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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 28, Number 04 (April 2003)

Managing Editor: Edward Venzke

Aira (Japan)

Ash plume observed in July 2002; plume photo from 17 April 2003

Anatahan (United States)

Eruption on 10 May is the first historical activity

Asamayama (Japan)

Four minor ash eruptions during February-April 2003

Chikurachki (Russia)

New eruption on 18 April generates long plumes and ashfall

Cosiguina (Nicaragua)

Earthquake swarm in September 2002

Erta Ale (Ethiopia)

Frequent changes in the active crater morphology and lava lake level

Guntur (Indonesia)

Increased seismicity since December 2002

Kikai (Japan)

Eruption plumes and ashfall during 24 May-5 June 2002

Miyakejima (Japan)

Small explosion in November 2002; continued high SO2 flux through April 2003

Niuafo'ou (Tonga)

Fumarolic and hot spring activity in the caldera during October 2002

Semeru (Indonesia)

Continued ash explosions, with frequent lava avalanches and pyroclastic flows

Soufriere Hills (United Kingdom)

Continued dome growth, rockfalls, and pyroclastic flows

Stromboli (Italy)

Strong explosion on 5 April covers much of the summit in pyroclastic deposits

Suwanosejima (Japan)

Ash explosions in September and December 2002, and activity in January 2003



Aira (Japan) — April 2003 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


Ash plume observed in July 2002; plume photo from 17 April 2003

An observer at Kagoshima Airport reported seeing an ash cloud from Sakura-jima at 0900 on 22 July 2002 that rose to 2.1-2.4 km altitude. An ash plume was visible on satellite imagery at 1052 (0152 UTC) that day extending to the SW.

A photograph taken by the webcam at ttp://yumemaru.com/s/ shows a plume of undetermined composition originating from the island on 17 April 2003 (figure 22). This type of event is common at Sakura-jima.

Figure (see Caption) Figure 22. Photograph of Sakura-jima taken on 17 April 2003 showing a plume originating from the island. Courtesy of Yunemaru.

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

Information Contacts: Charles Holliday, U.S. Air Force Weather Agency, 106 Peacekeeper Drive, Ste 2NE, Offut AFB, NE 68113-4039, USA (URL: http://www.557weatherwing.af.mil/); Yunemaru (URL: http://yumemaru.com/).


Anatahan (United States) — April 2003 Citation iconCite this Report

Anatahan

United States

16.35°N, 145.67°E; summit elev. 790 m

All times are local (unless otherwise noted)


Eruption on 10 May is the first historical activity

An explosive eruption on 10 May at Anatahan marked the first report of activity at the volcano since an earthquake swarm on 29 May 1993 that led to the evacuation of the island (BGVN 18:05 and 18:08). No eruptions had previously been documented in historical time from this small volcanic island in the Commonwealth of the Northern Mariana Islands (CNMI) (figure 2).

Figure (see Caption) Figure 2. Map of the Mariana Islands and outline of the adjacent Mariana Trench. The Commonwealth of the Northern Mariana Islands extends from Rota in the south to Farallon de Pajaros in the north. The island of Anatahan is approximately 9 km long and 4 km wide. Courtesy of CNMI Emergency Management Office.

A group of scientists was near Anatahan on 10 May deploying seismographs for the Margins Mariana Subduction Factory Imaging Project, which is comprised of members from Washington University, St. Louis; Scripps Inst. of Oceanography; and CNMI Emergency Management Office. They passed Anatahan as the eruption was occurring. The island was uninhabited at the time. According to members of the research group who viewed the eruption from about 10 km away, the eruption began on 10 May around 1700. The CNMI Emergency Management Office (EMO) reported that the ash cloud produced from the eruption eventually rose to an altitude of ~12 km (figure 3). During an observational helicopter flight, EMO personnel discovered that the eruption was emanating from the eastern crater (figure 4). They noted that only ash was being emitted, no lava flows were seen, and no explosions were seen or heard. The scientists had visited the island on 6 May and saw no signs of any unusual activity.

Figure (see Caption) Figure 3. Photograph taken on 10 May 2003 of an ash cloud produced from the eruption of Anatahan that began that day. The cloud top is at ~ 4.6 km and emanates from the eastern crater. The view is toward the SW. Courtesy of CNMI Emergency Management Office.
Figure (see Caption) Figure 4. Map of Anatahan showing the deep pit on the eastern side of the summit, which is referred to as the East Crater, and is the source of the eruption that began on 10 May 2003. Courtesy of Scott Rowland, University of Hawaii Manoa.

The Washington Volcanic Ash Advisory Center (VAAC) issued an advisory about the Anatahan eruption stating that an ash cloud was visible on satellite imagery on 10 May at 2232 at an estimated altitude of 10.5 km. One layer of the ash cloud drifted south at a speed of ~65 km/hour, and a lower level at an altitude of ~4.5 km drifted W at ~28 km/hr. By 0655 the next day ash was seen in satellite imagery drifting in three different directions: WNW at an altitude around 5.5 km, SW around 8.5 km, and two separate and smaller ash plumes were drifting SE at altitudes around 13.4 km. At this time, a hotspot was visible on GOES-9 imagery.

On 11 May the CNMI Emergency Management Office, Office of the Director issued a special advisory stating, "Due to this active volcano eruption with high level clouds and [an] ash plume, the general public especially fishermen, tour operators and commercial pilots are advise[d] to stay away from the island of Anatahan until further notice from the Office of Emergency Management." The eruption continued through at least 14 May, when the Washington VAAC issued an ash advisory stating that ash was visible on satellite imagery drifting W of Anatahan at an altitude of ~4.9 km.

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

Information Contacts: Doug Wiens, Washington University, St. Louis, McDonnell Hall 403 Box 1169, St. Louis, MO 63130; Allan Sauter, Scripps Institution of Oceanography, UCSD, 9500 Gilman Drive, La Jolla CA, 92093-0225; Juan Camacho, Commonwealth of the Northern Mariana Islands Emergency Management Office, P.O. Box 10007, Saipan, MP 96950 (URL: http://www.cnmihsem.gov.mp/); Washington VAAC, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/); Scott Rowland, University of Hawai'i at Manoa, Hawai'i Institute of Geophysics and Planetology, 1680 East-West Road, POST 602, Honolulu, HI 96822; Frank Trusdell, Hawaiian Volcano Observatory, PO Box 51, Hawaii National Park, HI, 96718-0051.


Asamayama (Japan) — April 2003 Citation iconCite this Report

Asamayama

Japan

36.406°N, 138.523°E; summit elev. 2568 m

All times are local (unless otherwise noted)


Four minor ash eruptions during February-April 2003

Asama, located near the resort town of Karuizawa ~150 km W of Tokyo, has been seismically active since 18 September 2000. Heightened seismicity occurred in June 2002, when the daily number of volcanic earthquakes exceeded 300 (BGVN 27:06). The Asama Volcano Observatory (ERI, University of Tokyo) and JMA reported that a new episode of elevated seismicity started around 0620 on 18 September 2002. A relatively large amount of volcanic gas trailed from the summit. The seismicity increased after 0800, 18 September, such that 243 volcanic earthquakes took place on 18 September and another 128 on the 19th, after which the seismic activity decreased. However, the temperature of the crater bottom remained at the elevated levels observed since May 2002. No change was observed in ground deformation.

According to the Japan Meteorological Agency (JMA), seismicity had been at background levels for several months, and the temperature of the crater had been rather low prior to four minor eruptions between 6 February and 18 April 2003. The first eruption occurred at about noon on 6 February as an ash cloud was seen rising to 300 m above the summit crater, with minor ashfall around the summit. Seismic tremor related to the emission started at around 1201 and lasted about 40 seconds. On 30 March at 0154 hours, a gray ash cloud rose 300 m, with minor ashfall around the summit. Then, on 7 April at 0924, an ash cloud rose 200 m. On 18 April at 0732 the volcano spewed a mixture of black smoke and pale ash ~300 m high. There were no reports of injuries or damage from these eruptions, and the JMA reported that more such activity is expected. All of the eruptions were brief, none having durations of more than 10 minutes. No unusual precursory seismic activity preceded these events, but plume activity has increased since the beginning of February.

Geologic Background. Asamayama, Honshu's most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has an historical record dating back at least to the 11th century CE. Maekake has had several major plinian eruptions, the last two of which occurred in 1108 (Asamayama's largest Holocene eruption) and 1783 CE.

Information Contacts: Hitoshi Yamasato and Tomoyuki Kanno, Japan Meteorological Agency (JMA), Volcanological Division, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan (URL: http://www.jma.go.jp/jma/index.html); Hidefumi Watanabe and Setysuya Nakada, Volcano Research Center-Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo, Tokyo, 113-0032 Japan (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html).


Chikurachki (Russia) — April 2003 Citation iconCite this Report

Chikurachki

Russia

50.324°N, 155.461°E; summit elev. 1781 m

All times are local (unless otherwise noted)


New eruption on 18 April generates long plumes and ashfall

A new eruption that began at Chikurachki on 18 April 2003 was reported by the Kamchatka Volcanic Eruptions Response Team (KVERT) and the Alaska Volcano Observatory (AVO). The most recent previous eruption occurred in early 2002 (BGVN 27:01 and 27:04). Ash explosions were seen by observers on Paramushir Island, and at 1500 and 2000 ashfall was observed in Podgorny town and Cape Vasiliev. The Aviation Meteorological Center at Yelizovo Airport reported that on 19 April ash plumes rose 2,000 m above the crater. According to satellite data from the USA, distinct volcanic events were detected at approximately 2300 on 19 April, 0200 on 20 April, and 0430 on 20 April (1200, 1500, and 1730 UTC, 19 April), with the ash moving towards the SE. Interpretation of satellite imagery revealed plumes extending more than 50 km SE and SSE during 18-19 April, with the longest reaching more than 250 km at 1501 on the 19th.

Visual data from Vasiliev Cape and Paramushir Island on 22 April showed a white gas-and-steam plume that rose 500 m above the crater. According to satellite data from the USA and Russia, ash plumes less than 100 km long were moving SE and E during 22-25 April. Longer plumes on 25 April were directed NNE. Observers from Vasiliev Cape noted a white plume rising ~500 m above the crater on 27 April. On 28 April residents in Severo-Kurilsk observed a very fine layer of gray ash (less than 1 mm thick) near the city, 3 km S of the volcano. The longest plume seen in satellite imagery during April was more then 300 km long when observed at 2028 on 29 April.

Geologic Background. Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidized basaltic-to-andesitic scoria deposits covering the upper part of the young cone give it a distinctive red color. Frequent basaltic plinian eruptions have occurred during the Holocene. Lava flows from 1781-m-high Chikurachki reached the sea and form capes on the NW coast; several young lava flows also emerge from beneath the scoria blanket on the eastern flank. The Tatarinov group of six volcanic centers is located immediately to the south of Chikurachki, and the Lomonosov cinder cone group, the source of an early Holocene lava flow that reached the saddle between it and Fuss Peak to the west, lies at the southern end of the N-S-trending Chikurachki-Tatarinov complex. In contrast to the frequently active Chikurachki, the Tatarinov volcanoes are extensively modified by erosion and have a more complex structure. Tephrochronology gives evidence of only one eruption in historical time from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959.

Information Contacts: Olga Girina, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry (IVGG), Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Cosiguina (Nicaragua) — April 2003 Citation iconCite this Report

Cosiguina

Nicaragua

12.98°N, 87.57°W; summit elev. 872 m

All times are local (unless otherwise noted)


Earthquake swarm in September 2002

In September 2002 an earthquake swarm was registered near Cosigüina. This swarm was the first to be recognized at that volcano in the 27 years of the existence of Nicaragua's seismic network. The historical seismic record contains no evidence of the type of cluster that occurred in September 2002, although there was seismic activity in 1951 that could have been of local origin (see below).

The seismicity began on 4 September, with M 2.4-3.6 events. The main earthquake occurred on 9 September with a magnitude of 3.9. The last event occurred on 16 September with a magnitude of 3.7. A total of 34 earthquakes occurred to the N of Cosigüina volcano. Unfortunately, the seismic station at the volcano failed to function due to radio signal transmission problems. Seismic readings were also obtained from the National System of Territorial Studies of El Salvador (SNET) for 31 earthquakes. Epicenters of the earthquakes, located with the readings obtained by the seismic networks of the Instituto Nicaragüense de Estudios Territoriales (INETER) and SNET, were concentrated in a zone approximately 4-5 km N and W of the crater (figure 1). The distribution, along a SW-NE axis, might be simply a product of the geometry of the configuration of seismic stations with which the events were located.

Figure (see Caption) Figure 1. Epicentral map of the earthquakes located N of Cosigüina volcano. September 2002. Black triangle indicates approximate summit location. Courtesy of INETER.

Randy White (USGS) indicated to INETER that the seismicity seems to have been of the volcano-tectonic type, caused by an intrusion of magma, based on several observations: 1) the two stages of the cluster on 4-6 and 9 September showed a release of similar seismic energy; 2) In the two stages there were many similarly sized events; 17 with a magnitude of 3.0 or less, but none greater than 3.9; 3) The maximum magnitude increased several times; and 4) The distribution of energy was highly unusual for tectonic seismicity. Apparently there were several groups of one or a few events in intervals of 5-7 hours. Regular pulsations are typical for volcanic earthquake swarms that last more than several hours.

INETER volcanologist Pedro Perez investigated the volcano on 12 September, but saw nothing anomalous. He also conducted interviews with local residents, went to the summit crater, and took measurements of thermal waters at the foot of the volcano. Within the crater walls, landslides were observed in the E, S, and W portions. Residents in the Marañonal, Potosí, Punta Ñata, and Apascali sectors did not feel the earthquakes.

Seismicity in August 1951. The following description is based on news reports compiled by INETER (The News, 1951 Ago. 07; The Press, 1951 Ago. 04, 05, 07, 09, 18).

In August 1951 there was strong seismic activity in western Nicaragua and southwestern Honduras. On 2 August one of a series of strong events produced a 200-m-long crack near Cosigüina that spewed large amounts of water, flooding the region. The seismic shocks also demolished three houses in Chinandega. These earthquakes were felt more strongly to the W and diminished to the N and in the direction of Managua. The population in these areas slept outside their homes for many days. The people of these sectors, mainly the western population, felt continuous and violent seismic shocks until 8 August. On 17 August a strong tremor shook the western region and Managua. Apparently, this seismic activity produced more than 100 events, not all of which were felt by all residents.

Geologic Background. Cosigüina (also spelled Cosegüina) is a low basaltic-to-andesitic composite volcano that is isolated from other eruptive centers in the Nicaraguan volcanic chain. The stratovolcano forms a large peninsula extending into the Gulf of Fonseca at the western tip of the country. It has a pronounced somma rim on the northern side; a young summit cone rises 300 m above the northern somma rim and buries the rim on other sides. The younger cone is truncated by a large elliptical prehistorical summit caldera, 2 x 2.4 km in diameter and 500 m deep, with a lake at its bottom. Lava flows predominate in the caldera walls, although lahar and pyroclastic-flow deposits surround the volcano. A brief but powerful explosive eruption in 1835 is Nicaragua's largest during historical time. Ash fell as far away as México, Costa Rica, and Jamaica, and pyroclastic flows reached the Gulf of Fonseca.

Information Contacts: Virginia Tenorio and Wilfried Strauch, Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado 1761, Managua, Nicaragua (URL: http://www.ineter.gob.ni/).


Erta Ale (Ethiopia) — April 2003 Citation iconCite this Report

Erta Ale

Ethiopia

13.6°N, 40.67°E; summit elev. 613 m

All times are local (unless otherwise noted)


Frequent changes in the active crater morphology and lava lake level

Over the last few years the Afar National Regional State has allowed a program of visitation to Erta Ale volcano by natural science field workers. As a result, numerous expeditions have visited the volcano since November 2000 and January-February 2001 (BGVN 26:12). The following brief reports are a result of some of these visits during January, February, and April 2002, November-December 2002, and January 2003. Typical lava lake activity was commonly reported, but some changes, such as a significant changes of the lake level, were also noted.

Activity during January 2002. Members of the Société de Volcanologie Genève (SVG) visited Erta Ale at the end January 2002. The lava lake remained elliptical with a N-S axis of ~130-133 m and an E-W axis of ~104-111 m; the width had increased ~10 m as a result of crumbling of the terrace along the lake edge. The size of the pit-crater was the same, with an E-W diameter of ~170 m, while the height of the vertical E wall was 46 m. Attempts to measure CO2 and SO2 concentrations inside the crater on 27 January 2002 were unsuccessful because the gas concentrations were below the detection limits of the Dräger tubes (10 ppm SO2 and 0.5% CO2).

Activity during February 2002. During a 14-19 February 2002 stay on Erta Ale by a team that included Roberto Carniel and Jürg Alean (Stromboli Online), the lava lake was active and produced spectacular fountains of lava. The lake level oscillated by several meters during their observation period. Seismic measurements were conducted along with thermal and video recordings of the lake.

Activity during April 2002. During 12-21 April 2002 a group from SVG led by Franck Pothé and Evelyne Pradal visited the volcano and reported significant changes in the morphology and activity of the lava lake since January 2002. The level of the lake had risen ~15 m and its surface area had decreased by ~33%. Over a 36-hour period the level varied intermittently by 1-2 m, the variation sometimes occurring within several minutes. Activity on the lake was intense, with continuous degassing and small lava fountains ~15 m high.

Activity during November-December 2002. A German group from Volcano Expeditions International visited the volcano during November-December 2002. They reported that the S crater was ellipsoidal with dimensions of ~130 m N-S and ~160 m E-W (figure 10). The lava lake occupied about half of the crater, and the lake surface was ~90 m below the W rim of the S pit. The remaining area in the E was covered by basalt that had a terrace ~45 m below the crater rim (figure 10). Previous observations had located the terrace at ~70 m below the rim. It was widely covered with talus; hence, the lava lake must had risen up to the present terrace level between spring 2002 and this visit. Almost no talus was found on the terrace, indicating that the lava cover was not old. Lava fountaining up to 20 m high occurred mainly in the W, S, and center areas of the crater lake. GPS measurements were used to accurately map part of the caldera rim and locate some key points (figure 11).

Figure (see Caption) Figure 10. A sketch map (top) and E-W cross-section (bottom) of the active S crater at Erta Ale on 4 December 2002.Courtesy of C. Weber.
Figure (see Caption) Figure 11. Partial survey of the Erta Ale caldera measured using a 12-channel GPS receiver. GPS reception was excellent due to the exposed nature of Erta Ale, where signals are shaded only when the receiver is close to the caldera wall inside the caldera. The GPS point HAK is the climbing location at 13.60402°N, 40.66401°E, and elevation 563.0 m. The highest point was a hornito on the N caldera rim, location HNN, at 13.60829°N, 40.66222°E, elevation 594.9 m. Courtesy of Lothar Fritsch.

Several earthquakes were felt during the visit. No seismic equipment was present, but five events were felt on 4 and 5 December 2002. No significant change in the lava lake was noticed during these events. Strong fumarolic activity was observed inside and outside the NW crater as well as on the outside of the caldera rim. The surface near the crater rim was broken by cracks in concentric circles, and the crater walls were formed of very unstable material. On 6 December three large rockfalls from crater wall collapses occurred along ~50 m of the crater wall circumference within a few minutes. About 40 m of the wall height collapsed with an estimated average thickness of 10 m, thus ~20,000 m3 of material slid into the lake, creating a large cloud of orange-brown dust that filled the pit and generated large amounts of Pélé's Hair.

Activity during January 2003. French teams from Terra Incognita visited the summit on 4 and 13-14 January 2003. The ~120 m long by 80 m wide lava lake was still in the W portion of the S pit crater; its surface was ~100 m below the crater rim (figure 12). The new platform, located ~50 m below the rim, was in the E part of the crater and covered ~25% of the crater floor. Gas emissions were abundant, and were assumed to be rich in SO2 based on their blue color and strong odor. The lava lake exhibited convection and lava fountains.

Figure (see Caption) Figure 12. Sketch map and cross-section of the Erta Ale lava lake, January 2003. Courtesy of Jacques-Marie Bardintzeff and Franck Pothé.

Geologic Background. Erta Ale is an isolated basaltic shield that is the most active volcano in Ethiopia. The broad, 50-km-wide edifice rises more than 600 m from below sea level in the barren Danakil depression. Erta Ale is the namesake and most prominent feature of the Erta Ale Range. The volcano contains a 0.7 x 1.6 km, elliptical summit crater housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera is renowned for one, or sometimes two long-term lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the N flank.

Information Contacts: P. Vetsch, Marc Caillet, Steven Haefeli, and Pierre-Yves Burgi, Société de Volcanologie Genève (SVG), PO Box 6423, CH-1211 Geneva 6, Switzerland (URL: http://www.volcan.ch/); Jürg Alean, Stromboli Online, Rheinstrasse 6, CH-8193 Eglisau, Switzerland (URL: http://www.swisseduc.ch/stromboli/); Christoph Weber and Lothar Fritsch, Volcano Expeditions International (VEI), Muehlweg 11, 74199 Untergruppenbach, Germany; Jacques-Marie Bardintzeff, Université Paris-Sud, F-91405 Orsay, France; Franck Pothé, Terra Incognita, CP 701, 36 quai Arloing 69256 Lyon Cédex, France.


Guntur (Indonesia) — April 2003 Citation iconCite this Report

Guntur

Indonesia

7.143°S, 107.84°E; summit elev. 2249 m

All times are local (unless otherwise noted)


Increased seismicity since December 2002

During December 2002, the Volcanological Survey of Indonesia (VSI) reported that activity at Guntur was higher than normal. As a result, the Alert Level was raised to 2 (on a scale of 1-4). No plume was observed, but deep and shallow volcanic earthquakes were registered, as well as tectonic earthquakes, through at least mid-May 2003. Tremor was also reported occasionally (table 1). On 28 December a "white ash plume around Guntur crater and Kabuyutan crater reached 3 m high." No ashfall was reported. The temperature at Guntur crater was 79.7°C and at Kabuyutan was 92.7°C. EDM deformation measurements taken on 22 November, 14 December, and 28 December 2002 revealed 11 cm of inflation. On 13 January 2003, an earthquake (MM 2-3) was felt in surrounding areas. Elevated tremor was noted during the first week of April 2003. Guntur remained at Alert Level 2 throughout mid-May.

Table 1. Seismicity at Guntur during 1 December 2002-18 May 2003. Courtesy of VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Tectonic
01 Dec-08 Dec 2002 8 8 19
09 Dec-15 Dec 2002 5 12 23
16 Dec-22 Dec 2002 2 6 16
23 Dec-29 Dec 2002 -- 5 14
30 Dec-05 Jan 2003 8 24 15
06 Jan-12 Jan 2003 3 6 12
13 Jan-19 Jan 2003 2 11 12
20 Jan-26 Jan 2003 3 23 20
27 Jan-02 Feb 2003 5 5 22
03 Feb-09 Feb 2003 5 4 11
10 Feb-16 Feb 2003 4 5 22
17 Feb-23 Feb 2003 3 11 17
24 Feb-02 Mar 2003 6 4 19
03 Mar-09 Mar 2003 3 10 30
10 Mar-16 Mar 2003 4 5 20
17 Mar-23 Mar 2003 1 3 28
24 Mar-30 Mar 2003 4 4 24
31 Mar-06 Apr 2003 13 6 23
07 Apr-13 Apr 2003 5 2 17
14 Apr-20 Apr 2003 3 3 22
21 Apr-27 Apr 2003 6 3 31
28 Apr-04 May 2003 4 2 18
05 May-11 May 2003 2 -- 24
12 May-18 May 2003 3 1 19

Geologic Background. Guntur is a complex of several overlapping stratovolcanoes about 10 km NW of the city of Garut in western Java. Young lava flows, the most recent of which was erupted in 1840, are visible on the flanks of the erosionally unmodified Gunung Guntur, which rises about 1550 m above the plain of Garut. It is one of a group of younger cones constructed to the SW of an older eroded group of volcanoes at the NE end of the complex. Guntur, whose name means "thunder," is the only historically active center, with eruptions having been recorded since the late-17th century. Although it has produced frequent explosive eruptions in the 19th century, making it one of the most active volcanoes of western Java, it has not erupted since.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).


Kikai (Japan) — April 2003 Citation iconCite this Report

Kikai

Japan

30.793°N, 130.305°E; summit elev. 704 m

All times are local (unless otherwise noted)


Eruption plumes and ashfall during 24 May-5 June 2002

According to a Japanese Meteorological Agency (JMA) report on 6 June 2002, discolored plumes associated with volcanic tremor had intermittently issued from Kikai since 11 May 2002. The U.S. Air Force Weather Agency reported that plumes emanating from Satsuma-Iwo-jima (an island forming part of the NW caldera rim of Kikai) were visible on satellite imagery during 24-28 May and 1-4 June 2002. The thin plumes drifted to the S, SE, and E during May, and were estimated to be lower than 3 km altitude. Ash was seen from the island of Yaku-shima on the afternoon of 26 May. JMA noted that the number of small volcanic earthquakes increased after 29 May. The JMA report also stated that discolored plumes were observed from Mishima village in the Ryukyu Islands, and that ash fell on residential areas, during 3-5 June 2002.

Geologic Background. Kikai is a mostly submerged, 19-km-wide caldera near the northern end of the Ryukyu Islands south of Kyushu. It was the source of one of the world's largest Holocene eruptions about 6,300 years ago when rhyolitic pyroclastic flows traveled across the sea for a total distance of 100 km to southern Kyushu, and ashfall reached the northern Japanese island of Hokkaido. The eruption devastated southern and central Kyushu, which remained uninhabited for several centuries. Post-caldera eruptions formed Iodake lava dome and Inamuradake scoria cone, as well as submarine lava domes. Historical eruptions have occurred at or near Satsuma-Iojima (also known as Tokara-Iojima), a small 3 x 6 km island forming part of the NW caldera rim. Showa-Iojima lava dome (also known as Iojima-Shinto), a small island 2 km E of Tokara-Iojima, was formed during submarine eruptions in 1934 and 1935. Mild-to-moderate explosive eruptions have occurred during the past few decades from Iodake, a rhyolitic lava dome at the eastern end of Tokara-Iojima.

Information Contacts: Naokuni Uchida, Japan Meteorological Agency (JMA), Fukuoka, Japan (URL: http://www.jma.go.jp/); Volcano Research Center, Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-0032, Japan (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html); Charles Holliday, U.S. Air Force Weather Agency, 106 Peacekeeper Drive, Ste 2NE, Offut AFB, NE 68113-4039, USA (URL: http://www.557weatherwing.af.mil/).


Miyakejima (Japan) — April 2003 Citation iconCite this Report

Miyakejima

Japan

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

All times are local (unless otherwise noted)


Small explosion in November 2002; continued high SO2 flux through April 2003

Miyake-jima has remained restless since the eruption that began in June 2000 (BGVN 25:05-25:07, 25:09, 26:02, 27:03, and 27:11). Small explosions with minor ash emission have been common (see BGVN 27:11). The most recent event reported by the Japan Meteorological Agency was at about 1320 on 24 November 2002, with the plume rising to an unknown height. The SO2 gas output remained high, ~4,000-9,000 tons/day, as of March 2003 (figure 19). Robust degassing was ongoing through the week of 16-22 April 2003. All residents on Miyake-jima island have been evacuated since September 2000, after which time SO2 fluxes reached extremely high values (over 80,000 tons/day in October 2000).

Figure (see Caption) Figure 19. SO2 flux at Miyake-jima during August 2000-March 2003. Triangles along the timeline indicate explosions. Courtesy of the Geological Survey of Japan and the Japan Meteorological Agency.

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: Akihiko Tomiya, Geological Survey of Japan, AIST, 1-1 Higashi, 1-Chome Tsukuba, Ibaraki 305-8567, Japan (URL: http://staff.aist.go.jp/a.tomiya/tomiyae.html); Japan Meteorological Agency (JMA), Fukuoka, Japan (URL: http://www.jma.go.jp/).


Niuafo'ou (Tonga) — April 2003 Citation iconCite this Report

Niuafo'ou

Tonga

15.6°S, 175.63°W; summit elev. 260 m

All times are local (unless otherwise noted)


Fumarolic and hot spring activity in the caldera during October 2002

Niuafo'ou is Tonga's most active volcano with at least 10 periods of activity, both explosive and effusive, since the early 1800s. The most recent period of activity in 1946 (Taylor 1999) resulted in the complete evacuation of the island. This volcanic center, ~450 km N of Tongatapu, is an isolated volcanic island located in the N-central Lau Basin (figure 4). In May 1999 a vent was producing hot water and H2S, and dead fish were observed near the vent (BGVN 26:05). Paul W. Taylor visited the volcano in October 2002 and noted fumarolic activity in two areas of the central caldera. On 20 October fumarolic and hot spring activity was noted in the NE part of the caldera.

Figure (see Caption) Figure 4. Locality map of the Lau Basin region, showing the location of Niuafo'ou. The symbols indicate centers with recorded eruptions (circles with stars); centers with no recorded activity (black stars); and probable submarine centers (white stars). Bathymetric contours are in kilometers. Courtesy of Paul Taylor.

Form and structure. Niuafo'ou is a subaerial shield volcano formed by submarine explosive and effusive activity during the Holocene. The island is approximately 8 km in diameter with a central caldera ~4 km in diameter with two lakes, Vai Lahi and Vai Si'i (figures 5 and 6). Periods of explosive activity have formed several small cinder cone complexes within the caldera. A detailed description of the geological features of Niuafo'ou is provided in Taylor (1991). Niuafo'ou rises to a height of 213 m above sea level at a point on the N rim of the caldera, a point known to the Niuafo'ouans as Piu Ofahifa.

Figure (see Caption) Figure 5. Geological map of Niuafo'ou (after Taylor, 1991) showing the major features of the island. Courtesy of Paul Taylor.
Figure (see Caption) Figure 6. Photograph of Niuafo'ou looking approximately W across the caldera. Both caldera lakes, Vai Lahi (background) and Vai Si'i (foreground) are visible. Courtesy of Paul Taylor.

Activity during October 2002. During a visit to Niuafo'ou in October 2002 to conduct a series of community workshops, it was noted that fumarolic activity was occurring in two areas of the central caldera. On 14 October Cecile Quesada (a French anthropologist) and Chris Simard visited the Vai Kona and Vai Sulfa areas along the S edge of the caldera (figure 6) and observed continued activity at the site. On 20 October, Taylor, Alejandra Meija-restrepo, Quesada, and Simard visited the Vai Si'i area in the NE part of the caldera and observed continued fumarolic and hot spring activity.

Vai Kona/Vai Sulfa Area. The Vai Kona/Vai Sulfa area of Niuafo'ou has been the site of persistent fumarolic and hot spring activity for many years. Activity was reported in 1958 (Richard, 1962) and again during 1982-83 and 1984 (Taylor, 1991). The level of Vai Kona fluctuates periodically. When Quesada and Simard visited the site on 14 October 2002, areas of persistent activity were observed.

Activity at Vai Kona was concentrated along the S shores of the lake (figure 7). Quesada and Simard observed numerous active vents on the floor of the lake, with large quantities of bubbles reaching the surface. The water temperature was estimated to be 25-30°C. Thick dark mud was present on the bottom of the lake and the temperature of the mud around the vents was estimated to be 35-40°C. Several active hot springs were also observed along the W shore of Vai Kona. These observations suggest that activity at the site has intensified since observed in 1958 and 1983.

Figure (see Caption) Figure 7. Niuafo'ou Island showing the location of fumarolic activity observed during October 2002. Courtesy of Paul Taylor.

Vai Sulfa occupies a small depression W of the southern end of Vai Kona (figure 7). The entire feature covers an area of about 30 m2 and consists of two sections. The W part of the depression is occupied by a small lake, while the E section is dry. At the center of this dry area is a vent ~40 cm across and 20-30 cm deep filled with mud and leaves. When leaves were removed from the hole during the visit it began to fill with water, and a boiling sound was heard. Extensive deposits of sulfur existed around the entire depression, and a strong smell of sulfur was present. Similar activity was also occurring when Quesada and Simard visited the area during July and September 2001. However, activity was less intense at those times.

Vai Si'i Area. A new site of fumarolic activity was first reported during May 1999 and observed during June 1999 (BGVN 26:05). When the site was visited on 20 October the focus of activity had moved to an area along the E shore of Vai Si'i. Numerous vents were present on the floor of the lake along the shoreline. The affected area stretched along the shoreline for ~25-30 m from where the vents were concentrated (figure 7). Active vents were aligned along the shoreline. Although the temperature of the lake water was an estimated 30°C (the prevailing air temperature), the temperature just below the surface of the sediment around the vents had increased to an estimated 65-75°C.

The vents were producing gas that was bubbling to the surface. A strong sulfur smell was noted, and large deposits of sulfur were present in the mud that comprised the floor of the lake around the vents. The deposits formed three elongated lobes that stretched S from the vents. The lobe-like distribution was probably the result of wind-induced currents. Vegetation along the shoreline was dead and encrusted with white sulfur (?). The observations suggests a net increase in activity at the Vai Si'i site since June 1999.

Conclusions. The observed fumarolic activity on Niuafo'ou indicates that the volcanic system is still active. Although not widespread, the fumarolic manifestations observed during 1999-2002 probably represent a net increase in the activity of the system since the last eruption in 1946. At this stage the level of activity is not of concern, but it should be monitored for signs of increase.

References. Richard, J.J., 1962, Kermadec, Tonga and Samoa: Catalogue of Active Volcanoes of the World, part 13.

Taylor, P.W., 1991, The Geology and Petrology of Niuafo'ou Island, Tonga: Subaerial Volcanism in an Active Back-arc Basin: Unpublished MSc thesis, Macquarie University, AVI Occasional Report, No. 91/01.

Taylor, P.W., 1999, The 1946 Eruption of Niuafo'ou: AVI Occasional Report, No. 99/03.

Geologic Background. Niuafo'ou ("Tin Can Island") is a low, 8-km-wide island that forms the summit of a largely submerged basaltic shield volcano. Niuafo'ou is an isolated volcanic island in the north central Lau Basin about 170 km west of the northern end of the Tofua volcanic arc. The circular island encloses a 5-km-wide caldera that is mostly filled by a lake whose bottom extends to below sea level. The inner walls of the caldera drop sharply to the caldera lake, named Big Lake (or Vai Lahi), which contains several small islands and pyroclastic cones on its NE shore. Historical eruptions, mostly from circumferential fissures on the west-to-south side of the island, have been recorded since 1814 and have often damaged villages on this small ring-shaped island. A major eruption at Niuafo'ou in 1946 forced evacuation of most of its 1200 inhabitants.

Information Contacts: Paul W. Taylor, Australian Volcanological Investigations, PO Box 291, Pymble, NSW 2073 Australia.


Semeru (Indonesia) — April 2003 Citation iconCite this Report

Semeru

Indonesia

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

All times are local (unless otherwise noted)


Continued ash explosions, with frequent lava avalanches and pyroclastic flows

At Semeru, the end of December 2002 was characterized by high numbers of explosions and pyroclastic flows (BGVN 27:12). The 29 December pyroclastic flow at Besuk Bang (figures 11 and 12) traveled ~9 km from the summit. During January through 23 March 2003, the Volcanological Survey of Indonesia (VSI) reported that seismicity was dominated by explosions and avalanches (table 11). A "white-gray ash" column rose 300-700 m above the summit. Activity was especially high during 1-12 January, when tens of ash explosions were visually observed per week (figures 13 and 14). Continuous tremor occurred on 8 January, with an amplitude of 11-12 mm. The Alert level remained at 2.

Figure (see Caption) Figure 11. The edge of 29 December 2002 Semeru pyroclastic-flow deposit at Besuk Bang in January 2003. This pyroclastic flow extended ~ 9 km from the summit. Courtesy of I. Mulyana, H. Triastuty, M. Hendrasto, and MA Purbawinata (VSI).
Figure (see Caption) Figure 12. Boulders from the Semeru pyroclastic-flow deposit at Besuk Bang around December 2002-January 2003. Courtesy of I. Mulyana, H. Triastuty, M. Hendrasto, and MA Purbawinata (VSI).

Table 11. Summary of weekly seismicity at Semeru during 1 January-23 March 2003. Courtesy VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Explosions Avalanches Tremor earthquakes Pyroclastic flows
01 Jan-05 Jan 2003 -- 4 354 89 7 0
06 Jan-12 Jan 2003 -- -- 382 84 38 1
13 Jan-19 Jan 2003 -- 1 554 89 7 0
20 Jan-26 Jan 2003 1 2 641 50 15 0
27 Jan-02 Feb 2003 18 -- 739 84 9 3
03 Feb-09 Feb 2003 2 -- 777 58 9 14
10 Feb-16 Feb 2003 3 4 641 53 13 5
17 Feb-23 Feb 2003 4 9 700 105 10 9
24 Feb-02 Mar 2003 6 -- 629 33 8 10
03 Mar-09 Mar 2003 -- 4 794 18 4 0
10 Mar-16 Mar 2003 2 -- 550 89 20 21
17 Mar-23 Mar 2003 -- -- 563 57 9 13
Figure (see Caption) Figure 13. View toward the summit of Semeru looking NW from G. Sawur (observatory post) around December 2002-January 2003. Courtesy of I. Mulyana, H. Triastuty, M. Hendrasto, and MA Purbawinata (VSI).
Figure (see Caption) Figure 14. Eruptive plumes rise from two different vents at the summit of Semeru around December 2002-January 2003. Courtesy of I. Mulyana, H. Triastuty, M. Hendrasto, and MA Purbawinata (VSI).

Lava avalanches in January 2003 extended up to 750 m from the crater rim and sometimes entered the Besuk Kembar river. One pyroclastic flow traveled 1,500 m and also entered Besuk Kembar. Pyroclastic flows were more numerous in February, travelling between 2.5 and 4 km from the summit into the Besuk Bang drainage. Lava avalanches were continuous during 17-23 February towards Besuk Kambar. Several pyroclastic flows in March moved toward Besuk Bang (up to 4 km long) and Besuk Kembar (up to 2 km long).

Infrared satellite data, January 2001-March 2003. Between January 2001 and March 2003, MODIS detected quasi-continuous thermal alerts at Semeru (figure 15). During January 2001-March 2002, the anomalies were characterized by 1-2 alert-pixels with a maximum alert ratio of -0.567 (4 May 2001). The Darwin VAAC reported ash plumes and clouds on several occasions throughout this period, and VSI reported numerous seismic events representing explosions and other phenomena (BGVN 26:08).

Figure (see Caption) Figure 15. MODIS thermal alerts on Semeru during January 2001-March 2003. Thermal alerts collated by Diego Coppola and David Rothery; data courtesy of the Hawaii Institute of Geophysics and Planetology's MODIS Thermal Alert Team.

From April 2002 until the end of the year, MODIS thermal alerts for Semeru increased in frequency and magnitude. This period was characterized by continuous explosions, avalanches and pyroclastic flows, and is related to seismicity increases beginning in March 2002 that prompted VSI to raise the Alert Level to 2 (BGVN 27:06). Thermal alerts reached a maximum amplitude on 16 August (two alert pixels with a maximum alert ratio of -0.364) and 1 September (one alert pixel with alert ratio of -0.389). VSI reported that seismic activity was higher than normal during June-September 2002 (BGVN 27:09), and the explosions produced plumes that reached 300-500 m above the crater. Observers reported that lava avalanches traveled toward the Besuk Kembar river to distances of ~750 m from the crater rim, and an ash explosion ejected glowing material ~150 m toward the upper Besuk Kembar drainage. Center coordinates of alert pixels were concentrated in four adjacent pixels close to Semeru's summit, especially on the S side.

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

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Diego Coppola and David A. Rothery, Department of Earth Sciences, The Open University, Milton Keynes, MK7 6AA, UK. Thermal alerts courtesy of the HIGP MODIS Thermal Alerts Team (URL: http://modis.higp.hawaii.edu/).


Soufriere Hills (United Kingdom) — April 2003 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


Continued dome growth, rockfalls, and pyroclastic flows

During 1 March through 2 May 2003, the dome continued to grow, producing numerous rockfalls and moderate pyroclastic flows. Most activity was concentrated on the northern flanks, producing numerous pyroclastic flows in White's Ghaut, the Tar River Valley, and Tuitt's Ghaut. Pyroclastic flows and rockfalls traveled down all flanks of the dome at some time during the period. On 20 March, the greatest dome height recorded to date was measured, 1,098 m. A prominent extrusive lobe was established on the E and SE sides of the summit at the beginning of April. On 22 April, a large spine, inclined to the E, was observed on the summit, the top of which was at an elevation of 1,163 m.

The Washington VAAC issued notices daily to the aviation community regarding ash clouds emanating from the summit. Seismicity during the report period was dominated by rockfalls (table 44). Average daily SO2 emission rates varied throughout the report period (table 45) with a low of 31 tons/day on 25 March to a maximum of 1,550 tons/day on 1 May.

Table 44. Summary of weekly seismicity at Soufrière Hills during 28 February 2003-2 May 2003. Courtesy MVO.

Date Rockfall Hybrid Long-period Long-period / Rockfall Volcano-tectonic
28 Feb-07 Mar 2003 997 0 79 71 4
07 Mar-14 Mar 2003 1050 5 87 108 0
14 Mar-21 Mar 2003 1050 2 93 152 2
21 Mar-28 Mar 2003 1097 16 99 138 7
28 Mar-04 Apr 2003 754 7 74 101 2
04 Apr-11 Apr 2003 332 1 66 77 --
11 Apr-18 Apr 2003 393 7 72 56 --
18 Apr-25 Apr 2003 966 4 83 88 1
26 Apr-02 May 2003 813 4 168 121 1

Table 45. Average daily SO2 emission rates at Soufrière Hills during 28 February 2003-2 May 2003. Courtesy MVO.

Date SO2 emissions (tons/day)
28 Feb 2003 1020
28 Feb-07 Mar 2003 500-1020
07 Mar-14 Mar 2003 220-355
14 Mar-21 Mar 2003 285-380
21 Mar-28 Mar 2003 31-497
25 Mar 2003 31
28 Mar-04 Apr 2003 230-770
04 Apr-11 Apr 2003 151-780
06 Apr 2003 151
11 Apr-18 Apr 2003 220-550
18 Apr-25 Apr 2003 450-550
25 Apr-02 May 2003 390-1550
01 May 2003 1550

Throughout the period, access to all areas S of the Belham Valley, to Waterworks, Happy Hill, Lower Friths and Old Towne, and to Bramble airport and beyond was prohibited and a maritime exclusion zone around the S part of the island extended 3.7 km beyond the coastline from Trant's Bay in the E to Lime Kiln Bay on the W coast.

Activity during March 2003. Activity remained at levels similar to that of the previous few weeks (BGVN 28:02), with continued dome growth and moderate pyroclastic-flow activity. Lava extrusion was accompanied by rockfall activity and pyroclastic flows that were focused, during 1-7 March, on the NE and N slopes and valleys. Pyroclastic flows occurred most frequently in Tuitt's Ghaut with a few on Farrell's Plain with run-out distances up to 1 km.

During 8-14 March, rockfalls and pyroclastic flows occurred down all flanks. Dome growth continued and lava extruding into the center of the summit dome complex continued to increase the dome height. Dome glow at night was spectacular in the Tar River Valley and on the NW in Tuitt's Ghaut and the N talus slopes. Small rockfalls and pyroclastic flows occurred infrequently on the W flank and at the top of Gage's Valley. Ash venting was continuous in the summit area.

Lava extrusion during 15-21 March formed a series of spines and ridges. Theodolite measurements on 20 March indicated a dome height of 1,098 m, the highest recorded to date. Activity was dominated by rockfalls and pyroclastic flows mainly in the Tar River Valley, with several small pyroclastic flows in White's and Tuitt's Ghaut and one observed in the upper part of Tyre's Ghaut on 20 March. Ash venting continued.

Dome growth continued through the end of the month. Rockfalls and pyroclastic flows spilled off the active summit in a broad arc extending from the S around the E flanks to the NW. Most activity was towards the NE, with pyroclastic flows in the Tar River Valley and small flows on the N flanks of the dome in White's Ghaut, Tuitt's Ghaut, the upper reaches of Tyre's Ghaut and on Farrell's Plain. Most volcano-tectonic earthquakes (see table 44) occurred in a small swarm late in the evening of 25 March. On the same day, following a brief, intense rainstorm, a 4-5 hour period of increased pyroclastic-flow and rockfall activity occurred on the N and NW flanks of the dome. Observation flights on 27-28 March indicated that rockfalls and small pyroclastic flows were spilling onto the S flanks of the dome.

Activity during April 2003. A prominent extrusive lobe was established on the E and SE sides of the summit at the beginning of April and a large vertical spine, extruded at the back of this lobe on the night of 1-2 April, was the highest point on the dome. During 1-12 April, rockfalls and pyroclastic flows occurred mainly on the E side of the dome in the Tar River Valley. Rockfall activity also continued on the S side of the dome and some pyroclastic flows occurred on the NE flanks in White's Ghaut and Tuitt's Ghaut, and on the NW flank; several of the latter flowed into the upper reaches of Tyre's Ghaut. On 10 April torrential rainfall produced mudflows in the Belham River and triggered pyroclastic flows on the E, N, and NW flanks of the dome.

Helicopter observations during 15 April indicated that the lobe extrusion continued on the ESE side of the dome summit above the Tar River Valley. Vigorous gas venting also was observed on the S side of the summit during this flight. Rockfall and pyroclastic-flow activity occurred throughout the week of 12-18 April on the E and SE sides of the dome with some rockfall activity on the N flanks. On 15 April a small pyroclastic flow occurred in the upper part of Tyre's Ghaut.

On 22 April a large spine was observed on the dome summit, positioned slightly S of the center and inclined at a high angle towards the E. The top of the spine was at an elevation of 1,163 m as compared to the ~1,090 m height of the general summit region of the dome. During 19-25 April, most of the rockfall and pyroclastic-flow activity occurred on the E and SE flank of the dome in the Tar River Valley. A few flows occurred to the NE in White's Ghaut and Tuitt's Ghaut, and to the N and NW onto Farrell's Plain and into the top of Tyre's Ghaut. Observations on 22 April indicated that rockfall debris was starting to spill S into the White River area. On 23 April several large rockfalls were observed on the W side of the dome in the Gages area.

During the last week of April, the prominent spine seen on the summit of the dome the previous week had partly disintegrated. Most of the rockfalls and pyroclastic flows into the Tar River Valley began along the face of the well-developed extrusion lobe present on the ESE side of the summit region. Rockfall debris spilled off the S side of the lobe into the upper reaches of White River, and some flows occurred towards the NE in White's Ghaut and Tuitt's Ghaut, and towards the N and NW on the top of Farrell's Plain and in the top of Tyre's Ghaut. Vigorous pulses of ash-venting occurred on the summit throughout this week.

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

Information Contacts: Montserrat Volcano Observatory (MVO), Mongo Hill, Montserrat, West Indies (URL: http://www.mvo.ms/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/).


Stromboli (Italy) — April 2003 Citation iconCite this Report

Stromboli

Italy

38.789°N, 15.213°E; summit elev. 924 m

All times are local (unless otherwise noted)


Strong explosion on 5 April covers much of the summit in pyroclastic deposits

On the morning of 5 April, scientists from INGV-CT were conducting a daily helicopter flight with a portable thermal camera, surveying the active lava flow field on the upper sector of the Sciara del Fuoco, above a flat zone at the base of the 28 December 2002 eruptive fissure. Three vents along this surface were feeding small lava flows, and the summit craters were producing a very diluted gas cloud. A few minutes after the start of the survey, which began about 0900, the gas plume from the craters being blown W was suddenly crossed by a reddish ash emission, which was interpreted as resulting from further collapses within the craters. However, the red ash was soon replaced by darker juvenile material coming from Crater 1 (the NE crater) that formed a hot jet with a cauliflower shape rapidly growing above the crater. A few seconds later, Crater 3 also produced a hot jet of juvenile material. Data from the seismic network confirmed that the explosion began at 0912.

The eruptive process then evolved very rapidly, with jets from craters 1 and 3 joining together. A very powerful explosion pushed the helicopter away from the crater. A mushroom-shaped dark cloud rose from the craters, expanding vertically to an altitude of ~2 km, 1 km above the volcano's summit (figure 73). The eruptive cloud was surrounded at its base by a dark-gray cloud, while it was still expanding vertically and assuming the mushroom shape. Bombs, ash, and blocks fell on the NE flank above 400 m elevation, burning vegetation. Most of the ejecta drifted W, falling on Ginostra (~1.5 km from the summit) and destroying two houses; no people were injured.

Figure (see Caption) Figure 73. Photograph of the expanding eruption plume at Stromboli on 5 April 2003. Courtesy of INGV.

Continuing the helicopter survey after the eruption, observers saw that the lava-flow field on the upper Sciara del Fuoco was completely covered by a brown carpet of debris ejected from Crater 1 during the initial phase of the event. A thick steam cloud rose above the debris due to vaporization from the wet material by the underlying lava flows. Meanwhile, several alternating black and reddish pulses occurred, mainly from Crater 3. Several fingers of light-brown debris were expanding from the NW flank of Crater 1 along the mid-section of the Sciara del Fuoco. The upper part of the volcano above 700 m elevation was completely covered by pyroclastic products. Within a few minutes after the start of the eruption, the upper Sciara del Fuoco had active flows emerging from the layer of debris covering the lava-flow field. The explosive event caused abundant emission of pumice mixed with small brown scoria. The pumice contained small crystals and was very vesiculated. Lithic fragments of lava with light-gray groundmass and centimeter-sized crystals of pyroxene were common in the pumice.

A helicopter survey on 8 April showed four active vents pouring lava onto the upper Sciara del Fuoco at 590 m elevation. Two of the flows were expanding along the middle Sciara del Fuoco, causing detachment of blocks from the flow front and small rockfalls that reached the sea. Within the summit craters a thick layer of debris had accumulated following the event of 5 April.

Geologic Background. Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/).


Suwanosejima (Japan) — April 2003 Citation iconCite this Report

Suwanosejima

Japan

29.638°N, 129.714°E; summit elev. 796 m

All times are local (unless otherwise noted)


Ash explosions in September and December 2002, and activity in January 2003

Though the volcano had been relatively quiet since 26 August 2002 (BGVN 27:07), the Japan Meteorological Agency reported that explosive eruptions became frequent on the morning of 12 September 2002. Rumbling was heard intermittently at a location ~4 km SSW of the summit, and light ashfall was observed on 12 September. Explosions occurred at 0816, 1246, 1746, and 1754 on 12 September, and at 0853, 1016, and 1027 on 13 September.

A pilot report contained in the Kagoshima Airport weather observation issued at 1000 on 5 December 2002 noted a plume estimated to be between 900 and 1,200 m altitude. The U.S. Air Force Weather Agency noted that the plume was also seen on DMSP (Defense Meteorological Satellite Program) imagery at 1034 and on NASA Terra MODIS imagery at 1055 on 5 December.

The REAL-Volc Project at the Volcano Research Center, Earthquake Research Institute, University of Tokyo, has detected several thermal anomalies on Suwanose-jima since they started an AVHRR monitoring system in 2001. Anomalies were seen on 11 October 2001, 20 November 2001, 30 December 2001, 20 April 2002, and 12 January 2003.

Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Information Contacts: Naokuni Uchida, Japan Meteorological Agency (JMA-Fukuoka Center), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan (URL: http://www.jma.go.jp/); Takayuki Kaneko, Volcano Research Center, Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-0032, Japan (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html); Charles Holliday, U.S. Air Force Weather Agency, 106 Peacekeeper Drive, Ste 2NE, Offut AFB, NE 68113-4039, USA (URL: http://www.557weatherwing.af.mil/).

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