Logo link to homepage

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).

Search Bulletin Archive by Publication Date

Select a month and year from the drop-downs and click "Show Issue" to have that issue displayed in this tab.

   

The default month and year is the latest issue available.

Bulletin of the Global Volcanism Network - Volume 43, Number 06 (June 2018)

Managing Editor: Edward Venzke

Chillan, Nevados de (Chile)

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

Ebeko (Russia)

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

Kirishimayama (Japan)

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

Langila (Papua New Guinea)

Gradual decline in activity after July 2017, but continuing through May 2018

Marapi (Indonesia)

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

Masaya (Nicaragua)

Lava lake persists during July 2017-April 2018

Nyiragongo (DR Congo)

Thermal anomalies show that lava lake remains active through May 2018

Sabancaya (Peru)

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

San Cristobal (Nicaragua)

Moderate explosion on 22 April 2018

San Miguel (El Salvador)

Intermittent small ash emissions between 14 January and 30 May 2018



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

Nevados de Chillan

Chile

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Servicio Nacional de Geología y Minería, (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI), Beaucheff 1637/1671, Santiago, Chile (URL: http://www.onemi.cl/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


Ebeko (Russia) — June 2018 Citation iconCite this Report

Ebeko

Russia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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


Kirishimayama (Japan) — June 2018 Citation iconCite this Report

Kirishimayama

Japan

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Geographical Survey Institute, Geospatial Information Authority of Japan, Ministry of Land, Infrastructure, Transport and Tourism, No. 1 North Town, Tsukuba city, Ibaraki Prefecture 305-0811 Japan Tel: 029-864-1111 (Representative) Fax: 029-864-1807 (URL: http://www.gsi.go.jp/index.html); Kyodo News (URL: https://www.kyodonews.jp/english/); Associated Press (URL: http://www.ap.org/ ); Reuters (http://www.reuters.com/).


Langila (Papua New Guinea) — June 2018 Citation iconCite this Report

Langila

Papua New Guinea

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

All times are local (unless otherwise noted)


Gradual decline in activity after July 2017, but continuing through May 2018

Langila, one of the most active volcanoes of New Britain (figure 7), has been intermittently ejecting ash since April 2016 (BGVN 42:09). Volcanic ash warnings continue to be issued by the Darwin Volcanic Ash Advisory Centre (VAAC). Recent ash plume altitudes (table 5) are in the range of 1.5-2.5 km, but several in mid-April to mid-May 2018 reached up to twice that level. Thermal anomaly data acquired by satellite-based MODIS instruments showed a gradual decrease in power level and occurrence through mid- to late-2017, followed by significantly fewer alerts and anomalies in the first half of 2018. Rabaul Volcano Observatory (RVO) data indicates the activity during 2017 was primarily located in Crater 2 (northern-most crater).

Figure (see Caption) Figure 7. Satellite imagery showing Langila volcano at the far NW end of New Britain island. The brown color of recent lava flows and other volcanic deposits are easily noticeable compared to green vegetated areas. The volcano is about 9 km due south of the community labeled Poini. Imagery in this view is from sources listed on the image; courtesy of Google Earth.

Table 5. Reported data by Darwin Volcanic Ash Advisory Centre (VAAC) on ash plume altitude and drift from Langila based on analyses of satellite imagery and wind model data between 21 June 2017 and 28 May 2018.

Dates Ash Plume Altitude (km) Ash Plume Drift Other Observations
07 Aug 2017 2.1 55 km NW --
09 Aug 2017 1.8 N --
16 Aug 2017 2.1 NW --
01-02 Sep 2017 1.8 N, NW --
07-08, 10-12 Sep 2017 1.8-2.4 NNW, NW, SW --
22-23 Sep 2017 2.1 NNW --
04 Oct 2017 1.8 N Minor ash emission
11, 15-16 Oct 2017 1.8-2.1 NE, NNW, NW --
17-18, 20 Oct 2017 1.5-1.8 NE, NNW, NW --
05 Nov 2017 3.7 SE, ESE --
15-16 Nov 2017 1.8-2.7 S, SW --
15 Apr 2018 3.7 S --
24 Apr 2018 4 SW Ash dissipated in 6 hours
13 May 2018 5.5 W At 0709; ash dissipated in 6 hours
17-18, 21-22 May 2018 2.1-2.4 WSW, W, WNW --
23, 26-28 May 2018 2.4-3 WSW, W, NW --

MIROVA analysis of thermal anomalies measured by MODIS satellite sensors show a gradual decline of radiative power from early June 2017 to the end of the year (figure 8). Sporadic low-power anomalies occurred in January, April, and May 2018.

Figure (see Caption) Figure 8. Thermal anomalies from MODIS data analyzed by MIROVA, plotted as log radiative power vs time for the year ending 6 June 2018. Courtesy of MIROVA.

Thermal alerts from MODVOLC analyses were concentrated between early June 2017 and late September 2017 (figure 9), with only one pixel being measured in 2018 through early June, that alert being on 5 January 2018.

Figure (see Caption) Figure 9. Map showing thermal anomalies from MODIS data analyzed by MODVOLC for the year ending 6 June 2018. Courtesy of HIGP - MODVOLC Thermal Alerts System.

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

Information Contacts: 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/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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.


Marapi (Indonesia) — June 2018 Citation iconCite this Report

Marapi

Indonesia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/).


Masaya (Nicaragua) — June 2018 Citation iconCite this Report

Masaya

Nicaragua

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

All times are local (unless otherwise noted)


Lava lake persists during July 2017-April 2018

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

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

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

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

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

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

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Alexander Schimmeck, flickr (URL: https://www.flickr.com/photos/alschim/), photo used under Creative Commons license Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) (URL: https://creativecommons.org/licenses/by-nc-nd/2.0/); Carsten ten Brink, flickr (URL: https://www.flickr.com/photos/carsten_tb/), photo used under Creative Commons license Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0) (URL: https://creativecommons.org/licenses/by-nc-nd/2.0/).


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

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Thermal anomalies show that lava lake remains active through May 2018

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

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

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

Information Contacts: Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


Sabancaya (Peru) — June 2018 Citation iconCite this Report

Sabancaya

Peru

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Observatorio Volcanologico del INGEMMET, (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa, Peru (URL: http://ovi.ingemmet.gob.pe); Instituto Geofisico del Peru, Observatoria Vulcanologico del Sur (IGP-OVS), Arequipa Regional Office, Urb La Marina B-19, Cayma, Arequipa, Peru (URL: http://ovs.igp.gob.pe/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


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

San Cristobal

Nicaragua

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

All times are local (unless otherwise noted)


Moderate explosion on 22 April 2018

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

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

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

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

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

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://webserver2.ineter.gob.ni/vol/dep-vol.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).


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

San Miguel

El Salvador

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

All times are local (unless otherwise noted)


Intermittent small ash emissions between 14 January and 30 May 2018

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

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

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

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

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

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

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

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

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

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

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

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

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

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/).