Logo link to homepage

Bulletin of the Global Volcanism Network

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

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

Recently Published Bulletin Reports

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).

Search Bulletin Archive by Publication Date

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

   

The default month and year is the latest issue available.

Bulletin of the Global Volcanism Network - Volume 20, Number 04 (April 1995)

Managing Editor: Richard Wunderman

Arenal (Costa Rica)

Gas analysis; high tremor and a large explosion

Asamayama (Japan)

First month with over 1,000 earthquakes since 1991

Atmospheric Effects (1995-2001) (Unknown)

Lidar data from Cuba

Barren Island (India)

Ash plumes from three vents; fire fountaining and lava flows

Deception Island (Antarctica)

Report from a 1994-95 austral summer survey

Fogo (Cape Verde)

Fire fountains continue but lava extrusion rate declines

Galeras (Colombia)

Earthquake swarm continues; higher pressure gas emissions

Irazu (Costa Rica)

Rainfall-induced mass wasting and three seismic events

Kanaga (United States)

Occasional mild steam plumes

Kilauea (United States)

Lava flows, breakouts, tremor, and more

Langila (Papua New Guinea)

Ash clouds to several hundred meters above the crater

Manam (Papua New Guinea)

Both seismicity and tilt low; gently steaming

Momotombo (Nicaragua)

Fumarole chemistry and temperature data for 1983 and 1995

Poas (Costa Rica)

Two new hot springs; moderate number of earthquakes and tremor

Popocatepetl (Mexico)

Located seismic events and summit crater observations

Rabaul (Papua New Guinea)

Tavurvur explosions stop on 16 April

Rincon de la Vieja (Costa Rica)

Description of the crater lake and fumaroles

Ruapehu (New Zealand)

Crater lake temperature drops 10°C from 13-year high

Stromboli (Italy)

Explosion on 5 March and tremor; crater observations

Unzendake (Japan)

No lava dome growth, small rockfalls, rare tremors

Veniaminof (United States)

Small plumes seen; warm spots identified from satellite images

Villarrica (Chile)

Tremor, mild explosions, and a new pyroclastic cone

Vulcano (Italy)

Fumaroles at Fossa Grande and Forgia Vecchia craters

Whakaari/White Island (New Zealand)

Currently non-eruptive but 2-year-long inflation continues



Arenal (Costa Rica) — April 1995 Citation iconCite this Report

Arenal

Costa Rica

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

All times are local (unless otherwise noted)


Gas analysis; high tremor and a large explosion

During April, Crater C continued its ongoing emission of gas, lava flows, and small Strombolian eruptions. The lava flow that started in October 1994, reached 1,100 m elevation along the W arm and at 850 m elevation along the NW arm. On Arenal's NW, W, and SW flanks the tips and borders of tree leaves showed signs of scalding by acidic rain; some species were merely discolored, others were dying.

During April, a total of 484 low-frequency seismic events took place (figure 72); the majority of these events correlated with Strombolian eruptions; some events were registered as far away as 30 km SW of the active crater (station JTS). In terms of total (broad-band) seismicity, the most seismically active single day was 30 April, with 53 events registered.

Figure (see Caption) Figure 72. Arenal low-frequency seismicity for 1994 and January-April 1995. Data courtesy of OVSICORI-UNA.

According to OVSICORI-UNA, tremor prevailed during April for a total of 326 hours, 160% larger than any month (with data) in 1994 and thus far in 1995 (figure 72). At station JTS the tremor's dominant frequency fell between 2.0 and 3.2 Hz, its amplitude was as large as 101 mm.

ICE reported that average daily ashfall near the vent fluctuated significantly in the past few collection intervals (table 10). In three of the four collection intervals, the percentage of material above and below a quarter of a millimeter (250 µm) typically broke down in a roughly 40:60 ratio (coarse to fine).

Table 10. Ash collected 1.8 km W of Arenal's active vent, 19 October 1994 through 21 April 1995. Courtesy of ICE.

Collection Interval Avg daily ashfall (grams/m2) Ash % 300+µ Ash % less than 300µ
19 Oct-23 Jan 1995 7.6 38.0 62.0
23 Jan-03 Mar 1995 8.2 54.7 45.3
03 Mar-30 Mar 1995 22.7 42.2 57.8
30 Mar-21 Apr 1995 16.3 39.5 60.5

On 9 May at 2003, one of the biggest explosions in the last year and a half took place--sufficiently large to capture the attention of local newspapers. The amplitude of the accompanying seismic signal recorded 23 km W of Arenal reached ~20x larger than a "normal explosion"; the signal took ~0.3 seconds to grow to maximum amplitude. The elevated signal from the 9 May seismic event lasted >1.2 minutes; in contrast, at this same station the elevated signal from a normal explosion lasts perhaps 0.1 minute.

Robust, monochromatic, 2.5 Hz tremor took place at least 40 minutes prior to the 9 May event. After the event, the tremor became spasmodic, and although the bulk of the energy remained at 2.5 Hz, there was also some centered around 2.0 and 3.2 Hz.

Glyn Williams-Jones and John Stix sent the following. "During the period from 20 February to 20 April 1995, CO2 and Rn soil gas samples and correlation spectrometer SO2 fluxes were measured on Arenal. Four lines of 19 soil gas stations consisting of meter-long, 7.6-cm-diameter PVC tubes and 1-cm-diameter metal tubes, buried to approximately 75 cm in the ground, were installed on the N, S, W, and E flanks of the volcano.

"Radon values are extremely low, ranging from 2values show a similar pattern, with proximal stations starting at 0.01% to a maximum of ~8% for the more distal stations. The more developed organic-rich soils appear to show higher values of CO2 and Rn, implying a possible organic or soil influence.

"The SO2 flux in the volcanic plume was measured using a Plume Tracker instrument, similar to a COSPEC correlation spectrometer. The instrument was mounted 'looking up' on a moving motor vehicle passing under the plume. Eleven days of SO2 data were collected, resulting in more than 100 measurements. The flux appears to be small but highly variable, with the highest measured value at 370 metric tons/day (t/d). The highest values were associated with explosive eruptions. Following eruptions, SO2 flux dropped to background levels of about 60 +- 10 t/d. Less apparent from the data is a possible gradual increase in SO2 output prior to an eruption.

"The values that we measured are comparable to those measured by Casadevall and others (1984) in 1 February 1982 (210 +- 30 t/d) and by Stoiber and others (SEAN 07:11) in November 1982 (~50 t/d). It is likely that these variations are related to changes in the volcano's activity."

Arenal's first chronicled eruption, in 1968, began an unbroken sequence of Strombolian explosions, and basaltic andesite discharges from multiple vents (see map in BGVN 18:08). The volcano lies adjacent to Lake Arenal, a dammed reservoir for generating hydroelectric power.

References. Casadevall, T.J., Rose, W.I., Fuller, W.H., Hunt, W.H., Hart, M.A., Moyers, J.L., Woods, D.C., Chuan, R.L., and Friend, J.P., 1984, Sulfur dioxide and particles in quiescent volcanic plumes from Póas, Arenal, and Colima volcanoes, Costa Rica and Mexico: J. Geophys. Res., v. 89, p. 9633-9641.

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

Information Contacts: Erick Fernandez, Vilma Barboza, and Jorge Barquero, Observatorio Vulcanologico y Sismologico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica; G.E. Alvarado, Waldo Taylor, and Gerardo J. Soto, Oficina de Sismologia y Vulcanologia del Arenal y Miravalles: OSIVAM; Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San José, Costa Rica; Glyn Williams-Jones and John Stix, Departement de Geologie, Universite de Montreal, Quebec, Canada, H3C 3J7.


Asamayama (Japan) — April 1995 Citation iconCite this Report

Asamayama

Japan

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

All times are local (unless otherwise noted)


First month with over 1,000 earthquakes since 1991

Last reported on in 1991 (BGVN 16:04), but one of Japan's most active volcanoes, Asama had an increase in seismicity during mid-April. On 17 April the seismic system at station B, 2 km S of the summit, recorded 107 earthquakes. After that, the daily number of earthquakes dropped to between about 10 and 80. The total number of April earthquakes at station B was 1031; the last month with over 1,000 detected earthquakes was April 1991 (1,051).

Asama has had over 100 explosive eruptions since ~350 AD. The vast majority of these eruptions have been assigned Volcanic Explosivity Index (VEI) values of 2-3, but several had VEI values of 4 or 5.

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: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.


Atmospheric Effects (1995-2001) (Unknown) — April 1995 Citation iconCite this Report

Atmospheric Effects (1995-2001)

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


Lidar data from Cuba

At Camaguey, Cuba, a volcanic aerosol layer was detected at 19-23 km altitude from 18 November through 28 December 1994 (table 2). Backscatter ratios (0.53 µm) were in the 1.26-1.40 range, with integrated backscatter values of 0.18-0.29 x 10-3. These data are similar to those acquired in Cuba during July-October 1994 (Bulletin v. 19, v. 10).

Table 2. Lidar data from Cuba showing altitudes of aerosol layers (bases only). Backscattering ratios are for the Nd-YAG wavelength of 0.53 µm. The integrated value shows total backscatter, expressed in steradians^-1, integrated over 300-m intervals from 16-33 km.

DATE LAYER ALTITUDE (km) (peak) BACKSCATTERING RATIO BACKSCATTERING INTEGRATED
Camaguey, Cuba (21.2°N, 77.5°W)
05 Nov 1994 18.1 (23.2) 1.38 0.22 x 10-3
09 Nov 1994 16.3 (25.0) 1.41 0.28 x 10-3
18 Nov 1994 18.4 (23.8) 1.40 0.25 x 10-3
24 Nov 1994 18.1 (22.6) 1.40 0.29 x 10-3
29 Nov 1994 17.5 (21.6) 1.42 0.29 x 10-3
03 Dec 1994 18.1 (22.0) 1.33 0.23 x 10-3
07 Dec 1994 18.4 (22.0) 1.33 0.18 x 10-3
17 Dec 1994 18.4 (22.6) 1.26 0.19 x 10-3
24 Dec 1994 17.8 (21.1) 1.39 0.22 x 10-3
28 Dec 1994 17.8 (19.0) 1.28 0.20 x 10-3

Geologic Background. 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 thorugh 1989. Lidar data and other atmospheric observations were again published intermittently between 1995 and 2001; those reports are included here.

Information Contacts: Juan Carlos Antuna, Centro Meteorologico de Camaguey, Apartado 134, Camaguey 70100, Cuba.


Barren Island (India) — April 1995 Citation iconCite this Report

Barren Island

India

12.278°N, 93.858°E; summit elev. 354 m

All times are local (unless otherwise noted)


Ash plumes from three vents; fire fountaining and lava flows

The GSI made an aerial survey on 2 March and a land survey on 8 March 1995 to monitor the ongoing eruption . . . . Surveys in late January revealed mainly Strombolian emissions from two vents near the S crater wall (figure 3; vents A and B). Lava flows had reached the sea by the end of January.

Figure (see Caption) Figure 3. Geologic sketch map of Barren Island showing lava flows and distribution of volcanic products from the 1995 and 1991 eruptions. Modified from Haldar and others (1992); courtesy of the GSI.

The GSI Photogeology and Remote Sensing Division analyzed seven Landsat TM IRS images . . . from November 1994 through February 1995. No signs of eruption were seen on 6 November or 8 December, but conspicuous activity was present on 29 December 1994. Vigorous activity was noted on 9 January. An image from 20 January showed decreasing emissions, but on 25 January the eruption was increasing again. Billowing smoke could be seen through gaps in the cloud cover on 11 February. The lava surface temperature was estimated to be well above 1,000°C on 9 and 25 January, based on preliminary analysis of a few thermally radiant pixels.

On 2 March aerial observers noted thick columns of dark to yellowish gray gas followed by white fumes gushing vigorously from the two vents active in late January. The gas column was rising ~1 km, and the eruption was confined to the S side of the summit crater. Denser air containing volcanic aerosols was encountered ~90 km WSW of the volcano at an altitude of ~2,100 m. Very dense air was noticed ~35 km W, and a very thick gas and smoke cloud was encountered ~15 km W at a height of ~1,500 m.

On 8 March the eruption was largely characterized by phreatomagmatic explosions. In addition to the two previously mentioned vents, the pre-existing conduit in the center of the 1991 crater (figure 3; vent C) was vigorously active. Huge billowing dark emissions from all three summit vents were followed by thick jets of white fumes at intervals of 30-60 seconds, with deep thundering explosions. The combined eruption column rose ~1.5 km before being blown SW by the wind into a horizontal plume. Space Shuttle astronauts observed this plume blowing generally W on 9 and 14 March (20:02).

A fourth vent had also opened at the S foot of the existing volcanic cone by 8 March (figure 3; vent D). It had constructed a small spatter cone from which thick lava was pouring out and a fire fountain was rising ~30 m. Ground temperature ~100-300 m from the foot of the cone was 62-83°C. Hot lava was cascading into the sea along the NW shore, ~200 m S of the landing site, causing the seawater to boil profusely. The lava front thickness had increased from ~6 m on 24 January to ~10 m on 8 March. Ejecta ranged in size up to 10 x 18 x 25 cm. Extensive ashfalls covered the S and W parts of the island, and ash was seen falling as far as 10 km S of the island. Marine life has not been seriously affected; fish were observed ~500 m from shore. Birds were also seen flying over the N part of the island.

Reference. Haldar, D., Laskar, T., Bandyopadhyay, P.C., Sarkar, N.K., and Biswas, J.K., 1992, Volcanic eruption of the Barren Island volcano, Andaman Sea: Journal of the Geological Society of India, v. 39, p. 411-419.

Geologic Background. Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S volcanic arc extending between Sumatra and Burma (Myanmar). It is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Information Contacts: Director General, GSI; Deputy Director General, GSI Eastern Region.


Deception Island (Antarctica) — April 1995 Citation iconCite this Report

Deception Island

Antarctica

63.001°S, 60.652°W; summit elev. 602 m

All times are local (unless otherwise noted)


Report from a 1994-95 austral summer survey

Deception has been monitored every austral summer since 1986; its flooded caldera forms a 5 x 9 km bay breached to the SW, giving Deception Island a ring shape. This report describes the 1994-95 summer survey, which included geophysical, geochemical, and volcanological work.

Near the Spanish Antarctic station "Gabriel de Castilla" a 500 x 600 m seismic array was deployed. Composed of three, 16-bit digital acquisition systems, the seismic array incorporated the following: 1) a Marck L15B with flat response between 1-48 Hz (12 vertical geophones and 4 horizontal geophones), 2) a Marck L4C with flat response between 0.1-48 Hz (two vertical geophones and four horizontal geophones), and 3) a broad-band, three-component Guralp CMG-3ESP with response between 0.033 and 48 Hz.

Figure 10 shows the acquired seismic data, which were collected from 7 December 1994 through 23 February 1995. The seismic data were subdivided into several groups on the basis of their time-domain and frequency-domain appearance. The resulting groups consisted of 262 volcanic tremors, 145 hybrid events, 300 low-frequency events, and 18 high-frequency (local) events (S - P time under 4 seconds). Applying classical array techniques, the preliminary locations for these events suggested that many came from two areas near 'Vapour Hill' (presumably located on the W side of the island at a spot previously designated 'Steaming Hill' on the map in BGVN 19:09).

Figure (see Caption) Figure 10. Deception Island seismicity, December 1994-February 1995. Courtesy of Alicia Garcia.

A summary of seismic events detected during previous surveys appears in table 2. Although seismic parameters were not always clearly delineated in previous BGVN reports, the seismic events registered in 1991 and 1992 were thought to have been less energetic than in 1994-95. Although the occurrence of earthquake activity was distributed throughout December, January, and February, the team observed at least 10 days with a notable increase in seismicity, days when volcanic swarms had average durations of ~3-6 hours. Given the absence of volcanic activity the researchers suggested that some of the seismicity may be contributed by thermally driven seasonal change.

Table 2. A summary of detected seismic events at Deception Island during austral summer surveys. "--" = not reported.

Season Duration (months) Total events recorded Magnitude SEAN/BGVN (Vol:No)
1987 2 -- ~0.5 mb 13:02
1988 2 -- ~0.5 mb 13:02
1988-89 3 more than 2,000 -- 14:03
1989-90 3 1,000 0.5-2.1 mb 15:03
1989-90 3 -- M 3.2 16:05
1991-92 3 766 0.8-2 (4 of M greater than 3) 17:04
1992-93 3 (?) 135 0.3-0.9 18:03
1993-94 3 "a few" 1.5-2 19:09
1994-95 3 725 -- 20:04

Although no data were presented, in addition to reoccupying the local gravimetric net, the magnetic field intensity was continuously recorded using three proton precession magnetometers.

Temperatures of fumaroles and hot soils remained stable with respect to those measured in the last survey. The anhydrous component of gases were mainly CO2 (96-99%) and H2S (0.2- 3.9%); SO2 was not detected.

Geologic Background. Ring-shaped Deception Island, one of Antarctica's most well known volcanoes, contains a 7-km-wide caldera flooded by the sea. Deception Island is located at the SW end of the Shetland Islands, NE of Graham Land Peninsula, and was constructed along the axis of the Bransfield Rift spreading center. A narrow passageway named Neptunes Bellows provides entrance to a natural harbor that was utilized as an Antarctic whaling station. Numerous vents located along ring fractures circling the low, 14-km-wide island have been active during historical time. Maars line the shores of 190-m-deep Port Foster, the caldera bay. Among the largest of these maars is 1-km-wide Whalers Bay, at the entrance to the harbor. Eruptions from Deception Island during the past 8700 years have been dated from ash layers in lake sediments on the Antarctic Peninsula and neighboring islands.

Information Contacts: J.M. Ibanez and J. Morales; Instituto Andaluz de Geofísica, Apartado 2145, Univ. Granada, Granada, Spain; A. Garcia and R. Ortiz, Dpto. Volcanologia. Museo Nac. Ciencias Naturales, C.S.I.C., Jose Gutierrez Abascal no. 2, 28006-Madrid, Spain; E. del Pezzo, Dpto. Fisica, Univ. Salerno, Salerno, Italy; C. Risso, Instituto Antartico Argentino, Cerrito 1248, Buenas Aires, Argentina.


Fogo (Cape Verde) — April 1995 Citation iconCite this Report

Fogo

Cape Verde

14.95°N, 24.35°W; summit elev. 2829 m

All times are local (unless otherwise noted)


Fire fountains continue but lava extrusion rate declines

On 2-3 April a fissure eruption began on Fogo Island from the SW flank of Pico cone (Fogo Peak) within the 8-km-diameter Cha Caldera (BGVN 20:03). During the initial stage of the eruption there was a burst or jetting of gas, followed by ejection of large blocks and fire fountaining. A lava flow cut off the main road to local villages by the morning of 3 April, and ash fell on the island. Approximately 1,300 residents in the caldera were evacuated.

Volcanologists from the United States, Portugal, and France were requested by the Cape Verdean government to help monitor and evaluate the activity. João Gaspar (Universidade dos Açores) and colleagues observed the activity until 11 April. U.S. Geological Survey (USGS) volcanologists, assisted by Cape Verdean geologists, installed a seismic station and monitored the eruption during 10-25 April. Additional information about the vent activity during 14-19 April was provided by Henry Gaudru and members of the Société Volcanologique Européenne who visited the volcano. François Le Guern (CNRS France) monitored the volcano on 25-27 April.

Summary of activity, 3-16 April. Detailed activity reports through 16 April have already been published (BGVN 20:03). Seven vents were active on the first day of the eruption, with fire-fountains feeding pahoehoe lava flows, ejection of volcanic bombs, and a gas-and-ash plume 2,000 m high. A scoria cone was soon built, from which lava flows were directed SW before turning NW towards the caldera wall. As the main aa flow approached the caldera scarp it turned N, covering the settlement of Boca de Fonte by 9 April and approaching Portela and Bangaeira (see map in BGVN 20:03). Less vigorous fire fountaining continued on 12-16 April, and fed new lava flows on top of the previous aa flow. There were occasional periods of Strombolian spatter ejections. By late on 16 April the remobilized flow-front was ~4 km from the source vent and only a little more than 500 m from the nearest house in Portela.

Activity during 17-25 April. Except where noted otherwise, the following observations are from the USGS team and their Cape Verdean colleagues. Activity continued on 17 April with little change at the vent. Spatter fountains rose 100-150 m, and the cone was ~150 m high. Volcanic tremor amplitude remained moderate to strong. The N end of the aa flow advanced ~150 m during 16-17 April, to ~420 m SW of the nearest house in Portela, and the E side of the flow moved 20-50 m ENE. The W side of the flow advanced >100 m and by 1430 had crushed half of the winery at Boca de Fonte. After these breakouts blocked the access road a new road was created through agricultural fields, forcing residents rescuing belongings to walk an additional 500 m. Flow movement was barely perceptible after 1430 and largely restricted to short spiny pahoehoe and aa oozes at flow margins, although lava output at the vent was unchanged.

Between 1630 and 2030 on 17 April, Gaudru noted that Strombolian explosions were less vigorous and that the main lava channel had widened from 2-3 m to 5-6 m because of lava-block obstructions. The W flank of the cone was also covered by cinders. Explosive activity increased at 1900, sending incandescent ejecta 150-200 m above the rim of the cone. A flame visible behind the E part of the cone was apparently coming from a small vent on the upper E flank. At 2000 explosions began ejecting material >300 m W instead of vertically.

Tremor amplitude began to increase around 0650 on 18 April, and at 0740 became continuous at about twice the previous amplitude. Eruptive style changed from fire fountaining to Strombolian activity, with spatter discharged by loud gas bursts every 3-8 seconds. Lava production increased during the morning; by noon the lava was largely pahoehoe in the upper 300 m of the channel. Estimated channel dimensions and the speed of lava in it yielded production rates of 4-8.5 x 106 m3/day. Microearthquakes were intermittent, with three larger events (all M <1) at 1314 and 1803 on 18 April, and at 0426 on 19 April.

Seismograph records showed that activity during 0110-0320 and 0426-0610 on 19 April was characterized by strong explosive bursts, which were interpreted to be vent clearing episodes after pieces of the cone and newly erupted spatter closed the conduit. After 0610 the seismicity indicated a return to fire-fountaining. A favorable wind direction permitted a close approach to the vent and lava channel to verify the volume estimate, but the lava appeared somewhat more viscous/sluggish. There was no measureable movement at the edges of the aa flow on 19 April after <3 m of movement the day before, however, lava continued ponding in its channel near the middle of the flow.

Observations made by Gaudru from 1230 on 18 April until 1230 on 19 April indicated that activity remained strong with incandescent fragments rising >200 m and loud detonations. Explosions every 1-2 seconds, accompanied by earthquakes, ejected particles ranging in size up to >1 m3. Gas outbursts were more intense, and black plumes hovered over the active cone. Partial obstruction of the crater caused a larger explosion at 1745 on 18 April that sent gas and cinders 500-600 m high. After several seconds of quiet, stronger explosive activity began again with sounds that shook the ground. The upper E flank crater sent an intermittent orange-red flame 10-15 m high for several hours during this period, higher than previous days. Eruptive activity observed by the Gaudru group became more regular at 0100 on 19 April, when an intense episode began that sent lava fountains >300 m high for several hours. Explosive activity began again at dawn that lasted throughout the morning of 19 April.

Tremor amplitude on 19 April changed from moderate-strong to moderate around 1500, when Strombolian activity reverted back to fire fountains. Fire fountain heights diminished somewhat on 20 April, rising generally 20-50 m above the vent. Intermittent Strombolian activity continued with more energetic bursts that sent viscous lava clots >160 m high. A full lava channel 200 m W of the vent appeared much like it did the day before. A new aa lobe was moving sluggishly on top of the earlier flow, and by 1700 its distal end was ~600 m from the N end of the flow, nearest to Portela.

Strong Strombolian activity on 21 April produced loud bursts of viscous spatter 50-150 m high. A levee formed on top of the spillway adjacent to the vent behind which fountains rose 10-20 m, often interrupted by explosions. Lava exited through a hole in the bottom of the levee into a W-flank channel roofed over in two places. At the bottom of the spillway the lava entered a sinuous channel, moving W and NW on top of the previously emplaced flow; this channel remained full all day. The volume of lava erupted was similar to values for the past several days, 4-8 x 106 m3/day. The 160-m-high cinder cone was no longer increasing significantly in height, but impact craters as large as 5 m wide and 1 m deep, created by fall of spatter bombs 0.5-2 m across, littered its flanks and parts of the cinder-mantled caldera floor up to 200 from the vent. As is common during eruptions of viscous mafic lava, the inner walls of the cone collapsed into the conduit, resulting in explosive vent-clearing episodes. The overriding aa flow on the E side of the N flow moved another 6 m N during 21 April.

Volcanic tremor on 21-22 April continued at moderate to strong levels, punctuated by frequent sonic bursts. Noisy Strombolian bursts sent clots of spatter over the top of the cone and onto its flanks. The volume of lava flowing into the channel was similar to that of 21 April. At noon, lava from a new crack on the N flank of the cone flowed 150 m N and soon stagnated. The aa flow advanced 2 m W near the new end of the road (150 m S of Boca de Fonte), and ~3 m NE on the E side of the N flow. Most of the volume of lava was concentrated in an aa lobe that was very slowly overriding the earlier flow. This lobe locally was at least 15 m thick and covered an estimated 75% of the existing flow field.

Activity on 23 April was spectacular. Deafening explosions from four discrete vents rocked the caldera all day; at times the ground was in continuous motion from concussion waves. The overriding aa lobe only moved ~4 m N on the E side of the main aa flow. However, early in the afternoon a new vent opened at the NW base of the cone. By 1700 lava was flowing W from this vent, and by 1807 spatter ejected to heights of 10-15 m was visible. Pahoehoe lava flowed on top of older aa and soon joined the large stagnating aa channel 500-700 m from the main cone. For the preceding 4 days the seismograph had recorded sonic bursts and microseisms. It was believed that shock waves associated with the bursts caused several fractures on the cone. One of these cracks provided a new pathway for lava to exit the cone, thus robbing the main channel of most of its lava. Strong volcanic tremor was interrupted by frequent sonic bursts.

Moderate to strong tremor continued on 24 April. At the main cone in the morning, Strombolian bursts every few seconds sent spatter fragments onto the cone's flanks. In the afternoon, the intense sonic bursts and Strombolian activity that had characterized the past few days were absent. A gray-black plume, laden with fine-grained (<1 mm) juvenile particles and volcanic gases, rose to heights approaching 1.5 km above the caldera floor. Lava in relatively low volumes continued to erupt from the NW base of the cone, moving horizontally from the cone into a tear-shaped cavity. Once the lava reached the surface, degassing occurred, at times intensely enough to drive low-level Strombolian activity. The amount of visible degassing rivaled the plume from the main vent. The depression and lava chute were 25-35 m long and 1-2 m wide. Lava moving at 1 m/s then spilled out of the chute and entered a channel, which was 3-5 m wide, with a speed of 6 m/minute. The flow in the chute and lava channel was initially pahoehoe, changing to aa with increasing distance. The new lava channel joined the former channel, now stagnant in its upper part, 500-700 m below the cone. This new channel caused the hydraulic head within the main cone to be lowered, resulting in decreased Strombolian activity.

By 25 April the lava extrusion rate slowed to ~250,000 m3/day, and tremor amplitude was somewhat diminished. Spatter generally was not visible within the cone and only rarely did isolated fragments clear its top. However, lava that had ponded in the aa channel advanced on the S side of the earlier large flow. This advance, which probably began late on 24 April, moved as much as 0.5 m/minute during the afternoon. Most of the new lobe was aa, with minor pahoehoe. The thermocouple temperature was 1,065°C (steady for several minutes) in the pahoehoe. At about 1500-1700 loud explosions at vents within the main cone increased in frequency, although spatter output did not change.

Activity in late April-early May. At the request of the Cape Verde government, the French Embassy in Praia and the Ministere de l' Environnement in Paris arranged for François Le Guern (CNRS) to observe the activity during 25-27 April. Incandescent scoria fountains rose 50 m over the crater 5-10 times/day followed by quiet periods. Sometimes explosions with black ash or transparent brown or blue haze lasted a few tens of minutes. Lava output was estimated to be 1 x 106 m3/day on 26 April with a lava front 300 m long, decreasing by 10-15% on the following days. On 27 April lava advanced <0.5 m/hour.

From late April through 2 May a team from the International Federation of Red Cross and Red Crescent Societies reported that lava continued to flow from the crater, though at a much reduced rate, and had already covered 5 km2 of cultivated land including five houses and a winery that was a major source of income for the displaced. At that time the flow was contained inside the existing banks of lava. News reports indicated that after a period of non-explosive emissions and weak lava flow production, the eruption strengthened slightly on 7 May with greater lava output. On 8 May the United Nations coordinator in Praia reported decreased activity with some explosions and moderate to strong tremor. The lava emission rate was relatively low, coming from vents at the NW base of the cone.

Displaced persons and future plans. Apart from the destruction to outlying buildings, the villages themselves remained intact but largely deserted in early May. During the day there was regular foot traffic as people removed items of use to the camps, including livestock. The Red Cross of Cape Verde has volunteers in four camps containing 157 families. The camps are: Sao Filipe, population 534 (including 313 children); Patim, population 88 (53 children); Achada Furna, population 156 (90 children); and Mosteiros, population 90 (55 children). Adding the ~150 people living with friends and relatives, the total number of displaced person comes to 1,014. These numbers fluctuate as people return to the area and re-evacuate following felt earthquakes.

With emergency needs met, government officials believe that the focus should be on the resettlement of displaced persons. The United Nations DHA-Disaster Mitigation Branch was focusing on civil protection preparedness planning for future volcanic eruptions and other natural disasters.

On 10 May, at the request of the Cape Verde government, a team of four geologists and two students from the Universidade dos Açores went to Fogo to study the eruption. Their objectives are to monitor the progress of the eruption and to begin research related to gas release and the risks of contamination of public water supplies.

Geologic Background. The island of Fogo consists of a single massive stratovolcano that is the most prominent of the Cape Verde Islands. The roughly circular 25-km-wide island is truncated by a large 9-km-wide caldera that is breached to the east and has a headwall 1 km high. The caldera is located asymmetrically NE of the center of the island and was formed as a result of massive lateral collapse of the ancestral Monte Armarelo edifice. A very youthful steep-sided central cone, Pico, rises more than 1 km above the caldera floor to about 100 m above the caldera rim, forming the 2829 m high point of the island. Pico, which is capped by a 500-m-wide, 150-m-deep summit crater, was apparently in almost continuous activity from the time of Portuguese settlement in 1500 CE until around 1760. Later historical lava flows, some from vents on the caldera floor, reached the eastern coast below the breached caldera.

Information Contacts: R. Moore, U.S. Geological Survey, Mail Stop 903, Federal Center Box 25046, Denver, CO 80225 USA; Frank Trusdell, U.S. Geological Survey, Hawaiian Volcano Observatory, Hawaii National Park, HI 96718, USA; Veronica Carvalho Martins, U.S. Embassy, Rua Hoji Ya Henda 81, C.P. 201, Praia, Cape Verde; Arrigo Querido and Helena Tatiana Osorio, INGRH Servicos Estudos Hidrologicos, C.P. 367, Praia, Cape Verde; François LeGuern, CNRS Centre des Faibles Radioactivités, 91190 Gif-sur-Yvette, France; João Gaspar and Nicolau Wallenstein, Departamento Geociências, Universidad dos Açores, rue da Mae de Deus 58, 9500 Ponta Delgada, Açores, Portugal; Henry Gaudru, Christine Pittet, Patrick Barois, and Marc Sagot, Société Volcanologique Européenne (SVE), C.P. 1, 1211 Geneva 17, Switzerland; United Nations Department of Humanitarian Affairs, Palais des Nations, 1211 Geneva 10, Switzerland; International Federation of Red Cross and Red Crescent Societies, C.P. 372, 1211 Geneva 19, Switzerland.


Galeras (Colombia) — April 1995 Citation iconCite this Report

Galeras

Colombia

1.22°N, 77.37°W; summit elev. 4276 m

All times are local (unless otherwise noted)


Earthquake swarm continues; higher pressure gas emissions

Volcanic activity was relatively low in April. During approximately 1-20 April there was an increase in the pressure of gas emissions. Heavy rains on 12 and 18 April caused mudflows along the W-flank Azufral river that reached heights of 5 and 15 m, respectively, above the usual water level in narrow sections of the canyon. These two events were detected by the seismic network at Galeras.

A high-frequency earthquake swarm (magnitudes up to 2.3) on 14 April associated with rock fracturing (15 events within 100 minutes) was located at depths of 1.5-4 km below the summit. Ten other high-frequency events had dispersed epicenters at depths of <5 km. Four nearly monochromatic long-duration earthquakes with slowly decaying codas (screw-type events) occurred during 19-20 April. Screws were not detected after increased gas emissions on 22 April sent a plume ~2 km high that was seen from Pasto (~9 km E).

The earthquake swarm NNE of the active crater that began in March continued in April, but with fewer and lower-magnitude events. However, there were two events felt in Pasto and in the towns of Jenoy and Narino on 3 and 27 April. By the end of April there had been 1,967 events from this source since 4 March, of which 67 were felt in small towns near the epicenter.

Geologic Background. Galeras, a stratovolcano with a large breached caldera located immediately west of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Long-term extensive hydrothermal alteration has contributed to large-scale edifice collapse on at least three occasions, producing debris avalanches that swept to the west and left a large horseshoe-shaped caldera inside which the modern cone has been constructed. Major explosive eruptions since the mid-Holocene have produced widespread tephra deposits and pyroclastic flows that swept all but the southern flanks. A central cone slightly lower than the caldera rim has been the site of numerous small-to-moderate historical eruptions since the time of the Spanish conquistadors.

Information Contacts: INGEOMINAS-Observatorio Vulcanologico y Sismologico de Pasto (OVP), Apartado Aereo 1795, San Juan de Pasto (Narino), Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html).


Irazu (Costa Rica) — April 1995 Citation iconCite this Report

Irazu

Costa Rica

9.979°N, 83.852°W; summit elev. 3432 m

All times are local (unless otherwise noted)


Rainfall-induced mass wasting and three seismic events

OVSICORI-UNA reported that, with respect to January, the lake level in April dropped 50 cm. The greenish yellow lake constantly bubbled on its N, NE, W, and SW shores. Small landslides took place along the crater's N, E, and SW walls.

On the NW flank, where there had been a small phreatic eruption vented from a well-established fumarole in December 1994, fumaroles remained active at both the eruption site and on the adjacent crater's N wall. Rainfall caused new mass wasting that sent debris into the Rio Sucio.

ICE reported that Mauricio Mora recorded three seismic events in the vicinity of the volcano. These appeared similar to tectonic earthquakes; their hypocenters fell within about 10 km of Irazú's main crater.

Geologic Background. Irazú, one of Costa Rica's most active volcanoes, rises immediately E of the capital city of San José. The massive volcano covers an area of 500 km2 and is vegetated to within a few hundred meters of its broad flat-topped summit crater complex. At least 10 satellitic cones are located on its S flank. No lava flows have been identified since the eruption of the massive Cervantes lava flows from S-flank vents about 14,000 years ago, and all known Holocene eruptions have been explosive. The focus of eruptions at the summit crater complex has migrated to the W towards the historically active crater, which contains a small lake of variable size and color. Although eruptions may have occurred around the time of the Spanish conquest, the first well-documented historical eruption occurred in 1723, and frequent explosive eruptions have occurred since. Ashfall from the last major eruption during 1963-65 caused significant disruption to San José and surrounding areas.

Information Contacts: Erick Fernandez, Vilma Barboza, and Jorge Barquero, Observatorio Vulcanologico y Sismologico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica; Gerardo J. Soto, Oficina de Sismologia y Vulcanologia del Arenal y Miravalles (OSIVAM), Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San Jose, Costa Rica; Mauricio Mora, Escuela Centroamericana de Geologia, Universidad de Costa Rica.


Kanaga (United States) — April 1995 Citation iconCite this Report

Kanaga

United States

51.923°N, 177.168°W; summit elev. 1307 m

All times are local (unless otherwise noted)


Occasional mild steam plumes

As of 31 March, observers in Adak (33 km E) continued to report occasional mild steam plumes above the summit. Through 31 March no thermal anomaly had been detected since 13 October 1994 when eruptive activity that began in December 1993 apparently ceased (BGVN 18:12 and 19:11). That eruption was characterized by intermittent, low-level steam and ash emissions producing plumes rarely rising over 3,000-4,500 m altitude and drifting a few tens of kilometers downwind. There are no seismometers on Kanaga, located 965 km WSW of the tip of the Alaska Peninsula on Kanaga Island, and monitoring is done through a combination of satellite image analysis and observations by pilots and residents of Adak.

Geologic Background. Symmetrical Kanaga stratovolcano is situated within the Kanaton caldera at the northern tip of Kanaga Island. The caldera rim forms a 760-m-high arcuate ridge south and east of Kanaga; a lake occupies part of the SE caldera floor. The volume of subaerial dacitic tuff is smaller than would typically be associated with caldera collapse, and deposits of a massive submarine debris avalanche associated with edifice collapse extend nearly 30 km to the NNW. Several fresh lava flows from historical or late prehistorical time descend the flanks of Kanaga, in some cases to the sea. Historical eruptions, most of which are poorly documented, have been recorded since 1763. Kanaga is also noted petrologically for ultramafic inclusions within an outcrop of alkaline basalt SW of the volcano. Fumarolic activity occurs in a circular, 200-m-wide, 60-m-deep summit crater and produces vapor plumes sometimes seen on clear days from Adak, 50 km to the east.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA, 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.


Kilauea (United States) — April 1995 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


Lava flows, breakouts, tremor, and more

The 12-year-long eruption on Kilauea's E rift zone continued in March-April, with vents on the SW flank of the Pu`u `O`o cone feeding directly into lava tubes. Recent heights of the lava lake are at the bottom of table 4 and a map showing recent flows appears on figure 97 (for comparison, the previous map appeared in BGVN 20:02).

Table 4. Summary of Kilauea seismic data, lava flux rate, and lava pond heights for stated dates or intervals in 1995. Courtesy of HVO.

Date/Interval Observation Type Comment
Late Feb-03 Mar 1995 Earthquakes Intermediate depth activity remained high, slowly decaying to background levels.
Late Feb-10 Mar 1995 East Rift Zone Tremor Tremor with stable amplitudes ~3-4x background.
03 Mar 1995 Pu`u `O`o lava pond 79 m below rim.
10 Mar 1995 East Rift Zone Tremor Tremor dropped to 2x background with intermittent bursts of higher amplitude (similar to banded tremor) at 1900.
14 Mar-15 Mar 1995 Earthquakes In a 37-hour period beginning at 0900 on 14 March there were 134 intermediate-depth events.
14 Mar-27 Mar 1995 East Rift Zone Tremor Tremor continued.
19 Mar 1995 Earthquakes M 4.3 earthquake at ~50 km depth, W of the Island of Hawaii.
21 Mar 1995 Pu`u `O`o lava pond 75 m below rim.
27 Mar 1995 Earthquakes M 4.1 earthquake at 25 km depth beneath the upper E rift zone.
28 Mar-10 Apr 1995 East Rift Zone Tremor Tremor fairly constant at 2-3x background.
28 Mar-10 Apr 1995 Pu`u `O`o lava pond 75-81 m below rim.
11 Apr-24 Apr 1995 Earthquakes Shallow, long-period microearthquake counts were slightly above average. The number of short-period events was low.
11 Apr-24 Apr 1995 East Rift Zone Tremor Tremor continued, amplitudes were low, ~1.5-2x background. Shallow, long-period microearthquake counts were slightly above average.
11 Apr-24 Apr 1995 Pu`u `O`o lava pond 90-86 m below rim. Continued lava circulation from W to E in the pond.
03 May 1995 Earthquakes Swarm of 13 located earthquakes, the largest M 3.9; they were interpreted as shallow crustal adjustments beneath Hilina Pali.
10-30 Apr 1995 Lava flux rate ~400,000 m3/day (Volcano Watch, 1995).
Figure (see Caption) Figure 97. Kilauea lava flows grouped into three time intervals: 1983 to 1992; 1992 to April 1995; and 11-20 April 1995. Heavy dashed line indicates lava tubes, and the contour interval is 500 m. Courtesy of USGS.

During 28 February-13 March fluid pahoehoe breakouts spread W and covered more of the Chain of Craters road. The eruption slowed during 14-16 March. Flows became more viscous and the amount of lava entering the ocean dwindled. On 16 March, cooler temperatures were measured on a thermocouple hanging through an opening in the roof of an active lava tube. By the morning of 17 March all flows entering the sea had temporarily stopped, but temperatures rose to normal values in the active tube and by early afternoon lava began escaping the tube system at three elevations; one reached within 500 m of the highway by 27 March.

In the 24 March-10 April interval, two tubes diverging toward the E and W sides of the flow field, the Kamoamoa and the Lae'apuki tubes, respectively, continued to feed flows on the coastal plain. The Highcastle lava flow escaped from the E tube (figure 97), advancing toward the ocean as a sheet flow, covering the lower part of another recent flow (the Jason flow), and reaching the ocean on 29 March. By 6 April, the Highcastle flows had built a 500-m-wide lava bench 20-30 m oceanward. On 7 April, a large breakout from the 104-m elevation on Paliuli headed towards the ocean on top of previously emplaced flows. By 8 April, flows on the coastal plain had stilled and the amount of lava entering the ocean decreased. The east rift zone eruption paused briefly on 11 April and flows on the coastal plain stagnated.

When the eruption later resumed, lava broke out of the tube system on Pulama pali, feeding numerous aa and pahoehoe flows. Two lava flows entered the ocean on about 18-20 April. Pahoehoe lava engulfed an older cone that had been created by littoral explosions in July 1994, leaving only a remnant of the cone visible on 20 April. The following day, a seismic station in the coastal area recorded a bench collapse-littoral explosion and at the same time observers saw the steam plume abruptly increase in size.

On the topic of a public policy issue relevant to volcanologists and public access to volcanoes, in 1992 US and local government personnel rescued a movie cameraman trapped on a ledge above Pu`u O`o lava lake. Although rescue workers were cited for valor, an Associated Press news report (Miller, 1995) also mentions how local authorities made subsequent attempts to gain partial reimbursement for $75,000 in rescue expenses. These latter efforts were unsuccessful. According to the news story, in the United States two strategies appear to have emerged for dealing with rescue and related costs: 1) stiff fees paid by park users (eg. $150 for a climbing permit in Denali National Park, Alaska), and 2) rules or laws that specifically dictate that fees be billed to those rescued.

References. Miller, Angela S., 1995, When Risk Leads to Rescue, Who Pays the Cost?: Associated Press, 10 February 1995.

Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: Tari Mattox and Paul Okubo, USGS Hawaiian Volcano Observatory, Hawaii Volcanoes National Park, HI 96718, USA.


Langila (Papua New Guinea) — April 1995 Citation iconCite this Report

Langila

Papua New Guinea

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

All times are local (unless otherwise noted)


Ash clouds to several hundred meters above the crater

Monitoring of Langila resumed on 3 April following a lapse from 18 March to 2 April. Up to that time, activity at Crater 3 remained low and activity at Crater 2 continued at a moderate level. After the lapse in monitoring, Crater 2 continued to emit white vapors in low to moderate volumes. Gray ash clouds were occasionally emitted to several hundred meters above the crater. Occasional rumbling sounds and night time glows were normally associated with the ash emissions. Loud explosions were heard on 3 and 30 April. Ashfall NW of the volcano (in the Kilenge area) was reported on 11 April. Crater 3 released thin white vapor accompanied by wisps of blue vapor on 12, 14, 21, and 27 April. There were neither audible sounds nor night glows. Both seismographs remained inoperative during the month.

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

Information Contacts: David Lolok and Ben Talai, RVO.


Manam (Papua New Guinea) — April 1995 Citation iconCite this Report

Manam

Papua New Guinea

4.08°S, 145.037°E; summit elev. 1807 m

All times are local (unless otherwise noted)


Both seismicity and tilt low; gently steaming

Although activity at Manam remained low in April, throughout the month both Main and Southern Craters infrequently discharged white vapor. Southern Crater discharged wispy blue vapor on the 11th; faint rumbling sounds were heard on one occasion only (at 2330 on 23 April); weak night glow was seen mainly during the 2nd and 4th weeks of April, when then summit was clearly visible. Main Crater issued occasional, thin to thick white vapors. These emissions were gentle and were not accompanied by night glow or audible sounds. The seismicity fluctuated at a low level throughout the month. No significant change was shown by the water-tube tiltmeter located about 4 km SW from the summit.

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical basaltic-andesitic stratovolcano to its lower flanks. These valleys channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most observed eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Information Contacts: David Lolok and Ben Talai, RVO.


Momotombo (Nicaragua) — April 1995 Citation iconCite this Report

Momotombo

Nicaragua

12.423°N, 86.539°W; summit elev. 1270 m

All times are local (unless otherwise noted)


Fumarole chemistry and temperature data for 1983 and 1995

On 25 February 1995 Lucano Giannini and Orlando Vaselli (University of Florence) visited the crater of Momotombo to collect fumarolic gas samples. The chemical composition of the gases at the highest observed temperature is shown on table 4. Also shown for comparison are values obtained in 1983, when seismic activity, ground deformation, and subsurface basaltic magma emplacement took place. The temperature decrease and gas compositional changes were thought to mainly reflect the twelve years of cooling.

Table 4. Chemical analyses on Momotombo fumaroles, 1983 and 1995. Courtesy of Marino Martini, University of Florence.

Component 1983 1995
Temperature (°C) 835 660
H2O (volume %) 94.00 91.18
CO2 (dry gas %) 56.95 72.79
SO2 (dry gas %) 22.33 8.72
H2S (dry gas %) 5.00 3.87
HCl (dry gas %) 5.83 6.25
HF (dry gas %) 0.30 0.36
B (dry gas %) 0.081 0.018
Br (dry gas %) 0.0088 0.0073
NH4 (dry gas %) 0.0088 0.0038
H2 (dry gas %) 8.47 5.12
N2 (dry gas %) 0.78 2.73
CO (dry gas %) 0.25 0.12

Geologic Background. Momotombo is a young stratovolcano that rises prominently above the NW shore of Lake Managua, forming one of Nicaragua's most familiar landmarks. Momotombo began growing about 4500 years ago at the SE end of the Marrabios Range and consists of a somma from an older edifice that is surmounted by a symmetrical younger cone with a 150 x 250 m wide summit crater. Young lava flows extend down the NW flank into the 4-km-wide Monte Galán caldera. The youthful cone of Momotombito forms an island offshore in Lake Managua. Momotombo has a long record of Strombolian eruptions, punctuated by occasional stronger explosive activity. The latest eruption, in 1905, produced a lava flow that traveled from the summit to the lower NE base. A small black plume was seen above the crater after a 10 April 1996 earthquake, but later observations noted no significant changes in the crater. A major geothermal field is located on the south flank.

Information Contacts: Marino Martini, University of Florence, Italy.


Poas (Costa Rica) — April 1995 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Two new hot springs; moderate number of earthquakes and tremor

Fumarolic activity continued at Poás in the active, northern crater lake. OVSICORI-UNA reported the lake level rose 50 cm in April with respect to March. When observed in April, the lake appeared light green and had a temperature of 41°C. On small areas along the lake's NW and W shore, small bubbles escaped continually. A low (less than 50-m tall) steam cloud hovered over the lake.

On the lake's SW terrace there were two new intermittent springs (74°C and 64°C) that were light-gray in color, presumably caused by suspended sediment. On the S terrace, fumaroles continued to emit gases and on the SW side there appeared a new fumarole with a 74°C temperature. The pyroclastic cone gave off gas that had a 89°C temperature.

Low-frequency seismicity at Poás in April declined by about 15% compared to March (table 6). Tremor began on about 8 March and the monthly duration reached 11 hours, more than the past few months but significantly less than the tens or hundreds of hours recorded during the months of May-September 1994.

Geologic Background. The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: Erick Fernandez, Vilma Barboza, and Jorge Barquero, Observatorio Vulcanologico y Sismologico de Costa Rica, Universidad Nacional (OVSICORI-UNA); Gerardo J. Soto, Oficina de Sismologia y Vulcanologia del Arenal y Miravalles: OSIVAM; Instituto Costarricense de Electricidad (ICE); Mauricio Mora, Escuela Centroamericana de Geologia, Universidad de Costa Rica.


Popocatepetl (Mexico) — April 1995 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


Located seismic events and summit crater observations

"We report on Popocatepetl seismic activity during the interval 21 December 1994 to 2 May 1995. Activity was monitored using seven seismic stations located around to the volcano above 2,600 m elevation (figure 9). These stations are part of the Popocatepetl Seismic Network. Beginning 21 December, the volcano changed dramatically in its seismic and fumarolic activity. Several explosions emitted ash that fell on Puebla City, an area located about 50 km away. About 22 hours after this activity, seismic tremor was observed for the first time at several stations.

Figure (see Caption) Figure 9. Stations of the Popocatepetl Seismic Network (triangles) and epicenters for located events detected 21 December to 2 May 1995 (dots). Courtesy of Instituto de Geofisica, UNAM.

"In the 21 December-2 May interval we located 75 seismic events in the vicinity of the volcano (figure 9). We used arrival times from digital records from at least three stations and located the events using Hypocenter software. The average standard location errors in the horizontal and vertical directions do not exceed 1 km with a standard deviation of 0.14 km (figure 10). Earthquake magnitudes (calculated using a coda length magnitude for tectonic events in Mexico) ranged between 1.4 and 3.4 (as represented by different sized dots on figure 10). The E-W cross section of the hypocenters (figure 10) shows a concentration of seismic events in a circle of 3.0 km diameter and in a conduit that connects to the overlying crater. These results crudely suggest a magma chamber located below sea level and connected to the volcano crater. A N-S cross section suggests the same findings.

Figure (see Caption) Figure 10. An E-W cross section of the hypocenters beneath Popocatepetl for the interval 21 December 1994 to 2 May 1995. Earthquake magnitudes are shown by dot sizes; the size of error bars are discussed in the text. Courtesy of Instituto de Geofisica, UNAM.

"During the first four days (21-24 December) seismic tremor was continuous and of high amplitude. During the following 20 days (25 December-13 January) tremor was also continuous, but the amplitude diminished five-fold compared to the first four days. After that, in the next 45 days (14 January-28 February), tremor turned sporadic with durations of about 10 minutes and with amplitudes comparable to those in the first four days. During the last 60 days, tremor became more sporadic with smaller durations, but it still had amplitudes similar to, and in some cases exceeding, those of the first four days.

"On 12 March an expedition lead by Enrique Chaves-Popuard reached the volcano's summit. The meteorological conditions allowed the team to videotape the interior of the crater. The following observations were made: a) the crater lake disappeared, b) three new craters appeared at the foot of the main crater's E wall, c) most of the fumarolic emissions came from these new craters, d) the number of small fumarolic vents has increased in the older inner crater, and e) several fumarolic vents were observed in the S and E walls of the main crater."

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

Information Contacts: Carlos Valdes-Gonzalez, Guillermo Gonzalez-Pomposo, and A. Arciniega-Ceballos, Departamento de Sismologia y Volcanologia, Instituto de Geofisica, UNAM, Ciudad Universitaria 04510 D.F., Mexico.


Rabaul (Papua New Guinea) — April 1995 Citation iconCite this Report

Rabaul

Papua New Guinea

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

All times are local (unless otherwise noted)


Tavurvur explosions stop on 16 April

Two strong explosions took place at the intra-caldera cone Tavurvur on 30 March; after that, the repose intervals between explosions at Tavurvur lengthened, lasting from several hours to more than 24 hours. Tavurvur discharged several noteworthy explosions on 13-15 April; explosions ceased on 16 April.

During the first half of April, explosions sent ash clouds 1-2 km above the crater, but they were typically spasmodic and relatively mild. Ash predominantly fell to the SE (mainly over Talwatt and occasionally at Kokopo, with smaller amounts in Rabaul on a few days). Accompanying the normally gray ash emissions were weak roaring sounds heard late on the 3rd, low rumbling sounds on the 9th, and lightning seen in and around the billowing ash column on the 11th.

At 1206 on 13 April an impressive explosion occurred. It began with fast-rising, spear-headed jets of dark ash, which fed a billowing ash cloud that rose to about 2 km above the crater. Some ballistic blocks landed in the bay immediately W and NW of Tavurvur. On 14 April, moderate-to-strong explosions started at about 0920, with the most intense activity occurring between 1030 and 1040. Resulting eruption clouds were dark gray and quite dense; fallout was heavy at Tavurvur and immediately downwind (SE). In and around the eruption column, lightning was noted. The activity declined slowly through the day and stopped at about 2320.

Strong explosions resumed at about 1320 on 15 April. During a roughly 1 hour period, several large eruption clouds rose to about 2 km. These ash clouds remained intact as they drifted to the SE. Prolonged moderate ash emission also took place from early to mid-afternoon. During the early hours of 16 April, mild explosive activity took place; it stopped at about 0600. From that time onward activity chiefly consisted of weak white vapor emissions. Following a period of heavy rainfall on the 24th, however, these emissions again became more voluminous, but by the next day they returned to a very low level.

Seismicity in the first half of April, until the 16th, partly consisted of low-frequency earthquakes associated with Tavurvur's explosions. Explosion sizes appeared to correspond to earthquake amplitudes. Six high-frequency earthquakes also occurred (compared to 5 in March and 4 in February). These earthquakes all had epicenters outside the caldera--five to the N-NE and one to the SW.

During April, electronically measured tilt in the interior of the caldera at Matupit Island continued to show a trend of very slow deflation. Other ground deformation measurements failed to show significant trends.

An aerial inspection, on 8 April, revealed that Tavurvur's surface was covered with fresh black ash. Numerous gray blocks had also landed, mainly on the S flank and inside the old crater. The fumarole previously emitting blue-vapor (located about 1/3 of the way down the 1994 lava flow) was inactive. One white-vapor fumarole was noted where the lava had advanced over the crater rim. The crater displayed variably colored sublimate deposits and small erosional gullies. A step-like structural form was seen on the crater's E side, and a smooth, bowl shape was seen on its W side. Inside the crater there were neither visible vents nor a lava mound.

Vulcan continued weak white vapor emissions, coming mainly from the crater of the 1994 cone. Fumaroles at the base of the 1994 crater had been mostly buried by mud leaving only one on the W side of the crater. The upper one of the two pit craters on the N flank of the 1994 cone had caved in. Temperature of hot springs along the N shore were consistent with previous months' readings at ~100°C.

The State of Emergency in Rabaul was lifted on 10 April, making way for the Gazelle Restoration Authority to promote the rehabilitation process.

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

Information Contacts: David Lolok and Ben Talai, RVO


Rincon de la Vieja (Costa Rica) — April 1995 Citation iconCite this Report

Rincon de la Vieja

Costa Rica

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

All times are local (unless otherwise noted)


Description of the crater lake and fumaroles

The remote Rincón de la Vieja volcanic complex continues to display unsettled seismic and fumarolic activity. OVSICORI-UNA reported that during April fumarolic venting continued from the W wall, creating noise audible from the crater's rim. Escaping gases stung the skin. Radial fractures encircled the crater on its NE, N, and NW sides.

G. Soto (ICE), Jean-Philippe Rancon, and Gorges Boudon climbed the volcano on 1 May and reported that the lake contained a scum of floating sulfur and was pale turquoise in color. No lake temperature measurements were made but the entire surface steamed slightly. In contrast to a previous visit in March 1994, the lake level seemed significantly higher, although the amount has yet to be quantified from photographic records; zones of bubbling (previously several meters across) were absent.

Fumaroles on the crater's inner SE wall were quite active and fumed noiselessly. Gas plumes, clearly visible from the volcano's N flank, rose up to 100 m above the crater before being blown by the wind. Small, steam-rich fumaroles adjacent to concentric fractures surrounded the crater, typically near the 1,640 m contour. These fumaroles were also active last year.

At least two other noteworthy fumaroles, expelling steam and sulfurous gases, sit on the N flank (along the valley called Quebrada Azumicrorada at around 1,200- and 1,300-m elevation). In clear weather, these fumaroles are visible from local villages and residents stated that they had been active for the past several years.

Geologic Background. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A Plinian eruption producing the 0.25 km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Information Contacts: Erick Fernandez, Vilma Barboza, and Jorge Barquero, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica; Gerardo J. Soto, Oficina de Sismologia y Vulcanologia del Arenal y Miravalles: OSIVAM; Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San José, Costa Rica; Jean-Philippe Rancon, BRGM, Orleans, France (presently at USGS Cascades Volcano Observatory, 5400 MacArthur Blvd., Vancouver, WA 98661-7095 USA); Georges Boudon, Observatoires Volcanologiques, Institut de Physique du Globe de Paris, 4 Place Jussieu, 75252 Paris 05, France.


Ruapehu (New Zealand) — April 1995 Citation iconCite this Report

Ruapehu

New Zealand

39.28°S, 175.57°E; summit elev. 2797 m

All times are local (unless otherwise noted)


Crater lake temperature drops 10°C from 13-year high

The following was extracted from the IGNS Ruapehu Immediate Report (RUA 95/02). Peaks on the crater lake temperature versus time curve have often correlated to small vent-clearing eruptions (see figure 16).

"Crater Lake has been in a heating phase since late November, reaching the highest temperature (55°C) in 13 years by 12 February, but a 10°C decline since then and a reduction in volume suggest this phase has peaked. Minor phreatic eruptions have been occurring since early January but appear to have become infrequent, or may have even ceased, during February. Despite the relatively high heat output, the recent activity has so far followed the cycle of heating and cooling typical of Ruapehu since at least 1985."

There were several reports of steam clouds and other phenomena after 20 January. A hiker on 24 January described the crater lake seen through the clouds as "a seething surface" that made "roaring sounds" lasting 1 to 2 minutes.

Two or more observers on 29 January described the crater lake, which was visible for almost 2 hours, as "pale gray, almost white" and two, 1.5 m (or smaller) upwelling and splashing episodes were seen. The report also mentioned "pure yellow styrofoam-sulfur" littering the Outlet area. The water temperature, measured with two calibrated thermometers, was 51.4°C.

Hikers in cloudy weather on 30 January witnessed a "small hydrothermal eruption up to 10-20 m." Hikers in cloudy weather on 5 February heard sloshing noises from the crater lake followed by two "loud explosions." On 15 February observers saw a 3 km tall, stationary steam plume over the crater lake; on 25 and 27 February observers also saw steam clouds. These clouds were undoubtedly steam, but they may have arisen from "atmospheric enhancement" due to a rise in relative humidity rather than from definite eruptions. Their interpretation thus remains ambiguous. A ground inspection on 2 March failed to confirm any significant surging took place around the shore of Lake Wade.

In the interval 31 January-early March there were few discrete earthquakes and mainly background tremor was detected on the volcano's Dome seismograph. On the other hand, there were short intervals of strong, high frequency tremor, an unusual occurrence for Ruapehu.

Although in the latest crater visit on 2 March all deformation survey stations were accessible and clear of snow, most of the length changes seen since 13 January were insignificant (<= 5 mm). Station I (see map, BGVN 19:12) appeared to have moved 18 mm ENE relative to all other stations since May 1994--a motion consistent with moderate deflation seen in the past 10 months, but also possibly due to displacement by local snow loading or other factors.

Mg and Cl analyses of lake water were made on 18 and 29 January, and on 2 March, but showed relatively change. The Mg/Cl ratio changed only about 4% (shifting downward from an 18 January value of 0.036 to a 2 March value of 0.035). The Mg/Cl ratios were interpreted to indicate that the heating event was driven by convective flow of lake water through the upper portion of the vent. Thus, the heating event was regarded as mainly due to fluid flow rather than heat input from magmatic sources within the edifice.

Geologic Background. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The dominantly andesitic 110 km3 volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 km3 ring plain of volcaniclastic debris, including the Murimoto debris-avalanche deposit on the NW flank. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. A single historically active vent, Crater Lake (Te Wai a-moe), is located in the broad summit region, but at least five other vents on the summit and flank have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent, and tephra characteristics suggest that the crater lake may have formed as early as 3,000 years ago. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to lower river valleys.

Information Contacts: P.M. Otway, Institute of Geological and Nuclear Sciences (IGNS), Private Bag 2000, Wairakei, New Zealand.


Stromboli (Italy) — April 1995 Citation iconCite this Report

Stromboli

Italy

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

All times are local (unless otherwise noted)


Explosion on 5 March and tremor; crater observations

Due to funding problems, the power supply to the 3-component summit seismic station maintained by the University of Udine was interrupted from 10 December 1994 until 13 January 1995. The previous report (BGVN 20:01) described seismic activity through 9 December. This station has been operating since 1989, but may be permanently shut down in June if funding is not continued.

Stromboli island was visited by Giada Giuntoli and Boris Behncke on 19-24 April. Generally, the volcano showed much less activity than during a previous visit in August 1994, but an increase was evident on 23 April, resulting in the resumption of eruptions from Crater 1, which had been inactive for several weeks. Behncke also provided a review of crater morphology changes since 1989.

Seismicity, early 1995. Throughout 13 January-4 April the daily number of shocks remained roughly constant at 200-400 (figure 39). On 26 February tremor intensity began to decrease, and for a few days its average value remained stable below 3 Volts x seconds (Vs). However, the number of major shocks remained high. On 5 March a large explosion accompanied the return of tremor intensity to more usual values of around 5 Vs. The explosion threw pyroclastic material towards Forgia Vecchia and Fossetta, a depression SW of the crater area. The ejecta rose high enough to be clearly seen from the village of Stromboli, where the explosion was strongly felt. Tremor level continued to increase following the explosion; after a short decrease it quickly increased again to a peak of 10.8 Vs on 30 March. The number of major shocks decreased after 13 March. The increase in tremor intensity after the 5 March event did not match the behavior recorded after the explosions of 10 February 1993 and 16 October 1993 (BGVN 18:01, 18:02, and 18:09). On those occasions a remarkable decrease of all seismicity, and of the tremor level in particular, was noted immediately afterwards.

Figure (see Caption) Figure 39. Seismicity recorded at Stromboli, 13 January-4 April 1995. Open bars show the number of recorded events/day, the solid bars those with ground velocities >100 micron/s (instrument saturation level). The line shows daily tremor energy computed by averaging hourly 60-second samples. The seismic station is located 300 m from the craters at 800 m elevation. Courtesy of Roberto Carniel.

Activity on 20 April 1995. During a summit visit on 20 April between 0000 and 1500, activity was low compared to previous visits (September 1989, March and November 1990, August 1991, and March and August 1994); only three vents were erupting, in contrast to 10 in August. A detailed record of the eruptions was made for ~4 hours (table 2). The most notable change was the almost complete inactivity of Crater 1 (figures 40 and 41), which had contained at least six erupting vents in August 1994. Only vent 1/3 displayed some brief weak explosions, mostly of burning gas carrying a few incandescent fragments from the conduit walls. Crater 2 was not erupting, as in March and August 1994, but was the site of loud gas emissions.

Table 2. Eruptive activity at Stromboli observed between 0800 and 1210 on 20 April 1995, from Pizzo sopra la Fossa. Courtesy of Boris Behncke.

Time Crater-Vent Description
0800 1-3 Brief (1 sec) gas explosion.
0810 1-3 Explosion (2 sec) with dark fumes.
0811 3-2 Very small explosion, no bombs visible.
0811 3-1 Strong bomb ejection to ~30 m.
0813 3-2 Lava fountain (15 sec) with some ash, to ~60 m above crater terrace.
0816 1-3 Brief thud with gas puff.
0825 3-2 Small, low fountain inside crater (5 sec).
0830 2-? Loud gas emission, no solid ejections (2-3 sec).
0845 3-2 Small ash explosion (10 sec) to 30 m.
0857 3-2 Small ash explosion (5 sec).
0859 3-2 Large bomb and ash fountain to 80 m (10 sec).
0902 3-2 Small bomb fountain with no ash to 30 m (5 sec).
0906 3-2 Very small explosion (mainly gas) inside crater (4 sec).
0908 3-2 Large bomb and ash fountain to 50 m, ash plume to 250 m (10 sec).
0912 1-3 Small gas explosion (2 sec).
0937 3-1 Single burst of large bombs to 30 m.
0944 3-1 Bomb ejection to ~20 m.
0952 1-3 Brief (1 sec) gas burst.
0954 3-1 Large bomb ejection with very large (up to 5 m) clots to ~30 m.
1010 3-2 Ash fountain to 150 m.
1043 3-2 Vigorous bomb and ash fountain; bombs to 80 m; dense ash column to >200 m (~30 sec).
1045 1-3 Small gas explosion (1 sec).
1110 3-2 Large bomb and ash fountain similar to that of 1043.
1124 1-3 Small gas explosion (1 sec).
1132 1-3 Small gas explosion (1 sec).
1136 3-2 Bomb and ash fountain, ash to >200 m.
1148 3-1 Abundant very large bombs to ~25 m; "whooshing" sound.
1152 3-1 Similar to 1148 but with less bombs.
1155 3-1 Similar to 1148 but with less bombs.
1207 1-3 Small gas explosion (1 sec).
1208 3-2 Bomb fountain to

The most active vents were in Crater 3. Vent 3/1 activity consisted of almost continuous low spattering from a small lava pond with occasional bursts to ~60 m above the vent; similar activity was seen in March 1994 (BGVN 19:03). Rare bursts of large incandescent lava clots (up to 5 m in diameter) were accompanied by faint "whooshing" noises. Only twice were bombs ejected beyond the pit of 3/1, onto the NE wall of Crater 3. Eruptions from vent 3/2 occurred at intervals ranging from 2 minutes to >1 hour (see table 1), with periods of more frequent eruptions alternating with periods of very low activity. For example, six eruptions occurred during a 25-minute period (0845-0910), while from 0910 until 1210 there were only five more. Some of these eruptions consisted of loud gas emissions with very low spatter fountains, but most produced incandescent fountains 80-100 m high. Between sunrise on 20 April (at about 0700) and noon, the eruptions produced ash plumes up to 250 m high. Most of the ejected material fell back into the pit, but sometimes the entire NW rim of Crater 3 was covered with pyroclastics, and bombs rolled down the Sciara del Fuoco.

Activity on 21 and 23 April 1995. When observed from Punta Labronzo, on the N side of the island, on the evening of 21 April activity consisted of frequent low lava fountains from vent 3/2 and fluctuating incandescence over vent 3/1. Small ash plumes produced by eruptions from 3/2 were driven down the Sciara del Fuoco by strong winds. A dramatic change was evident late on 23 April, when the volcano was again observed from Punta Labronzo. Crater glow was much more intense, though still intermittent, and a persistent glow was visible at a small spot in the gap on the NE rim of Crater 1 (formed by the 5 March explosion). Vent 3/2 erupted as during the preceding days with somewhat larger ash plumes. However, a vent in the N part of Crater 1 ended the period of unusual inactivity of this crater, erupting spectacularly at intervals of 10-25 minutes. These eruptions were very brief (< 5 seconds) and produced cannon-shot-like bangs. Narrow incandescent columns rose obliquely to at least 150 m above the vent before falling onto the Sciara del Fuoco, depositing abundant incandescent material on the steep slope. For 3-5 minutes, incandescent material would cascade down to about half of the Sciara's extension, with a few large blocks tumbling farther. None appeared to reach the sea during the 1-hour observation period.

Figure (see Caption) Figure 40. Sketch map of the summit area of Stromboli, April 1995, showing the three craters and locations of vents. Courtesy of Boris Behncke.

Morphologic changes occur almost continuously, with alternating constructive and destructive processes. Periods of spatter-cone growth and crater filling usually last from a few months to several years and are followed by either crater-floor subsidence or explosive disruption of the cones. Cone growth was continuous from at least 1989 (maybe 1986) until October 1993, interrupted only by small-scale cone collapse and minor explosions. At the same time, the craters were filled to their rims with tephra and minor lava flows (as in May 1993; BGVN 18:04). Two large explosions in October 1993 blew out all of the material from the craters, leaving deep (>60 m) and wide chasms with near-vertical walls, still present in March 1994 (BGVN 19:03). New spatter cones grew rapidly during unusually vigorous activity in the summer and autumn of 1994, reaching much larger dimensions than the 1989-93 cones. In March 1995, parts of these cones were again removed by powerful explosions similar to, but smaller than, the October 1993 explosions. Also during early 1995, subsidence in Crater 3 created two pits at least 50 m deep.

Crater 1 has been the site of the most pronounced spatter-cone growth during 1989-95. Very small cones rarely formed at vent 3/1 and within the one vent of Crater 2. Most of the filling of craters 2 and 3 was due to the accumulation of pyroclastics. Three large, steep-sided cones and several smaller ones grew within Crater 1 between March and August 1994, the largest at vent 1/2 in the central portion of the crater, reaching ~30 m above its base. A powerful explosion in March 1995 blew out a pit 60-70 m in diameter and some 40 m deep with vertical walls, removing half of the cone (figure 41), and exposing the now-inactive conduit. Some of the smaller 1994 cones were also destroyed during the March explosion. The "twin cones" above vents 1/4 and 1/5 had grown much larger since August 1994, reaching ~25 m above their bases. Crater 2 had changed little since the summer of 1994. The small (~5 m high) hornito in its center, first observed in October 1994 (BGVN 19:10) was still present.

Figure (see Caption) Figure 41. View of the crater terrace from Pizzo Sopra la Fossa, 20 April 1995. Courtesy of Boris Behncke.

Crater 3, which had been filled with pyroclastics in August 1994, had two major depressions at the sites of vents 3/1 and 3/2. These depressions differ from the explosion pit in Crater 1, lacking its vertical walls and sharp rim, and may have formed in response to the lowering of the magmatic column sometime during November 1994 when the period of high-level activity ended. Another major change since 1989 is the significant upward growth of the entire crater terrace, most notable on the NW side facing the Sciara del Fuoco. This change is also evident on the profile views of Crater 1 taken from an observation point ~400 m NW (figure 42). Since the early and mid-20th century, the crater terrace has grown upwards by 50-100 m, completely burying the formerly conspicuous Filo di Baraona (figure 40), a frequently cited reference point in older literature at the SW end of the crater terrace. The highest point of the crater terrace is the SW rim of Crater 3, lying at ~780-800 m elevation (some 40 m above its NE rim), at the site of the former Filo di Baraona. This is significantly higher than the ~725 m estimated by Hornig-Kjarsgaard and others (1993).

Figure (see Caption) Figure 42. Comparative profile views of Crater 1 from the NE, illustrating the repeated growth and destruction of spatter cones between September 1989 and April 1995. The June 1993 sketch is based on photographs taken by Jon Dehn (Geological Survey of Japan, Hokkaido) and shows two lava lobes (arrows) from the vigorous May 1993 activity extending downslope. Courtesy of Boris Behncke.

Reference. Hornig-Kjarsgaard, I., Keller, J., Koberski, K., Stadlbauer, E., Francalanci, L., and Lenhart, R., 1993, Geology, stratigraphy and volcanological evolution of the island of Stromboli, Aeolian arc, Italy: Acta Vulcanologica, v. 3, p. 21-68.

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: Roberto Carniel, Dipartimento di Georisorse e Territorio, via Cotonificio 114, I-33100 Udine, Italy; Giada Giuntoli and Boris Behncke, GEOMAR Research Center, Dept. of Volcanology and Petrology, Christian-Albrechts-Universitat zu Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany.


Unzendake (Japan) — April 1995 Citation iconCite this Report

Unzendake

Japan

32.761°N, 130.299°E; summit elev. 1483 m

All times are local (unless otherwise noted)


No lava dome growth, small rockfalls, rare tremors

No lava dome growth was revealed by theodolite surveys, helicopter inspections, or fieldwork during March and April. Rare rockfalls in March, 1-2/week, traveled 5m3. However, little lava was supplied after mid-February (figure 79). Theodolite survey results indicated that the endogenous dome started to shrink a little (1-2 m maximum) in April, compared with the data from February.

Figure (see Caption) Figure 79. Daily eruption volume at Unzen, May 1991-April 1995, showing two distinct pulses of magma-supply. No effusion of lava has been observed since mid-February 1995. The total volume of magma erupted during this 4-year period was ~0.20 km3. Eruption volumes were estimated by Geological Party, Joint University Research Group (JURG), using photographs from daily helicopter inspections and theodolite surveys. Only aerial photographs were used by the Geographical Survey Institute (GSI), the Public Works Research Institute (PWRI), and the Geological Survey of Japan (GSJ) to calculate the volume changes. Courtesy of Setsuya Nakada.

Volcanic gas emission decreased in April, such that no fume was observed from distant sites. Scientists from the Shimabara Earthquake and Volcano Observatory (SEVO), Kyushu University, installed mirrors for EDM and GPS stations near the top of the endogenous dome during April fieldwork. A sample from the dike on the top of the endogenous dome, which extruded at the end of 1994 and is the latest juvenile material, had a composition similar to lobe-13 samples collected in August 1994 (~65 wt.% SiO2); the specific gravity was ~2.46.

Only 15 microearthquakes beneath the dome and 10 tremor events were detected in March at the Japan Meteorological Agency seismograph 3.6 km SW of the dome. The same station detected 29 earthquakes and 18 tremor events in April. No pyroclastic flows were detected in March or April, but tiltmeters recorded upward movement of the summit on 9 and 24 March. SEVO noted small tremors on 8 and 15 April that were associated with minor tiltmeter changes; epicenters were several hundred meters W of the dome.

Geologic Background. The massive Unzendake volcanic complex comprises much of the Shimabara Peninsula east of the city of Nagasaki. An E-W graben, 30-40 km long, extends across the peninsula. Three large stratovolcanoes with complex structures, Kinugasa on the north, Fugen-dake at the east-center, and Kusenbu on the south, form topographic highs on the broad peninsula. Fugendake and Mayuyama volcanoes in the east-central portion of the andesitic-to-dacitic volcanic complex have been active during the Holocene. The Mayuyama lava dome complex, located along the eastern coast west of Shimabara City, formed about 4000 years ago and was the source of a devastating 1792 CE debris avalanche and tsunami. Historical eruptive activity has been restricted to the summit and flanks of Fugendake. The latest activity during 1990-95 formed a lava dome at the summit, accompanied by pyroclastic flows that caused fatalities and damaged populated areas near Shimabara City.

Information Contacts: Setsuya Nakada, Volcano Research Center - Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113, Japan; Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.


Veniaminof (United States) — April 1995 Citation iconCite this Report

Veniaminof

United States

56.17°N, 159.38°W; summit elev. 2507 m

All times are local (unless otherwise noted)


Small plumes seen; warm spots identified from satellite images

During the first quarter of 1995, thermal anomalies were detected on satellite images of Veniaminof intermittently through 13 March. However, because neither ground observers nor pilots reported eruptive activity, these anomalies were thought to be related to the cooling lava flow in the summit caldera. On 17 April an observer in Port Heiden (97 km NE) saw small, dark plumes from Veniaminof. Observers from Perryville (32 km S) reported on 21 April that there had been a small steam plume during the preceding several days. This activity coincided with warm spots near the active vent seen on satellite images from 14, 21, and 22 April.

Geologic Background. Veniaminof, on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA, 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.


Villarrica (Chile) — April 1995 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Tremor, mild explosions, and a new pyroclastic cone

Gustavo Fuentealba contributed the following on 4 May. "Seismic activity has increased in the past few days compared to March. In mid-April explosions were visible to the level of the crater rim and these explosions coincided with seismicity registered on portable instruments 15 km from the crater. The seismic signals arrived at 90-second intervals.

"In agreement with mid-April explosions and seismic data, aerial observations and photos around that time (taken by members of the Corporacion Nacional Forestal) revealed the growth of a new pyroclastic cone. Starting on 28 April and 1 May, there were intervals of poor visibility, but a new increase in seismic activity included tremor at 30-second intervals. Seismic activity declined suddenly, starting about 1915 on 1 May, but it reappeared ~8 hours later with tremor at 60-second intervals. Although continued poor visibility thwarted direct observations, it was thought probable that the April pyroclastic cone had collapsed."

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

Information Contacts: Gustavo Fuentealba1 and Paola Pena, Observatorio Volcanologico de los Andes del Sur. 1 Also at Universidad de la Frontera, Ciencias Fisicas, Avenida Francisco Salazar 01145, Casilla 54-D A 238, Temuco, Chile.


Vulcano (Italy) — April 1995 Citation iconCite this Report

Vulcano

Italy

38.404°N, 14.962°E; summit elev. 500 m

All times are local (unless otherwise noted)


Fumaroles at Fossa Grande and Forgia Vecchia craters

During an 18 Apri visit by Boris Behncke to the Fossa Grande crater the most vigorous fumaroles were present on the N inner crater rim and near its bottom. The main focus of fumarolic activity had shifted notably from the crater rim towards its center since his March 1992 visit (BGVN 17:03). Some of the spectacular fissures on the outer N crater wall were inactive, but several large fumaroles had formed near the crater floor. Molten sulfur was present in many fumaroles on the crater rim. Fumarolic activity on the oversteepened S part of the 18th century Forgia Vecchia craters and on the upper SE slope of the cone has changed little since 1992. Fumaroles were also active at Gran Cratere in October 1994.

Geologic Background. The word volcano is derived from Vulcano stratovolcano in Italy's Aeolian Islands. Vulcano was constructed during six stages during the past 136,000 years. Two overlapping calderas, the 2.5-km-wide Caldera del Piano on the SE and the 4-km-wide Caldera della Fossa on the NW, were formed at about 100,000 and 24,000-15,000 years ago, respectively, and volcanism has migrated to the north over time. La Fossa cone, active throughout the Holocene and the location of most of the historical eruptions, occupies the 3-km-wide Caldera della Fossa at the NW end of the elongated 3 x 7 km island. The Vulcanello lava platform forms a low, roughly circular peninsula on the northern tip of Vulcano that was formed as an island beginning in 183 BCE and was connected to Vulcano in about 1550 CE. Vulcanello is capped by three pyroclastic cones and was active intermittently until the 16th century. The latest eruption from Vulcano consisted of explosive activity from the Fossa cone from 1898 to 1900.

Information Contacts: Giada Giuntoli and Boris Behncke, GEOMAR Research Center, Dept. of Volcanology and Petrology, Christian-Albrechts-Universitat zu Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany.


Whakaari/White Island (New Zealand) — April 1995 Citation iconCite this Report

Whakaari/White Island

New Zealand

37.52°S, 177.18°E; summit elev. 294 m

All times are local (unless otherwise noted)


Currently non-eruptive but 2-year-long inflation continues

No eruptive activity occurred during January-March 1995. Wade Crater's floor remained occupied by an aqua-blue lake; photographs taken on 11 November 1994 and 27 February 1995 disclosed a lake-level rise of ~15-20 m. The lake appeared free of convection, but did contain conspicuous orange-colored material floating on its surface. The lake surface in March was thus considerably above the floors of Wade and Princess craters.

Dominant locations of fumaroles in or adjacent to Wade Crater included those high on the W wall, on the W side of the May 1991 embayment (particularly large and conspicuous fumaroles), and NE of Wade Lake on the divide between Wade and TV1 craters.

A 4 March leveling survey had a low error of closure (<=1.5 mm). The survey detected continued uplift, apparent since at least early 1993 (figure 23), with a maximum rate of 4.8 mm/month (58 mm/year) centered about 250 m SE of the middle of Wade Crater (Peg N). An area of shorter-term relative subsidence, apparent since at least August 1994, persists in the TV1-Donald Duck Crater area.

Figure (see Caption) Figure 23. White Island deformation at leveling Peg C, ~750 m SE of the shore of Lake Wade, 1967-1995. Courtesy of IGNS.

The magnitudes of these upward and downward motions were as follows. For the interval 21 November 1994 to 4 March 1995 the motion was 15 mm (up at Peg N) and -1 to -16 mm (down near TV1). For the interval 19 January 1994 to 4 March 1995 the motion was about 64 mm (up at peg N) and 26 mm (up near TV1).

Continued uplift of the crater floor suggested a crater-wide inflation that has been in progress for more than 2 years (figure 23). This inflation bears a close resemblance to the 5-year inflation that led up to a noteworthy eruption beginning in December 1976. An early phase of the 1976 eruption "sprinkled mustard-green colored ash" up to 1 m or more thick, over the crater and lesser thickness over the E part of the Island (SEAN 02:01).

Geologic Background. The uninhabited Whakaari/White Island is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

Information Contacts: B.J. Scott, Institute of Geological and Nuclear Sciences (IGNS), Private Bag 2000, Wairakei, New Zealand.

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