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Bulletin of the Global Volcanism Network

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

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

Recently Published Bulletin Reports

Masaya (Nicaragua) Lava lake level drops but remains active through May 2020; weak gas plumes

Shishaldin (United States) Intermittent thermal activity and a possible new cone at the summit crater during February-May 2020

Krakatau (Indonesia) Strombolian explosions, ash plumes, and crater incandescence during April 2020

Taal (Philippines) Eruption on 12 January with explosions through 22 January; steam plumes continuing into March

Unnamed (Tonga) Additional details and pumice raft drift maps from the August 2019 submarine eruption

Klyuchevskoy (Russia) Strombolian activity November 2019 through May 2020; lava flow down the SE flank in April

Nyamuragira (DR Congo) Intermittent thermal anomalies within the summit crater during December 2019-May 2020

Nyiragongo (DR Congo) Activity in the lava lake and small eruptive cone persists during December 2019-May 2020

Kavachi (Solomon Islands) Discolored water plumes seen using satellite imagery in 2018 and 2020

Kuchinoerabujima (Japan) Eruption and ash plumes begin on 11 January 2020 and continue through April 2020

Soputan (Indonesia) Minor ash emissions during 23 March and 2 April 2020

Heard (Australia) Eruptive activity including a lava flow during October 2019-April 2020



Masaya (Nicaragua) — June 2020 Citation iconCite this Report

Masaya

Nicaragua

11.985°N, 86.165°W; summit elev. 594 m

All times are local (unless otherwise noted)


Lava lake level drops but remains active through May 2020; weak gas plumes

Masaya, which is about 20 km NW of the Nicaragua’s capital of Managua, is one of the most active volcanoes in that country and has a caldera that contains a number of craters (BGVN 43:11). The Santiago crater is the one most currently active and it contains a small lava lake that emits weak gas plumes (figure 85). This report summarizes activity during February through May 2020 and is based on Instituto Nicaragüense de Estudios Territoriales (INETER) monthly reports and satellite data. During the reporting period, the volcano was relatively calm, with only weak gas plumes.

Figure (see Caption) Figure 85. Satellite images of Masaya from Sentinel-2 on 18 April 2020, showing and a small gas plume drifting SW (top, natural color bands 4, 3, 2) and the lava lake (bottom, false color bands 12, 11, 4). Courtesy of Sentinel Hub Playground.

According to INETER, thermal images of the lava lake and temperature data in the fumaroles were taken using an Omega infrared gun and a forward-looking infrared (FLIR) SC620 thermal camera. The temperatures above the lava lake have decreased since November 2019, when the temperature was 287°C, dropping to 96°C when measured on 14 May 2020. INETER attributed this decrease to subsidence in the level of the lava lake by 5 m which obstructed part of the lake and concentrated the gas emissions in the weak plume. Convection continued in the lava lake, which in May had decreased to a diameter of 3 m. Many landslides had occurred in the E, NE, and S walls of the crater rim due to rock fracturing caused by the high heat and acidity of the emissions.

During the reporting period, the MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system recorded numerous thermal anomalies from the lava lake based on MODIS data (figure 86). Infrared satellite images from Sentinel-2 regularly showed a strong signature from the lava lake through 18 May, after which the volcano was covered by clouds.

Figure (see Caption) Figure 86. Thermal anomalies at Masaya during February through May 2020. The larger anomalies with black lines are more distant and not related to the volcano. Courtesy of MIROVA.

Measurements of sulfur dioxide (SO2) made by INETER in the section of the Ticuantepe - La Concepción highway (just W of the volcano) with a mobile DOAS system varied between a low of just over 1,000 metric tons/day in mid-November 2019 to a high of almost 2,500 tons/day in late May. Temperatures of fumaroles in the Cerro El Comalito area, just ENE of Santiago crater, ranged from 58 to 76°C during February-May 2020, with most values in the 69-72°C range.

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras caldera and is itself 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 Nindirí and Masaya cones, 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 6,500 years ago. Historical lava flows cover much of the caldera floor and there is a lake at the far eastern end. 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 have caused 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Shishaldin (United States) — June 2020 Citation iconCite this Report

Shishaldin

United States

54.756°N, 163.97°W; summit elev. 2857 m

All times are local (unless otherwise noted)


Intermittent thermal activity and a possible new cone at the summit crater during February-May 2020

Shishaldin is located near the center of Unimak Island in Alaska, with the current eruption phase beginning in July 2019 and characterized by ash plumes, lava flows, lava fountaining, pyroclastic flows, and lahars. More recently, in late 2019 and into January 2020, activity consisted of multiple lava flows, pyroclastic flows, lahars, and ashfall events (BGVN 45:02). This report summarizes activity from February through May 2020, including gas-and-steam emissions, brief thermal activity in mid-March, and a possible new cone within the summit crater. The primary source of information comes from the Alaska Volcano Observatory (AVO) reports and various satellite data.

Volcanism during February 2020 was relatively low, consisting of weakly to moderately elevated surface temperatures during 1-4 February and occasional small gas-and-steam plumes (figure 37). By 6 February both seismicity and surface temperatures had decreased. Seismicity and surface temperatures increased slightly again on 8 March and remained elevated through the rest of the reporting period. Intermittent gas-and-steam emissions were also visible from mid-March (figure 38) through May. Minor ash deposits visible on the upper SE flank may have been due to ash resuspension or a small collapse event at the summit, according to AVO.

Figure (see Caption) Figure 37. Photo of a gas-and-steam plume rising from the summit crater at Shishaldin on 22 February 2020. Photo courtesy of Ben David Jacob via AVO.
Figure (see Caption) Figure 38. A Worldview-2 panchromatic satellite image on 11 March 2020 showing a gas-and-steam plume rising from the summit of Shishaldin and minor ash deposits on the SE flank (left). Aerial photo showing minor gas-and-steam emissions rising from the summit crater on 11 March (right). Some erosion of the snow and ice on the upper flanks is a result of the lava flows from the activity in late 2019 and early 2020. Photo courtesy of Matt Loewen (left) and Ed Fischer (right) via AVO.

On 14 March, lava and a possible new cone were visible in the summit crater using satellite imagery, accompanied by small explosion signals. Strong thermal signatures due to the lava were also seen in Sentinel-2 satellite data and continued strongly through the month (figure 39). The lava reported by AVO in the summit crater was also reflected in satellite-based MODIS thermal anomalies recorded by the MIROVA system (figure 40). Seismic and infrasound data identified small explosions signals within the summit crater during 14-19 March.

Figure (see Caption) Figure 39. Sentinel-2 thermal satellite images (bands 12, 11, 8A) show a bright hotspot (yellow-orange) at the summit crater of Shishaldin during mid-March 2020 that decreases in intensity by late March. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 40. MIROVA thermal data showing a brief increase in thermal anomalies during late March 2020 and on two days in late April between periods of little to no activity. Courtesy of MIROVA.

AVO released a Volcano Observatory Notice for Aviation (VONA) stating that seismicity had decreased by 16 April and that satellite data no longer showed lava or additional changes in the crater since the start of April. Sentinel-2 thermal satellite imagery continued to show a weak hotspot in the crater summit through May (figure 41), which was also detected by the MIROVA system on two days. A daily report on 6 May reported a visible ash deposit extending a short distance SE from the summit, which had likely been present since 29 April. AVO noted that the timing of the deposit corresponds to an increase in the summit crater diameter and depth, further supporting a possible small collapse. Small gas-and-steam emissions continued intermittently and were accompanied by weak tremors and occasional low-frequency earthquakes through May (figure 42). Minor amounts of sulfur dioxide were detected in the gas-and-steam emissions during 20 and 29 April, and 2, 16, and 28 May.

Figure (see Caption) Figure 41. Sentinel-2 thermal satellite images (bands 12, 11, 8A) show occasional gas-and-steam emissions rising from Shishaldin on 26 February (top left) and 24 April 2020 (bottom left) and a weak hotspot (yellow-orange) persisting at the summit crater during April and early May 2020. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 42. A Worldview-1 panchromatic satellite image showing gas-and-steam emissions rising from the summit of Shishaldin on 1 May 2020 (local time) (left). Aerial photo of the N flank of Shishaldin with minor gas-and-steam emissions rising from the summit on 8 May (right). Photo courtesy of Matt Loewen (left) and Levi Musselwhite (right) via AVO.

Geologic Background. The beautifully symmetrical Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steam plume often rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the W and NE sides at 1,500-1,800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of Strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Krakatau (Indonesia) — June 2020 Citation iconCite this Report

Krakatau

Indonesia

6.102°S, 105.423°E; summit elev. 155 m

All times are local (unless otherwise noted)


Strombolian explosions, ash plumes, and crater incandescence during April 2020

Krakatau, located in the Sunda Strait between Indonesia’s Java and Sumatra Islands, experienced a major caldera collapse around 535 CE, forming a 7-km-wide caldera ringed by three islands. On 22 December 2018, a large explosion and flank collapse destroyed most of the 338-m-high island of Anak Krakatau (Child of Krakatau) and generated a deadly tsunami (BGVN 44:03). The near-sea level crater lake inside the remnant of Anak Krakatau was the site of numerous small steam and tephra explosions. A larger explosion in December 2019 produced the beginnings of a new cone above the surface of crater lake (BGVN 45:02). Recently, volcanism has been characterized by occasional Strombolian explosions, dense ash plumes, and crater incandescence. This report covers activity from February through May 2020 using information provided by the Indonesian Center for Volcanology and Geological Hazard Mitigation, also known as Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), the Darwin Volcanic Ash Advisory Center (VAAC), and various satellite data.

Activity during February 2020 consisted of dominantly white gas-and-steam emissions rising 300 m above the crater, according to PVMBG. According to the Darwin VAAC, a ground observer reported an eruption on 7 and 8 February, but no volcanic ash was observed. During 10-11 February, a short-lived eruption was detected by seismograms which produced an ash plume up to 1 km above the crater drifting E. MAGMA Indonesia reported two eruptions on 18 March, both of which rose to 300 m above the crater. White gas-and-steam emissions were observed for the rest of the month and early April.

On 10 April PVMBG reported two eruptions, at 2158 and 2235, both of which produced dark ash plumes rising 2 km above the crater followed by Strombolian explosions ejecting incandescent material that landed on the crater floor (figures 108 and 109). The Darwin VAAC issued a notice at 0145 on 11 April reporting an ash plume to 14.3 km altitude drifting WNW, however this was noted with low confidence due to the possible mixing of clouds. During the same day, an intense thermal hotspot was detected in the HIMAWARI thermal satellite imagery and the NASA Global Sulfur Dioxide page showed a strong SO2 plume at 11.3 km altitude drifting W (figure 110). The CCTV Lava93 webcam showed new lava flows and lava fountaining from the 10-11 April eruptions. This activity was evident in the MIROVA (Middle InfraRed Observation of Volcanic Activity) graph of MODIS thermal anomaly data (figure 111).

Figure (see Caption) Figure 108. Webcam (Lava93) images of Krakatau on 10 April 2020 showing Strombolian explosions, strong incandescence, and ash plumes rising from the crater. Courtesy of PVMBG and MAGMA Indonesia.
Figure (see Caption) Figure 109. Webcam image of incandescent Strombolian explosions at Krakatau on 10 April 2020. Courtesy of PVMBG and MAGMA Indonesia.
Figure (see Caption) Figure 110. Strong sulfur dioxide emissions rising from Krakatau and drifting W were detected using the TROPOMI instrument on the Sentinel-5P satellite on 11 April 2020 (top row). Smaller volumes of SO2 were visible in Sentinel-5P/TROPOMI maps on 13 (bottom left) and 19 April (bottom right). Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 111. Thermal activity at Anak Krakatau from 29 June-May 2020 shown on a MIROVA Log Radiative Power graph. The power and frequency of the thermal anomalies sharply increased in mid-April. After the larger eruptive event in mid-April the thermal anomalies declined slightly in strength but continued to be detected intermittently through May. Courtesy of MIROVA.

Strombolian activity rising up to 500 m continued into 12 April and was accompanied by SO2 emissions that rose 3 km altitude, drifting NW according to a VAAC notice. PVMBG reported an eruption on 13 April at 2054 that resulted in incandescence as high as 25 m above the crater. Volcanic ash, accompanied by white gas-and-steam emissions, continued intermittently through 18 April, many of which were observed by the CCTV webcam. After 18 April only gas-and-steam plumes were reported, rising up to 100 m above the crater; Sentinel-2 satellite imagery showed faint thermal anomalies in the crater (figure 112). SO2 emissions continued intermittently throughout April, though at lower volumes and altitudes compared to the 11th. MODIS satellite data seen in MIROVA showed intermittent thermal anomalies through May.

Figure (see Caption) Figure 112. Sentinel-2 thermal satellite images showing the cool crater lake on 20 March (top left) followed by minor heating of the crater during April and May 2020. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

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/); 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).


Taal (Philippines) — June 2020 Citation iconCite this Report

Taal

Philippines

14.002°N, 120.993°E; summit elev. 311 m

All times are local (unless otherwise noted)


Eruption on 12 January with explosions through 22 January; steam plumes continuing into March

Taal volcano is in a caldera system located in southern Luzon island and is one of the most active volcanoes in the Philippines. It has produced around 35 recorded eruptions since 3,580 BCE, ranging from VEI 1 to 6, with the majority of eruptions being a VEI 2. The caldera contains a lake with an island that also contains a lake within the Main Crater (figure 12). Prior to 2020 the most recent eruption was in 1977, on the south flank near Mt. Tambaro. The United Nations Office for the Coordination of Humanitarian Affairs in the Philippines reports that over 450,000 people live within 40 km of the caldera (figure 13). This report covers activity during January through February 2020 including the 12 to 22 January eruption, and is based on reports by Philippine Institute of Volcanology and Seismology (PHIVOLCS), satellite data, geophysical data, and media reports.

Figure (see Caption) Figure 12. Annotated satellite images showing the Taal caldera, Volcano Island in the caldera lake, and features on the island including Main Crater. Imagery courtesy of Planet Inc.
Figure (see Caption) Figure 13. Map showing population totals within 14 and 17 km of Volcano Island at Taal. Courtesy of the United Nations Office for the Coordination of Humanitarian Affairs (OCHA).

The hazard status at Taal was raised to Alert Level 1 (abnormal, on a scale of 0-5) on 28 March 2019. From that date through to 1 December there were 4,857 earthquakes registered, with some felt nearby. Inflation was detected during 21-29 November and an increase in CO2 emission within the Main Crater was observed. Seismicity increased beginning at 1100 on 12 January. At 1300 there were phreatic (steam) explosions from several points inside Main Crater and the Alert Level was raised to 2 (increasing unrest). Booming sounds were heard in Talisay, Batangas, at 1400; by 1402 the plume had reached 1 km above the crater, after which the Alert Level was raised to 3 (magmatic unrest).

Phreatic eruption on 12 January 2020. A seismic swarm began at 1100 on 12 January 2020 followed by a phreatic eruption at 1300. The initial activity consisted of steaming from at least five vents in Main Crater and phreatic explosions that generated 100-m-high plumes. PHIVOLCS raised the Alert Level to 2. The Earth Observatory of Singapore reported that the International Data Center (IDC) for the Comprehensive test Ban Treaty (CTBT) in Vienna noted initial infrasound detections at 1450 that day.

Booming sounds were heard at 1400 in Talisay, Batangas (4 km NNE from the Main Crater), and at 1404 volcanic tremor and earthquakes felt locally were accompanied by an eruption plume that rose 1 km; ash fell to the SSW. The Alert Level was raised to 3 and the evacuation of high-risk barangays was recommended. Activity again intensified around 1730, prompting PHIVOLCS to raise the Alert Level to 4 and recommend a total evacuation of the island and high-risk areas within a 14-km radius. The eruption plume of steam, gas, and tephra significantly intensified, rising to 10-15 km altitude and producing frequent lightning (figures 14 and 15). Wet ash fell as far away as Quezon City (75 km N). According to news articles schools and government offices were ordered to close and the Ninoy Aquino International Airport (56 km N) in Manila suspended flights. About 6,000 people had been evacuated. Residents described heavy ashfall, low visibility, and fallen trees.

Figure (see Caption) Figure 14. Lightning produced during the eruption of Taal during 1500 on 12 January to 0500 on 13 January 2020 local time (0700-2100 UTC on 12 January). Courtesy of Chris Vagasky, Vaisala.
Figure (see Caption) Figure 15. Lightning strokes produced during the first days of the Taal January 2020 eruption. Courtesy of Domcar C Lagto/SIPA/REX/Shutterstock via The Guardian.

In a statement issued at 0320 on 13 January, PHIVOLCS noted that ashfall had been reported across a broad area to the north in Tanauan (18 km NE), Batangas; Escala (11 km NW), Tagaytay; Sta. Rosa (32 km NNW), Laguna; Dasmariñas (32 km N), Bacoor (44 km N), and Silang (22 km N), Cavite; Malolos (93 km N), San Jose Del Monte (87 km N), and Meycauayan (80 km N), Bulacan; Antipolo (68 km NNE), Rizal; Muntinlupa (43 km N), Las Piñas (47 km N), Marikina (70 km NNE), Parañaque (51 km N), Pasig (62 km NNE), Quezon City, Mandaluyong (62 km N), San Juan (64 km N), Manila; Makati City (59 km N) and Taguig City (55 km N). Lapilli (2-64 mm in diameter) fell in Tanauan and Talisay; Tagaytay City (12 km N); Nuvali (25 km NNE) and Sta (figure 16). Rosa, Laguna. Felt earthquakes (Intensities II-V) continued to be recorded in local areas.

Figure (see Caption) Figure 16. Ashfall from the Taal January 2020 eruption in Lemery (top) and in the Batangas province (bottom). Photos posted on 13 January, courtesy of Ezra Acayan/Getty Images, Aaron Favila/AP, and Ted Aljibe/AFP via Getty Images via The Guardian.

Magmatic eruption on 13 January 2020. A magmatic eruption began during 0249-0428 on 13 January, characterized by weak lava fountaining accompanied by thunder and flashes of lightning. Activity briefly waned then resumed with sporadic weak fountaining and explosions that generated 2-km-high, dark gray, steam-laden ash plumes (figure 17). New lateral vents opened on the N flank, producing 500-m-tall lava fountains. Heavy ashfall impacted areas to the SW, including in Cuenca (15 km SSW), Lemery (16 km SW), Talisay, and Taal (15 km SSW), Batangas (figure 18).

Figure (see Caption) Figure 17. Ash plumes seen from various points around Taal in the initial days of the January 2020 eruption, posted on 13 January. Courtesy of Eloisa Lopez/Reuters, Kester Ragaza/Pacific Press/Shutterstock, Ted Aljibe/AFP via Getty Images, via The Guardian.
Figure (see Caption) Figure 18. Map indicating areas impacted by ashfall from the 12 January eruption through to 0800 on the 13th. Small yellow circles (to the N) are ashfall report locations; blue circles (at the island and to the S) are heavy ashfall; large green circles are lapilli (particles measuring 2-64 mm in diameter). Modified from a map courtesy of Lauriane Chardot, Earth Observatory of Singapore; data taken from PHIVOLCS.

News articles noted that more than 300 domestic and 230 international flights were cancelled as the Manila Ninoy Aquino International Airport was closed during 12-13 January. Some roads from Talisay to Lemery and Agoncillo were impassible and electricity and water services were intermittent. Ashfall in several provinces caused power outages. Authorities continued to evacuate high-risk areas, and by 13 January more than 24,500 people had moved to 75 shelters out of a total number of 460,000 people within 14 km.

A PHIVOLCS report for 0800 on the 13th through 0800 on 14 January noted that lava fountaining had continued, with steam-rich ash plumes reaching around 2 km above the volcano and dispersing ash SE and W of Main Crater. Volcanic lighting continued at the base of the plumes. Fissures on the N flank produced 500-m-tall lava fountains. Heavy ashfall continued in the Lemery, Talisay, Taal, and Cuenca, Batangas Municipalities. By 1300 on the 13th lava fountaining generated 800-m-tall, dark gray, steam-laden ash plumes that drifted SW. Sulfur dioxide emissions averaged 5,299 metric tons/day (t/d) on 13 January and dispersed NNE (figure 19).

Figure (see Caption) Figure 19. Compilation of sulfur dioxide plumes from TROPOMI overlaid in Google Earth for 13 January from 0313-1641 UT. Courtesy of NASA Global Sulfur Dioxide Monitoring Page and Google Earth.

Explosions and ash emission through 22 January 2020. At 0800 on 15 January PHIVOLCS stated that activity was generally weaker; dark gray, steam-laden ash plumes rose about 1 km and drifted SW. Satellite images showed that the Main Crater lake was gone and new craters had formed inside Main Crater and on the N side of Volcano Island.

PHIVOLCS reported that activity during 15-16 January was characterized by dark gray, steam-laden plumes that rose as high as 1 km above the vents in Main Crater and drifted S and SW. Sulfur dioxide emissions were 4,186 t/d on 15 January. Eruptive events at 0617 and 0621 on 16 January generated short-lived, dark gray ash plumes that rose 500 and 800 m, respectively, and drifted SW. Weak steam plumes rose 800 m and drifted SW during 1100-1700, and nine weak explosions were recorded by the seismic network.

Steady steam emissions were visible during 17-21 January. Infrequent weak explosions generated ash plumes that rose as high as 1 km and drifted SW. Sulfur dioxide emissions fluctuated and were as high as 4,353 t/d on 20 January and as low as 344 t/d on 21 January. PHIVOLCS reported that white steam-laden plumes rose as high as 800 m above main vent during 22-28 January and drifted SW and NE; ash emissions ceased around 0500 on 22 January. Remobilized ash drifted SW on 22 January due to strong low winds, affecting the towns of Lemery (16 km SW) and Agoncillo, and rose as high as 5.8 km altitude as reported by pilots. Sulfur dioxide emissions were low at 140 t/d.

Steam plumes through mid-April 2020. The Alert Level was lowered to 3 on 26 January and PHIVOLCS recommended no entry onto Volcano Island and Taal Lake, nor into towns on the western side of the island within a 7-km radius. PHIVOLCS reported that whitish steam plumes rose as high as 800 m during 29 January-4 February and drifted SW (figure 20). The observed steam plumes rose as high as 300 m during 5-11 February and drifted SW.

Sulfur dioxide emissions averaged around 250 t/d during 22-26 January; emissions were 87 t/d on 27 January and below detectable limits the next day. During 29 January-4 February sulfur dioxide emissions ranged to a high of 231 t/d (on 3 February). The following week sulfur dioxide emissions ranged from values below detectable limits to a high of 116 t/d (on 8 February).

Figure (see Caption) Figure 20. Taal Volcano Island producing gas-and-steam plumes on 15-16 January 2020. Courtesy of James Reynolds, Earth Uncut.

On 14 February PHIVOLCS lowered the Alert Level to 2, noting a decline in the number of volcanic earthquakes, stabilizing ground deformation of the caldera and Volcano Island, and diffuse steam-and-gas emission that continued to rise no higher than 300 m above the main vent during the past three weeks. During 14-18 February sulfur dioxide emissions ranged from values below detectable limits to a high of 58 tonnes per day (on 16 February). Sulfur dioxide emissions were below detectable limits during 19-20 February. During 26 February-2 March steam plumes rose 50-300 m above the vent and drifted SW and NE. PHIVOLCS reported that during 4-10 March weak steam plumes rose 50-100 m and drifted SW and NE; moderate steam plumes rose 300-500 m and drifted SW during 8-9 March. During 11-17 March weak steam plumes again rose only 50-100 m and drifted SW and NE.

PHIVOLCS lowered the Alert Level to 1 on 19 March and recommended no entry onto Volcano Island, the area defined as the Permanent Danger Zone. During 8-9 April steam plumes rose 100-300 m and drifted SW. As of 1-2 May 2020 only weak steaming and fumarolic activity from fissure vents along the Daang Kastila trail was observed.

Evacuations. According to the Disaster Response Operations Monitoring and Information Center (DROMIC) there were a total of 53,832 people dispersed to 244 evacuation centers by 1800 on 15 January. By 21 January there were 148,987 people in 493 evacuation. The number of residents in evacuation centers dropped over the next week to 125,178 people in 497 locations on 28 January. However, many residents remained displaced as of 3 February, with DROMIC reporting 23,915 people in 152 evacuation centers, but an additional 224,188 people staying at other locations.

By 10 February there were 17,088 people in 110 evacuation centers, and an additional 211,729 staying at other locations. According to the DROMIC there were a total of 5,321 people in 21 evacuation centers, and an additional 195,987 people were staying at other locations as of 19 February.

The number of displaced residents continued to drop, and by 3 March there were 4,314 people in 12 evacuation centers, and an additional 132,931 people at other locations. As of 11 March there were still 4,131 people in 11 evacuation centers, but only 17,563 staying at other locations.

Deformation and ground cracks. New ground cracks were observed on 13 January in Sinisian (18 km SW), Mahabang Dahilig (14 km SW), Dayapan (15 km SW), Palanas (17 km SW), Sangalang (17 km SW), and Poblacion (19 km SW) Lemery; Pansipit (11 km SW), Agoncillo; Poblacion 1, Poblacion 2, Poblacion 3, Poblacion 5 (all around 17 km SW), Talisay, and Poblacion (11 km SW), San Nicolas (figure 21). A fissure opened across the road connecting Agoncillo to Laurel, Batangas. New ground cracking was reported the next day in Sambal Ibaba (17 km SW), and portions of the Pansipit River (SW) had dried up.

Figure (see Caption) Figure 21. Video screenshots showing ground cracks that formed during the Taal unrest and captured on 15 and 16 January 2020. Courtesy of James Reynolds, Earth Uncut.

Dropping water levels of Taal Lake were first observed in some areas on 16 January but reported to be lake-wide the next day. The known ground cracks in the barangays of Lemery, Agoncillo, Talisay, and San Nicolas in Batangas Province widened a few centimeters by 17 January, and a new steaming fissure was identified on the N flank of the island.

GPS data had recorded a sudden widening of the caldera by ~1 m, uplift of the NW sector by ~20 cm, and subsidence of the SW part of Volcano Island by ~1 m just after the main eruption phase. The rate of deformation was smaller during 15-22 January, and generally corroborated by field observations; Taal Lake had receded about 30 cm by 25 January but about 2.5 m of the change (due to uplift) was observed around the SW portion of the lake, near the Pansipit River Valley where ground cracking had been reported.

Weak steaming (plumes 10-20 m high) from ground cracks was visible during 5-11 February along the Daang Kastila trail which connects the N part of Volcano Island to the N part of the main crater. PHIVOLCS reported that during 19-24 February steam plumes rose 50-100 m above the vent and drifted SW. Weak steaming (plumes up to 20 m high) from ground cracks was visible during 8-14 April along the Daang Kastila trail which connects the N part of Volcano Island to the N part of the main crater.

Seismicity. Between 1300 on 12 January and 0800 on 21 January the Philippine Seismic Network (PSN) had recorded a total of 718 volcanic earthquakes; 176 of those had magnitudes ranging from 1.2-4.1 and were felt with Intensities of I-V. During 20-21 January there were five volcanic earthquakes with magnitudes of 1.6-2.5; the Taal Volcano network (which can detect smaller events not detectable by the PSN) recorded 448 volcanic earthquakes, including 17 low-frequency events. PHIVOLCS stated that by 21 January hybrid earthquakes had ceased and both the number and magnitude of low-frequency events had diminished.

Geologic Background. Taal is one of the most active volcanoes in the Philippines and has produced some of its most powerful historical eruptions. Though not topographically prominent, its prehistorical eruptions have greatly changed the landscape of SW Luzon. The 15 x 20 km Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 km2 surface lies only 3 m above sea level. The maximum depth of the lake is 160 m, and several eruptive centers lie submerged beneath the lake. The 5-km-wide Volcano Island in north-central Lake Taal is the location of all historical eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones that have grown about 25% in area during historical time. Powerful pyroclastic flows and surges from historical eruptions have caused many fatalities.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Department of Science and Technology, University of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph/); Disaster Response Operations Monitoring and Information Center (DROMIC) (URL: https://dromic.dswd.gov.ph/); United Nations Office for the Coordination of Humanitarian Affairs, Philippines (URL: https://www.unocha.org/philippines); James Reynolds, Earth Uncut TV (Twitter: @EarthUncutTV, URL: https://www.earthuncut.tv/, YouTube: https://www.youtube.com/user/TyphoonHunter); Chris Vagasky, Vaisala Inc., Louisville, Colorado, USA (URL: https://www.vaisala.com/en?type=1, Twitter: @COweatherman, URL: https://twitter.com/COweatherman); Earth Observatory of Singapore, Nanyang Technological University, 50 Nanyang Avenue, Singapore (URL: https://www.earthobservatory.sg/); 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/); Relief Web, Flash Update No. 1 - Philippines: Taal Volcano eruption (As of 13 January 2020, 2 p.m. local time) (URL: https://reliefweb.int/report/philippines/flash-update-no-1-philippines-taal-volcano-eruption-13-january-2020-2-pm-local); Bloomberg, Philippines Braces for Hazardous Volcano Eruption (URL: https://www.bloomberg.com/news/articles/2020-01-12/philippines-raises-alert-level-in-taal-as-volcano-spews-ash); National Public Radio (NPR), Volcanic Eruption In Philippines Causes Thousands To Flee (URL: npr.org/2020/01/13/795815351/volcanic-eruption-in-philippines-causes-thousands-to-flee); Reuters (http://www.reuters.com/); Agence France-Presse (URL: http://www.afp.com/); Pacific Press (URL: http://www.pacificpress.com/); Shutterstock (URL: https://www.shutterstock.com/); Getty Images (URL: http://www.gettyimages.com/); Google Earth (URL: https://www.google.com/earth/).


Unnamed (Tonga) — March 2020 Citation iconCite this Report

Unnamed

Tonga

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

All times are local (unless otherwise noted)


Additional details and pumice raft drift maps from the August 2019 submarine eruption

In the northern Tonga region, approximately 80 km NW of Vava’u, large areas of floating pumice, termed rafts, were observed starting as early as 7 August 2019. The area of these andesitic pumice rafts was initially 195 km2 with the layers measuring 15-30 cm thick and were produced 200 m below sea level (Jutzeler et al. 2020). The previous report (BGVN 44:11) described the morphology of the clasts and the rafts, and their general westward path from 9 August to 9 October 2019, with the first sighting occurring on 9 August NW of Vava’u in Tonga. This report updates details regarding the submarine pumice raft eruption in early August 2019 using new observations and data from Brandl et al. (2019) and Jutzeler et al. (2020).

The NoToVE-2004 (Northern Tonga Vents Expedition) research cruise on the RV Southern Surveyor (SS11/2004) from the Australian CSIRO Marine National Facility traveled to the northern Tonga Arc and discovered several submarine basalt-to-rhyolite volcanic centers (Arculus, 2004). One of these volcanic centers 50 km NW of Vava’u was the unnamed seamount (volcano number 243091) that had erupted in 2001 and again in 2019, unofficially designated “Volcano F” for reference purposes by Arculus (2004) and also used by Brandl et al. (2019). It is a volcanic complex that rises more than 1 km from the seafloor with a central 6 x 8.7 km caldera and a volcanic apron measuring over 50 km in diameter (figures 19 and 20). Arculus (2004) described some of the dredged material as “fresh, black, plagioclase-bearing lava with well-formed, glassy crusts up to 2cm thick” from cones by the eastern wall of the caldera; a number of apparent flows, lava or debris, were observed draping over the northern wall of the caldera.

Figure (see Caption) Figure 19. Visualization of the unnamed submarine Tongan volcano (marked “Volcano F”) using bathymetric data to show the site of the 6-8 August 2020 eruption and the rest of the cone complex. Courtesy of Philipp Brandl via GEOMAR.
Figure (see Caption) Figure 20. Map of the unnamed submarine Tongan volcano using satellite imagery, bathymetric data, with shading from the NW. The yellow circle indicates the location of the August 2019 activity. Young volcanic cones are marked “C” and those with pit craters at the top are marked with “P.” Courtesy of Brandl et al. (2019).

The International Seismological Centre (ISC) Preliminary Bulletin listed a particularly strong (5.7 Mw) earthquake at 2201 local time on 5 August, 15 km SSW of the volcano at a depth of 10 km (Brandl et al. 2019). This event was followed by six slightly lower magnitude earthquakes over the next two days.

Sentinel-2 satellite imagery showed two concentric rings originating from a point source (18.307°S 174.395°W) on 6 August (figure 21), which could be interpreted as small weak submarine plumes or possibly a series of small volcanic cones, according to Brandl et al. (2019). The larger ring is about 1.2 km in diameter and the smaller one measures 250 m. By 8 August volcanic activity had decreased, but the pumice rafts that were produced remained visible through at least early October (BGVN 44:11). Brandl et al. (2019) states that, due to the lack of continued observed activity rising from this location, the eruption was likely a 2-day-long event during 6-8 August.

Figure (see Caption) Figure 21. Sentinel-2 satellite image of possible gas/vapor emissions (streaks) on 6 August 2019 drifting NW, which is the interpreted site for the unnamed Tongan seamount. The larger ring is about 1.2 km in diameter and the smaller one measures 250 m. Image using False Color (urban) rendering (bands 12, 11, 4); courtesy of Sentinel Hub Playground.

The pumice was first observed on 9 August occurred up to 56 km from the point of origin, according to Jutzeler et al. (2020). By calculating the velocity (14 km/day) of the raft using three satellites, Jutzeler et al. (2020) determined the pumice was erupted immediately after the satellite image of the submarine plumes on 6 August (UTC time). Minor activity at the vent may have continued on 8 and 11 August (UTC time) with pale blue-green water discoloration (figure 22) and a small (less than 1 km2) diffuse pumice raft 2-5 km from the vent.

Figure (see Caption) Figure 22. Sentinel-2 satellite image of the last visible activity occurring W of the unnamed submarine Tongan volcano on 8 August 2019, represented by slightly discolored blue-green water. Image using Natural Color rendering (bands 4, 3, 2) and enhanced with color correction; courtesy of Sentinel Hub Playground.

Continuous observations using various satellite data and observations aboard the catamaran ROAM tracked the movement and extent of the pumice raft that was produced during the submarine eruption in early August (figure 23). The first visible pumice raft was observed on 8 August 2019, covering more than 136.7 km2 between the volcanic islands of Fonualei and Late and drifting W for 60 km until 9 August (Brandl et al. 2019; Jutzeler 2020). The next day, the raft increased to 167.2-195 km2 while drifting SW for 74 km until 14 August. Over the next three days (10-12 August) the size of the raft briefly decreased in size to less than 100 km2 before increasing again to 157.4 km2 on 14 August; at least nine individual rafts were mapped and identified on satellite imagery (Brandl et al. 2019). On 15 August sailing vessels observed a large pumice raft about 75 km W of Late Island (see details in BGVN 44:11), which was the same one as seen in satellite imagery on 8 August.

Figure (see Caption) Figure 23. Map of the extent of discolored water and the pumice raft from the unnamed submarine Tongan volcano between 8 and 14 August 2019 using imagery from NASA’s MODIS, ESA’s Sentinel-2 satellite, and observations from aboard the catamaran ROAM (BGVN 44:11). Back-tracing the path of the pumice raft points to a source location at the unnamed submarine Tongan volcano. Courtesy of Brandl et al. (2019).

By 17 August high-resolution satellite images showed an area of large and small rafts measuring 222 km2 and were found within a field of smaller rafts for a total extent of 1,350 km2, which drifted 73 km NNW through 22 August before moving counterclockwise for three days (figure f; Jutzeler et al., 2020). Small pumice ribbons encountered the Oneata Lagoon on 30 August, the first island that the raft came into contact (Jutzeler et al. 2020). By 2 September, the main raft intersected with Lakeba Island (460 km from the source) (figure 24), breaking into smaller ribbons that started to drift W on 8 September. On 19 September the small rafts (less than 100 m x less than 2 km) entered the strait between Viti Levu and Vanua Levu, the two main islands of Fiji, while most of the others were stranded 60 km W in the Yasawa Islands for more than two months (Jutzeler et al., 2020).

Figure (see Caption) Figure 24. Time-series map of the raft dispersal from the unnamed submarine Tongan volcano using multiple satellite images. A) Map showing the first days of the raft dispersal starting on 7 August 2019 and drifting SW from the vent (marked with a red triangle). Precursory seismicity that began on 5 August is marked with a white star. By 15-17 August the raft was entrained in an ocean loop or eddy. The dashed lines represent the path of the sailing vessels. B) Map of the raft dispersal using high-resolution Sentinel-2 and -3 imagery. Two dispersal trails (red and blue dashed lines) show the daily dispersal of two parts of the raft that were separated on 17 August 2019. Courtesy of Jutzeler et al. (2020).

References: Arculus, R J, SS2004/11 shipboard scientists, 2004. SS11/2004 Voyage Summary: NoToVE-2004 (Northern Tonga Vents Expedition): submarine hydrothermal plume activity and petrology of the northern Tofua Arc, Tonga. https://www.cmar.csiro.au/data/reporting/get file.cfm?eovpub id=901.

Brandl P A, Schmid F, Augustin N, Grevemeyer I, Arculus R J, Devey C W, Petersen S, Stewart M , Kopp K, Hannington M D, 2019. The 6-8 Aug 2019 eruption of ‘Volcano F’ in the Tofua Arc, Tonga. Journal of Volcanology and Geothermal Research: https://doi.org/10.1016/j.jvolgeores.2019.106695

Jutzeler M, Marsh R, van Sebille E, Mittal T, Carey R, Fauria K, Manga M, McPhie J, 2020. Ongoing Dispersal of the 7 August 2019 Pumice Raft From the Tonga Arc in the Southwestern Pacific Ocean. AGU Geophysical Research Letters: https://doi.orh/10.1029/2019GL086768.

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: Jan Steffen, Communication and Media, GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany; Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Klyuchevskoy (Russia) — June 2020 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


Strombolian activity November 2019 through May 2020; lava flow down the SE flank in April

Klyuchevskoy is part of the Klyuchevskaya volcanic group in northern Kamchatka and is one of the most frequently active volcanoes of the region. Eruptions produce lava flows, ashfall, and lahars originating from summit and flank activity. This report summarizes activity during October 2019 through May 2020, and is based on reports by the Kamchatkan Volcanic Eruption Response Team (KVERT) and satellite data.

There were no activity reports from 1 to 22 October, but gas emissions were visible in satellite images. At 1020 on 24 October (2220 on 23 October UTC) KVERT noted that there was a small ash component in the ash plume from erosion of the conduit, with the plume reaching 130 km ENE. The Aviation Colour Code was raised from Green to Yellow, then to Orange the following day. An ash plume continued on the 25th to 5-7 km altitude and extending 15 km SE and 70 km SW and reached 30 km ESE on the 26th. Similar activity continued through to the end of the month.

Moderate gas emissions continued during 1-19 November, but the summit was obscured by clouds. Strong nighttime incandescence was visible at the crater during the 10-11 November and thermal anomalies were detected on 8 and 10-13 November. Explosions produced ash plumes up to 6 km altitude on the 20-21st and Strombolian activity was reported during 20-22 November. Degassing continued from 23 November through 12 December, and a thermal anomaly was visible on the days when the summit was not covered by clouds. An ash plume was reported moving to the NW on the 13th, and degassing with a thermal anomaly and intermittent Strombolian activity then resumed, continuing through to the end of December with an ash plume reported on the 30th.

Gas-and-steam plumes continued into January 2020 with incandescence noted when the summit was clear (figure 33). Strombolian activity was reported again starting on the 3rd. A weak ash plume produced on the 6th extended 55 km E, and on the 21st an ash plume reached 5-5.5 km altitude and extended 190 km NE (figure 34). Another ash plume the next day rose to the same altitude and extended 388 km NE. During 23-29 Strombolian activity continued, and Vulcanian activity produced ash plumes up to 5.5 altitude, extending to 282 km E on the 30th, and 145 km E on the 31st.

Figure (see Caption) Figure 33. Incandescence and degassing were visible at Klyuchevskoy through January 2020, seen here on the 11th. Courtesy of KVERT.
Figure (see Caption) Figure 34. A low ash plume at Klyuchevskoy on 21 January 2020 extended 190 km NE. Courtesy of KVERT.

Strombolian activity continued throughout February with occasional explosions producing ash plumes up to 5.5 km altitude, as well as gas-and-steam plumes and a persistent thermal anomaly with incandescence visible at night. Starting in late February thermal anomalies were detected much more frequently, and with higher energy output compared to the previous year (figure 35). A lava fountain was reported on 1 March with the material falling back into the summit crater. Strombolian activity continued through early March. Lava fountaining was reported again on the 8th with ejecta landing in the crater and down the flanks (figure 36). A strong persistent gas-and-steam plume containing some ash continued along with Strombolian activity through 25 March (figure 37), with Vulcanian activity noted on the 20th and 25th. Strombolian and Vulcanian activity was reported through the end of March.

Figure (see Caption) Figure 35. This MIROVA thermal energy plot for Klyuchevskoy for the year ending 29 April 2020 (log radiative power) shows intermittent thermal anomalies leading up to more sustained energy detected from February through March, then steadily increasing energy through April 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 36. Strombolian explosions at Klyuchevskoy eject incandescent ash and gas, and blocks and bombs onto the upper flanks on 8 and 10 March 2020. Courtesy of IVS FEB RAS, KVERT.
Figure (see Caption) Figure 37. Weak ash emission from the Klyuchevskoy summit crater are dispersed by wind on 19 and 29 March 2020, with ash depositing on the flanks. Courtesy of IVS FEB RAS, KVERT.

Activity was dominantly Strombolian during 1-5 April and included intermittent Vulcanian explosions from the 6th onwards, with ash plumes reaching 6 km altitude. On 18 April a lava flow began moving down the SE flank (figures 38). A report on the 26th reported explosions from lava-water interactions with avalanches from the active lava flow, which continued to move down the SE flank and into the Apakhonchich chute (figures 39 and 40). This continued throughout April and May with sustained Strombolian and intermittent Vulcanian activity at the summit (figures 41 and 42).

Figure (see Caption) Figure 38. Strombolian activity produced ash plumes and a lava flow down the SE flank of Klyuchevskoy on 18 April 2020. Courtesy of IVS FEB RAS, KVERT.
Figure (see Caption) Figure 39. A lava flow descends the SW flank of Klyuchevskoy and a gas plume is dispersed by winds on 21 April 2020. Courtesy of Yu. Demyanchuk, IVS FEB RAS, KVERT.
Figure (see Caption) Figure 40. Sentinel-2 thermal satellite images show the progression of the Klyuchevskoy lava flow from the summit crater down the SE flank from 19-29 April 2020. Associated gas plumes are dispersed in various directions. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 41. Strombolian activity at Klyuchevskoy ejects incandescent ejecta, gas, and ash above the summit on 27 April 2020. Courtesy of D. Bud'kov, IVS FEB RAS, KVERT.
Figure (see Caption) Figure 42. Sentinel-2 thermal satellite images of Klyuchevskoy show the progression of the SE flank lava flow through May 2020, with associated gas plumes being dispersed in multiple directions. Courtesy of Sentinel Hub Playground.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Nyamuragira (DR Congo) — June 2020 Citation iconCite this Report

Nyamuragira

DR Congo

1.408°S, 29.2°E; summit elev. 3058 m

All times are local (unless otherwise noted)


Intermittent thermal anomalies within the summit crater during December 2019-May 2020

Nyamuragira (also known as Nyamulagira) is located in the Virunga Volcanic Province (VVP) in the Democratic Republic of the Congo and consists of a lava lake that reappeared in the summit crater in mid-April 2018. Volcanism has been characterized by lava emissions, thermal anomalies, seismicity, and gas-and-steam emissions. This report summarizes activity during December 2019 through May 2020 using information from monthly reports by the Observatoire Volcanologique de Goma (OVG) and satellite data.

According to OVG, intermittent eruptive activity was detected in the lava lake of the central crater during December 2019 and January-April 2020, which also resulted in few seismic events. MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows thermal anomalies within the summit crater that varied in both frequency and power between August 2019 and mid-March 2020, but very few were recorded afterward through late May (figure 88). Thermal hotspots identified by MODVOLC from 15 December 2019 through March 2020 were mainly located in the active central crater, with only three hotspots just outside the SW crater rim (figure 89). Sentinel-2 thermal satellite imagery also showed activity within the summit crater during January-May 2020, but by mid-March the thermal anomaly had visibly decreased in power (figure 90).

Figure (see Caption) Figure 88. The MIROVA graph of thermal activity (log radiative power) at Nyamuragira during 27 July through May 2020 shows variably strong, intermittent thermal anomalies with a variation in power and frequency from August 2019 to mid-March 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 89. Map showing the number of MODVOLC hotspot pixels at Nyamuragira from 1 December 2019 t0 31 May 2020. 37 pixels were registered within the summit crater while 3 were detected just outside the SW crater rim. Courtesy of HIGP-MODVOLC Thermal Alerts System.
Figure (see Caption) Figure 90. Sentinel-2 thermal satellite imagery (bands 12, 11, 8A) confirmed ongoing thermal activity (bright yellow-orange) at Nyamuragira from February into April 2020. The strength of the thermal anomaly in the summit crater decreased by late March 2020, but was still visible. Courtesy of Sentinel Hub Playground.

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

Information Contacts: Information contacts: Observatoire Volcanologique de Goma (OVG), Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo; 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/exp.


Nyiragongo (DR Congo) — June 2020 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Activity in the lava lake and small eruptive cone persists during December 2019-May 2020

Nyiragongo is located in the Virunga Volcanic Province (VVP) in the Democratic Republic of the Congo, part of the western branch of the East African Rift System and contains a 1.2 km-wide summit crater with a lava lake that has been active since at least 1971. Volcanism has been characterized by strong and frequent thermal anomalies, incandescence, gas-and-steam emissions, and seismicity. This report summarizes activity during December 2019 through May 2020 using information from monthly reports by the Observatoire Volcanologique de Goma (OVG) and satellite data.

In the December 2019 monthly report, OVG stated that the level of the lava lake had increased. This level of the lava lake was maintained for the duration of the reporting period, according to later OVG monthly reports. Seismicity increased starting in November 2019 and was detected in the NE part of the crater, but it decreased by mid-April 2020. SO2 emissions increased in January 2020 to roughly 7,000 tons/day but decreased again near the end of the month. OVG reported that SO2 emissions rose again in February to roughly 8,500 tons/day before declining to about 6,000 tons/day. Unlike in the previous report (BGVN 44:12), incandescence was visible during the day in the active lava lake and activity at the small eruptive cone within the 1.2-km-wide summit crater has since increased, consisting of incandescence and some lava fountaining (figure 72). A field survey was conducted on 3-4 March where an OVG team observed active lava fountains and ejecta that produced Pele’s hair from the small eruptive cone (figure 73). During this survey, OVG reported that the level of the lava lake had reached the second terrace, which was formed on 17 January 2002 and represents remnants of the lava lake at different eruption stages. There, the open surface lava lake was observed; gas-and-steam emissions accompanied both the active lava lake and the small eruptive cone (figures 72 and 73).

Figure (see Caption) Figure 72. Webcam image of Nyiragongo in February 2020 showing an open lava lake surface and incandescence from the active crater cone within the 1.2 km-wide summit crater visible during the day, accompanied by white gas-and-steam emissions. Courtesy of OVG (Rapport OVG February 2020).
Figure (see Caption) Figure 73. Webcam image of Nyiragongo on 4 March 2020 showing an open lava lake surface and incandescence from the active crater cone within the 1.2 km-wide summit crater visible during the day, accompanied by white gas-and-steam emissions. Courtesy of OVG (Rapport OVG Mars 2020).

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data continued to show frequent strong thermal anomalies within 5 km of the summit crater through May 2020 (figure 74). Similarly, the MODVOLC algorithm reported multiple thermal hotspots almost daily within the summit crater between December 2019 and May 2020. These thermal signatures were also observed in Sentinel-2 thermal satellite imagery within the summit crater (figure 75).

Figure (see Caption) Figure 74. Thermal anomalies at Nyiragongo from 27 July through May 2020 as recorded by the MIROVA system (Log Radiative Power) were frequent and strong. Courtesy of MIROVA.
Figure (see Caption) Figure 75. Sentinel-2 thermal satellite imagery (bands 12, 11, 8A) showed ongoing thermal activity (bright yellow-orange) in the summit crater at Nyiragongo during January through April 2020. Courtesy of Sentinel Hub Playground.

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: Observatoire Volcanologique de Goma (OVG), Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo; 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).


Kavachi (Solomon Islands) — May 2020 Citation iconCite this Report

Kavachi

Solomon Islands

8.991°S, 157.979°E; summit elev. -20 m

All times are local (unless otherwise noted)


Discolored water plumes seen using satellite imagery in 2018 and 2020

Kavachi is a submarine volcano located in the Solomon Islands south of Gatokae and Vangunu islands. Volcanism is frequently active, but rarely observed. The most recent eruptions took place during 2014, which consisted of an ash eruption, and during 2016, which included phreatomagmatic explosions (BGVN 42:03). This reporting period covers December 2016-April 2020 primarily using satellite data.

Activity at Kavachi is often only observed through satellite images, and frequently consists of discolored submarine plumes for which the cause is uncertain. On 1 January 2018 a slight yellow discoloration in the water is seen extending to the E from a specific point (figure 20). Similar faint plumes were observed on 16 January, 25 February, 2 March, 26 April, 6 May, and 25 June 2018. No similar water discoloration was noted during 2019, though clouds may have obscured views.

Figure (see Caption) Figure 20. Satellite images from Sentinel-2 revealed intermittent faint water discoloration (yellow) at Kavachi during the first half of 2018, as seen here on 1 January (top left), 25 February (top right), 26 April (bottom left), and 25 June (bottom right). Images with “Natural color” rendering (bands 4, 3, 2); courtesy of Sentinel Hub Playground.

Activity resumed in 2020, showing more discolored water in satellite imagery. The first instance occurred on 16 March, where a distinct plume extended from a specific point to the SE. On 25 April a satellite image showed a larger discolored plume in the water that spread over about 30 km2, encompassing the area around Kavachi (figure 21). Another image on 30 April showed a thin ribbon of discolored water extending about 50 km W of the vent.

Figure (see Caption) Figure 21. Sentinel-2 satellite images of a discolored plume (yellow) at Kavachi beginning on 16 March (top left) with a significant large plume on 25 April (right), which remained until 30 April (bottom left). Images with “Natural color” rendering (bands 4, 3, 2); courtesy of Sentinel Hub Playground.

Geologic Background. Named for a sea-god of the Gatokae and Vangunu peoples, Kavachi is one of the most active submarine volcanoes in the SW Pacific, located in the Solomon Islands south of Vangunu Island. Sometimes referred to as Rejo te Kvachi ("Kavachi's Oven"), this shallow submarine basaltic-to-andesitic volcano has produced ephemeral islands up to 1 km long many times since its first recorded eruption during 1939. Residents of the nearby islands of Vanguna and Nggatokae (Gatokae) reported "fire on the water" prior to 1939, a possible reference to earlier eruptions. The roughly conical edifice rises from water depths of 1.1-1.2 km on the north and greater depths to the SE. Frequent shallow submarine and occasional subaerial eruptions produce phreatomagmatic explosions that eject steam, ash, and incandescent bombs. On a number of occasions lava flows were observed on the ephemeral islands.

Information Contacts: Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Kuchinoerabujima (Japan) — May 2020 Citation iconCite this Report

Kuchinoerabujima

Japan

30.443°N, 130.217°E; summit elev. 657 m

All times are local (unless otherwise noted)


Eruption and ash plumes begin on 11 January 2020 and continue through April 2020

Kuchinoerabujima encompasses a group of young stratovolcanoes located in the northern Ryukyu Islands. All historical eruptions have originated from the Shindake cone, with the exception of a lava flow that originated from the S flank of the Furudake cone. The most recent previous eruptive period took place during October 2018-February 2019 and primarily consisted of weak explosions, ash plumes, and ashfall. The current eruption began on 11 January 2020 after nearly a year of dominantly gas-and-steam emissions. Volcanism for this reporting period from March 2019 to April 2020 included explosions, ash plumes, SO2 emissions, and ashfall. The primary source of information for this report comes from monthly and annual reports from the Japan Meteorological Agency (JMA) and advisories from the Tokyo Volcanic Ash Advisory Center (VAAC). Activity has been limited to Kuchinoerabujima's Shindake Crater.

Volcanism at Kuchinoerabujima was relatively low during March through December 2019, according to JMA. During this time, SO2 emissions ranged from 100 to 1,000 tons/day. Gas-and-steam emissions were frequently observed throughout the entire reporting period, rising to a maximum height of 1.1 km above the crater on 13 December 2019. Satellite imagery from Sentinel-2 showed gas-and-steam and occasional ash emissions rising from the Shindake crater throughout the reporting period (figure 7). Though JMA reported thermal anomalies occurring on 29 January and continuing through late April 2020, Sentinel-2 imagery shows the first thermal signature appearing on 26 April.

Figure (see Caption) Figure 7. Sentinel-2 thermal satellite images showed gas-and-steam and ash emissions rising from Kuchinoerabujima. Some ash deposits can be seen on 6 February 2020 (top right). A thermal anomaly appeared on 26 April 2020 (bottom right). Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

An eruption on 11 January 2020 at 1505 ejected material 300 m from the crater and produced ash plumes that rose 2 km above the crater rim, extending E, according to JMA. The eruption continued through 12 January until 0730. The resulting ash plumes rose 400 m above the crater, drifting SW while the SO2 emissions measured 1,300 tons/day. Ashfall was reported on Yakushima Island (15 km E). Minor eruptive activity was reported during 17-20 January which produced gray-white plumes that rose 300-500 m above the crater. On 23 January, seismicity increased, and an eruption produced an ash plume that rose 1.2 km altitude, according to a Tokyo VAAC report, resulting in ashfall 2 km NE of the crater. A small explosion was detected on 24 January, followed by an increase in the number of earthquakes during 25-26 January (65-71 earthquakes per day were registered). Another small eruptive event detected on 27 January at 0148 was accompanied by a volcanic tremor and a change in tilt data. During the month of January, some inflation was detected at the base on the volcano and a total of 347 earthquakes were recorded. The SO2 emissions ranged from 200-1,600 tons/day.

An eruption on 1 February 2020 produced an eruption column that rose less than 1 km altitude and extended SE and SW (figure 8), according to the Tokyo VAAC report. On 3 February, an eruption from the Shindake crater at 0521 produced an ash plume that rose 7 km above the crater and ejected material as far as 600 m away. As a result, a pyroclastic flow formed, traveling 900-1,500 m SW. The previous pyroclastic flow that was recorded occurred on 29 January 2019. Ashfall was confirmed in the N part of Yakushima Island with a large amount in Miyanoura (32 km ESE) and southern Tanegashima. The SO2 emissions measured 1,700 tons/day during this event.

Figure (see Caption) Figure 8. Webcam images from the Honmura west surveillance camera of an ash plume rising from Kuchinoerabujima on 1 February 2020. Courtesy of JMA (Weekly bulletin report 509, February 2020).

Intermittent small eruptive events occurred during 5-9 February; field observations showed a large amount of ashfall on the SE flank which included lapilli that measured up to 2 cm in diameter. Additionally, thermal images showed 5-km-long pyroclastic flow deposits on the SW flank. An eruption on 9 February produced an ash plume that rose 1.2 km altitude, drifting SE. On 13 February a small eruption was detected in the Shindake crater at 1211, producing gray-white plumes that rose 300 m above the crater, drifting NE. Small eruptive events also occurred during 20-21 February, resulting in gas-and-steam emissions that rose 200 m above the crater. During the month of February, some horizontal extension was observed since January 2020 using GNSS data. The total number of earthquakes during this month drastically increased to 1225 compared to January. The SO2 emissions ranged from 300-1,700 tons/day.

By 2 March 2020, seismicity decreased, and activity declined. Gas-and-steam emissions continued infrequently for the duration of the reporting period. The SO2 emissions during March ranged from 700-2,100 tons/day, the latter of which occurred on 15 March. Seismicity increased again on 27 March. During 5-8 April 2020, small eruptive events were detected, generating ash plumes that rose 900 m above the crater (figure 9). The SO2 emissions on 6 April reached 3,200 tons/day, the maximum measurement for this reporting period. These small eruptive events continued from 13-20 and 23-25 April within the Shindake crater, producing gray-white plumes that rose 300-800 m above the crater.

Figure (see Caption) Figure 9. Webcam images from the Honmura Nishi (top) and Honmura west (bottom) surveillance cameras of ash plumes rising from Kuchinoerabujima on 6 March and 5 April 2020. Courtesy of JMA (Weekly bulletin report 509, March and April 2020).

Geologic Background. A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyu Islands, 15 km W of Yakushima. The Furudake, Shindake, and Noikeyama cones were erupted from south to north, respectively, forming a composite cone with multiple craters. All historical eruptions have occurred from Shindake, although a lava flow from the S flank of Furudake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shindake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, 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 100-8122, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Soputan (Indonesia) — May 2020 Citation iconCite this Report

Soputan

Indonesia

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

All times are local (unless otherwise noted)


Minor ash emissions during 23 March and 2 April 2020

Soputan is a stratovolcano located in the northern arm of Sulawesi Island, Indonesia. Previous eruptive periods were characterized by ash explosions, lava flows, and Strombolian eruptions. The most recent eruption occurred during October-December 2018, which consisted mostly of ash plumes and some summit incandescence (BGVN 44:01). This report updates information for January 2019-April 2020 characterized by two ash plumes and gas-and-steam emissions. The primary source of information come from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and the Darwin Volcanic Ash Advisory Center (VAAC).

Activity during January 2019-April 2020 was relatively low; three faint thermal anomalies were observed at the summit at Soputan in satellite imagery for a total of three days on 2 and 4 January, and 1 October 2019 (figure 17). The MIROVA (Middle InfraRed Observation of Volcanic Activity) based on analysis of MODIS data detected 12 distal hotspots and six low-power hotspots within 5 km of the summit during August to early October 2019. A single distal thermal hotspot was detected in early March 2020. In March, activity primarily consisted of white to gray gas-and-steam plumes that rose 20-100 m above the crater, according to PVMBG. The Darwin VAAC issued a notice on 23 March 2020 that reported an ash plume rose to 4.3 km altitude; minor ash emissions had been visible in a webcam image the previous day (figure 18). A second notice was issued on 2 April, where an ash plume was observed rising 2.1 km altitude and drifting W.

Figure (see Caption) Figure 17. Sentinel-2 thermal satellite imagery detected a total of three thermal hotspots (bright yellow-orange) at the summit of Soputan on 2 and 4 January and 1 October 2019. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 18. Minor ash emissions were seen rising from Soputan on 22 March 2020. Courtesy of MAGMA Indonesia.

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

Information Contacts: 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/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Heard (Australia) — May 2020 Citation iconCite this Report

Heard

Australia

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

All times are local (unless otherwise noted)


Eruptive activity including a lava flow during October 2019-April 2020

Heard Island is located on the Kerguelen Plateau in the southern Indian Ocean and contains Big Ben, a snow-covered stratovolcano with intermittent volcanism reported since 1910. Due to its remote location, visual observations are rare; therefore, thermal anomalies and hotspots detected by satellite-based instruments are the primary source of information. This report updates activity from October 2019 to April 2020.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed three prominent periods of strong thermal anomaly activity during this reporting period: late October 2019, December 2019, and the end of April 2020 (figure 41). These thermal anomalies were relatively strong and occurred within 5 km of the summit. Similarly, the MODVOLC algorithm reported a total of six thermal hotspots during 28 October, 1 November 2019, and 26 April 2020.

Figure (see Caption) Figure 41. Thermal anomalies at Heard from 29 April 2019 through April 2020 as recorded by the MIROVA system (Log Radiative Power) were strong and frequent in late October, during December 2019, and at the end of April 2020. Courtesy of MIROVA.

Six thermal satellite images ranging from late October 2019 to late March showed evidence of active lava at the summit (figure 42). These images show hot material, possibly a lava flow, extending SW from the summit; a hotspot also remained at the summit. Cloud cover was pervasive during the majority of this reporting period, especially in April 2020, though gas-and-steam emissions were visible on 25 April through the clouds.

Figure (see Caption) Figure 42. Thermal satellite images of Heard Island’s Big Ben showing strong thermal signatures representing a lava flow in the SW direction from 28 October to 17 December 2019. These thermal anomalies are located NE from Mawson Peak. A faint thermal anomaly is also captured on 26 March 2020. Satellite images with atmospheric penetration (bands 12, 11, and 8A), courtesy of Sentinel Hub Playground.

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

Information Contacts: 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).

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Bulletin of the Global Volcanism Network - Volume 37, Number 11 (November 2012)

Managing Editor: Richard Wunderman

Arenal (Costa Rica)

Continued calm with minor gas emissions

Gamalama (Indonesia)

Seismicity precedes small ash-bearing eruptions in September 2012

Kasatochi (United States)

Ramifications of the 7-8 August 2008 eruption

Krakatau (Indonesia)

Many earthquakes and some mild eruptions during October-November 2011

Lengai, Ol Doinyo (Tanzania)

Update on observations and activity during 2011-2012

Machin (Colombia)

Monitoring efforts and intermittent shaking from local earthquakes during 2011-2012

Miyakejima (Japan)

Minor plumes and low seismicity during April 2010-June 2012

Tangkuban Parahu (Indonesia)

Earthquakes and hot gas emissions in August 2012



Arenal (Costa Rica) — November 2012 Citation iconCite this Report

Arenal

Costa Rica

10.463°N, 84.703°W; summit elev. 1670 m

All times are local (unless otherwise noted)


Continued calm with minor gas emissions

Since 1968, Arenal experienced periods of moderate-to-robust volcanic activity that continued through September 2010, when activity declined (BGVN 35:07 and 36:04). This report discusses events between December 2010 and October 2012, a period of continued relative tranquility.

Although sporadic Strombolian explosions were reported in December 2010, they soon ceased; since then, no explosions had occurred through as late as October 2012. According to the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI), activity was limited to weak gas emissions, primarily through the NE vent in Crater C and through fumaroles in Crater D (figure 113).

Figure (see Caption) Figure 113. A photograph of Arenal's summit taken on 20 February 2011, featuring the volcano's two peaks, both showing weak fumaroles. To the right is crater C, which has been active since 1968; to the left is crater D. Courtesy of Jairo Murillo Solís.

During the reporting period, the pH of rain-water gradually increased near the volcano. According to OVSICORI, the gradual decrease in rainfall acidity was associated with reduced magmatic activity.

According to OVSICORI, 2012 was one of the years of lowest activity for Arenal since 1968. No volcano-tectonic earthquakes, volcanic earthquakes, or tremors were recorded during the year, and no magmatic activity was detected. OVSICORI (citing Muller and others, 2011) reported that the Electronic Distance Measurement (EDM) network on the W flank of Arenal showed some subsidence from 2008 to near the end of 2011, but then the rate of subsidence decreased and no deformation occurred in 2012.

In June 2012, OVSICORI reported that night observations and long-exposure photographs of the summit revealed no incandescence. According to OVSICORI, the lack of incandescence indicated that gas emissions were of low temperature (probably <300°C), allowing water vapor to condense rapidly upon contact with the atmosphere. Hydrothermal activity remained low with only a few diffuse fumaroles rising from the N flank of Crater C (figure 113).

According to OVSICORI, an Mw 7.6 earthquake on 5 September 2012 centered on the Nicoya Peninsula (Costa Rica) caused moderate rock avalanches at Arenal, mainly dislodging unstable blocks on the active crater's N and NW rim. However, no changes were noted either in the hot springs around the volcano or in surficial expressions of volcanism.

A special issue of Journal of Volcanology and Geothermal Research was devoted to Arenal volcano (see Reference subsection below).

References. Marsh, B. (ed.), 2006, Arenal volcano, Costa Rica: Magma genesis and volcanological processes, Journal of Volcanology and Geothermal Research, v. 157, issues 1-3.

Muller, C., del Potro, R., Gottsmann, J., Biggs, J., and Van der Laat, R., 2011, Combined GPS, EDM and triangulation surveys of the rapid down-slope motion of the western flank of Arenal Volcano, Costa Rica, American Geophysical Union, Fall Meeting 2011, abstract ## V53C-2639 (Poster).

Geologic Background. Conical Volcán Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1670-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. Arenal lies along a volcanic chain that has migrated to the NW from the late-Pleistocene Los Perdidos lava domes through the Pleistocene-to-Holocene Chato volcano, which contains a 500-m-wide, lake-filled summit crater. The earliest known eruptions of Arenal took place about 7000 years ago, and it was active concurrently with Cerro Chato until the activity of Chato ended about 3500 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone. An eruptive period that began with a major explosive eruption in 1968 ended in December 2010; continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows characterized the eruption from vents at the summit and on the upper western flank.

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/); CostaRica21 (URL: http://www.costarica21.com/).


Gamalama (Indonesia) — November 2012 Citation iconCite this Report

Gamalama

Indonesia

0.8°N, 127.33°E; summit elev. 1715 m

All times are local (unless otherwise noted)


Seismicity precedes small ash-bearing eruptions in September 2012

This report discusses a series of small but punctuated eruptions on 15-17 September 2012 associated with the return of seismicity at Gamalama. Fog obscured visibility but ash fell on inhabited areas. The eruptions were judged similar to those seen 4 December 2011 (BGVN 36:12).

As we noted previously, heavy rains after the 4 December 2011 eruptions led to lahars on 27-28 December that killed four people, injured dozens, and displaced thousands (BGVN 36:12). Photos showed that these lahars had carried many meter-diameter blocks into inhabited areas on the lower flanks. Videos from helicopter flights confirmed that in the upslope region, chutes and drainages had also fed finer ash into the lahars.

According to the Center for Volcanology and Geological Hazard Mitigation (CVGHM), on 24 January 2012, after witnessing an interval of generally reduced seismicity, an absence of significant ash-bearing plumes, and weak steam plumes rising only ~100 m above the summit, they lowered the Alert Level from 3 to 2 (on a scale from 1-4).

As geographic background, Gamalama volcano emerges from the sea to form the near-conical 76 km2 Ternate island. The island is situated in the Molucca (Maluku) islands in NE Indonesia about midway between the islands of Borneo and New Guinea (figure 5).

Figure (see Caption) Figure 5. (A) An index map of Indonesia, including the Molucca islands and regional landmarks. Courtesy of U.S. Department of State. (B) A map of the Molucca (Maluku) islands, highlighting Gamalama (Ternate). Courtesy of Indonesia Explore.

Seismicity and eruptions of September 2012. Significant seismicity and other activity at Gamalama remained low from early 2012 until September. During 1-14 September white plumes were sometimes observed rising ~10 m above the crater. When visibility allowed, these plumes were observed from the local obseratory post at Marikuruba and from the W coast of the island, but fog and clouds generally obscured the view.

The telemetered seismograph system (PS-2) recorded deep volcanic earthquakes, shallow volcanic earthquakes, and local tectonic earthquakes, each occurring fewer than five times during 1-14 September. During that same period, there were 63 long-distance tectonic earthquakes and 42 hot air blasts recorded; once they began, signals interpreted as the hot air blasts amounted to 8 occurrences per day. Visual observations and tremor during this time period appeared similar to this volcano's past behavior.

On 15 September 2012 the following seismic events were recorded: 6 long distance tectonic earthquakes, 9 deep volcanic earthquakes, 2 shallow volcanic earthquakes, 14 hot air blasts accompanied by rumbling sounds, and an interval of tremor began with amplitudes reaching 3-4 mm. Six minutes after the tremor, eruption signals occurred with a maximum amplitude of 40 mm. A phreatic explosion produced ash fall and debris fall. Fog obscured the visibility.

On 16 September 2012, CVGHM reported low-amplitude tremor continuing during 0000-1200 (with 1.5-2.5 mm amplitudes). Medium-to-heavy rain fell at the summit around 1200. At 1358 tremor amplitudes increased to 28 mm, followed 17 min later by a "severe eruption."

That eruption drove an ash-laden plume to ~1 km above the crater. The plume drifted S and SE (figure 6A), and 5 min later ash fell at the observation post. The Alert Level was raised to 3 and visitors and residents were warned not to come within 2.5 km of the crater. CVGHM suggested that the eruption vented at the same location as those of December 2011.

Figure (see Caption) Figure 6. (A) Photo of the Gamalama eruption on 16 September 2012 viewed from the NW. The ash plume is immediately blown to the S and SE with almost no vertical development. (B) The 17 September 2012 eruption of Gamalama viewed from the ESE. Both photos courtesy of Associated Press and The Jakarta Globe.

An eruption on 17 September 2012 produced a white-and-gray plume that rose 300 m above the crater and drifted E and SE (figure 6B). Ashfall was reported in the S, SE, and E parts of the island.

Calm prevailed for at least a few weeks after the eruption. Seismicity decreased in early October; on 8 October white plumes rose a mere 10-50 m. The Alert Level was lowered to 2 on 9 October, and the resulting exclusionary zone extended 1.5 km from the crater.

Geologic Background. Gamalama is a near-conical stratovolcano that comprises the entire island of Ternate off the western coast of Halmahera, and is one of Indonesia's most active volcanoes. The island was a major regional center in the Portuguese and Dutch spice trade for several centuries, which contributed to the thorough documentation of Gamalama's historical activity. Three cones, progressively younger to the north, form the summit. Several maars and vents define a rift zone, parallel to the Halmahera island arc, that cuts the volcano. Eruptions, recorded frequently since the 16th century, typically originated from the summit craters, although flank eruptions have occurred in 1763, 1770, 1775, and 1962-63.

Information Contacts: Center for Volcanology and Geological Hazard Mitigation (CVGHM), Jl. Diponegoro 57, Bandung, West Java, Indonesia, 40 122 (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/); The Jakarta Post, Jl. Palmerah Barat 142-143, Jakarta 10270, Indonesia (URL: http://www.thejakartapost.com/); Associated Press (AP) (URL: http://www.apimages.com/); USA Today, 7950 Jones Branch Road, McLean, VA 22102 (URL: http://www.usatoday.com/); BBC News (URL: http://www.bbc.co.uk/); United States Department of State - Bureau of Consular Affairs (URL: http://travel.state.gov/); Indonesia Explore (URL: http://indonesiaexplore.com/).


Kasatochi (United States) — November 2012 Citation iconCite this Report

Kasatochi

United States

52.177°N, 175.508°W; summit elev. 314 m

All times are local (unless otherwise noted)


Ramifications of the 7-8 August 2008 eruption

Our last report on Kasatochi discussed the eruption of 7-8 August 2008 (BGVN 33:07). Since the 2008 eruption, the volcano has remained quiet except for gas emissions. Erosion and deposition of erupted pyroclastic material are rapidly altering slopes and beaches on the island (Scott and others, 2010). This report highlights studies conducted during 2008-2009 of the uninhabited island. Alaska Volcano Observatory (AVO) still monitors Kasatochi (figure 8) indirectly from the Great Sitkin Island seismic network located 42 km away and from satellite imagery. After the 2008 eruption, and the associated almost total biosystem extinction in 2009, Kasatochi Island became a site for monitoring ecosystem succession.

Figure (see Caption) Figure 8. Map showing the location of Kasatochi in the Aleutian Islands. The extent of ash fall from the 7-8 August 2008 eruption is represented by dots with unverified areas indicated by question marks. Courtesy of Alaska Science Center (DeGange, 2010).

The terrestrial and surrounding marine environments of Kasatochi Island examined in June and July of 2009 saw changes in abundance or distribution of the ecosystem when compared to patterns observed on earlier surveys conducted in 1996 through June 2008. The largest direct effect of the eruption to individual animals was probably mortality of young birds. Indirect effects on wildlife consisted of the loss of suitable foraging habitats for species that relied on former terrestrial, intertidal, or nearshore-subtidal habitats and the near-total destruction of all former nesting habitats for most species. Although several species attempted to breed in 2009, all except Steller's sea lions failed due to the lack of suitable breeding sites.

The 7-8 August 2008 eruption. One or more of six remote International Monitoring System (IMS) infrasound arrays (figure 9) detected three well-defined eruption pulses of the 7 August 2008 eruption. The first was an infrasonic very long period (IVLP) acoustic pulse (pulse 1) that began at 21:59:44 UTC on 7 August with a gradual onset and duration of ~123 min and a peak RMS pressure of 0.22 Pa. The acoustic origin time was consistent with that computed for seismic signals (22:01 UTC). Pulse 2 began at 01:34:44 UTC on 8 August with a more impulsive onset, a duration of ~59 min and a peak RMS pressure of 0.46 Pa. Pulse 3 started at 04:20:34 on 8 August with an RMS pressure slightly higher than pulse 1 but lower than pulse 2 and a duration of ~33 min.

Figure (see Caption) Figure 9. Kasatochi's 2008 eruption generated infrasonic signals detected by at least one of these six International Monitoring System (IMS) numbered stations (Fee and others, 2010).

The formerly steep and rugged island which previously had dense low-growing vegetation similar to other Aleutian Islands (figure 10a), became visibly devoid of vegetation after the 7-8 August 2008 eruption (figure 10b). In brief, the island habitat appeared to have been destroyed.

Figure (see Caption) Figure 10. Kasatochi island as viewed before and after the 7-8 August 2008 eruption. (a) Aerial image from 9 July 2008 looking S showed extensive vegetation. (b) Aerial image from 23 October 2008 looking E showed pervasive pyroclastic material mantling the island. By this time, a shallow, gray, acidic lake had reformed in the widened summit crater. Photographs taken by Jerry Morris, Security Aviation; (from Waythomas and others, 2010).

Table 1 compares physical measurements of the island on 9 April 2004 (4 years prior to the 7-8 August 2008 eruption) to those taken on 17 September 2008 (nearly 6 weeks after the eruption). The aerial extent of the island increased by 40% after the eruption, the crater area increased by 25%, and the lake surface area enlarged by 73%. The accumulation of pyroclastic debris (most visible to the right in figure 10b) resulted in the seaward extension of the entire coastline by about 400 m, thus increasing the diameter of the island by about 800 m.

Table 1. Kasatochi Island's physiographic changes resulting from the 7-8 August 2008 eruption. *Data from 18 April 2009 Quickbird image. Reproduced from Waythomas and others (2010).

Location 09 Apr 2004 (pre-eruption) 17 Sep 2008 (post-eruption) Percent change
Island area (km2) 5.0 7 40
Island perimeter (km) 10.2 10.4 2
Crater area (km2) 1.2 1.5* 25
Lake area (km2) 0.4 1.7* 73

Post-eruption geology - eruptive deposit studies. Waythomas and others (2010) performed tephra studies in summer 2009 and reported that the bulk of the eruptive products from the 2008 eruption were pyroclastic-flow deposits, produced mainly by phreatomagmatic activity. The eruption lasted ~24 hours and included two initial explosive pulses and pauses over a 6-hr period that produced ash-poor eruption clouds, a 10-hr period of continuous ash-rich emissions initiated by an explosive pulse and punctuated by two others, and a final 8-hr period of nearly continuous ash emission and intermittent phreatic and phreatomagmatic activity. The authors reported that the eruption "...resulted in the accumulation of a uniform cover of medium gray-brown fine ash and pyroclastic-surge deposits over all flanks of the volcano. These deposits are 2-3 m thick and consist of silt, fine sand, and granules that are easily eroded by channelized water flows, and turn to sticky muck when wet." The deposits included a basal muddy tephra from eruptions through the shallow crater lake and accidental lithic debris derived from pre-existing lava flows in the crater. The juvenile material, which accounts for about 20-50% of the volume of the deposits, is pumiceous andesite (58-59% SiO2).

Surface erosion on the slopes of Kasatochi volcano determined the transfer of sediment to the marine environment and is largely a function of the local hydrologic conditions. Analysis of satellite images and field studies in 2008 and 2009 have shown that within about one year of the 7-8 August 2008 eruption, significant geomorphic changes associated with surface and coastal erosion occurred (figure 11).

Figure (see Caption) Figure 11. Cliffs eroded by wave action on an ENE shoreline of Kasatochi, photographed on 12 June 2009. Courtesy of AVO.

Although technically, sizes of rills and gullies differ, Waythomas and others (2010), using 1 m resolution imagery, could not resolve the size difference; thus they defined both as a narrow, relatively deep, v-shaped or rectangular gully on a hillside formed by flowing water. They observed extensive gully erosion beginning shortly after the eruption and continuing thereafter. Gully erosion removed 300,000 to 600,000 m3 of mostly fine-grained volcanic sediment from the flanks of the volcano, much of which reached the ocean (figure 12).

Figure (see Caption) Figure 12. Images of erosion into pyroclastic deposits from the 7-8 eruption of Kasatochi. (A) The gully pattern that developed on the SW flank (person for scale indicated by arrow). (B) Looking in an E flank gully; maximum gully depth is ~3 m. Courtesy of Waythomas/AVO.

As seen during the summer of 2009 (Scott and others, 2010), the 2008 volcanic deposits that mantle much of the island mainly consisted of decimeter-thick veneers. Veneers greater than 10 m were found locally on middle-to-upper flanks. Broad aprons and fans up to several tens of meters thick were found along much of the lower flanks below former sea cliffs.

Fans originally extended out to 460 m from the former sea cliffs, but by the summer of 2009, fans on the W, N, and E flanks had been truncated to about half that distance or less by coastal erosion. They terminated in active sea cliffs about 15-20 m high. Fans on the S-side of the island either terminated in low cliffs or, more typically, were buried by post-eruption fans of alluvium and debris-flow deposits or by accreting beach sediments that displaced the shoreline an additional 150-250 m seaward.

Post-eruption habitat - vegetation studies. Talbot and others (2010) searched Kasatochi Island for remnant vegetation and signs of re-vegetation at pre-eruption sampling sites. Plants that apparently survived the eruption dominated early plant communities. The most diverse post-eruption community resembled a widespread pre-eruption community. Figure 13 shows a representative plot containing 11 species assigned to bluff ridge vegetation type that inhabited wave-cut cliffs prior to the eruption. Although this ridge vegetation type is nominally species-poor, in this sampling, the mean-species diversity was generally higher than the other post eruption types (Talbot and others, 2010).

Figure (see Caption) Figure 13. A representative plot of 11 species assigned to bluff ridge vegetation type that existed on wave-cut cliffs prior to the 7-8 August 2008 eruption. Photo by Lawrence Walker, UNLV; courtesy of Talbot and others (2010).

Jewett and others (2010) examined the subtidal zone and reported that algal and faunal communities as well as rocky substrates were buried with volcanic deposits from the Kasatochi 2008 eruption. Existing plants were buried and the former stable rocky habitat was buried well into the subtidal zone. The loss of this rocky habitat may constrain kelp recolonization. However, little information is known regarding ocean current directions and velocities that may ultimately help erode soft-sediments and expose the hard rocky substrates necessary for kelp bed recolonization. Higher trophic marine organisms (for example, phytoplankton, the photosynthesizers that provide energy for a vast number of primary consumers, which in turn provide energy for secondary consumers and decomposers) were also affected by the eruption.

Post-eruption habitat - arthropod studies. A 2009 field campaign recorded 17 post-eruption insect species presumed to be non-breeding survivors and 4-9 breeding species. By 2010, 7 of the species seen in 2009 were lost while 18 post-eruption species survived, most of which were breeding (Ridling, 2012). The arthropod, Agyrtidae: Lyrosoma opacum Mannerheim (figure 14) was found to be the only breeding beetle among the 4-9 species found on post-eruption Kasatochi during the 2009 campaign.

Figure (see Caption) Figure 14. During the 2009 field campaign one beetle species remained breeding on Kasatochi (Agyrtidae: Lyrosoma opacum Mannerheim) as seen the on remains of an unidentified bird species. From Ridling (2012).

Post-eruption habitat - avian and mammalian studies. Birds have been studied on Kasatochi by the U.S. Fish and Wildlife Service continually since 1996, providing a critical data base to evaluate ecosystem impact and long-term recovery. The pre-eruption avifauna on Kasatochi was dominated by over 200,000 crested and least auklets. Williams and others (2010) determined that most, if not all, of the auklet nesting habitat was covered by the eruption products (figure 15).

Figure (see Caption) Figure 15. Kasatochi Island auklet rookery seen (a) before the 7-8 August 2012 eruption and (b) after the 2008 eruption, when the auklet hatch had failed completely. Photographs taken by G. Drew, courtesy of Alaska Park Science.

The largest direct effect of the eruption on individual animals was likely the mortality of chicks, with an estimated total 20,000-40,000 young birds lost during and shortly after the August 2008 eruption. Drew and others (2010) found that surviving older least auklets around Kasatochi Island showed little change in densities which ranged from 26 to 34 birds per km2. Similar to the least auklet finding, numbers crested auklets were not significantly reduced by the initial explosion. They also returned to attempt breeding in 2009, even though their nesting habitat had been rendered unusable.

Although seven species of birds and mammals attempted to breed in 2009, all but one specie failed due to lack of suitable breeding sites. The one successful breeding specie identified was Steller's sea lions. Williams and others (2010) noted the abundance of sea lions and many seabird species in 2009 was comparable to pre-eruption estimates, suggesting that adult mortality was low for these species. In contrast, shorebirds and passerines, commonly called perching birds, that formerly bred on the island were no longer observed in 2009 and probably perished in the eruption.

Drew and others (2010) also surveyed the marine environment surrounding Kasatochi in June and July of 2009 to document changes, including nutrient abundance, compared to patterns observed in 1996 and 2003. Analysis of SeaWiFS satellite imagery indicated that a large marine chlorophyll-a anomaly may have been the result of ash fertilization during the eruption. Drew and others (2010) found no evidence of continuing marine fertilization from terrestrial runoff 10 months after the eruption.

Post-eruption habitat - volcanic degassing and the landscape. Kasatochi remained quiet except for gas emissions after the 7-8 August 2008 eruption while erosion and deposition have altered the slopes and beaches (figure 16). By April 2009 the level of the crater lake had risen and the lake surface area was 67% larger than it was before the eruption due to an increase in crater diameter (Scott and others, 2010). Fieldwork in summer 2009 determined the locations of various rills and gullies at representative locations on the island. As the gully system on Kasatochi Island began to stabilize and sediment yield declined accordingly, wave action was expected to become the dominant process affecting the landscape (Waythomas and others, 2010).

Figure (see Caption) Figure 16. The prominent cliff-like feature (arrow) seen here in this view from the SW sits well inboard of Kasatochi's present coastline. The cliff was the island's former (pre-eruptive) shoreline. At the post-eruptive coastline, surge deposits are 1-2 m thick, and are much thicker higher up on the flanks. This image, taken 23 August 2008, shows gas emitted from the crater, drifting over the crater rim. Lithic clasts up to 2 m in diameter have been eroded out of the pyroclastic flow deposits by the sea and form a boulder-lag deposit along the coastline. Courtesy of Waythomas/AVO.

Post-eruptive landscape - drainage density. As stated by Waythomas and others (2010), "A fundamental landscape property that describes the degree of dissection by gullies and stream channels is drainage density... Drainage density is the ratio of total channel length to drainage-basin area [km/km2]. Changes in drainage density with time indicate that the threshold for erosion by runoff has been exceeded during individual rainfall events, and that the drainage system has yet to reach a state of quasi-equilibrium where routine rainfall events no longer bring about appreciable changes in drainage density. Time-dependent changes in drainage density also are surrogate measures of erosion because an increase in channel length must reflect channel head processes such as landsliding or gullying... Eventually the rates of gully development will decline and drainage density will approach a steady-state value or perhaps decrease. This is commonly due to the stabilizing effects of vegetation growth... We note that prior to the 2008 eruption of Kasatochi, the flanks of the volcano were covered with a nearly continuous mantle of herbaceous tundra, and no surface streams or drainages were present. Thus, prior to the eruption, the drainage density was very low, if not zero, and over time, we expect that the island will return to this condition."

Based on Waythomas and others (2010) and additional satellite image data from years 2008, 2009, and 2011, Julie Herrick calculated two Kasatochi surface drainage parameters: change in drainage density and change in gully volume. These two calculations used vector images to locate gully lines. These lines were superimposed as vectors on the rasterized (bit digitized) images and then a density analysis was performed. Comparisons of the three years by raster calculations (a form of bit analysis) determined the drainage line density as shown in figure 17A. Spatial analysis determined relative increase, decrease and unchanged surface volumes throughout the island as shown in figure 17B.

Figure (see Caption) Figure 17. Two surface models of drainage trends at Kasatochi developed by Julie Herrick. (A) 3D visualization of 9 March 2011 sedimentation drainage line density in units of km/km2 (see text). Colors represent drainage density as shown in the key (bottom left). Notice that the SE and NE sectors have relatively higher densities. (B) Map (N at top of image) showing volume change of 2008-2011 tephra superimposed on a topographic image (legend at right). The relative net loss of volume areas (blue), are mainly on the island's northerly shorelines. The relatively unchanged areas (gray) are near or on the crater rim. The S shorelines have expanded, as shown by the net gain volume areas (red).

The recovery of habitats at Kasatochi will depend on erosion of the tephra layer blanketing the island to re-expose former breeding habitats as well as anecdotal introduction of various species.

References. DeGange, A.R., Byrd, G.V., Walker, L.R., and Waythomas, C.F., 2010, Introduction-The Impacts of the 2008 Eruption of Kasatochi Volcano on Terrestrial and Marine Ecosystems in the Aleutian Islands, Alaska, Arctic, Antarctic, and Alpine Research, Vol. 42, No. 3, pp. 245-249.

Drew, G.S., Dragoo, D.E., Renner, M., and Piatt, J.F., 2010, At-sea Observations of Marine Birds and Their Habitats before and after the 2008 Eruption of Kasatochi Volcano, Alaska, Arctic, Antarctic, and Alpine Research, Vol. 42, No. 3, pp. 306-314.

Fee, D., Steffke A., and Garces, M., 2010, Characterization of the 2008 Kasatochi and Okmok eruptions using remote infrasound arrays, Journal of Geophysical Research, 115, D00L10 (DOI: 10.1029/2009JD013621).

Jewett, S.C., Bodkin, J.L., Chenelot, H., Esslinger, G.G., and Hoberg, M.K., 2010, The nearshore Benthic Community of Kasatochi Island, One Year after the 2008 Eruption, Arctic, Antarctic, and Alpine Research, Vol. 42, No. 3, pp. 315-324.

Neal, C.A., McGimsey, R.G., Dixon, J.P., Cameron, C.E., Nuzhdaev, A.A., and Chibisova, M., 2011, 2008 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory, U.S. Geological Survey Scientific Investigations Report 2010-5243, 94 p.

Ridling, S., 2012, Origins of Post-Eruption Insect Populations on the Volcanic Aleutian Island of Kasatochi (Presentation, URL: www.akentsoc.org/doc/Ridling_S_2012.pptx).

Scott, W.E., Nye, C.J., Waythomas, C.F., and Neal, C.A., 2010, August 2008 Eruption of Kasatochi Volcano, Aleutian Islands, Alaska-Resetting an Island Landscape, Arctic, Antarctic, and Alpine Research, Vol. 42, No. 3, pp. 250-259.

Talbot, S.S., Talbot, S.L., and Walker, L.R., 2010, Post-eruption Legacy Effects and Their Implications for Long-Term Recovery of the Vegetation on Kasatochi Island, Alaska, Arctic, Antarctic, and Alpine Research, Vol. 42, No. 3, pp. 285-296.

Wang, B., Michaelson, G., Ping, C.L., Plumlee, G., and Hageman, P., 2010, Characterization of Pyroclastic Deposits and Pre-eruptive Soils following the 2008 Eruption of Kasatochi Island Volcano, Alaska, Arctic, Antarctic, and Alpine Research, Vol. 42, No. 3, pp. 276-284.

Waythomas, C.F., Scott, W.E., and Nye, C.J., 2010, The Geomorphology of an Aleutian Volcano following a Major Eruption: the 7-8 August 2008 Eruption of Kasatochi Volcano, Alaska, and Its Aftermath, Arctic, Antarctic, and Alpine Research, Vol. 42, No. 3, pp. 260-275.

Williams, J.C., Drummond, B.A., and Buxton, R.T., 2010, Initial effects of the August 2008 volcanic eruption on breeding birds and marine mammals at Kasatochi Island, Alaska, Arctic, Antarctic, and Alpine Research, Vol. 42, No. 3, pp. 306-314.

Geologic Background. Located at the northern end of a shallow submarine ridge trending perpendicular to the Aleutian arc, Kasatochi is small 2.7 x 3.3 km island volcano with a 750-m-wide summit crater lake. The summit reaches only about 300 m elevation, and the lake surface lies less than about 60 m above the sea. A lava dome is located on the NW flank at about 150 m elevation. The asymmetrical island is steeper on the northern side than the southern, and the crater lies north of the center of the island. Reports of activity from the heavily eroded Koniuji volcano to the east probably refer to eruptions from Kasatochi. A lava flow may have been emplaced during the first recorded eruption in 1760. A major explosive eruption in 2008 produced pyroclastic flows and surges that swept into the sea, extending the island's shoreline.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA; Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA; and Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.avo.alaska.edu/); Julie Herrick, Global Volcanism Program, Smithsonian National Museum of Natural History, Washington, DC 20560.


Krakatau (Indonesia) — November 2012 Citation iconCite this Report

Krakatau

Indonesia

6.102°S, 105.423°E; summit elev. 155 m

All times are local (unless otherwise noted)


Many earthquakes and some mild eruptions during October-November 2011

Our previous report (BGVN 36:08) discussed two eruption episodes: one from 25 October 2010 to March 2011, and another from August 2011 to about 1 October 2011. During the last two weeks of September 2011, the volcano produced persistent volcanic earthquake swarms and thin emissions (BGVN 36:08). This report discusses two visits to the volcano in 2011. Scientists that visited on 8 October 2011 reported degassing and an ongoing seismic swarm then consisting chiefly of M ~1 and smaller earthquakes. During 12-13 November 2011 a photographer noted steady degassing, then observed the start of a 12-hour interval of minor but repeated Stombolian eruptions (see next section).

2011 visits by Øystein Lund Andersen. The photographer and guide Øystein Lund Andersen lives in Jakarta, Indonesia and visits Anak Krakatau often. His website contains photos of the volcano. He shows one photo of a seismograph at CVGHM's Pasauran Observatory recording part of a prolonged swarm of small earthquakes from 8 October 2011. Youtube features a video he took on the same subject.

His visit to Anak Krakatau during 12-13 November 2011 took place during an interval of gas emissions devoid of ash. He stayed up all night to observe Anak Krakatau emit a steady, white, ash-free plume. At dusk on 12 November he noticed that the crater glowed bright red and after a few hours a series of mild Strombolian eruptions occurred in a sequence that lasted 12 hours (figure 29). The time between the eruptions was from 30 seconds to a few minutes. Some of Andersen's photos captured glowing pyroclasts arcing tens of meters above the crater rim (figure 29b, c). Anderson saw ash lava bombs in the plume during these eruptions. He noted that the lava bombs ejected over the crater mainly fell back into the crater. During the night the crater remained almost constantly illuminated by the glowing bombs and the fragments they created when they landed. The eruptions were often accompanied by loud sounds from the volcano.

Figure (see Caption) Figure 29. Three photos of Anak Krakatau associated with mild Stombolian eruptions taken during 12-13 November 2011 amid unusually clear conditions. Provided to Bulletin editors by Øystein Lund Andersen.

Background. See earlier Bulletin reports for maps of the Krakatau complex and of the post-collapse cone that formed an island and now continues as the active vent (Anak Krakatau, Daughter of Krakatau; for example, figure 23 in BGVN 36:08). Krakatau sits ~130 km W of the Indonesian capital, Jakarta. The complex is famous for the devastating caldera-forming eruption in 1883 (Simkin and Fiske, 1983). That eruption injected millions of tons of fine ash, aerosols, and sulfate particles into the atmosphere. That eruption and associated tsunami claimed over 36,000 lives and awakened the world to caldera collapse (Self and Rampino, 1981).

Lockwood and Hazlett (2010) noted that the 1883 eruption "impressed European observers with remarkable, smog-like sunsets and silvery midday skies. This inspired a number of paintings, possibly including the lurid sky in Edvard Munch's famous work The Scream, which he painted in 1893."

According to the Center of Volcanology and Geological Hazard Mitigation (CVGHM), between the emergence of Anak Krakatau from the sea surface on 11 June 1927 up to 2011, the volcano had undergone over 100 eruptions. During that period, the volcano's non-eruptive periods lasted between 1 and 6 years. During the past few years, Anak Krakatau underwent several eruptive phases, followed by relatively quiet phases (BGVN 34:05, 34:11, and 36:08).

References. Lockwood, J. and Hazlett, R.W., 2010, Volcanoes: global perspectives. Wiley-Blackwell.

Simkin, T. and Fiske, R.S., 1983, Krakatau, 1883--the volcanic eruption and its effects, Smithsonian Institution Press.

Self, S., Rampino, M.R., 1981, The 1883 eruption of Krakatau, Nature, 294, pp. 699-704.

Geologic Background. The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Øystein Lund Andersen (URL: http://www.oysteinlundandersen.com/).


Ol Doinyo Lengai (Tanzania) — November 2012 Citation iconCite this Report

Ol Doinyo Lengai

Tanzania

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

All times are local (unless otherwise noted)


Update on observations and activity during 2011-2012

Ol Doinyo Lengai, located close to the N border of Tanzania (figure 153), is both accessible and monitored closely.

Figure (see Caption) Figure 153. Map of Tanzania showing Ol Doinyo Lengai's proximity to Meru and Kilimanjaro. Courtesy of USGS/CVO.

Frederick Belton's Ol Doinyo Lengai web site has provided many interesting photos from the expeditions that he has taken to the volcano since his initial visit in 1997, including annual visits until 2006, followed by his last expedition in 2008. In addition, Belton has included in his web site observations, photographs, and other graphics provided by many visitors to Ol Doinyo Lengai; these descripions have been the primary source of reports found in the Bulletin. Recently, Belton informed Bulletin editors that he rarely gets any updates on visits to Ol Doinyo Lengai for his web site, but he did receive one in September 2012. Bulletin editors wrote to a number of past contributors to BGVN; some of their comments are included below.

Belton's web site reported that Frank Möckel and Wendy Blank visited Ol Doinyo Lengai's summit area (figure 154) in September 2012. They climbed the volcano during 14-15 September and camped in the S Crater during the nights of 15 and 16 September (figure 155). Figures 155-160 contain some views they captured at the summit of the volcano. Figures 157 and 158 show what appear to be active spatter cones inside the N Crater. According to Belton, the activity looks very typical of the type frequently seen prior to the last explosive eruption in 2007-2008 (BGVN 32:11). Möckel and Blank reported that on the bottom of the active N Crater they saw fresh black natrocarbonatite lava and active vents, and they heard boiling noises from the bottom of the N Crater. They reported a strong smell of hydrogen sulfide (H2S) everywhere in the area.

Figure (see Caption) Figure 154. Topographic map modified from the Ol Doinyo Lengai quadrangle of 1990, with a contour interval of 20 m. The original map was modified in the N Crater area from observations made on 12 March 2010. Courtesy of Sherrod and others (2010).
Figure (see Caption) Figure 155. Ol Doinyo Lengai's S Crater, seen with tents for scale (center). Photo taken 14-15 September 2012. Courtesy of Frank Möckel and Wendy Blank.
Figure (see Caption) Figure 156. View of Ol Doinyo Lengai's N Crater as seen from the summit. Photo taken 14-15 September 2012. Courtesy of Frank Möckel and Wendy Blank.
Figure (see Caption) Figure 157. Ol Doinyo Lengai's active N Crater as seen from an unidentified point on the crater rim. Photo taken 14-15 September 2012. Courtesy of Frank Möckel and Wendy Blank.
Figure (see Caption) Figure 158. View looking down into Ol Doinyo Lengai's N Crater at interior spatter cones. Photo taken 14-15 September 2012. Courtesy of Frank Möckel and Wendy Blank.
Figure (see Caption) Figure 159. A closer view of Ol Doinyo Lengai's N Crater floor showing several vent openings (black) and an area of fresh spatter covering a region downhill of a vent. Photo taken 14-15 September 2012. Courtesy of Frank Möckel and Wendy Blank.
Figure (see Caption) Figure 160. Climbers on the NE rim of Ol Doinyo Lengai's N crater. Photo taken 14-15 September 2012. Courtesy of Frank Möckel and Wendy Blank.

Abigail Church, who studied Ol Doinyo Lengai for her PhD dissertation in 1996 and has published several articles on the petrogensis of the natrocarbonatite lavas, now lives in Nairobi, Kenya, and regularly flies over Ol Doinyo Lengai in chartered aircraft. She has flown over and landed on Ol Doinyo Lengai in a helicopter probably 5 times in the last few years. She camped close to the volcano in November 2012 and flew around the summit, however, it was cloudy. On many occasions when she was able to see into the crater, she observed what appeared to be small-scale activity continuing in the base of the deep pit. There are normally 1 or 2 active vents in which one can see very dark material which she assumed was fresh natrocarbonatite lava. She also has good contacts with people in the area and with pilots who fly the routes between Arusha and the Serengeti. On recent flights over Ol Doinyo Lengai, Church has observed that the sides of the central crater within the N Crater are collapsing inwardly, reducing the depth of the crater hole, and that small scale activity in the crater continues. Figures 161-165 show some photographs from 2011 and 2012 of the inside of Ol Doinyo Lengai's N crater.

Figure (see Caption) Figure 161. Ol Doinyo Lengai's N crater floor showing a vent and some spatter. Photo taken 2 December 2011. Courtesy of Phil Mathews and Abigail Church.
Figure (see Caption) Figure 162. A collapse in the floor of Ol Doinyo Lengai's N crater, showing natrocarbonatite lava flows. Photo taken 2 December 2011. Courtesy of Phil Mathews and Abigail Church.
Figure (see Caption) Figure 163. Small active vent in the N Crater floor of Ol Doinyo Lengai. Photo taken 2 December 2011. Courtesy of Phil Mathews and Abigail Church.
Figure (see Caption) Figure 164. A view of Ol Doinyo Lengai's N Crater from over the rim. Photo taken in August 2012. Courtesy of Phil Mathews and Abigail Church.
Figure (see Caption) Figure 165. A recently active vent on Ol Doinyo Lengai's N Crater floor. Photo taken in August 2012. Courtesy of Phil Mathews and Abigail Church.

Hannes Mattsson reported to Bulletin staff that he has 3 PhD projects running on different aspects of Ol Doinyo Lengai volcanism, but he has not been at the volcano for about 1.5 years. He is planning a 6-week field campaign scheduled in mid 2013. He noted that very little current or recent information on Ol Doinyo Lengai is currently available.

Joerg Keller also noted that there are not many recent reports about activity in the crater area. According to reports of Möckel's visit in February 2010 (BGVN 35:05), the access route to and from Ol Doinyo Lengai's summit seems much more difficult to negotiate than before the 2007 eruption. Keller believes that another possible factor leading to less observations of Ol Doinyo Lengai is the change in the crater formations since the eruption of 2007. There seems to be little change since 2008, a stable situation with the new ash cone dominating the entire N crater area completely (see figures in BGVN 32:11 and 33:02, as well as the above photos). The unique crater landscape seen before 2007, with accessible hornitos and lava flows of different ages, and the chance to see active spatter cones, lava pools and flowing lava, was an attraction to visiters. The logistical problems for visiting and climbing the volcano since 2008, incluing safety and political factors, have resulted in greatly diminished numbers of visitors.

Keller reported that Elias Danner, a teenage photographer, filmer, and designer, started Ol Doinyo Lengai photo documentation that shows the ash cone, its deep pit, and, in particular, looks inside the pit with fresh, overlapping lava lobes and vigorously boiling lava pools. Keller received from Danner a video of the boiling lava pools which was so typical and so impressive that he wrote in a recent paper (Keller and Zaitsev, 2012) the following: "The present vertically sided, almost 100 m deep pit crater formed by the 2007-2008 explosive activity is inaccessible. However, since 2008 frequent overflights and reports and photographs by visitors climbing the mountain (Belton, 2012) suggest that new natrocarbonatite effusions are occurring at the bottom of the deep pit. This is indicated from a distance by the typical morphological features of natrocarbonatite appearing as small hornitos and gray pahoehoe flows on the floor of the crater. On 26th June 2011, Elias Danner ... filmed a vigorously boiling and splashing, obviously carbonatitic lava pool at the bottom of the pit, with features very reminiscent of Figs. 5 and 6 in Keller and Krafft (1990)."

MODIS/MODVOLC Satellite Thermal Alerts. Table 26 gives an update of MODVOLC satellite thermal alerts at the Ol Doinyo Lengai summit since a similar update found in BGVN 33:06. It is not uncommon to find thermal alerts down and beyond the sides of the volcano, probably caused by fires. It is possible that fewer thermal alerts are measured by the MODIS satellites because the current deep crater (since the 2007-2008 eruptions) shields some of the hotter areas from the satellite sensors.

Table 26. MODVOLC thermal alerts measured at Ol Doinyo Lengai from 3 April 2008 to December 2012. Courtesy of the Hawai`i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System.

Date Time (UTC) Number of pixels MODIS Satellite
03 Apr 2008 2325 1 Aqua
13 Dec 2008 2005 1 Terra
13 Nov 2010 0810 1 (N side of crater) Terra
02 Oct 2011 1135 2 (N side of crater) Aqua
02 Oct 2011 1925 2 (N side of crater) Terra
22 Jun 2012 0750 4 (S side of crater) Terra

References. Belton, F., 2012, Oldoinyo Lengai, The Mountain of God (URL: www.oldoinyolengai.pbworks.com).

Keller, J., and Krafft, M., 1990, Effusive natrocarbonatite activity of Oldoinyo Lengai, June 1988, Bulletin of Volcanology v. 52, pp. 629-645.

Keller, J., and Zaitsev, A.N., 2012, Geochemistry and petrogenetic significance of natrocarbonatites at Oldoinyo Lengai, Tanzania: Composition of lavas from 1988 to 2007, Lithos, v.148, pp. 45-53.

Sherrod, D., Mollel, K., and Nantatwa, O., 2010, Oldoinyo Lengai: Trip Report, March 12-14, 2010, informal report (URL: http:/Sherrod_OldonyoLengai_March12_20106-1.pdf).

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

Information Contacts: Frederick Belton, University Studies Department, Middle Tennessee State University, Murfreesboro, TN (URL: http://oldoinyolengai.pbworks.com/); Sonja Bosshard, Institute of Geochemistry and Petrology, Swiss Federal Institute of Technology Zürich (ETH Zürich), Zürich, Switzerland; Laura Carmody, Planetary Geoscience Institute, Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN; Abigail Church, The Ker & Downey Safari Tradition, P.O. Box 86, Karen 00502, Kenya; Elias Danner, Elias Danner Productions (URL: http://www.mammut-studios.com/); Joerg Keller, Institut für Geowissenschaften/Mineralogie-Geochemie, Universität Freiburg, Albertstrasse 23b, 79104 Freiburg, Germany; Hannes B. Mattsson, Institute of Geochemistry and Petrology, Swiss Federal Institute of Technology Zürich (ETH Zürich), Zürich, Switzerland; Frank Möckel; Celia Nyamweru, St. Lawrence University; David Sherrod, Cascades Volcano Observatory (CVO), U.S. Geological Survey, Vancouver, WA (URL: https://volcanoes.usgs.gov/observatories/cvo/); Christoph Weber, Volcano Expeditions International (VEI), Muehlweg 11, 74199 Untergruppenbach, Germany (URL: http://www.v-e-i.de/); Ben Wilhelmi, commercial pilot (URL: http://benwilhelmi.typepad.com/benwilhelmi/).


Machin (Colombia) — November 2012 Citation iconCite this Report

Machin

Colombia

4.487°N, 75.389°W; summit elev. 2749 m

All times are local (unless otherwise noted)


Monitoring efforts and intermittent shaking from local earthquakes during 2011-2012

Elevated seismicity during January 2011 was discussed in our last report on Cerro Machín volcano (BGVN 36:04). Between September 2010 and January 2011, more than 800 volcano-tectonic (VT) earthquakes were detected per month and local residents reported shaking from these events, particularly during November 2010-February 2011. Here we describe trends in seismicity at Machín from January 2011 to November 2012 and the frequency of seismic swarms. We also include descriptions of monitoring efforts by the Volcanic and Seismological Observatory of Manizales at the Colombia Institute of Geology and Mining (INGEOMINAS) including two field campaigns focused on CO2 emissions from the crater.

Geophysical monitoring. Since January 2011, INGEOMINAS had been monitoring Cerro Machín with a network that included broadband and short-period seismometers, magnetometers, self potential, and an acoustic monitoring system (acoustic flow detection for early flood warning). The deformation network included electronic and dry tilt (longterm monitoring since 2005), and starting in November 2012, three GPS stations were also operating (figure 4). Electronic-distance measurements (EDM) were conducted in 2012 at seven stations (EDM data was available since 2008). Data from these monitoring efforts were available in the INGEOMINAS online technical reports.

Figure (see Caption) Figure 4. The deformation monitoring network at Cerro Machín in 2012 included three GPS stations and five electronic tilt stations. EDM measurements in September 2011 used three base stations (San Lorenzo, "SLOR;" La Palma, "PALM;" and Anillo, "ANIL") while measurements in October 2012 relied on one base station (San Lorenzo, "SLOR"). Courtesy of INGEOMINAS.

Geochemical monitoring. Geochemical monitoring at Cerro Machín has been conducted within the circular crater and the central dome complex (figures 5 and 6). During 2011-2012, geochemical monitoring included diffuse CO2 detection, alkaline traps, and radon monitoring from soil emissions (13 stations were online in November 2012) as well as regular testing at fumarolic and hot spring locations.

Figure (see Caption) Figure 5. Geochemical monitoring during 2011-2012 at Cerro Machín included several dozen sampling sites mainly spread across the ~2-km diameter crater. INGEOMINAS released long-term datasets from radon-gas traps, an alkaline trap, and a fumarole in their monthly technical bulletins. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 6. Two aerial views of Cerro Machín were captured during an overflight on 16 November 2011. (Top) In this view of the NE flank of Machín, the crater lake is visible near the left-hand side of the image within a moat-like region surrounding the dome. (Bottom) This view shows an access road along the breached, SW edge of the dome complex (lower center). This view also reveals a glimpse of the crater lake (appears gray) in the distant portion of the moat (right, from center). Courtesy of INGEOMINAS.

In May and September 2012, INGEOMINAS conducted field surveys to measure diffuse carbon dioxide emissions (figure 7). With a mobile LICOR 820 monitoring device, INGEOMINAS technicians traversed the interior crater rim detecting CO2, air temperature, and pressure. The survey on 28 May determined baseline levels of CO2 flux at 28 points within the crater. The survey conducted during 19 and 20 September 2012 detected relatively high CO2 emissions from seven locations along a traverse within the crater. The highest CO2 fluxes ranged between 739 and 8,077 mol·m-2·day-1, and in their technical report, INGEOMINAS noted that future gas monitoring should focus on those sites with peak values.

Figure (see Caption) Figure 7. On 28 May 2012, INGEOMINAS conducted a CO2 campaign within the crater of Cerro Machín. Courtesy of INGEOMINAS.

Seismicity in 2011. Elevated seismicity in late 2010 continued through early 2011 (BGVN 36:04) and local communities reported shaking in January and February 2011 (figure 8). For many months after May 2011, earthquakes per month had declined to below 400 per month. The clear exception to that trend took place during September 2011, a month with over 1,200 earthquakes.

Figure (see Caption) Figure 8. Volcano-tectonic (VT) seismicity at Cerro Machín abruptly increased in September 2010. This histogram shows time on the x-axis and number of earthquakes on the y-axis. Earthquake count per month decreased in January and February 2011 and reached low levels in August. Except for peaks in September and December 2011, the number of earthquakes remained below 400 events per month until November 2012. Courtesy of INGEOMINAS.

Compared with 2010 activity, fewer seismic swarms were detected in 2011 and in the available record for 2012 (table 2). In 2011, swarms tended to cluster beneath the dome complex and in areas ~2 km S and SE. INGEOMINAS frequently noted earthquake epicenters in an area known as Moralito, a location SE of the volcano near the MRAL GPS station (see figure 4). Deeper earthquakes (frequently at depths between 7 and 18 km) were detected in that region and were attributed to displacements along a fault zone.

Table 2. Seismic swarms detected at Machín during 2010-2012. Days were counted and tallied based on whether one or more swarms occurred. For example, during January-February 2010 there were six swarms recorded. Courtesy of INGEOMINAS.

Time Period Days with swarms
Jan-Feb 2010 6
Mar 2010 1
Apr-Jun 2010 8
Jul-Dec 2010 27
Jan-May 2011 14
Aug 2011 1
Jan-Apr 2012 4
Sep-Oct 2012 6

Local residents felt shaking from earthquakes in September 2011 when six occurred with magnitudes greater than 2.5. INGEOMINAS reported that this month had the largest combined free-energy release that year. The largest magnitude event of that group was an M 3.6 volcano-tectonic (VT) earthquake detected at 2013 on 12 September. The average depth of the earthquakes was 4.5 km with some events as deep as 13 km. Epicenters were primarily clustered in the area of Moralito (near the MORA seismic station, see figure 9).

Figure (see Caption) Figure 9. During September 2011, several moderate-sized earthquakes were located in an area SE of Cerro Machín. Seismic stations are labeled and located at purple squares. Note that the summit of Machín sits ~4 km NW of the clustered earthquakes, near the CIMA seismic station. Courtesy of INGEOMINAS.

In December 2011, INGEOMINAS reported that rockfall-type seismic signals were detected within the area. A total of 19 signatures were counted on 11 December; some events had durations up to 73 seconds. The largest earthquake that month was an M 2.32 that occurred at 0542 on 1 December.

Seismicity from January to November 2012. Rockfall-type signatures were also recorded in January 2012. These events occurred on 10 January at 1556 and lasted up to 64 seconds. As frequently observed during previous months, VT earthquakes tended to occur beneath the dome, S, and SE in the area of Moralito.

From January to August 2012, seismic swarms occurred intermittently (table 2). Elevated seismicity occurred during April 2012 and was felt by local residents. During this time period, the largest earthquake was an M 2.8 VT detected on 11 April at 0655. In April, VT earthquakes clustered ~1 km S of the dome complex and were ~4 km deep.

During May-August 2012, earthquakes were rarely clustered and occurred at a wide range of depths (0-16 km). In August, several earthquakes were located ~8 km SE of the CIMA station at depths between 12-15 km. The largest earthquake that month was an M 1.45 detected at 2026 on 9 August.

During September-October, seismic swarms occurred on six days (table 2). Local residents in the municipalities of Cajamarca and Ibagué (locations appear in figure 2 of BGVN 36:04) as well as the nearby departments of Quindio, Risaralda, and Caldas reported shaking due to these earthquakes (locations of these districts appear in the regional map of figure 5 in this report). These events were clustered beneath the dome complex at depths between 2 and 5 km. In October, however, relatively large earthquakes were detected in an area ~8 km SE of the dome at depths around 13 km. The largest earthquakes were on 9 September (M 3.6) and on 7 October (M 4.6) prompting INGEOMINAS staff to visit residences and investigate the impact of the events (figure 10). The M 4.6 earthquake was one of several located SE of the dome (near the TAPI seismic station, see figure 9).

Figure (see Caption) Figure 10. A visit to areas around Machín by INGEOMINAS staff in order to evaluate the possible damage from seismic unrest that was detected on 7 October 2012. Courtesy of INGEOMINAS.

In November, INGEOMINAS reported that VT earthquakes continued to occur beneath the dome although at a reduced rate compared to October. Earthquakes tended to occur 2-5 km beneath the dome, and deeper events were detected to the SE at depths between 9 and 15 km. The largest earthquake detected was an M 2.8 on 20 November at 1754. This earthquake was located at a depth of 2.75 km and was ~2 km SW of the dome complex.

Geologic Background. The small Cerro Machín stratovolcano lies at the southern end of the Ruiz-Tolima massif about 20 km WNW of the city of Ibagué. A 3-km-wide caldera is breached to the south and contains three forested dacitic lava domes. Voluminous pyroclastic flows traveled up to 40 km away during eruptions in the mid-to-late Holocene, perhaps associated with formation of the caldera. Late-Holocene eruptions produced dacitic block-and-ash flows that traveled through the breach in the caldera rim to the west and south. The latest known eruption of took place about 800 years ago.

Information Contacts: Instituto Colombiano de Geologia y Mineria (INGEOMINAS), Observatorio Vulcanológico y Sismológico de Manizales, Manizales, Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html).


Miyakejima (Japan) — November 2012 Citation iconCite this Report

Miyakejima

Japan

34.094°N, 139.526°E; summit elev. 775 m

All times are local (unless otherwise noted)


Minor plumes and low seismicity during April 2010-June 2012

During April 2010-June 2012 the Japan Meteorological Agency (JMA) maintained the hazard status for Miyake-jima at Alert Level 2, where it had stood since 31 March 2008. Our last report (BGVN 34:06) mentioned a minor eruption at Miyake-jima on 1 April 2009 which produced an ash plume that rose ~600 m above the crater. Since that time, activity was relatively low with up to four minor eruptions occurring during April-July 2010, as reported by the Tokyo Volcanic Ash Advisory Center (VAAC) based on information from JMA.

Eruptions occurred on 11 April, 4 July (two possible eruptions during the early morning), and 21 July 2010; the 21 July eruption was the only eruption for which the Tokyo VAAC issued an altitude and drift direction for the plume (~1.2 km altitude with E drift; table 5). The eruptions were characterized by gas and steam emissions lacking significant ash content (e.g. figure 23).

Table 5. Summary of detailed activity reports for Miyakejima during April 2010-June 2012; '--' indicates data not reported. Courtesy of JMA and Tokyo VAAC.

Month Gas-and-steam plume heights (m above crater rim) SO2 flux (metric tons/day) Remarks
Apr 2010 -- -- 11 Apr: Based on information from JMA, Tokyo VAAC reported an eruption at 0840.
Jul 2010 -- -- 4 Jul: Based on information from JMA, Tokyo VAAC reported possible eruptions at 1019 and 1434.
Jul 2010 400 -- 21 Jul: Based on information from JMA, Tokyo VAAC reported an eruption at 0928 that produced a plume which rose to an altitude of ~1.2 km (400 m above the crater) and drifted E.
Oct 2010 100-400 500-1,600 --
Nov 2010 100-400 500-1,600 Short duration tremor on 11 and 25 November not accompanied by air-shocks or plume changes.
Dec 2010 100-400 500-900 --
Jan 2011 100-600 800-1,000 --
Feb 2011 100-400 1,000 --
Mar 2011 100-500 600-1,100 GPS showed continuous deflation from a shallow source.
Apr 2011 100-500 700 --
May 2011 100-400 600-900 --
Jun 2011 100-300 600 Low seismicity except for 6 June. Hypocenters located just beneath summit crater. No tremor observed.
Jul 2011 200-400 500 Low seismicity centered just beneath summit crater. No tremor observed.
Aug 2011 200-500 800-1,000 Low seismicity with small amplitude, short-duration tremor (~80-90 sec); two increases observed on 18 and 27 Aug. Hypocenters located just beneath summit crater.
Sep 2011 100-600 900 Low seismicity centered just beneath summit crater. Banded tremor every 20 min. began 23 Sep and continued with smaller amplitudes into Oct.
Oct 2011 100-400 700-900 Low seismicity centered just beneath summit crater. Continuing banded tremor from Sep ceased on 28 Oct.
Nov 2011 100-300 500-800 Low seismicity centered just beneath summit crater. Volcanic tremor with small amplitude and short duration (~60 sec) occurred on 12 Nov at 0252; however, no infrasonic signal or ashfall was observed.
Dec 2011 100-300 1,100 Low seismicity centered just beneath summit crater. No tremor was observed.
Jan 2012 100-400 900-1,200 Low seismicity centered just beneath summit crater. Five episodes of volcanic tremor with small amplitude and short duration (~40-100 sec) occurred on 18, 22 and 30 Jan.
Feb 2012 100-400 900 Low seismicity centered just beneath summit crater.
Mar 2012 100-300 600-900 Aerial observations on 7 Mar revealed high temperature areas located on summit crater's S wall as previously seen in Jan 2010. Low seismicity centered just beneath summit crater; no tremor observed.
Apr 2012 100-300 500-700 Low seismicity centered just beneath summit crater; no tremor observed.
May 2012 100-300 400 Low seismicity centered just beneath summit crater; no tremor observed.
Jun 2012 100-200 -- A relatively large A-type earthquake with its hypocenter located around the crater occurred at 0940 on 28 Jun. A seismic intensity of 1 was detected at Miyakejima-Kamitsuki. No tremor observed.
Figure (see Caption) Figure 23. A S-looking photograph of Miyake-jima's crater taken from a flight on 17 March 2011 showing an apparent small gas-and-steam emission. Miyake Jima Airport is located along the coast, just out of view to the E. Courtesy of Flickr user R. Forrest.

JMA reported low levels of seismicity centered just beneath the crater during the reporting interval. Occasional episodes of volcanic tremor occurred, but were not correlated with other data indicating emissions or eruptions (table 5). Sources in Miyakemura village reported that high SO2 concentrations were occasionally detected in some inhabited flank areas.

GPS data revealed contraction in some parts of the edifice, a process that, although diminishing, had continued since 2000. Over the same time period, long-term extension of the baseline along the N-S section of Miyake-jima had been observed since 2006, indicating inflation in deeper portions of the volcano.

Geologic Background. The circular, 8-km-wide island of Miyakejima forms a low-angle stratovolcano that rises about 1,100 m from the sea floor in the northern Izu Islands about 200 km SSW of Tokyo. The basaltic volcano is truncated by small summit calderas, one of which, 3.5 km wide, was formed during a major eruption about 2,500 years ago. Parasitic craters and vents, including maars near the coast and radially oriented fissure vents, dot the flanks of the volcano. Frequent historical eruptions have occurred since 1085 CE at vents ranging from the summit to below sea level, causing much damage on this small populated island. After a three-century-long hiatus ending in 1469, activity has been dominated by flank fissure eruptions sometimes accompanied by minor summit eruptions. A 1.6-km-wide summit caldera was slowly formed by subsidence during an eruption in 2000; by October of that year the crater floor had dropped to only 230 m above sea level.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); Tokyo Volcanic Ash Advisory Center (VAAC), Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/).


Tangkuban Parahu (Indonesia) — November 2012 Citation iconCite this Report

Tangkuban Parahu

Indonesia

6.77°S, 107.6°E; summit elev. 2084 m

All times are local (unless otherwise noted)


Earthquakes and hot gas emissions in August 2012

Our most recent report on Tangkubanparahu (also known as Tangkuban Perahu) described increased seismicity during April 2005, consisting primarily of volcanic earthquakes and tremor (BGVN 30:12). This report describes elevated seismicity during August-September 2012. The Center of Volcanology and Geological Hazard Mitigation (CVGHM) notes that at least three magmatic eruptions and four phreatic eruptions had occurred at Ratu Crater, the most active vent, during 1829-1994. Ratu Crater is about 30 km N of Bandung in W Java. Figure 1 indicates the general location of the volcano.

Figure (see Caption) Figure 1. Sketch maps of Indonesia and W Java indicating the location of Tangkubanparahu (Tangkuban Perahu). Courtesy of Kartadinata and others (2002).

The next report we received on Tangkubanparahu described activity starting in August 2012. According to CVGHM, the frequency of earthquakes and tremor increased on both 13 and 23 August. Around this time, hot blasts of sulfuric gases, white in color, rose from Ratu Crater to heights of 50-400 m above the crater's floor. CVGHM reported that the temperature of emissions from Ratu Crater on 24 August was 246°C, compared to a measurement of 111°C on 18 August. On 23 August, the Alert Level was raised to 2 (on a scale of 1-4), and visitors and residents were prohibited within a 1.5-km radius of the active crater.

Seismic activity declined on 23 August; shallow volcanic earthquakes continued to be recorded but were less frequent through 21 September (table 2 provides data through 20 September). Hypocenters of volcanic tremors during this period were located beneath an area W of Ratu Crater at depths of 4-12 km. Soil temperatures at Ratu Crater were 30.5°C on 26 August, then were 35°C on 30 August, but then gradually declined during 31 August-21 September to ~34°C.

Table 2. Type and occurrence of earthquakes at Tangkubanparahu between 24 August and 20 September 2012. Courtesy of CVGHM.

Date Shallow Volcanic Deep Volcanic Distant Tectonic Local Tectonic Air Blast Tremor episodes (amplitude; duration)
24 Aug-30 Aug 2012 76 11 1 2 -- 1 (3-16 mm; 8,100 sec.)
31 Aug-06 Sep 2012 66 12 8 3 19 3 (1-30 mm; 60-18,000 sec.)
07 Sep-13 Sep 2012 42 6 3 2 53 7 (1-10 mm; 63-1,842 sec.)
14 Sep-20 Sep 2012 27 19 13 4 33 5 (5-14 mm; 171-600 sec.)

Between 5-11 September, sulfur dioxide gas emissions were elevated in an area NW of the crater associated with the plume, but in the latter part of September 2012 concentrations averaged4in Ratu Crater increased from 0.11 in December 2011 to ~4 on 24 August 2012 and remained at that level on 11 September 2012, which suggested to CVGHM that hot fluid was rising to the surface.

Based on seismicity, visual observations, deformation data, gas measurements, and soil and crater lake water temperatures, the Alert Level was lowered to 1 on 21 September 2012.

The eruptive history of Tangkubanparahu was described by Kartadinata and others (2002).

Reference. Kartadinata, M., Okuno, M., Nakamura, T., and Kobayashi, T., 2002, Eruptive history of Tangkuban Perahu volcano, West Java, Indonesia: A preliminary report, Journal of Geography, v. 111, issue 3, p. 404-409.

Geologic Background. Gunung Tangkuban Parahu is a broad shield-like stratovolcano overlooking Indonesia's former capital city of Bandung. The volcano was constructed within the 6 x 8 km Pleistocene Sunda caldera, which formed about 190,000 years ago. The volcano's low profile is the subject of legends referring to the mountain of the "upturned boat." The Sunda caldera rim forms a prominent ridge on the western side; elsewhere the rim is largely buried by deposits of the current volcano. The dominantly small phreatic eruptions recorded since the 19th century have originated from several nested craters within an elliptical 1 x 1.5 km summit depression.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).

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  Obituaries

Misc 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 subject.

Additional Reports  False Reports