 2017 the number of daily explosions had increased to 25-30, with similar energy levels and ash plume heights as earlier in the year. The Cabello de Ángel River continued downcutting through the 2014-2015 lava flows (figure 42, BGVN 41:09) creating a new channel that was 15-50 m deep (figure 65). During May, the number of daily explosions ranged from 9 to 26 (figure 66), and block avalanches from the new lava dome traveled short distances down the flanks. Two lahars were reported in May; on 6 May a lahar 30 m wide and 2.5 m deep descended the Cabello de Ángel drainage (a tributary of the Nimá I river on the S flank) carrying branches, tree trunks, and blocks up to 2 m in diameter. A smaller lahar on 31 May traveled down the Nimá I drainage and dragged smaller blocks and tree trunks down the channel.

Figure (see Caption) Figure 65. The Cabello de Ángel river cuts new channels through the 2014-2015 lava flows on the SE flank of Caliente dome at Santa María during April 2017. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA ABRIL 2017).
Figure (see Caption) Figure 66. A moderate explosion on 30 May 2017 from Santiaguito at Santa María sends an ash plume to 2.6 km altitude that then drifted SW. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA Mayo 2017).

Explosions during June 2017 continued at the rate of 14-36 per day, with ash plumes rising to 2.7-3.3 km altitude (figure 67). Juvenile material continued to fill and overtop the crater rim, creating weak block avalanches down the flanks. Increased precipitation during June resulted in five lahars descending the Cabello de Ángel, Nimá I, and San Isidro drainages on 1, 5, 7, 9, and 16 June. They ranged in size from 15 to 25 m wide and 1 to 1.5 m high, and transported blocks 1-2 m in diameter. A larger lahar on 1 June that traveled down the Cabello de Ángel drainage was 30 m wide and 2 m high.

Figure (see Caption) Figure 67. An ash plume at Santa María's Santiaguito complex on 21 June 2017 rises to 2.9 km. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA Junio 2017).

Similar explosive activity continued during July. On 5 July, a moderately-sized lahar descended the Cabello de Ángel drainage, a tributary of the Nimá I river. Near the El Faro estate, the lahar was 30 m wide and 1 m deep, and carried blocks 50 cm in diameter. On 14 July, another lahar traveled down the Nimá I drainage, which is a tributary of the Samalá. By August the summit crater of Caliente was nearly filled with the new lava dome, and overflows of block avalanches were more frequent, mostly traveling down the E flank (figure 68). A moderately-sized lahar descended the Nimá I drainage on 9 August.

Figure (see Caption) Figure 68. Fresh block avalanches were visible covering an area about 126 m wide and 246 m long near the summit of Caliente at Santa María when images from 31 July (left) and 2 August 2017 (right) were compared. Most of the block avalanches traveled down the east flank (A), but smaller avalanches traveled shorter distances down the NE flank (B). Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 29 de julio al 04 de agosto de 2017).

Explosions with ash plumes rising hundreds of meters above the crater rim continued daily during September and October, and sent block avalanches down the NE and SE flanks of the dome. INSIVUMEH reported that on 11 October 2017 a 12-m-wide and 1.5-m-high lahar descended the Cabello de Ángel and the Nimá I drainages, carrying blocks up to 1 m in diameter. On 13 October, the seismic network detected moderate-to-strong lahars in the Cabello de Ángel and the Nimá I drainages triggered by heavy rain.

Relatively few VAAC reports were issued for Santa María during 2017 compared with the previous two years. The Washington VAAC observed an ash plume in satellite imagery drifting 15 km W at 4.6 km altitude on 14 January. Morning visible imagery on 1 February showed an ash plume 25 km SW at 3.8 km altitude. An ash emission was observed on 27 February a few kilometers WSW at or slightly above the summit. Multiple small puffs of ash extended 55 km WSW of the summit on 9 March, at 4.6 km altitude. An ash plume was centered 15 km NW of the summit at 3.8 km altitude and rapidly dissipating on 4 April. The next VAAC observation, on 2 June, was a small puff of ash located 30 km S of the summit. On 6 September, possible volcanic ash was drifting SW of the summit at 4.3 km altitude.

Infrared MODIS satellite data suggest low-level, persistent activity at Santa María throughout January-October 2017 (figure 69). This is consistent with photographs of a slowly growing lava dome at the summit, and persistent low-energy explosions with ash emissions and block avalanches during the year. There were no MODVOLC thermal anomalies during this time.

Figure (see Caption) Figure 69. Infrared MODIS thermal data graphed through the MIROVA system indicates a low but persistent level of thermal activity at Santa María for the year ending on 8 June 2017. This is consistent with the observations of a slowly growing lava dome inside the summit crater. Courtesy of MIROVA.

Geologic Background. Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing W towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

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/ ); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


Sinabung (Indonesia) — December 2017 Citation iconCite this Report

Sinabung

Indonesia

3.17°N, 98.392°E; summit elev. 2460 m

All times are local (unless otherwise noted)


Constant activity through September 2017, with ash plumes, block avalanches, and pyroclastic flows

Indonesia's Sinabung volcano, located on North Sumatra, had its first confirmed Holocene eruption between 27 August and 18 September 2010; ash plumes rose up to 2 km above the summit, and falling ash and tephra caused fatalities and thousands of evacuations (BGVN 35:07). It remained quiet after the initial eruption until 15 September 2013, when a new eruption began that has continued for over three years. Details of events during October 2016-September 2017 are covered in this report. Information is provided by, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), referred to by some agencies as CVGHM, the Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Centre (VAAC), and the Badan Nacional Penanggulangan Bencana (National Disaster Management Authority, BNPB).

Summary of activity during November 2013-September 2016. Thousands of evacuations took place during November and December 2013 when ash plumes reached heights between 6 and 11 km altitude multiple times. Ashfall from hundreds of pyroclastic flows in January 2014 covered communities in the region. Lava flows emerged from the summit in mid-January 2014 and traveled down the S flank. Pyroclastic flows on 1 February 2014 killed 17 people in the village of Sukameriah, located 3 km S of the summit (BGVN 39:01). The lava flow had advanced 2.5 km from the summit by 6 April 2014. Lava flows, ash plumes, and pyroclastic flows persisted throughout 2014 and 2015. Ash plumes generally rose up to about 5 km altitude, and pyroclastic flows traveled up to 4.5 km from the summit throughout this period (BGVN 39:10). Repeated lava dome growth and destruction was also reported by PVMBG during this time (BGVN 40:10).

Increases in lava dome volume and instability during June 2015 again led to evacuations of thousands living within 7 km of the volcano. Ash deposits were common in the communities up to 10-15 km away. Similar activity continued into 2016, with tens of pyroclastic flows affecting nearby communities during many months. In April 2016, over 9,000 people remained in evacuation centers. Ash plumes were reported 3-8 times each month by the Darwin VAAC between April and October 2016, with plume altitudes ranging generally from 3-5.5 km. Several fatalities were reported during May 2016 (BGVN 42:02). A lahar passed through Kutambaru village, 20 km NW of Sinabung, on 9 May and killed one and injured four people. A pyroclastic flow on 21 May 2016 killed 7 people in the village of Gamber, 4 km SE from the summit. Ashfall was reported during July 2016 more than 50 km NE, and incandescent lava was visible up to a kilometer from the summit. Continuous pyroclastic flows were reported on 25 August 2016, with an ash plume observed at 6.1 km altitude the following day.

Summary of activity during October 2016-September 2017. Ash plumes, block avalanches, and pyroclastic flows were all nearly constant at Sinabung throughout this period (table 7). The number of explosions recorded every month ranged from 37 (March 2017) to 105 (June 2017). The number of Volcanic Observatory Notices to Airmen (VONAs) each month ranged from 34 (September 2017) to 93 (June 2017). The Darwin VAAC reported ash plumes on 17 or more days every month of 2017 through September. Thermal anomaly signals also persisted throughout, likely caused primarily by dome growth and incandescent block avalanches.

Table 7. Ash plumes and explosions reported for Sinabung, October 2016-September 2017. Data from Darwin VAAC and PVMBG reports.

Month Days with Ash Plume Reports Ash Plume Altitudes (km) Ash Plume Drift Explosions reported (PVMBG) Number of VONA's issued (MAGMA) Comments
Oct 2016 5, 12, 26, 28-29, 31 3.4-4.6 km SE, E, SSE, NE -- -- --
Nov 2016 1, 2, 6, 11, 13, 14, 20, 29, 30 3.4-5.8 km E, W, E, NE, SE -- -- Multiple brief explosions; pyroclastic flows observed 1, 2 Nov
Dec 2016 15, 17, 19-21, 26, 27, 29-31 3.0-6.1 km SSE, E, S, SE, NW, S, SW -- -- Hotspot visible in satellite images on 30 Dec
Jan 2017 1, 8-15, 17-20, 22, 24, 26-31 3.4-5.5 km WSW, W, E, ESE, SW 101 58 Ash 50 km E and 75 km NE on 8 Jan; hot spot in satellite imagery 10 Jan
Feb 2017 1-14, 16-22, 24-26, 28 3.0-5.5, 6.7, 7.4 km SSE, S, NE, E, SE, SW, WSW, W 88 70 4 Feb explosion caused ash plume to 7.4 km altitude
Mar 2017 1, 2, 5, 7-18, 21, 22, 24, 25, 27, 29 3.0-5.5 km WNW, NW, SSE, NNW, W, S, SW, NE, N, E, ESE 37 34 Highest plumes, on 17 and 18 March, rose to 5.5 km altitude and drifted W and WSW
Apr 2017 5, 7, 9-20, 22, 24-30 3.0-5.5, 8.4 km ESE, E, SE, WNW, SSE, SSW, W, SW, WSW, NNE, S 104 58 Large explosion on 9 April, ash plume reported by a ground observer to 8.4 km altitude, drifting SE
May 2017 2-12, 14-17, 19-20, 23-31 3.4-8.8 km WSW, WNW, NW, SW, S, E, SE, NE, ESE, W, ENE 87 58 Series of large explosions during 17-20 May, several plumes rose to altitudes between 6.1 and 8.8 km
Jun 2017 1-27, 29, 30 2.7-5.5, 6.4 km NE, N, WNW, ENE, ESE, SE, SW, W, S, E, NW, NE, SSW, SSE 105 93 --
Jul 2017 2-3, 6, 8-11, 14, 15, 17-31 2.7-6.1 km ESE, NW, ENE, E, SE, W, WSW, SSW, ENE, NE 91 64 --
Aug 2017 1, 2, 6-10, 12, 16, 23-29, 31 2.7-5.5, 6.4 km ENE, SE, E, S, W, ESE, WNW, NNW, WSW 61 76 Large explosion on 2 Aug with ashfall in many places; Hotspots reported 6, 7 Aug
Sep 2017 1, 3, 7, 8, 12-16, 18, 22, 23, 25-29 3.0-5.5, 6.1-6.4 km ENE, WSW, E, W, NW, SE, ESE, SW 55 34 --

Activity during October 2016-September 2017. The visiting head of PVMGB observed an ash plume from an explosion on 28 September 2016. Ash emissions continued at Sinabung, with multiple aviation advisories issued by the Darwin VAAC through the end of 2016. Explosions generated ash plumes that rose to altitudes of 3.0-6.1 km, and drifted in multiple directions during the last quarter of 2016 (table 7). Pyroclastic flows were observed several times during November (figure 28), and a hotspot was visible in satellite imagery on 30 December.

Figure (see Caption) Figure 28. A large pyroclastic flow descended the E flank of Sinabung on 29 November 2016 in this view taken a few kilometers SE of the volcano. . Courtesy of Sadrah Peranginangin.

Activity during January 2017 was dominated by incandescent block avalanches (figure 29). PVMBG reported 101 ash-bearing explosions with plumes rising up to 1 km above the summit, and pyroclastic flows that traveled up to 3 km ESE and 500 m S. A You Tube video captured a pyroclastic flow and ash plume on 17 January 2017. Ash plumes were reported by the Darwin VAAC on 21 days during the month with plume heights ranging from 3.4-5.5 km altitude.

Figure (see Caption) Figure 29. Block avalanches descended the E flank of Sinabung many times during January 2017, including at 0134 local time on 17 January, as seen looking to the WSW. Courtesy of Endro Lewa.

Near-daily ash plumes from 88 explosive events during February 2017 rose to heights of 500-5,000 m above the summit (3.0-7.5 km altitude), and pyroclastic flows traveled 3.5 km E and 1 km S. The Darwin VAAC reported ash emissions on all but three days of the month. A large explosion on 4 February sent an ash plume to 7.4 km altitude that then drifted SE (figure 30), and on 9 February a large ash plume drifted WSW at 6.7 km altitude.

Figure (see Caption) Figure 30. Photo of an ash plume at Sinabung on 4 February 2017 that rose more than 5 km above the summit and slowly drifted SE. Photo taken from Kabanjahe, about 13 km SE. Courtesy of Sadrah Peranginangin.

Block avalanches continued to travel 500-2,000 m down the ESE flank during March 2017. Ash plume heights ranged from 500 to 3,000 m above the summit (3.0-5.5 km altitude) during the 37 explosion events reported by PVMBG (figure 31). Pyroclastic flows traveled 2.5 km down the S flank. The highest plumes of the month were recorded on 17 and 18 March; they rose to 5.5 km altitude and drifted W and WSW. The Darwin VAAC reported ash plumes during 21 days of the month.

Figure (see Caption) Figure 31. Photo of an ash plume at Sinabung on 29 March 2017 at 1548 local time, in this view looking W. Courtesy of Igan S. Sutawijaya.

During April 2017, block avalanches were observed traveling between 800 and 3,500 m down the SSE flank (figure 32), and 104 explosions were recorded by PVMBG. Ash plumes from these explosions rose to heights of 800 to 3,500 m above the summit. Pyroclastic flows descended 2.8 km down the S flank. A large explosion on 9 April reported in a VONA by a ground observer sent an ash plume to 8.4 km altitude, drifting SE. Pyroclastic flows were also observed on the SE flank. The Darwin VAAC reported ash plumes on 22 days of the month.

Figure (see Caption) Figure 32. Pyroclastic flows descended the S flank (left) and block avalanches descended the E flank of Sinabung near midnight on 4 April 2017, while a small explosion took place at the summit. Image taken from a small village a few kilometers from the base of the SE flank. Courtesy of Sadrah Peranginangin.

Ash plumes rose between 500 and 6,000 m above the summit during May 2017. Eighty-seven explosive events were recorded (figure 33), and block avalanches were observed traveling 500-1,500 m down the S and SE flanks. The Darwin VAAC reported ash plumes on 26 days during the month. A series of large explosions during 17-20 May resulted in several plumes that rose to altitudes between 6.1 and 8.8 km, in addition to numerous others at lower altitudes between 3.7 and 5.8 km. As of late May, over 9,000 people were still displaced from the volcano, living in either shelters or evacuation camps, according to BNPB.

Figure (see Caption) Figure 33. Strombolian activity at the summit of Sinabung on 1 May 2017. Courtesy of Sadrah Peranginangin.

Incandescent block avalanches and pyroclastic flows were persistent during June 2017. They moved down the SE and S flanks up to 2,500 m. PVMBG reported 105 explosive events with plume heights ranging from 500-4,000 m above the summit (figure 34). The largest explosions of the month, on 17 June, generated ash plumes that rose to 6.4 km altitude and drifted 15 km SW. The Darwin VAAC reported ash emissions every day except for 28 June.

Figure (see Caption) Figure 34. Ash plume rose from Sinabung on 26 June 2017. The view is from a small village about 7 kilometers ENE of the summit. Courtesy of Endro Lewa.

PVMBG reported 91 explosive events during July 2017 that produced ash plumes that rose 500-3,500 m above the summit. They also noted four pyroclastic flows that traveled 1-3 km down the S and SE flanks. Block avalanches continued on the S and E flanks, traveling as far as 3 km. The Darwin VAAC issued reports on 24 days during July. The largest explosions occurred on 20 and 23 July when ash plumes rose to 5.8 and 6.1 km altitude and drifted WSW, ENE, and SE (figure 35).

Figure (see Caption) Figure 35. A large ash plume from Sinabung rose more than 5 km above the summit on 20 July 2017. The view is from a small village about 7 kilometers ENE of the summit. Courtesy of Endro Lewa.

Although fewer explosive events (61) were reported during August, block avalanches continued to travel 500-2,300 m down the SE flank. Ash plumes rose 500-2,000 m above the summit; 22 pyroclastic flows traveled up to 4.5 km down the SE flank. The Darwin VAAC issued reports of ash emissions on 17 days of the month.

A large explosion on 2 August sent ash emissions to 5.5-6.4 km altitude (figure 36). The S-drifting plume brought ashfall to the communities of the Ndokum Siroga District (SE), Simpang (7 km SE), Gajah (8 kmE), Kabanjahe (13 km SE), and Naman Teran (5 km NE) (figures 37 and 38). PVMBG reported that the explosions of 2 August destroyed the lava dome at the summit, which had grown since April 2017 to about 2.3 million m3 in size before the explosion (figure 39). The volume of the lava dome was an estimated 23,700 m3 on 6 August, after the explosions.

Figure (see Caption) Figure 36. Photo showing the large eruption from Sinabung on 2 August 2017, with a dark ash plume and pyroclastic flows. Image taken 5 kilometers E of the summit, looking W. Courtesy of Endro Lewa.
Figure (see Caption) Figure 37. Many communities were affected by ashfall and pyroclastic flows from the large explosion at Sinabung on 2 August 2017. This village is located near the base of the E flank. Courtesy of Endro Lewa.
Figure (see Caption) Figure 38. A village on the SE flank of Sinabung, was covered with ash on 3 August 2017 after a large eruption the previous day that sent a column of ash to 4.2 km altitude and a pyroclastic flow down the adjacent slope, destroying vegetation in its path. Courtesy of Xinhuanet (Xinhua/YT Haryono).
Figure (see Caption) Figure 39. The dome at Sinabung on 3 August 2017 one day after its destruction in a large explosion. The volume according to PVMBG was 2.3 million cubic meters in early July and measured only 23,700 cubic meters after the explosion. Courtesy of Endro Lewa.

The explosions also produced pyroclastic flows that traveled SE and E 2.5-4.5 km and reached the Laborus river, increasing the size of a natural dam on the river that had been evolving from previous deposits. Ashfall was also reported to the E and NE at Berastagi (12 km E). Hot spots were recorded in satellite imagery on 6 and 7 August. Additional ash plumes to similar altitudes (5.5-6.4 km) were reported several other times during August (figure 40 and 41).

Figure (see Caption) Figure 40. An explosion at Sinabung on 8 August 2017. The ash plume rises 2,000 m and a pyroclastic flow descends the E flank in this view from a small village about 7 km ENE of the summit. Courtesy of Endro Lewa.
Figure (see Caption) Figure 41. Ash and steam plumes and block avalanches at Sinabung on 25 August 2017 in this view from a small village about 7 km ENE of the summit. Courtesy of Endro Lewa.

The impact of numerous pyroclastic flows on the SE and E flanks during 2016-2017 caused a natural dam to form on the Laborus River near Desa Sukanalu and Kutanonggal Village (figure 42). The estimate of the area covered by water behind the dam was over 100,000 m2 prior to the early August explosions, about one-tenth the size of Lake Laukawar, located further upstream.

Figure (see Caption) Figure 42. A natural dam on the Laborus River (right, 'Bendungan Laborus') was created by numerous pyroclastic flows; the lake area was 123,000 square meters prior to the 2-3 August explosions. Courtesy of PVMBG (Kegiatan Gunungapi Sinabung Pasca Letusan 2-3 Agustus 2017, 22 August 2017).

Activity diminished only slightly during September 2017. PVMGB reported 55 explosive events with ash plumes that rose 500-4,000 m above the summit (figure 43). Block avalanches fell 500-1,500 m down the SE flank, and five pyroclastic flows were observed in the same area which traveled 1.5 – 2.0 km. Reports of ash emissions were issued by the Washington VAAC on 17 days of the month. The highest ash plume during the month rose to 6.4 km altitude on 25 September.

Figure (see Caption) Figure 43. A lava dome and ash plume at the summit of Sinabung on 17 September 2017. Courtesy of Sadrah Peranginangin.

Thermal anomalies. Thermal anomalies persisted throughout October 2016-September 2017. MODVOLC thermal alerts were reported 1-10 times every month except for June 2017. The MIROVA system recorded persistent low to moderate radiative power (figure 44) consistent with the dome growth, explosions, and block avalanches reported by PVMBG.

Figure (see Caption) Figure 44. Thermal anomaly data shown on a MIROVA graph of log Radiative Power at Sinabung for the year ending 18 December 2017. Persistent intermittent pulses of thermal energy are consistent with dome growth and block avalanches reported by PVMBG. Courtesy of MIROVA.

References: Associated Press, 2017, Raw: Indonesia's Sinabung Volcano Spews Hot Ash (URL: https://www.youtube.com/watch?v=R3KhjpHVeaw), posted to YouTube 17 January 2017.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URLs: http://www.vsi.esdm.go.id/, https://magma.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral, (URL: https://magma.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/); Xinhua News (URL: http://news.xinhuanet.com/english/2017-08/03/c_136497362.htm); Igan S. Sutawijaya (URL: https://www.facebook.com/igansutawijaya/); Endro Lewa (URL: https://www.instagram.com/endro_lewa/); Sadrah Peranginangin (URL: https://www.facebook.com/sadrah.peranginangin).


Tungurahua (Ecuador) — December 2017 Citation iconCite this Report

Tungurahua

Ecuador

1.467°S, 78.442°W; summit elev. 5023 m

All times are local (unless otherwise noted)


Nearly constant ash emissions and frequent lahars during July-December 2015

Eight distinct episodes of activity occurred at Ecuador's Tungurahua from November 2011 through December 2014 that included 10-km-high ash plumes, Strombolian activity, pyroclastic flows, lahars and a lava flow (BGVN 42:05). Another distinct eruptive episode, during April and May 2015, consisted primarily of persistent ash emissions (BGVN 42:08). Abundant rainfall during the first half of 2015 led to numerous lahars, some of which disrupted travel on local roads. Continuing activity from July through December 2015 is described below based on information provided by the Observatorio del Volcán Tungurahua (OVT) of the Instituto Geofísico (IG-EPN) of Ecuador, and aviation alerts from the Washington Volcanic Ash Advisory Center (VAAC).

After the last ash emissions reported in mid-May 2015, only minor emissions of steam with no ash rising to 500 m above the crater were reported during June. However, activity increased again during July, when ashfall was reported nearly every day at the lookout stations around Tungurahua, and several larger explosions produced ash plumes that rose as high as 7.5 km altitude, about 2.5 km above the summit. Frequent rains during July resulted in lahars in six different drainages. Multiple explosions during August caused ash plumes and ashfall in communities within 20 km several times every week with the highest plume rising to 8.5 km altitude. A similar pattern continued during September 2015, with longer periods of seismic tremor, persistent ash emissions, and Strombolian activity that sent block avalanches down the flanks. The number and intensity of explosions increased in October; multiple explosions every week resulted in ashfall in communities within 25 km, mostly to the NW, and low-energy Strombolian activity persisted throughout the month. The strongest explosions of the period began with a series of seismic tremors on 10 November that persisted for nine days; daily ash plumes rose to between 7 and 8 km altitude, with the highest plume reported rising to at least 9.1 km altitude. Several millimeters of ashfall were reported in the nearby communities and at lookout stations, and the ash plume was recognized in satellite data more than 250 km from the summit before dissipating. Activity tapered off by the end of November, and only weak steam emissions were reported during December 2015.

Activity during July-September 2015. Persistent steam plumes in July rose up to 500 m above the summit crater and drifted generally W, often carrying small quantities of ash. Several lookout stations in communities located within 20 km NW and SW reported ashfall almost every day, including Choglontús (13 km WSW), Bilbao, and El Manzano (8 km SW). Other stations that reported ashfall during the month included Palitahua, Mocha, Chacauco, and Pillate. IG-EPN reported explosions with larger ash plumes on 3, 12, and 14 July that rose as high as 7.5 km (figure 86). Increased seismicity on 21 and 22 July was associated with emissions that caused ashfall in most of the reporting locations.

Figure (see Caption) Figure 86. An ash plume rises 1 km above the summit crater at Tungurahua on 3 July 2015. Courtesy of OVT, IG-EPN, photo by P. Espin (Informe No. 802, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 30 de junio al 07 de julio de 2015).

The Washington VAAC reported the ash plume on 3 July extending 25 km WSW from the summit at 5.2 km altitude (200 m above the crater); they also detected a faint hotspot in satellite imagery. They reported an ash plume extending 35 km WSW late in the day at 6.4 km on 14 July visible in satellite imagery (figure 87). An ash plume reported by the Washington VAAC on 31 July was moving SW at 6.7 km altitude.

Figure (see Caption) Figure 87. One of several explosions on 14 July 2015 at Tungurahua created an ash plume that rose at least 2 km above the summit and drifted W. Courtesy of OVT, IG-EPN, photo by F. Vasconez (Informe No. 803, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 07 de julio al 14 de julio de 2015).

Lahars were reported during 5-7, 18-19, 22-23, and 29-30 July in the Chontapamba, Rea, Achupashal, Juive, Pondoa and Puela river drainages. Heavy rain on 18 and 19 July generated mudflows in the Juive, Pondoa and La Pampa ravines. Blocks 40 cm in diameter were reported in the Puela River on 22 July, and blocks 1 meter in diameter were reported in the Chontapamba river on 29 July.

There were fewer events with ash emissions during August compared to July. A lahar sent 40-cm-diameter blocks down the Mapayacu ravine on 14 August. Two explosions on 15-16 August caused ashfall in Choglontus, Manzano, and Chontapamba. Small lahars from the Rea and Romero drainages blocked the Baños-Penipe road on 16 August. An explosion on 18 August sent an ash plume WSW and caused ashfall in Choglontus; the next day reddish ash and steam emissions around 1000 local time caused ashfall again in Choglontus. Black ashfall was reported there on 22 August. Increased seismic activity with several explosions on 25 August was accompanied by ash plumes that caused ashfall in Chontapamba, Pillate, Bilbao, and Juive Grande. Gray ash was reported in Chinchicoto and Yanayacu, and thick black ash was reported in Rumipamba, Pingili and Mocha. Fine-grained gray ash was reported in Mocha on 27 August.

The Washington VAAC reported occasional emissions of gas and minor volcanic ash on 1 August 2015. A pilot report of an ash plume rising to 7 km altitude and drifting W on 15 August was not detected in satellite imagery due to weather clouds, although ashfall was reported within 15 km of the summit. Another pilot report on 20 August noted an ash plume to 8.5 km altitude. The altitude of an ash plume spotted drifting W on 25 August was estimated to be between 7.6 and 9 km. Ongoing emission of gas and possible minor ash was reported on 30 August at 6.7 km altitude moving W; the faint plume later detected in satellite imagery was moving WNW and extended about 50 km from the summit.

Mudflows from substantial rain on 1 and 7 September 2015 affected the Achupashal ravine and again disrupted travel on the Baños-Penipe road (figure 88). An ash plume on 2 September reached 3 km above the crater and drifted NW, causing ashfall in Pillate, Quero, Santuario, La Galera and El Rosario. Asfall was reported the next day in El Manzano and Choglontus. The Washington VAAC reported the ash plume at 8 km altitude on 2 September; the satellite imagery showed it extending 15 km WNW.

Figure (see Caption) Figure 88. The Baños-Penipe road is frequently damaged by lahars in the Quebrada de Achupashal at Tungurahua, making travel difficult. The muddy water on 7 September 2015 washed out the road again. Courtesy of OVT, IG-EPN, photo by B. Bernard at 1359 local time (Informe No. 811, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 01 de septiembre de 2015 al 08 de septiembre).

Moderate to high amounts of ash characterized the emissions on 11 September 2015 (figure 89). The plumes rose 2 km above the crater, drifted W and caused slight ashfall in Chonglontus and El Manzano. Only Chonglontus reported additional ashfall the next day. The Washington VAAC initially reported the ash plume at 7.3 km altitude extending 40 km SW on 11 September. About 6 hours later, the leading edge of the plume was dissipating about 170 km SW. This was followed by a new ash plume late in the day that rose to 5.8 km altitude and drifted 15 km WSW from the summit. Slight incandescence was reported on 13 September along with minor ash and steam emissions that were moving W at 7.6 km altitude.

Figure (see Caption) Figure 89. An ash plume drifts W from Tungurahua on 11 September 2015. Courtesy of OVT, IG-EPN, photo by S. Santamaria (Informe No. 811, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 08 de septiembre de 2015 al 15 de septiembre).

Constant emission of moderate amounts of ash on 19 September 2015 created an ash plume that rose to 2 km above the crater and drifted NW. Ashfall was reported in El Manzano and Pillate. An explosion late in the day rattled structures in Pondoa, and was followed by observations of incandescence at the crater shortly after midnight. Ashfall was reported to the W in Pillate, El Manzano, Bilbao, Motilones, Chontapamba, and Choglontus the following day. Ongoing emissions were not visible in satellite imagery due to weather clouds. A sudden deflation in the deformation data was recorded on 19 September. Similar deflation events preceded major explosions in July 2013 and February 2014.

Several hours of seismic tremor on 27 September produced an ash-rich plume and incandescent blocks which descended the W flank. This was followed by additional explosions and periods of tremor, some lasting for more than an hour (figure 90), that produced ash plumes drifting SW. Ashfall was reported in the towns of Manzano, Choglontus, Cahuají, and Palictahua. Additional ashfall was reported the next day in Choglontus and Manzano. The Washington VAAC spotted a faint ash plume moving W in multispectral imagery on 27 September, and another plume at 6.7 km altitude moving slowly NW the next day around noon. New fumaroles not previously observed below the W flank of the crater were observed on 29 September for the first time.

Figure (see Caption) Figure 90. Lengthy tremors that registered at the seismic station RETU coincided with ash-rich plumes and incandescent blocks at Tungurahua between midnight and noon local time on 27 September 2015. Courtesy of OVT, IG-EPN (Informe No. 814, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 22 al 29 de septiembre de 2015).

Activity during October-December 2015. Tremors were followed by a significant explosion on 4 October 2015 that produced ash emissions and block avalanches that traveled down the W flank. Ashfall reports were issued from the communities of Manzano, Choglontus, and Cahuají, all located to the SW. The Washington VAAC reported the ash plume 35 km WSW of the summit at 9.1 km altitude. Seismic activity increased beginning on 8 October. On 11 October, four explosions produced Strombolian-style activity with incandescent blocks traveling down the Chomtapamba and Achupashal ravines, an ash plume rising 2 km above the crater, and ashfall in regions to the NW and SW including Manzano, Choglontus, Puela and Mocha. The Washington VAAC reported the ash plume extending W from the summit at 7.9 km altitude. Around 2000 local time, the ash plume resembled a large mushroom cloud, and loud noises were reported from Cusua. There were numerous reports of incandescent blocks and explosions heard on the N and E flanks during the evening and overnight into the next morning (figure 91). Ashfall was again reported in Choglontus on 13 October.

Figure (see Caption) Figure 91. Incandescent blocks descend the upper flank of Tungurahua at 1909 local time on 11 October 2015. Courtesy of OVT, IG-EPN, photo by E. Telenchana (Informe No. 816, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 06 al 13 de octubre de 2015).

An explosion in the early morning hours of 14 October was heard at all of the stations around the volcano. It was followed by ashfall in Choglontus. An ash emission on 19 October rose 1 km above the crater and drifted W and SW, producing ashfall in Choglontus, Bilbao, Pillate, and Cotaló. The Washington VAAC reported the plume extending 55 km NW of the summit at 6.7 km altitude. The next day, ongoing seismic data suggested frequent diffuse ash emissions. A plume was detected in multispectral data at 7.6 km altitude radiating E and rapidly dissipating. That afternoon (20 October), ashfall was reported in the Punzupala area. Ashfall continued from daily emissions for the next week with the most ashfall reported from Manzano, Choglontus, Bilbao, and Chacauco. Communities with trace amounts of ashfall included Ambato, Quero, Cevallos, Huachi, Chiquicha, Huambaló, Cotaló, and Pillate.

Incandescent material was observed traveling more than 1,000 m down the W flank from an explosion on 25 October. Local television reported ashfall in Ambato, Cevallos, Quero, and parts of Mocha and Tisaleo later that day. Swarms of LP earthquakes followed by episodes of ash emissions and low-energy Strombolian activity continued for the remainder of the month and into early November, causing sporadic ashfall in nearby villages. A small lahar was reported in the La Pampa ravine on 30 October.

An emission on 2 November 2015 created an ash plume that rose about 1.5 km above the crater and drifted E and NE; small quantities of ash were reported in the upper Runtun area. Incandescence at the summit crater from Strombolian activity was observed that night and for several days following. Heavy rains on 7 November caused mudflows in the Romero, Pingullo, and Achupashal ravines, and a larger lahar with meter-size blocks in the Chontapamba ravine. The Washington VAAC noted a dark emission from the volcano drifting W on 8 November at 5.5 km altitude.

A new series of tremors beginning on 10 November, coincided with more than a week of continuous ash emissions which reached 3.5 km above the crater and drifted in several directions. Incandescence was observed at night, and incandescent blocks descended generally up to 500 m down the NW, N, and E flanks during this period (figure 92).The Washington VAAC first reported an ash plume at 7.6 km altitude late in the evening on 10 November and continued with a constant series of reports for the next nine days. Most of the plumes were reported between 7 and 8 km altitude, drifting generally W (figure 93). The ash plumes produced heavy black ashfall in Manzano, Choglontus, Bilbao, Mocha, Quero, Cotaló, Tisaleo, Penipe and Cevallos. An ash plume was visible about 130 km W by midday on 11 November, and the plume had reached 8.2 km altitude. Loud noises were reported numerous times from the nearby communities for several days. On 12 November the Washington VAAC reported volcanic ash observed in satellite data extending 200 km WNW at 9.1 km altitude. Ashfall was heavy enough on 14 November to cause tree branches near Choglontus to bend under the weight of the ash.

Figure (see Caption) Figure 92. Strombolian activity from the summit of Tungurahua causes incandescent blocks to fall 500 m down the flanks of on 14 November 2015. Courtesy of OVT, IG-EPN, photo by V. Valverde (Informe No. 821, Síntesis seminal del estado del Volcán Tungurahua, Semana: 10 al 17 de noviembre de 2015).
Figure (see Caption) Figure 93. A dense ash plume rises from the summit of Tungurahua and drifts W on 17 November 2015. A small pyroclastic flow is visible on the NW flank (right side of image). Courtesy of OVT, IG-EPN, photo by S. Santamaria (Informe No. 822, Síntesis seminal del estado del Volcán Tungurahua, Semana: 17 al 24 de noviembre de 2015).

A plume on 15 November 2015 rose more than 5 km above the crater (10 km altitude), according to IG-EPN, and sent blocks about 1,000 m down the flanks. On 18 November, the Washington VAAC reported a narrowing plume extending 270 km W from the summit. The largest ashfalls occurred during the night of 18-19 November. Strombolian activity sent blocks 800 m down the flanks during the night, and a strong "jet" was observed in the eastern part of the crater. Incandescent material was observed from two eruptive vents late on 18 November. Five millimeters of ash were reported from the solar panels at the Tablor station on 19 November, deposited in less than 24 hours (figure 94). IG-EPN reported this event as one of the most significant ashfall events since 2010; many crops and livestock animals were affected. Dense ash emissions tapered off after 19 November, and smaller, less dense plumes rose 2 km above the crater on 22-23 November. The University of Hawaii's MODVOLC system issued thermal alerts for Tungurahua on 15 (2) and 19 (3) November, the only time during 2015. Significant sulfur dioxide (SO2) emissions were captured by the OMI instrument on the Aura Satellite during the mid-November episode from 11-19 November (figure 95).

Figure (see Caption) Figure 94. A 5-mm thick layer of ash was deposited on the solar panels of the Tablon station at Tungurahua in less that 24 hours on 19 November 2015. Courtesy of OVT, IG-EPN, photo by S. Santamaria (Informe No. 822, Síntesis seminal del estado del Volcán Tungurahua, Semana: 17 al 24 de noviembre de 2015).
Figure (see Caption) Figure 95. Substantial SO2 plumes originating from Tungurahua were recorded by the OMI instrument on the Aura satellite during 10-19 November 2015. Top left: the plume from Tungurahua drifts WSW while a smaller plume from Cotopaxi is visible about 90 km N on 10 November. Top right: the plume from Tungurahua drifts WNW on 12 November at the bottom of the image, a much smaller plume drifts W from Cotopaxi immediately above it, and a third SO2 plume is visible drifting WSW from Nevado del Ruiz in Columbia 750 km NNE. Lower left: a larger plume on 14 November drifts WSW from Tungurahua and probably includes some gas from Cotopaxi. Lower right: a large plume from Tungurahua disperses W on 17 November for well over 500 km. Courtesy of NASA Goddard Space Flight Center.

A seismic swarm with 33-35 events per hour began on 25 November, and tapered off to 3-5 events per hour by 30 November 2015. There was no increase in surface activity during the swarm, but rather a gradual decrease, with no significant ashfall reported during the last week of November. Activity diminished significantly during December 2015. Weak steam emissions that reached no higher than 500 m above the crater were typical. Seismicity remained low, and there were no reports of ash emissions or ashfall in the area.

Geologic Background. Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. Historical eruptions have all originated from the summit crater, accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.

Information Contacts: Instituto Geofísico (IG), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec ); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Ulawun (Papua New Guinea) — December 2017 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Intermittent ash plumes during June-November 2017

Activity at Ulawun has been characterized by intermittent seismic activity and weak ash emissions. The last significant episode was during October-November 2016 (BGVN 41:12). This report summarizes the next eruption, which began on 11 June 2017 and continued sporadically at least through October 2017. Data were provided by the Rabaul Volcano Observatory (RVO) and Darwin Volcanic Ash Advisory Centre (VAAC).

RVO reported that during 1 May-23 June 2017, white plumes rose from Ulawun. Seismicity was low and dominated by small low-frequency earthquakes, although RSAM values slowly increased and then spiked on 13 June. Ash emissions began on 11 June and then became dense during 21-23 June. Volcanic ash advisories from the Darwin VAAC warned of ash plumes from between 24 June and 3 November 2017 (table 5); no further volcanic ash warnings were issued after 3 November. Plumes generally rose to altitudes of 2.4-3 km, or a maximum of 700 m above the summit.

Table 5. Ash plumes from Ulawun during January-November 2017, based upon analyses of satellite imagery. Courtesy of Darwin VAAC.

Dates Plume altitude (km) Plume drift
24-26 Jun 2017 3 W
28 Jun 2017 2.7 W
04-08 Aug 2017 2.4-2.7 NW, W, and SW
09-10 Aug 2017 2.4 NW, W
17-18 Aug 2017 2.7 W
31 Aug-01 Sep 2017 2.7 SW, W, NW, and N
05 Sep 2017 2.7 SW
25 Sep 2017 3 WSW
26-27 Oct 2017 2.4 130 km S and SE
03 Nov 2017 3 NNE

Geologic Background. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the N coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1,000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Information Contacts: 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/); Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea.


Villarrica (Chile) — December 2017 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Lava lake level fluctuates and Strombolian activity persists during October 2016-November 2017

Historical eruptions at Chile's Villarrica (figure 35), documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Lava flows emerging from the glacier-covered summit created deadly lahars in 1964 and 1971 (CSLP 95-71); a similar event in late 1984 led to evacuations and no fatalities occurred. Since then, an intermittently active lava lake has been the source of explosive activity, incandescence, and thermal anomalies. Renewed activity in early December 2014 was followed by a large explosion on 3 March 2015 that included a 9-km-altitude ash plume. Significant thermal anomalies from continued Strombolian activity at the lava lake and small ash emissions persisted through October 2016 (BGVN 41:11). Activity has continued during October 2016-November 2017, with information provided primarily by the Southern Andes Volcano Observatory, (Observatorio Volcanológico de Los Andes del Sur, OVDAS) part of Chile's National Service of Geology and Mining (Servicio Nacional de Geología y Minería, SERNAGEOMIN), and Projecto Observación Villarrica Internet (POVI), part of the Fundacion Volcanes de Chile, a research group that studies volcanoes across Chile.

Figure (see Caption) Figure 35. View of Villarrica from the town of Villarrica located 30 km NW on 10 November 2016. The active lava vent was also photographed the same day (see figure 41). Courtesy of Cristian Gonzalez G.

Steam-and-gas emissions rising 200-1,000 m above the summit were observed throughout the period. The lava lake level inside the summit crater changed elevation by as much as 15 m during October 2016. Fluctuations of several meters up and down each month were reported through February 2017, and again in October 2017. Persistent minor gas-and-ash emissions, with small blocks and lapilli ejected onto the crater rim, were captured by the webcams and observed by visitors near the summit every month. Strombolian explosions and a "lava jet" sent ejecta more than 100 m above the crater rim during February 2017, and incandescent material rose 60 m above the crater rim on 1 July. Increased seismicity was detected during November 2017.

Activity during October-December 2016. Weak emissions of steam, gases, and volcanic ash near the summit were visible in the webcam during October 2016. The Buenos Aires Volcanic Ash Advisory Center (VAAC) noted a pilot report of an ash plume moving NNW on 20 October 2016 at 3.7 km altitude, slightly less than a kilometer above the summit. OVDAS reported that during the month, steam plumes rose less than 700 m and incandescence was visible at night when weather conditions permitted viewing of the summit. The MODVOLC thermal anomaly system issued 11 alerts during October. During several visits to the summit that month, POVI scientists observed that the lava lake had risen 15 m (figure 36) to a level that had been previously observed on 18 December 2015, 29 January, 28 March, and 18 September 2016. A small pyroclastic cone was visible inside the summit crater on 28 October (figure 37); by 30 October, most of it had collapsed and molten lava was again visible at the center (figure 38).

Figure (see Caption) Figure 36. Between 17 and 27 October 2016, the lava lake rose about 15 meters inside the summit crater of Villarrica, reaching a similar level observed on 18 December 2015, 29 January, 28 March, and 18 September 2016. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 37. A small pyroclastic cone is visible at the bottom of the summit crater at Villarrica on 28 October 2016 (red arrows). On the left slope sub-parallel annular fissures are visible (yellow arrows), indicating the imminent collapse of the nested structure. The white arrows point to residue precipitated from gas emissions. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 38. The nested cone visible on 28 October had collapsed by 30 October 2016 at Villarrica, and incandescent lava was visible inside the vent. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).

During November and December 2016, steam emissions rose only 400 m above the crater and incandescence was only occasionally visible in the webcams at night. Thermal activity detected by satellite, however, was relatively high; MODVOLC issued twelve thermal alerts during November and nine during December. The repeated growth and destruction of small pyroclastic cones within the summit crater was well documented by several visits of POVI scientists to the summit (figures 39 and 41). They also collected bombs ejected near the crater rim (figure 40), and observed persistent minor ash-and-gas emissions (figure 42).

Figure (see Caption) Figure 39. A new pyroclastic cone grows inside the summit crater of Villarrica on 7 November 2016, days after the collapse of the previous cone on 28 October. Black spatter from lava splashes stand out on the exposed slope. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 40. A piece of ejecta collected at the edges of the summit crater at Villarrica on 9 November 2016. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 41. The pyroclastic cone at the summit crater of Villarrica photographed on 7 November had partially collapsed by 10 November 2016, the same day of the photograph showing a quiet, clear summit (figure 35). The splashes of lava rose no more than 10 m above the crater floor. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 42. A small ash emission of rose from the summit of Villarrica on 17 November 2016 around 1050 local time. The larger image was taken by climbers, and the inset images are from the webcam. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).

Observations by POVI scientists during December 2016 included continued evidence of cone creation and destruction in the vent (figure 43), and small lava fountains (figure 44). Strombolian explosions with bombs were recorded by the webcam on 1, 2, and 3 December. Bombs were ejected more than 50 m above the crater rim, some as large as 1.5 m in diameter. Between 2 and 3 December they observed an 8-10 m drop of the lava in the vent, leaving behind a circular depression with a small incandescent chimney on the NNW side. The webcam captured ash emissions on 2, 14, 15, 18, and 19 December.

Figure (see Caption) Figure 43. The partial collapse of the nested semicircular cone, reported by POVI on 30 November, was evident by 2 December 2016 inside the summit crater of Villarrica. The active vent is about 10-15 m in diameter. On the left wall of the crater the debris of a small recent landslide is visible above the lava. Courtesy of POVI (Informe Preliminar, Comportamiento del Volcán Villarrica, 01 al 31 de Diciembre 2016).
Figure (see Caption) Figure 44. A small Strombolian explosion created a lava fountain inside the summit crater of Villarrica on 8 December 2016. Courtesy of POVI (Informe Preliminar, Comportamiento del Volcán Villarrica, 01 al 31 de Diciembre 2016).

Activity during January-May 2017. OVDAS reported nighttime incandescence and steam emissions less than 250 m high during January 2017. They were higher in February, rising 700 m above the crater rim. Six MODVOLC thermal alerts were issued in January and one in February.

Volcanologists from POVI reported an increase in activity during February (figure 45), including a sudden collapse of about 10 m of much of the material in the lava pit on 9 February, after which a new rise began almost immediately (figure 46). During 10-15 February, explosions from a narrow vent sent lava fountains and ejecta more than 100 m high (figures 47). On 13 February, they witnessed powerful "lava jets" that rose 150 m (figure 48); bombs up to a meter in diameter were ejected 50 m from the vent and spatter covered much of the inner walls of the crater. Between 5 and 26 February, pyroclastic debris raised the level of the bottom of the crater by 10-12 m (figure 49).

Figure (see Caption) Figure 45. An increase in thermal and explosive activity was apparent between 1 and 5 February 2017 at the summit crater of Villarrica. Recently deposited lapilli (L) between 2-64 mm were scattered around the funnel shaped crater on 5 February (right). Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 46. Fresh lava spattered on the inner wall of the summit crater at Villarrica on 11 February 2017, during a new rise in the magma level after a collapse two days earlier. The diameter of the active vent had increased significantly during the previous 24 hours. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 47. Lava fountains exceeded 100 meters above the crater rim at Villarrica on 13 February 2017. Images captured just after midnight show the first explosion (lower right) at 0023 local time, followed two minutes later by the upper image, and another explosion (lower left) about 20 minutes later. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 48. The active vent in the summit crater of Villarrica was about 7 m in diameter on 13 February 2017, and sporadically emitted powerful and noisy "lava jets" more than 150 m high. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 49. Between 5 and 26 February 2017, the level of the bottom of the summit crater at Villarrica rose by about 10-12 m. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).

During March 2017, OVDAS reported steam-and-gas emissions rising 1,000 m. They issued a special report on 23 March indicating an increase in the gas plume height and the occurrence of sporadic explosions of ballistic material that remained within the summit crater. Single MODVOLC thermal alerts were issued on 7 and 14 March 2017.

Nighttime incandescence and steam plumes rising to 550 m characterized activity reported by OVDAS during April 2017. Only a single MODVOLC thermal alert was issued on 4 April. Steam plumes were reported to only 250 m above the crater rim during May along with incandescence at night, but there were seven MODVOLC thermal alerts on four different days; 1 (2), 19 (3), 20, and 29 May.

Activity during June-November 2017. OVDAS reported low levels of activity during June 2017, with incandescence at night and steam plumes rising no higher than 170 m. Only a single MODVOLC thermal alert was issued on 20 June. On a visit to the summit crater on 5 June, POVI scientists observed a 10-m-diameter vent at the bottom of the crater, and lapilli fragments 2-64 mm in diameter distributed around the crater rim. A second visit on 19 June revealed increased explosive activity at the bottom of the crater, ash deposits on the inner walls of the crater, and more lapilli around the mouth of the crater (figure 50). POVI webcams recorded a significant increase in the intensity of incandescence from the summit crater on 24 June 2017 (figure 51).

Figure (see Caption) Figure 50. An increase in explosive activity with respect to that observed on 5 June was noted by POVI scientists on a visit to the summit crater of Villarrica on 19 June 2017. Fresh ash deposits and lapilli appeared on the snow around the crater rim (yellow arrows). Courtesy of POVI (Volcán Villarrica, Resumen del Comportamiento, Observado en Junio 2017).
Figure (see Caption) Figure 51. A significant increase in the intensity of the incandescence emitted from the summit crater at Villarrica was observed in the webcams during the night of 23-24 June 2017. The upper images show the incandescence in the early evening of 23 June, and the lower images were taken just after midnight on 24 June 2017 from the POVI webcam. Courtesy of POVI (Volcán Villarrica, Resumen del Comportamiento, Observado en Junio 2017).

On 1 July 2017, POVI captured a webcam image of Strombolian explosions that sent incandescent material 60 m high from the summit crater. OVDAS reported steam plumes rising no more than 550 m and incandescence at night during July; there were no reported MODVOLC thermal alerts that month, and only a single alert on 30 August. OVDAS reported steam plumes during August rising to 150 m, sporadic ash and larger pyroclastic emissions around the crater rim, and nighttime incandescence.

Activity decreased during September and October 2017, with continued steam emissions rising 300-500 m, minor ash emissions around the crater rim, and nighttime incandescence. Two MODVOLC thermal alerts were issued, on 4 and 16 September, and none during October. POVI scientists visited the summit during October 2017 and noted that the vent remained active, especially after 22 October. They observed that at least half of the inner walls of the crater were covered with fresh ash and lapilli, concentrated on the W, S, and NE sides. They estimated that the active vent was about 8 m in diameter, approximately 100 m down inside the crater (figure 52). The bottom of the crater appeared about 4 m higher than it was on 26 September 2017, and the vent diameter had expanded by 2 m. Ash and lapilli fragments were found around the edge of the crater on 15, 22, and 25 October. Ejections of small fragments of lava were captured by the webcam on 22 and 23 October.

Figure (see Caption) Figure 52. A panoramic image of the summit crater at Villarrica, looking S on 15 October 2017, showed pyroclastic material covering much of the inner surface of the crater wall. The vent was estimated to be about 8 m in diameter, at a depth of 100 m. Courtesy of POVI (Seguimiento y Estudio del Comportamiento, Volcán Villarrica, Octubre 2017).

OVDAS reported that during November 2017, the webcams near the summit showed evidence of low intensity, predominantly white degassing to low altitudes (100 m above the summit). Nighttime incandescence associated with occasional explosions around the crater were typical. They also noted that long-period (LP) seismicity increased in both energy amplitude and frequency during the last few days of the month. A gradual increase in RSAM values began on 15 November with a continuous tremor signal. A 4.1 magnitude event was reported on 24 November located 2.6 km ESE of the summit at a depth of 1.8 km. A single MODVOLC thermal alert was reported on 28 November.

Seismicity and thermal anomalies. Seismicity at Villarrica during October 2016-November 2017 was relatively stable (figure 53), although it varied between about 2,500 and 6,500 events per month, with over 90% recorded as LP events, and only a few VT (volcano-tectonic) events. The highest frequency values occurred in May (5,749) and November 2017 (6,484).

Figure (see Caption) Figure 53. Chart of the frequency of seismic events at Villarrica, October 2016-November 2017. LP are Long-Period events, and VT are Volcano-Tectonic events. Data courtesy of OVDAS, SERNAGEOMIN monthly reports.

Infrared data graphed by the MIROVA system (figure 54) indicated the continuous but decreasing frequency and intensity of thermal anomalies at Villarrica between November 2016 and November 2017.

Figure (see Caption) Figure 54. Infrared data graphed by the MIROVA system indicated the continuous but decreasing frequency and intensity of thermal anomalies at Villarrica between November 2016 and November 2017. Courtesy of MIROVA.

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: Servicio Nacional de Geología y Minería, (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Proyecto Observación Villarrica Internet (POVI) (URL: http://www.povi.cl/); 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://hotspot.higp.hawaii.edu/; http://modis.higp.hawaii.edu/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php?lang=es); 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/); Cristian Gonzalez G., flickr (URL:https://www.flickr.com/photos/cg_fotografia/), photo used under Creative Commons license (https://creativecommons.org/licenses/by-nd/2.0/).

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/).