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Bulletin of the Global Volcanism Network

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

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

Recently Published Bulletin Reports

Klyuchevskoy (Russia) Renewed activity in October 2020 with explosions, lava flows, and ash plumes

Kadovar (Papua New Guinea) Occasional ash and gas-and-steam plumes along with summit thermal anomalies

Tinakula (Solomon Islands) Intermittent gas-and-steam plumes and weak thermal anomalies during July-December 2020

Erebus (Antarctica) Fewer thermal anomalies during 2020 compared to recent years

Aira (Japan) Intermittent explosions continue during July through December 2020

Nishinoshima (Japan) Eruption ends in late August 2020; lengthy cooling from extensive lava flows and large crater

Nyiragongo (DR Congo) Strong thermal anomalies and gas emission from lava lake through November 2020

Whakaari/White Island (New Zealand) Gas-and-steam emissions with some re-suspended ash in November 2020

Kerinci (Indonesia) Intermittent ash plumes and gas-and-steam emissions during June-November 2020

Suwanosejima (Japan) Explosion rate increases during July-December 2020, bomb ejected 1.3 km from crater on 28 December

Karangetang (Indonesia) Hot material on the NW flank in November 2020; intermittent crater thermal anomalies

Nevado del Ruiz (Colombia) Dome growth and ash emissions continue during July-December 2020



Klyuchevskoy (Russia) — January 2021 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


Renewed activity in October 2020 with explosions, lava flows, and ash plumes

Klyuchevskoy, located in northern Kamchatka, has had historical eruptions dating back 3,000 years characterized by major explosive and effusive eruptions from the flank craters. The current eruption began in April 2019 and has recently consisted of Strombolian activity, ash plumes, and an active lava flow descending the SE flank (BGVN 45:09). This report covers September-December 2020 and describes similar activity of Strombolian explosions, ash plumes, and active lava flows beginning in early October. Information primarily comes from weekly and daily reports from the Kamchatkan Volcanic Eruption Response Team (KVERT), the Tokyo Volcanic Ash Advisory (VAAC), and satellite data.

Activity from July through September was relatively low, with no thermal activity detected during August-September. On 2 October renewed Strombolian explosions began at 1003, ejecting ash 300-400 m above the summit and producing gas-and-steam plumes with some ash that drifted down the E flank (figure 48). That night, crater incandescence was visible. On 5 October KVERT reported that a lava flow began to effuse along the Apakhonchich chute at 0100. During 7-8 October activity intensified and was characterized by strong explosions, collapses of the sides of the drainage, strong thermal anomalies, and ash plumes that extended over 200 km SE from the crater; the lava flow remained active and continued to descend the SE flank. A Tokyo VAAC advisory issued on 7 October reported that an ash plume rose to 8.8 km altitude and drifted E and SE; during 8-9 October ash plumes rose to 5.5 km altitude and drifted as far as 270 km SE. A strong, bright, thermal anomaly was observed daily in satellite imagery, which represented the new lava flow. Strombolian explosions continued throughout the month, accompanied by gas-and-steam plumes containing some ash and an active lava flow advancing down the Apakhonchich chute on the SE flank (figure 49).

Figure (see Caption) Figure 48. Photos of a gray ash plume (left) and the beginning of the lava flow (right), represented as summit crater incandescence at Klyuchevskoy on 2 October 2020 at 1030 and 2100, respectively. Photos by Y. Demyanchuk; courtesy of Volkstat.
Figure (see Caption) Figure 49. Photo of Strombolian explosions at the summit of Klyuchevskoy accompanied by ash emissions and a lava flow advancing down the SE-flank Apakhonchich chute on 25 October 2020. Photo by Y. Demyanchuk (color corrected); courtesy of Volkstat.

Similar activity continued to be reported in November, consisting of Strombolian explosions, ash plumes, and a lava flow advancing down the SE flank. A bright thermal anomaly was observed in thermal satellite imagery each day during the month. During 16-19 November explosions recorded in satellite and video data showed ash plumes rising to 7.5 km altitude and drifting as far as 108 km to the NE, E, SE, and S (figure 50). On 19 November an ash cloud 65 x 70 km in size drifted 50 km SE, according to a KVERT VONA (Volcano Observatory Notice for Aviation). During 26-30 November video and satellite data showed that gas-and-steam plumes containing some ash rose to 7 km altitude and extended as far as 300 km NW and E, accompanied by persistent moderate explosive-effusive activity (figure 51).

Figure (see Caption) Figure 50. Photo of the Strombolian and Vulcanian explosions at Klyuchevskoy on 18 November 2020 which produced a dense gray ash plume. Photo by Yu. Demyanchuk, IVS FEB RAS, KVERT
Figure (see Caption) Figure 51. Photo of the summit of Klyuchevskoy (right foreground) showing incandescent Strombolian explosions, the lava flow descending the Apakhonchich chute on the SE flank, and a gray ash plume on 29 November 2020. Kamen volcano is the cone at back left. Photo by Y. Demyanchuk (color corrected); courtesy of Volkstat.

Moderate explosive-effusive activity continued through December; a strong daily thermal anomaly was visible in satellite images. During 2-3 December gas-and-steam plumes containing some ash rose to 7 km altitude and extended 300 km NW and E. Intermittent gas-and-ash plumes continued through the month. On 7 December KVERT reported that a new lava flow began to advance down the Kozyrevsky chute on the S flank, while the flow on the SE flank continued. Strombolian explosions in the crater ejected incandescent material up to 300 m above the crater on 8 December while hot material was deposited and traveled 350 m below the crater. A cinder cone was observed growing in the summit crater and measured 75 m tall.

Strombolian and Vulcanian activity continued during 11-25 December, accompanied by the lava flow on the S flank; according to Sentinel-2 thermal satellite images, the effusion on the SE flank had stopped around 13 December and had begun to cool. The lava flow in the Kozyrevsky chute spalled off incandescent material that continued to travel an additional 350 m. Gas-and-steam plumes that contained some ash rose to 6 km altitude and drifted up to 350 km generally E. On 24 December the Kamchatka Volcanological Station field team visited Klyuchevskoy to do work on the field stations. The scientists observed explosions that ejected incandescent material 300 m above the crater and the S-flank lava flow (figure 52). On 28 December KVERT reported that the moderate explosive-effusive eruption continued, but the intensity of the explosions had significantly decreased. The lava flow on the S flank continued to effuse, but its flow rate had already decreased.

Figure (see Caption) Figure 52. Photos of a dense ash plume (left) and a color corrected photo of the lava flow advancing on the S flank (right) of Klyuchevskoy on 24 December 2020, accompanied by incandescent Strombolian explosions and a gray ash plume. Photos by Y. Demyanchuk; courtesy of Volkstat.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows frequent and strong thermal activity beginning in early October and continuing through December 2020, which is represented by the active lava flows reported in the summit crater (figure 53). According to the MODVOLC thermal algorithm, a total of 615 thermal alerts were detected at or near the summit crater from 1 October to 31 December; none were reported in September. Sentinel-2 thermal satellite imagery frequently showed the progression of the active lava flows as a strong thermal anomaly descending the SE flank during October through late November and the SW flank during December, sometimes even through weather clouds (figure 54). The thermal anomalies were commonly accompanied by a gas-and-steam plume that drifted mainly E and NE. A total of 164 VAAC advisories were issued from 2 October through 31 December.

Figure (see Caption) Figure 53. Strong and frequent thermal anomalies were detected in early October at Klyuchevskoy and continued through December 2020, as recorded by the MIROVA graph (Log Radiative Power). Courtesy of MIROVA.
Figure (see Caption) Figure 54. Sentinel-2 thermal satellite images showing the progression of two lava flows (bright yellow-orange) originating from the summit crater at Klyuchevskoy from 4 October through December 2020. Crater incandescence was visible on 4 October (top left), which marked the beginning of the lava flow. By 31 October (top right) the active flow had traveled down the Apakhonchich chute on the SE flank, accompanied by a gas-and-steam plume that drifted NE. On 10 November (bottom left) the lava flow continued down the SE flank; the darker black color represents parts of the lava flow that began to cool. The gas-and-steam plume drifted E from the summit. On 25 December (bottom right) a new lava flow was observed descending the SW flank, also accompanied by a strong gas-and-steam plume. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; 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/); Kamchatka Volcanological Station, Klyuchi, Kamchatka Krai, Russia (URL: http://volkstat.ru/); 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/); 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).


Kadovar (Papua New Guinea) — January 2021 Citation iconCite this Report

Kadovar

Papua New Guinea

3.608°S, 144.588°E; summit elev. 365 m

All times are local (unless otherwise noted)


Occasional ash and gas-and-steam plumes along with summit thermal anomalies

Kadovar is located in the Bismark Sea offshore from the mainland of Papua New Guinea about 25 km NNE from the mouth of the Sepik River. Its first confirmed eruption began in early January 2018, characterized by ash plumes and a lava extrusion that resulted in the evacuation of around 600 residents from the N side of the island (BGVN 43:03). Activity has recently consisted of intermittent ash plumes, gas-and-steam plumes, and thermal anomalies (BGVN 45:07). Similar activity continued during this reporting period of July-December 2020 using information from the Rabaul Volcano Observatory (RVO), the Darwin Volcanic Ash Advisory Center (VAAC), and various satellite data.

RVO issued an information bulletin on 15 July reporting minor eruptive activity during 1-5 July with moderate light-gray ash emissions rising a few hundred meters above the Main Crater. On 5 July activity intensified; explosions recorded at 1652 and 1815 generated a dense dark gray ash plume that rose 1 km above the crater and drifted W. Activity subsided that day, though fluctuating summit crater incandescence was visible at night. Activity increased again during 8-10 July, characterized by explosions detected on 8 July at 2045, on 9 July at 1145 and 1400, and on 10 July at 0950 and 1125, each of which produced a dark gray ash plume that rose 1 km above the crater. According to Darwin VAAC advisories issued on 10, 16, and 30 July ash plumes were observed rising to 1.5-1.8 km altitude and drifting NW.

Gas-and-steam emissions and occasional ash plumes were observed in Sentinel-2 satellite imagery on clear weather days during August through December (figure 56). Ash plumes rose to 1.2 and 1.5 km altitude on 3 and 16 August, respectively, and drifted NW, according to Darwin VAAC advisories. On 26 August an ash plume rose to 2.1 km altitude and drifted WNW before dissipating within 1-2 hours. Similar activity was reported during September-November, according to several Darwin VAAC reports; ash plumes rose to 0.9-2.1 km altitude and drifted mainly NW. VAAC notices were issued on 12 and 22 September, 4, 7-8, and 18 October, and 18 November. A single MODVOLC alert was issued on 27 November.

Figure (see Caption) Figure 56. Sentinel-2 satellite data showing a consistent gas-and-steam plume originating from the summit of Kadovar during August-December 2020 and drifting NW. On 21 September (top right) a gray plume was seen drifting several kilometers from the island to the NW. Images with “Natural color” (bands 4, 3, 2) rendering; courtesy of Sentinel Hub Playground.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows intermittent low-power anomalies during July through December 2020 (figure 57). Some of this thermal activity in the summit crater was observed in Sentinel-2 thermal satellite imagery, accompanied by gas-and-steam emissions that drifted primarily NW (figure 58).

Figure (see Caption) Figure 57. Intermittent low-power thermal anomalies at Kadovar were detected in the MIROVA graph (Log Radiative Power) during July through December 2020. The island location is mislocated in the MIROVA system by about 5.5 km SE due to older mis-registered imagery; the anomalies are all on the island. Courtesy of MIROVA.
Figure (see Caption) Figure 58. Sentinel-2 satellite data showing thermal anomalies at the summit of Kadovar on 23 July (top left), 7 August (top right), 1 September (bottom left), and 21 September (bottom right) 2020, occasionally accompanied by a gas-and-steam plume drifting dominantly NW. Two thermal anomalies were visible on the E rim of the summit crater on 23 July (top left) and 7 August (top right). Images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. It is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. Prior to an eruption that began in 2018, a lava dome formed the high point of the andesitic volcano, filling an arcuate landslide scarp open to the south; submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. A period of heightened thermal phenomena took place in 1976. An eruption began in January 2018 that included lava effusion from vents at the summit and at the E coast.

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Tinakula (Solomon Islands) — January 2021 Citation iconCite this Report

Tinakula

Solomon Islands

10.386°S, 165.804°E; summit elev. 796 m

All times are local (unless otherwise noted)


Intermittent gas-and-steam plumes and weak thermal anomalies during July-December 2020

Tinakula is located 100 km NE of the Solomon Trench at the N end of the Santa Cruz. The current eruption began in December 2018 and has recently been characterized by intermittent small thermal anomalies and gas-and-steam plumes (BGVN 45:07), which continued into the current reporting period of July-December 2020. Information primarily comes from various satellite data, as ground observations are rarely available.

Infrared MODIS satellite data processed by MIROVA (Middle InfraRed Observation of Volcanic Activity) showed a total of ten low-power thermal anomalies during July through December; one anomaly was detected in early July, two in late August, three in November, and four in December (figure 44). A single MODVOLC alert was issued on 16 December, which was visible in Sentinel-2 thermal satellite imagery on 17 December (figure 45). Though clouds often obscured the view of the summit crater, Sentinel-2 satellite imagery showed intermittent dense gas-and-steam plumes rising from the summit that drifted in different directions (figure 45).

Figure (see Caption) Figure 44. Low-power thermal anomalies at Tinakula were detected intermittently during April-December 2020 by the MIROVA system (Log Radiative Power). Courtesy of MIROVA.
Figure (see Caption) Figure 45. Sentinel-2 satellite imagery shows ongoing gas-and-steam plumes rising from Tinakula during July-December 2020. A small thermal anomaly (bright yellow-orange) is visible on 17 December (bottom right) using “Atmospheric penetration” (bands 12, 11, 8a) rendering. All other images using “Natural color” rendering (bands 4, 3, 2); courtesy of Sentinel Hub Playground.

Geologic Background. The small 3.5-km-wide island of Tinakula is the exposed summit of a massive stratovolcano at the NW end of the Santa Cruz islands. Similar to Stromboli, it has a breached summit crater that extends from the summit to below sea level. Landslides enlarged this scarp in 1965, creating an embayment on the NW coast. The satellitic cone of Mendana is located on the SE side. The dominantly andesitic volcano has frequently been observed in eruption since the era of Spanish exploration began in 1595. In about 1840, an explosive eruption apparently produced pyroclastic flows that swept all sides of the island, killing its inhabitants. Frequent historical eruptions have originated from a cone constructed within the large breached crater. These have left the upper flanks and the steep apron of lava flows and volcaniclastic debris within the breach unvegetated.

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).


Erebus (Antarctica) — January 2021 Citation iconCite this Report

Erebus

Antarctica

77.53°S, 167.17°E; summit elev. 3794 m

All times are local (unless otherwise noted)


Fewer thermal anomalies during 2020 compared to recent years

Erebus, located on Ross Island, Antarctica, and overlooking the McMurdo research station, is the southernmost active volcano in the world. The stratovolcano, which frequently has active lava lakes in its 250-m wide summit crater, is primarily monitored by satellite.

Thermal activity during 2020 was at lower levels than in recent years. The total number of thermal pixels, as recorded by MODIS thermal emission instruments aboard NASA’s Aqua and Terra satellites, was 76 (table 6), similar to low totals recorded in 2000 and 2015.

Table 6. Number of monthly MODIS-MODVOLC thermal alert pixels recorded at Erebus during 2017-2020. See BGVN 42:06 for data from 2000 through 2016. The table was compiled using data provided by the Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System.

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec SUM
2017 0 21 9 0 0 1 11 61 76 52 0 3 234
2018 0 21 58 182 55 17 137 172 103 29 0 0 774
2019 2 21 162 151 55 56 75 53 29 19 1 0 624
2020 0 2 16 18 4 4 1 3 18 3 1 6 76

Sentinel-2 satellite images showed two lava lakes, with one diminishing in size during the year (figure 29). Occasionally a gas plume could be observed. The volcano was frequently covered by atmospheric clouds on days when the satellite passed over.

Figure (see Caption) Figure 29. Infrared Sentinel-2 thermal images of the summit crater area of Erebus in 2020. Left: Image on 28 February 2020 showing two lava lakes in the summit crater. Right: Image on 4 October 2020 showing a single primary lake, with a much diminished second lake immediately SW. The main crater is 500 x 600 m wide. Both images are using the Atmospheric Penetration filter (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

Geologic Background. Mount Erebus, the world's southernmost historically active volcano, overlooks the McMurdo research station on Ross Island. It is the largest of three major volcanoes forming the crudely triangular Ross Island. The summit of the dominantly phonolitic volcano has been modified by one or two generations of caldera formation. A summit plateau at about 3,200 m elevation marks the rim of the youngest caldera, which formed during the late-Pleistocene and within which the modern cone was constructed. An elliptical 500 x 600 m wide, 110-m-deep crater truncates the summit and contains an active lava lake within a 250-m-wide, 100-m-deep inner crater; other lava lakes are sometimes present. The glacier-covered volcano was erupting when first sighted by Captain James Ross in 1841. Continuous lava-lake activity with minor explosions, punctuated by occasional larger Strombolian explosions that eject bombs onto the crater rim, has been documented since 1972, but has probably been occurring for much of the volcano's recent history.

Information Contacts: Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Aira (Japan) — January 2021 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


Intermittent explosions continue during July through December 2020

Sakurajima is the active volcano within the Aira Caldera in Kyushu, Japan. With several craters historically active, the current activity is concentrated in the Minamidake summit crater. Activity usually consists of small explosions producing ashfall and ballistic ejecta, with occasional pyroclastic flows and lahars. The current eruption has been ongoing since 25 March 2017, but activity has been frequent over the past few hundred years. This bulletin summarizes activity that occurred during July through December 2020 and is largely based on reports by the Japan Meteorological Agency (JMA) and satellite data. The Alert Level remains at 3 on a 5-level scale. There was no activity at the Showa crater in 2020.

The number of recorded explosive and ash eruptions for 2020 at the Minamidake crater were 221 and 432, respectively (228 and 393 the previous year). Activity declined in July and remained low through the end of December. There was ash reported on 79 days of the year, most frequently in January, and only 26 of those days during August-December (table 24 and figure 104). The largest ash plumes during this time reached 5 km at 0538 on 9 August, 3 km at 1959 on 17 December, and 3.5 km at 1614 on 29 December. The decline in events was reflected in thermal data, with a decline in energy detected during June through October (figure 105). Recorded SO2 was generally high in the first half of the year then began to decrease from April to around 1,000 tons/day until around late May. Emissions increased after August and were extremely high in October. There were no notable changes in the geothermal areas around the craters.

Table 24. Number of monthly total eruptions, explosive eruptions, days of ashfall, and ashfall amounts from Sakurajima's Minamidake crater at Aira during 2020. Note that smaller events that did not reach the threshold of explosions or eruptions also occurred. Ashfall was measured at Kagoshima Local Meteorological Observatory; ash weights are rounded down to the nearest 0.5 g/m2 and zero values indicate that less than this amount was recorded. Data courtesy of JMA.

MonthExplosive EruptionsAsh EruptionsDays of AshfallAshfall Amount (g/m2)
Jan 2020 65 104 12 75
Feb 2020 67 129 14 21
Mar 2020 10 26 8 3
Apr 2020 14 51 2 0
May 2020 24 51 8 19
Jun 2020 16 28 9 71
Jul 2020 0 0 0 0
Aug 2020 1 1 1 0
Sep 2020 0 7 4 2
Oct 2020 0 2 6 2
Nov 2020 6 8 11 5
Dec 2020 18 25 4 14
Total 2020 221 432 79 212
Figure (see Caption) Figure 104. The total calculated observed ash erupted from Aira's Sakurajima volcano. Top: Annual values from January 1980 to November 2020. Bottom: the monthly values during January 2009 through November 2020. Courtesy of JMA (January 2021 Sakurajima monthly report).
Figure (see Caption) Figure 105. Thermal data detected at Aira's Sakurajima volcano during February through December 2020 by the MIROVA thermal detection system that uses MODIS satellite middle infrared data. There was a decline in activity during June-September, with energy emitted in November-December remaining lower than earlier in the year. Courtesy of MIROVA.

During July "very small" explosions were observed on the 1st, 2nd, and 8th, with the last explosion producing a plume up to 600 m above the crater. These events didn't generate enough of an ash plume to be counted as either a quiet or explosive eruption, leaving no eruptions reported during July. No incandescence was observed at the crater since 3 June. Field surveys on 2, 13, and 21 July detected 600 to 1,300 tons of SO2 per day.

An explosion occurred at 0538 on 9 August, producing an ash plume to 5 km above the crater, dispersing NE (figure 106). This was the largest explosion observed through the Sakurajima surveillance camera since 8 November 2019. Ashfall was reported in Kagoshima City, Aira City, Kirishima City, Yusui Town, and parts of Miyazaki and Kumamoto Prefectures. Ashfall measured to be 300 g/m2 in Shirahama on Sakurajima island (figure 106). No ballistic ejecta were observed due to clouds at the summit, but very small explosions were occasionally observed afterwards.

Figure (see Caption) Figure 106. An explosion at Aira's Sakurajima volcano at 0538 on 9 August 2020 (top, taken from the Ushine surveillance camera in Kagoshima) produced ashfall in Shirahama on Sakurajima (bottom). The plume contains a white steam-rich portion on the left, and a darker relatively ash-rich portion on the right. Images courtesy of JMA (Sakurajima August 2020 monthly report).

A small lake or pond in the eastern Minamidake crater was first observed in PlanetScope satellite imagery on 1 August (through light cloud cover) and intermittently observed when the summit was clear through to the 22nd (figure 107). The summit is obscured by cloud cover in many images before this date. An observation flight on 14 August confirmed weak gas emission from the inner southern wall of the Showa crater, and a 200-m-high gas plume rose from the Minamidake crater, dispersing SE (figure 108). Thermal imaging showed elevated temperatures within the crater. SO2 measurements were conducted during field surveys on the 3rd, 13th, 24th and 31st, with amounts similar to July at 600 to 1,400 tons per day.

Figure (see Caption) Figure 107. A crater lake is visible in the eastern part of the Minamidake summit crater at Aira's Sakurajima volcano on 5, 18, and 22 August 2020. Four-band PlanetScope satellite images courtesy of Planet Labs.
Figure (see Caption) Figure 108. Gas emissions from the Minamidake and Showa craters at Sakurajima in the Aira caldera on 14 August 2020. Photos taken from the from Kagoshima Prefecture disaster prevention helicopter at 1510-1513. Courtesy of JMA (Sakurajima August monthly report).

Activity continued at Minamidake crater throughout September with seven observed eruptions sending plumes up to 1.7 km above the crater, and additional smaller events (figure 109). An ash plume reached 1 km at 0810 on the 15th. Ashfall was reported on four days through the month with a total of 2 g/m2 measured. Incandescence was observed in nighttime surveillance cameras from the 9-10th for the first time since 2 June, then continued through the month. There was an increase in detected SO2, with measurements on the 11th and 25th ranging from 1,300 to 2,000 tons per day.

Figure (see Caption) Figure 109. Examples of activity at Aira's Sakurajima volcano on 4, 10, and 14 September 2020. The images show an ash plume reaching 1.7 km above the crater (top left), a gas-and-steam plume (bottom left), and incandescence at night visible in a gas-and steam plume (right). Images courtesy of JMA (September 2020 Sakurajima monthly report).

During October two eruptions and occasional smaller events occurred at the Minamidake crater and there were six days where ashfall occurred at the Kagoshima Local Meteorology Observatory (including remobilized ash). An ash plume rose to 1.7 km above the crater at 1635 on the 3rd and 1 km on the 30th. Incandescence was observed at night through the month (figure 110). Gas surveys on the 20th, 21st, 23rd, and 26th recorded 2,200-6,600 tons of SO2 per day, which are high to very high levels and a large increase compared to previous months. An observation flight on the 13th confirmed lava in the bottom of the Minamidake crater (figure 111). Gas emissions were rising to 300 m above the Minamidake crater, but no emissions were observed at the Showa crater (figure 112).

Figure (see Caption) Figure 110. Gas emissions and incandescence seen above the Sakurajima Minamidake crater at Aira on 10 and 23 October 2020. Courtesy of JMA (Sakurajima October 2020 monthly report).
Figure (see Caption) Figure 111. Lava was observed on the floor of the Minamidake summit crater at Aira's Sakurajima volcano on 13 October 2020, indicated by the yellow dashed line. Courtesy of JMA (Sakurajima October 2020 monthly report).
Figure (see Caption) Figure 112. An observation flight on 13 October 2020 noted gas emissions up to 300 m above the Minamidake crater at Sakurajima, but no emissions from the Showa crater. Courtesy of JMA (Sakurajima October 2020 monthly report).

Eight ash eruptions and six explosive eruptions occurred during November as well as additional very small events. At 1551 on the 3rd an ash plume reached 1.8 km above the crater and an event at 1335 on the 10th produced large ballistic ejecta out to 600-900 m from the crater (figure 113). Ashfall was reported on 11 days this month (including remobilized ash). Incandescence was observed at night and elevated temperatures in the Minamidake crater were detected by satellites (figure 114). Detected SO2 was lower this month, with amounts ranging between 1,300 and 2,200 on the 9th, 18th and 24th.

Figure (see Caption) Figure 113. Ash plumes at Aira's Sakurajima volcano rise from the Minamidake crater in November 2020. Left: an ash plume rose to 1.8 km above the crater at 1551 on the 3rd and drifted SE. on 3 (left) and 10 (right) November 2020. Right: An explosion at 1335 on the 10th produced an ash plume to 1.6 km above the crater and ballistic ejecta out to 600-900 m, with one projectile indicated by the red arrow. Courtesy of JMA (Sakurajima November 2020 monthly report).
Figure (see Caption) Figure 114. An ash plume drifts SE from the Minamidake crater at Aira's Sakurajima volcano on 8 November 2020. This thermal image also shows elevated temperatures in the crater. Sentinel-2 False color (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

During December there were 25 ash eruptions and 18 explosive eruptions recorded, with large ballistic ejecta reaching 1.3-1.7 km from the crater (figure 115). An explosion on the 2nd sent an ash plume up to 1 km above the crater and ballistic ejecta out to 1-1.3 km, and an event at 0404 on the 12th produced incandescent ballistic ejecta reached out to 1.3-1.7 km from the crater. At 1959 on 17 December an explosion generated an ash plume up to 3 km above the crater and ejecta out to 1.3-1.7 km. A photograph that day showed an ash plume with volcanic lightning and incandescent ejecta impacting around the crater (figure 116). On the 18th an ash plume reached 1.8 km and ejecta impacted out to 1-1.3 km. An event at 1614 on the 29th produced an ash plume reaching 3.5 km above the crater. Elevated temperatures within the Minamidake crater and plumes were observed intermittently in satellite data through the month (figure 117). This month there were four days where ashfall was recorded with a total of 14 g/m2. Incandescence continued to be observed at night through the month. High levels of gas emission continued, with field surveys on 2nd, 7th, 16th and 21st recording values ranging from 1,500 to 2,900 tons per day at the Observatory located 11 km SW.

Figure (see Caption) Figure 115. Explosions at Aira's Sakurajima volcano from the Minamidake summit crater in December 2020. Top: An explosion recorded at 0404 on the 12th produced incandescent ballistic ejecta out to 1.3-1.7 km from the crater, with an example indicated in the red circle. Bottom: An explosion at 1614 on the 29th produced an ash plume up to 3.5 km above the crater, and ballistic ejecta out to 1.3-1.7 km. Courtesy of JMA (top, from Sakurajima December 2020 monthly report) and Volcano Time Lapse (bottom).
Figure (see Caption) Figure 116. An explosion from Sakurajima's Minamidake crater at Aira produced an ash plume with volcanic lightning on 17 December 2020. Photograph taken from Tarumizu city, courtesy of Kyodo/via Reuters.
Figure (see Caption) Figure 117. Activity at Aira's Sakurajima volcano during December 2020. Top: Sentinel-2 thermal satellite image showing a diffuse gas-and-steam plume dispersing to the SE with elevated temperatures within the Minamidake summit crater on the 22nd. PlanetScope satellite image showing an ash plume dispersing between the N and E on the 26th. Sentinel-2 False color (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground. PlanetScope satellite image courtesy of Planet Labs.

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

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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); Planet Labs, Inc. (URL: https://www.planet.com/); Kyodo/via REUTERS, "Photos of the Week" (URL: https://www.reuters.com/news/picture/photos-of-the-week-idUSRTX8HYLR); Volcano Time-Lapse, YouTube (URL: https://www.youtube.com/watch?v=jTgd152oGVo).


Nishinoshima (Japan) — February 2021 Citation iconCite this Report

Nishinoshima

Japan

27.247°N, 140.874°E; summit elev. 25 m

All times are local (unless otherwise noted)


Eruption ends in late August 2020; lengthy cooling from extensive lava flows and large crater

Japan’s Nishinoshima volcano, located about 1,000 km S of Tokyo in the Ogasawara Arc, erupted above sea level in November 2013 after 40 years of dormancy. Activity lasted for two years followed by two brief eruptions in 2017 and 2018. The next eruption, from early December 2019 through August 2020, included ash plumes, incandescent ejecta, and lava flows; it produced a large pyroclastic cone with a wide summit crater and extensive lava flows that significantly enlarged the island. This report covers the end of the eruption and cooling during September 2020-January 2021. Information is provided primarily from Japan Meteorological Agency (JMA) monthly reports and the Japan Coast Guard (JCG), which makes regular observation overflights.

Ash emissions were last reported on 27 August 2020. The very high levels of thermal energy from numerous lava flows, ash, and incandescent tephra that peaked during early July decreased significantly during August and September. Continued cooling of the fresh lava and the summit crater lasted into early January 2021 (figure 107). Monthly overflights and observations by scientists confirmed areas of steam emissions at the summit and on the flanks and discolored water around the island, but no eruptive activity.

Figure (see Caption) Figure 107. High levels of thermal activity at Nishinoshima during June and July 2020 resulted from extensive lava flows and explosions of incandescent tephra. Although the last ash emission was reported on 27 August 2020, cooling of new material lasted into early January 2021. The MIROVA log radiative power graph of thermal activity covers the year ending on 3 February 2021. Courtesy of MIROVA.

Thermal activity declined significantly at Nishinoshima during August 2020 (BGVN 45:09). Only two days had two MODVOLC alerts (11 and 30), and four other days (18, 20, 21, 29) had single alerts. During JCG overflights on 19 and 23 August there were no ash emissions or lava flows observed, although steam plumes rose over 2 km above the summit crater during both visits. The last ash emission was reported by the Tokyo VAAC on 27 August 2020. No eruptive activity was observed by JMA during an overflight on 5 September, but steam plumes were rising from the summit crater (figure 108). No significant changes were observed in the shape of the pyroclastic cone or the coastline. Yellowish brown discolored water appeared around the western half of the island, and high temperature was still measured on the inner wall of the crater. Faint traces of SO2 plumes were present in satellite images in early September; the last plume identified was on 18 September. Six days with single MODVOLC alerts were recorded during 3-19 September, and the final thermal alert appeared on 1 October 2020.

Figure (see Caption) Figure 108. No eruptive activity was observed during a JMA overflight of Nishinoshima on 5 September 2020, but steam rose from numerous places within the enlarged summit crater (inset). Courtesy of JMA and JCG (Monthly report of activity at Nishinoshima, September 2020).

Steam plumes and high temperatures were noted at the summit crater on 28 October, and brown discolored water was present around the S coast of the island (figure 109), but there were no other signs of volcanic activity. Observations from the sea conducted on 2 November 2020 by researchers aboard the Maritime Meteorological Observatory marine weather observation ship "Ryofu Maru" confirmed there was no ongoing eruptive activity. In addition to steam plumes at the summit, they also noted steam rising from multiple cracks on the cooling surface of the lava flow area on the N side of the pyroclastic cone (figure 110). Only steam plumes from inside the summit crater were observed during an overflight on 24 November.

Figure (see Caption) Figure 109. On a JCG overflight above Nishinoshima on 28 October 2020 there were no signs of eruptive activity; steam plumes were present in the summit crater and brown discolored water was visible around the S coast of the island. Courtesy of JMA and JCG (Monthly report of activity at Nishinoshima, October 2020).
Figure (see Caption) Figure 110. Observations of Nishinoshima by staff aboard the Maritime Meteorological Observatory ship "Ryofu Maru" on 2 November 2020 showed a steam plume rising from the lava flow area on the N side of the pyroclastic cone (arrow) and minor steam above the cone. Courtesy of JMA (Monthly report of activity at Nishinoshima, November 2020).

JMA reduced the warning area around the crater on 18 December 2020 from 2.5 to 1.5 km due to decreased activity. On 7 December a steam plume rose from the inner wall of the summit crater and thermal imaging indicated the area was still hot. Brown discolored water was observed on the SE and SW coasts. Researchers aboard a ship from the Earthquake Research Institute at the University of Tokyo and the Marine Research and Development Organization reported continued steam plumes in the summit crater, around the lava flows on the N flank, and along the S coast during 15-29 December (figure 111). Steam plumes and elevated temperatures were still measured inside the summit crater during an overflight by the Japan Coast Guard on 25 January 2021, and discolored water persisted on the SE and SW coasts; there was no evidence of eruptive activity.

Figure (see Caption) Figure 111. Observations of Nishinoshima from the sea by researchers from the Earthquake Research Institute (University of Tokyo) and the Marine Research and Development Organization, which took place from 15-29 December 2020, showed fumarolic acitivity not only inside the summit crater, but also in the lava flow area on the N side of the pyroclastic cone (left, 20 December) and in places along the southern coast (right, 23 December). (Monthly report of activity at Nishinoshima, December 2020).

Geologic Background. The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Another eruption that began offshore in 2013 completely covered the previous exposed surface and enlarged the island again. Water discoloration has been observed on several occasions since. The island is the summit of a massive submarine volcano that has prominent satellitic peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the sea surface 9 km SSE.

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); Japan Coast Guard (JCG) Volcano Database, Hydrographic and Oceanographic Department, 3-1-1, Kasumigaseki, Chiyoda-ku, Tokyo 100-8932, Japan (URL: http://www.kaiho.mlit.go.jp/info/kouhou/h29/index.html); Volcano Research Center (VRC-ERI), Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113, Japan (URL: http://www.eri.u-tokyo.ac.jp/topics/ASAMA2004/index-e.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA 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/).


Nyiragongo (DR Congo) — December 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)


Strong thermal anomalies and gas emission from lava lake through November 2020

Nyiragongo is a stratovolcano in the DR Congo with a deep summit crater containing a lava lake and a small active cone. During June 2018-May 2020, the volcano exhibited strong thermal signals primarily due to the lava lake, along with incandescence, seismicity, and gas-and-steam plumes (BGVN 44:05, 44:12, 45:06). The volcano is monitored by the Observatoire Volcanologique de Goma (OVG). This report summarizes activity during June-November 2020, based on satellite data.

Infrared MODIS satellite data showed almost daily strong thermal activity during June-November 2020 from MIROVA (Middle InfraRed Observation of Volcanic Activity), consistent with a large lava lake. Numerous hotspots were also identified every month by MODVOLC. Although clouds frequently obscured the view from space, a clear Sentinel-2 image in early June showed a gas-and-steam plume as well as a strong thermal anomaly (figure 76).

Figure (see Caption) Figure 76. Sentinel-2 satellite imagery of Nyiragongo on 1 June 2020. A gas-and-steam is visible in the natural color image (bands 4, 3, 2) rising from a pit in the center of the crater (left), while the false color image (bands 12, 11, 4) reveals a strong thermal signal from a lava lake (right). Courtesy of Sentinel Hub Playground.

During the first half of June 2020, OVG reported that SO2 levels had decreased compared to levels in May (7,000 tons/day); during the second half of June the SO2 flux began to increase again. High levels of sulfur dioxide were recorded almost every day in the region above or near the volcano by the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Copernicus Sentinel-5 Precursor satellite (figure 77). According to OVG, SO2 flux ranged from 819-5,819 tons/day during June. The number of days with a high SO2 flux decreased somewhat in July and August, with high levels recorded during about half of the days. The volume of SO2 emissions slightly increased in early July, based on data from the DOAS station in Rusayo, measuring 6,787 tons/day on 8 July (the highest value reported during this reporting period), and then declined to 509 tons/day by 20 July. The SO2 flux continued to gradually decline, with high values of 5,153 tons/day in August and 4,468 tons/day in September. The number of days with high SO2 decreased further in September and October but returned to about half of the days in November.

Figure (see Caption) Figure 77. TROPOMI image of SO2 plume on 27 June 2020 in the Nyiragongo-Nyamulagira area. The plume drifted SSE. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

During 12-13 July a multidisciplinary team of OVG scientists visited the volcano to take measurements of the crater using a TCRM1102 Plus2 laser. They noted that the crater had expanded by 47.3 mm in the SW area, due to the rise in the lava lake level since early 2020. The OVG team took photos of the small cone in the lava lake that has been active since 2014, recently characterized by white gas-and-steam emissions (figure 78). OVG noted that the active lava lake had subsided roughly 20 m (figure78).

Figure (see Caption) Figure 78. Photos (color corrected) of the crater at Nyiragongo showing the small active cone generating gas-and-steam emissions (left) and the active lava lake also characterized by white gas-and-steam emissions on 12 July 2020 (right). Courtesy of OVG (Rapport OVG Juillet 2020).

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); NASA 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/).


Whakaari/White Island (New Zealand) — December 2020 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)


Gas-and-steam emissions with some re-suspended ash in November 2020

Whakaari/White Island, located in the Bay of Plenty 50 km offshore of North Island, has been New Zealand’s most active volcano since 1976. Activity has been previously characterized by phreatic activity, explosions, and ash emissions (BGVN 42:05). The most recent eruption occurred on 9 December 2019, which consisted of an explosion that generated an ash plume and pyroclastic surge that affected the entire crater area, resulting in 21 fatalities and many injuries (BGVN 45:02). This report updates information from February through November 2020, which includes dominantly gas-and-steam emissions along with elevated surface temperatures, using reports from the New Zealand GeoNet Project, the Wellington Volcanic Ash Advisory Centre (VAAC), and satellite data.

Activity at Whakaari/White Island has declined and has been dominated by white gas-and-steam emissions during the reporting period; no explosive eruptive activity has been detected since 9 December 2019. During February through 22 June, the Volcanic Activity Level (VAL) remained at a 2 (moderate to heightened volcanic unrest) and the Aviation Color Code was Yellow. GeoNet reported that satellite data showed some subsidence along the W wall of the Main Crater and near the 1914 landslide scarp, though the rate had reduced compared to previous months. Thermal infrared data indicated that the fumarolic gases and five lobes of lava that were first observed in early January 2020 in the Main Crater were 550-570°C on 4 February and 660°C on 19 February. A small pond of water had begun to form in the vent area and exhibited small-scale gas-and-steam-driven water jetting, similar to the activity during September-December 2019. Gas data showed a steady decline in SO2 and CO2 levels, though overall they were still slightly elevated.

Similar activity was reported in March and April; the temperatures of the fumaroles and lava in the Main Crater were 746°C on 10 March, the highest recorded temperature to date. SO2 and CO2 gas emissions remained elevated, though had overall decreased since December 2019. Small-scale water jetting continued to be observed in the vent area. During April, public reports mentioned heightened gas-and-steam activity, but no eruptions were detected. A GeoNet report issued on 16 April stated that high temperatures were apparent in the vent area at night.

Whakaari remained at an elevated state of unrest during May, consisting of dominantly gas-and-steam emissions. Monitoring flights noted that SO2 and CO2 emissions had increased briefly during 20-27 May. On 20 May, the lava lobes remained hot, with temperatures around 500°C; a nighttime glow from the gas emissions surrounding the lava was visible in webcam images. Tremor levels remained low with occasional slightly elevated episodes, which included some shallow-source volcanic earthquakes. Satellite-based measurements recorded several centimeters of subsidence in the ground around the active vent area since December 2019. During a gas observation flight on 28 May there was a short-lived gas pulse, accompanied by an increase in SO2 and CO2 emissions, and minor inflation in the vent area (figure 96).

Figure (see Caption) Figure 96. Photo of a strong gas-and-steam plume rising above Whakaari/White Island on 28 May 2020. Courtesy of GeoNet.

An observation flight made on 3 June reported a decline in gas flux compared to the measurements made on 28 May. Thermal infrared images taken during the flight showed that the lava lobes were still hot, at 450°C, and continued to generate incandescence that was visible at night in webcams. On 16 June the VAL was lowered to 1 (minor volcanic unrest) and on 22 June the Aviation Color Code had decreased to Green.

Minor volcanic unrest continued in July; the level of volcanic tremors has remained generally low, with the exception of two short bursts of moderate volcanic tremors in at the beginning of the month. Temperatures in the active vents remained high (540°C) and volcanic gases persisted at moderate rate, similar to those measured since May, according to an observation flight made during the week of 30 July. Subsidence continued to be observed in the active vent area, as well as along the main crater wall, S and W of the active vents. Recent rainfall has created small ponds of water on the crater floor, though they did not infiltrate the vent areas.

Gas-and-steam emissions persisted during August through October at relatively high rates (figures 97 and 98). A short episode of moderate volcanic tremor was detected in early August, but otherwise seismicity remained low. Updated temperatures of the active vent area were 440°C on 15 September, which had decreased 100°C since July. Rain continued to collect at the crater floor, forming a small lake; minor areas of gas-and-steam emissions can be seen in this lake. Ongoing subsidence was observed on the Main Crater wall and S and W of the 2019 active vents.

Figure (see Caption) Figure 97. Photo of an observation flight over Whakaari/White Island on 8 September 2020 showing white gas-and-steam emissions from the vent area. Photo courtesy of Brad Scott, GeoNet.
Figure (see Caption) Figure 98. Image of Whakaari/White Island from Whakatane in the North Island of New Zealand showing a white gas-and-steam plume on 26 October 2020. Courtesy of GeoNet.

Activity during November was primarily characterized by persistent, moderate-to-large gas-and-steam plumes that drifted downwind for several kilometers but did not reach the mainland. The SO2 flux was 618 tons/day and the CO2 flux was 2,390 tons/day. New observations on 11 November noted some occasional ash deposits on the webcams in conjunction with mainland reports of a darker than usual plume (figure 99). Satellite images provided by MetService, courtesy of the Japan Meteorological Agency, confirmed the ash emission, but later images showed little to no apparent ash; GNS confirmed that no eruptive activity had occurred. Initial analyses indicated that the ash originated from loose material around the vent was being entrained into the gas-and-steam plumes. Observations from an overflight on 12 November showed that there was no substantial change in the location and size of the active vents; rainfall continued to collect on the floor of the 1978/90 Crater, reforming the shallow lake. A small sequence of earthquakes was detected close to the volcano with several episodes of slightly increased volcanic tremors.

During 12-14 November the Wellington VAAC issued multiple advisories noting gas, steam, and ash plumes that rose to 1.5-1.8 km altitude and drifted E and SE, based on satellite data, reports from pilots, and reports from GeoNet. As a result, the VAL was increased to 2 and the Aviation Color Code was raised to Yellow. Scientists on another observation flight on 16 November reported that small amounts of ash continued to be present in gas-and-steam emissions, though laboratory analyses showed that this ash was resuspended material and not from new eruptive or magmatic activity. The SO2 and CO2 flux remained above background levels but were slightly lower than the previous week’s measurements: 710 tons/day and 1,937 tons/day. Seismicity was similar to the previous week, characterized by a sequence of small earthquakes, a larger than normal volcanic earthquake located near the volcano, and ongoing low-level volcanic tremors. During 16-17 November plumes with resuspended ash were observed rising to 460 m altitude, drifting E and NE, according to a VAAC advisory (figure 99). During 20-24 November gas-and-steam emissions that contained a minor amount of resuspended ash rose to 1.2 km altitude and drifted in multiple directions, based on webcam and satellite images and information from GeoNet.

Figure (see Caption) Figure 99. Left: Photo of a gas observation flight over Whakaari/White Island on 11 November 2020 showing some dark particles in the gas-and-steam plumes, which were deposited on some webcams. Photo has been color corrected and straightened. Courtesy of GeoNet. Right: Photo showing gas, steam, and ash emissions rising above the 2019 Main Crater area on 16 November 2020. Courtesy of GNS Science (17 November 2020 report).

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows a total of eleven low-power thermal anomalies during January to late March 2020; a single weak thermal anomaly was detected in early July (figure 100). The elevated surface temperatures during February-May 2020 were detected in Sentinel-2 thermal satellite images in the Main Crater area, occasionally accompanied by gas-and-steam emissions (figure 101). Persistent white gas-and-steam emissions rising above the Main Crater area were observed in satellite imagery on clear weather days and drifting in multiple directions (figure 102). The small lake that had formed due to rainfall was also visible to the E of the active vents.

Figure (see Caption) Figure 100. Low-power, infrequent thermal activity at Whakaari/White Island was detected during January through late March 2020, as reflected in the MIROVA data (Log Radiative Power). A single thermal anomaly was shown in early July. Courtesy of MIROVA.
Figure (see Caption) Figure 101. Sentinel-2 thermal satellite images in the Main Crater area of Whakaari/White Island show residual elevated temperatures from the December 2019 eruption, accompanied by gas-and-steam emissions and drifting in different directions during February-May 2020. Images using “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 102. Sentinel-2 images showing persistent white gas-and-steam plumes rising from Main Crater area of Whakaari/White Island during March-November 2020 and drifting in multiple directions. A small pond of water (light blue-green) is visible in the vent area to the E of the plumes. On 11 November (bottom right), the color of the plume is gray and contains a small amount of ash. Images using “Natural color” rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

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: New Zealand GeoNet Project, a collaboration between the Earthquake Commission and GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.geonet.org.nz/); GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.gns.cri.nz/); Wellington Volcanic Ash Advisory Centre (VAAC), Meteorological Service of New Zealand Ltd (MetService), PO Box 722, Wellington, New Zealand (URL: http://www.metservice.com/vaac/, http://www.ssd.noaa.gov/VAAC/OTH/NZ/messages.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Brad Scott, GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: https://twitter.com/Eruptn).


Kerinci (Indonesia) — December 2020 Citation iconCite this Report

Kerinci

Indonesia

1.697°S, 101.264°E; summit elev. 3800 m

All times are local (unless otherwise noted)


Intermittent ash plumes and gas-and-steam emissions during June-November 2020

Kerinci, located in Sumatra, Indonesia, has had numerous explosive eruptions since 1838, with more recent activity characterized by gas-and-steam and ash plumes. The current eruptive episode began in April 2018 and has recently consisted of intermittent brown ash emissions and white gas-and-steam emissions (BGVN 45:07); similar activity continued from June through November 2020. Information primarily comes from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM, or the Center of Volcanology and Geological Hazard Mitigation), MAGMA Indonesia, the Darwin Volcanic Ash Advisory Centre (VAAC), and satellite data.

Activity has been characterized by dominantly white and brown gas-and-steam emissions and occasional ash plumes, according to PVMBG. Near daily gas-and-steam emissions were observed rising 50-6,400 m above the crater throughout the reporting period: beginning in late July and continuing intermittently though November. Sentinel-2 satellite imagery showed frequent brown emissions rising above the summit crater at varying intensities and drifting in different directions from July to November (figure 21).

Figure (see Caption) Figure 21. Sentinel-2 satellite imagery of brown emissions at Kerinci from July through November 2020 drifting in multiple directions. On 27 July (top left) the brown emissions drifted SW. On 31 August (top right) the brown emissions drifted W. On 2 September (bottom left) slightly weaker brown emissions drifting W. On 4 November (bottom right) weak brown emissions mostly remained within the crater, some of which drifted E. Images using “Natural Color” rendering (bands 4, 3, 2), courtesy of Sentinel Hub Playground.

During June through July the only activity reported by PVMBG consisted of white gas-and-steam emissions and brown emissions. On 4 June white gas-and-steam emissions rose to a maximum height of 6.4 km above the crater. White-and-brown emissions rose to a maximum height of 700 m above the crater on 2 June and 28 July.

Continuous white-and-brown gas-and-steam emissions were reported in August that rose 50-1,000 m above the crater. The number of ash plumes reported during this month increased compared to the previous months. In a Volcano Observatory Notice for Aviation (VONA) issued on 7 August at 1024, PVMBG reported an ash plume that rose 600 m above the crater and drifted E, SE, and NE. In addition, the Darwin VAAC released two notices that described continuous minor ash emissions rising to 4.3 km altitude and drifting E and NE. On 9 August an ash plume rose 600 m above the crater and drifted ENE at 1140. An ash plume was observed rising to a maximum of 1 km above the crater, drifting E, SE, and NE on 12 August at 1602, according to a PVMBG VONA and Darwin VAAC advisory. The following day, brown emissions rose to a maximum of 1 km above the crater and were accompanied by a 600-m-high ash plume that drifted ENE at 1225. Ground observers on 15 August reported an eruption column that rose to 4.6 km altitude; PVMBG described brown ash emissions up to 800 m above the crater drifting NW at 0731 (figure 22). During 20-21 August pilots reported an ash plume rising 150-770 m above the crater drifting NE and SW, respectively.

Figure (see Caption) Figure 22. Webcam image of an ash plume rising above Kerinci on 15 August 2020. Courtesy of MAGMA Indonesia.

Activity in September had decreased slightly compared to the previous month, characterized by only white-and-brown gas-and-steam emissions that rose 50-300 m above the crater; solely brown emissions were observed on 30 September and rose 50-100 m above the crater. This low level of activity persisted into October, with white gas-and-steam emissions to 50-200 m above the crater and brown emissions rising 50-300 m above the crater. On 16 October PVMBG released a VONA at 0340 that reported an ash plume rising 687 m above the crater and drifting NE. On 17 October white, brown, and black ash plumes that rose 100-800 m above the crater drifted NE according to both PVMBG and a Darwin VAAC advisory (figure 23). During 18-19 October white, brown, and black ash emissions rose up to 400 m above the crater and drifted NE and E.

Figure (see Caption) Figure 23. Webcam image of a brown ash emission from Kerinci on 17 October 2020. Courtesy of MAGMA Indonesia.

Geologic Background. Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Suwanosejima (Japan) — January 2021 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Explosion rate increases during July-December 2020, bomb ejected 1.3 km from crater on 28 December

Suwanosejima, an andesitic stratovolcano in Japan's northern Ryukyu Islands, was intermittently active for much of the 20th century, producing ash plumes, Strombolian explosions, and ashfall. Continuous activity since October 2004 has included intermittent explosions which generate ash plumes that rise hundreds of meters above the summit to altitudes between 1 and 3 km. Incandescence is often observed at night and ejecta periodically reaches over a kilometer from the summit. Ashfall is usually noted several times each month in the nearby community on the SW flank of the island. Ongoing activity for the second half of 2020, which includes significantly increased activity in December, is covered in this report with information provided by the Japan Meteorological Agency (JMA), the Tokyo Volcanic Ash Advisory Center (VAAC), and several sources of satellite data.

A steady increase in activity was reported during July-December 2020. The number of explosions recorded increased each month from only six during July to 460 during December. The energy of the explosions increased as well; ejecta was reported 600 m from the crater during August, but a large bomb reached 1.3 km from the crater at the end of December. After an increased period of explosions late in December, JMA raised the Alert Level from 2 to 3 on a 5-level scale. The MIROVA graph of thermal activity indicated intermittent anomalies from July through December 2020, with a pulse of activity in the second half of December (figure 48).

Figure (see Caption) Figure 48. MIROVA thermal activity for Suwanosejima for the period from 3 February through December 2020 shows pulses of activity in February and April, with intermittent anomalies until another period of frequent stronger activity in December. Courtesy of MIROVA.

Six explosions were recorded during July 2020, compared with only one during June. According to JMA, the tallest plume rose 2,000 m above the crater rim. Incandescent ejecta was occasionally observed at night. The Tokyo VAAC reported a number of ash plumes that rose to 1.2-2.7 km altitude and drifted NW and W during the second half of the month (figure 49). Activity increased during August 2020 when thirteen explosions were reported. The Tokyo VAAC reported a few ash plumes during 1-6 August that rose to 1.8-2.4 km altitude and drifted NW; a larger pulse of activity during 18-22 August produced plumes that rose to altitudes ranging from 1.8 to over 2.7 km. Ashfall was reported on 19 and 20 August in the village located 4 km SSW of the crater; incandescence was visible at the summit and ash plumes drifted SW in satellite imagery on 19 August (figure 50). A MODVOLC thermal alert was issued on 19 August. On 21 August a large bomb was ejected 600 m from the Otake crater in an explosion early in the day; later that afternoon, an ash plume rose to more than 2,000 m above the crater rim. During 19-22 August, SO2 emissions were recorded each day by the TROPOMI instrument on the Sentinel-5P satellite (figure 51).

Figure (see Caption) Figure 49. An ash emission at Suwanosejima rose to 2.7 km altitude and drifted NW on 27 July 2020. Courtesy of JMA (Volcanic activity commentary material on Suwanosejima, July 2020).
Figure (see Caption) Figure 50. Ash drifted SW from the summit crater of Suwanosejima on 19 August 2020 and a bright thermal anomaly was present at the summit. Residents of the village 4 km SW reported ashfall that day and the next. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 51. A period of increased activity at Suwanosejima during 19-22 August 2020 produced SO2 emissions that were measured by the TROPOMI instrument on the Sentinel-5P satellite. Nishinoshima, was also producing significant SO2 at the same time. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Thirteen explosions were recorded during September 2020, with the highest ash plumes reaching 2,000 m above the crater rim, and bombs falling 400 m from the crater. Ashfall was recorded on 20 September in the community located 4 km SSW. The Tokyo VAAC reported intermittent ash plumes during the month that rose to 1.2-2.1 km altitude and drifted in several directions. Incandescence was frequently observed at night (figure 52). Explosive activity increased during October with 22 explosions recorded. Ash plumes rose over 2,000 m above the crater rim, and bombs reached 700 m from the crater. Steam plumes rose 2,300 m above the crater rim. Ashfall and loud noises were confirmed several times between 2 and 14 October in the nearby village. A MODVOLC thermal alert was issued on 6 October. The Tokyo VAAC reported multiple ash plumes throughout the month; they usually rose to 1.5-2.1 km altitude and drifted in many directions. The plume on 28 October rose to over 2.7 km altitude and was stationary.

Figure (see Caption) Figure 52. Incandescence at night and ash emissions were observed multiple times at Suwanosejima during September and October 2020 including on 21 and 26 September (top) and 29 October 2020. Courtesy of JMA (Volcanic activity commentary material on Suwanosejima, September and October 2020).

Frequent explosions occurred during November 2020, with a sharp increase in the number of explosions to 105 events compared with October. Ash plumes rose to 1,800 m above the crater rim and bombs were ejected 700 m. Occasional ashfall and loud noises were reported from the nearby community throughout the month. Scientists measured no specific changes to the surface temperature around the volcano during an overflight early on 5 November compared with the previous year. At 0818 on 5 November a small ash explosion at the summit crater was photographed by the crew during an observation flight (figure 53). On 12 and 13 November, incandescent ejecta fell 600 m from the crater and ash emissions rose 1,500 m above the crater rim (figure 54).

Figure (see Caption) Figure 53. A minor explosion produced a small ash plume at Suwanosejima during an overflight by JMA on the morning of 5 November 2020. The thermal activity was concentrated at the base of the explosion (inset). Image taken from off the E coast. Courtesy of JMA (Volcanic activity commentary material on Suwanosejima, November 2020).
Figure (see Caption) Figure 54. On 12 and 13 November 2020 incandescent ejecta from Suwanosejima reached 600 m from the crater (top) and ash emissions rose 1,500 m above the crater rim (bottom). Courtesy of JMA (Volcanic activity commentary material on Suwanosejima, November 2020).

During December 2020 there were 460 explosions reported, a significant increase from the previous months. Ash plumes reached 1,800 m above the summit. Three MODVOLC thermal alerts were issued on 25 December and two were issued the next day. The number of explosions increased substantially at the Otake crater between 21 and 29 December, and early on 28 December a large bomb was ejected to 1.3 km SE of the crater (figure 55). A second explosion a few hours later ejected another bomb 1.1 km SE. An overflight later that day confirmed the explosion, and ash emissions were still visible (figure 56), although cloudy weather prevented views of the crater. Ashfall was noted and loud sounds heard in the nearby village. A summary graph of observations throughout 2020 indicated that activity was high from January through May, quieter during June, and then increased again from July through the end of the year (figure 57).

Figure (see Caption) Figure 55. Early on 28 December 2020 a large explosion at Suwanosejima sent a volcanic bomb 1.3 km SE from the summit (bright spot on left flank in large photo). Thermal imaging taken the same day showed the heat at the eruption site and multiple fragments of warm ejecta scattered around the crater area (inset). Courtesy of JMA (Volcanic activity commentary material on Suwanosejima, December 2020).
Figure (see Caption) Figure 56. Ash emissions were still visible midday on 28 December 2020 at Suwanosejima during a helicopter overflight by the 10th Regional Coast Guard. Image taken from the SW flank of the volcano. Two large explosions earlier in the day had sent ejecta more than a kilometer from the crater. Courtesy of JMA (Volcanic activity commentary material on Suwanosejima, December 2020).
Figure (see Caption) Figure 57. Activity summary for Suwanosejima for January-December 2020 when 764 explosions were recorded. Black bars represent the height of steam, gas, or ash plumes in meters above the crater rim, gray volcano icons represent explosions, usually accompanied by an ash plume, red icons represent large explosions with ash plumes, orange diamonds indicate incandescence observed in webcams. Courtesy of JMA (Suwanosejima volcanic activity annual report, 2020).

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

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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); NASA 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/).


Karangetang (Indonesia) — December 2020 Citation iconCite this Report

Karangetang

Indonesia

2.781°N, 125.407°E; summit elev. 1797 m

All times are local (unless otherwise noted)


Hot material on the NW flank in November 2020; intermittent crater thermal anomalies

Karangetang (also known as Api Siau) is located on the island of Siau in the Sitaro Regency, North Sulawesi, Indonesia and consists of two active summit craters: a N crater (Kawah Dua) and a S crater (Kawah Utama, also referred to as the “Main Crater”). More than 50 eruptions have been observed since 1675. The current eruption began in November 2018 and has recently been characterized by frequent incandescent block avalanches, thermal anomalies in the crater, and gas-and-steam plumes (BGVN 45:06). This report covers activity from June through November 2020, which includes dominantly crater anomalies, few ash plumes, and gas-and-steam emissions. Information primarily comes from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM, or the Center of Volcanology and Geological Hazard Mitigation), MAGMA Indonesia, and various satellite data.

Activity decreased significantly after mid-January 2020 and has been characterized by dominantly gas-and-steam emissions and occasional ash plumes, according to PVMBG. Daily gas-and-steam emissions were observed rising 25-600 m above the Main Crater (S crater) during the reporting period and intermittent emissions rising 25-300 m above Kawah Dua (N crater).

The only activity reported by PVMBG in June, August, and October was daily gas-and-steam emissions above the Main Crater and Kawah Dua (figure 47). MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows intermittent low-power thermal anomalies during June through late July, which includes a slight increase in power during late July (figure 48). During 14-15 July strong rumbling from Kawah Dua was accompanied by white-gray emissions that rose 150-200 m above the crater. Crater incandescence was observed up to 10 m above the crater. According to webcam imagery from MAGMA Indonesia, intermittent incandescence was observed at night from both craters through 25 July. In a Volcano Observatory Notice for Aviation (VONA) issued on 5 September, PVMBG reported an ash plume that rose 800 m above the crater.

Figure (see Caption) Figure 47. Webcam image of gas-and-steam plumes rising above the two summit craters at Karangetang on 16 June 2020. Courtesy of MAGMA Indonesia.
Figure (see Caption) Figure 48. Intermittent low-power thermal anomalies at Karangetang were reported during June through July 2020 with a slight increase in power in late July, according to the MIROVA graph (Log Radiative Power). No thermal activity was detected during August to late October; in mid-November a short episode of increased activity occurred. Courtesy of MIROVA.

Thermal activity increased briefly during mid-November when hot material was reported extending 500-1,000 m NW of the Main Crater, accompanied by gas-and-steam emissions rising 200 m above the crater. Corresponding detection of MODIS thermal anomalies was seen in MIROVA graphs (see figure 48), and the MODVOLC system showed alerts on 13 and 15 November. On 16 November blue emissions were observed above the Main Crater drifting W. Sentinel-2 thermal images showed elevated temperatures in both summit craters throughout the reporting period, accompanied by gas-and-steam emissions and movement of hot material on the NW flank on 19 November (figure 49). White gas-and-steam emissions rose to a maximum height of 300 m above Kawah Dua on 22 November and 600 m above the Main Crater on 28 November.

Figure (see Caption) Figure 49. Persistent thermal anomalies (bright yellow-orange) at Karangetang were detected in both summit craters using Sentinel-2 thermal satellite imagery during June through November 2020. Gas-and-steam emissions were also occasionally detected in both craters as seen on 17 June (top left) and 20 September (bottom left) 2020. On 19 November (bottom right) the Main Crater (S) showed a hot thermal signature extending NW. Images using “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Geologic Background. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi island. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented in the historical record (Catalog of Active Volcanoes of the World: Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

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/); 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).


Nevado del Ruiz (Colombia) — January 2021 Citation iconCite this Report

Nevado del Ruiz

Colombia

4.892°N, 75.324°W; summit elev. 5279 m

All times are local (unless otherwise noted)


Dome growth and ash emissions continue during July-December 2020

Colombia’s broad, glacier-capped Nevado del Ruiz has an eruption history documented back 8,600 years, including documented observations since 1570. Ruiz remained quiet for 20 years after the deadly September 1985-July 1991 eruption until a period of explosive activity from February 2012 into 2013. Renewed activity beginning in November 2014 included ash and gas-and-steam plumes, ashfall, and the appearance of a slowly growing lava dome inside the Arenas crater in August 2015. Additional information has caused a revision to earlier reporting that eruptive activity ended in May 2017 and began again that December (BGVN 44:12); activity appears to have continued throughout 2017 with intermittent ash emissions and thermal evidence of dome growth. Periods of increased thermal activity alternated with periods of increased explosive activity during 2018-2019 and into 2020; SO2 emissions persisted at significant levels. The lava dome has continued to grow through 2020. This report covers ongoing activity from July-December 2020 using information from reports by the Servicio Geologico Colombiano (SGC) and the Observatorio Vulcanológico y Sismológico de Manizales, the Washington Volcanic Ash Advisory Center (VAAC) notices, and various sources of satellite data.

Gas and ash emissions continued throughout July-December 2020; they generally rose to 5.8-6.1 km altitude with the highest reported plume at 6.7 km altitude on 7 December. SGC interpreted repeated episodes of “drumbeat seismicity” as an indication of continued dome growth throughout the period. Satellite thermal anomalies also suggested that dome growth continued. The MIROVA graph of thermal activity suggests that the dome was quiet in July and early August, but small pulses of thermal energy were recorded every few weeks for the remainder of 2020 (figure 115). Plots of the cumulative number and magnitude of seismic events at Nevado del Ruiz between January 2010 and November 2020 show a stable trend with periodic sharp increases in activity or magnitude throughout that time. SGC has adjusted the warning levels over time according to changes in the slope of the curves (figure 116).

Figure (see Caption) Figure 115. Thermal energy shown in the MIROVA graph of log radiative power at Nevado del Ruiz from 3 February 2020 through the end of the year indicates that higher levels of thermal energy lasted through April 2020; a quieter period from late May-early August was followed by low-level persistent anomalies through the end of the year. Courtesy of MIROVA.
Figure (see Caption) Figure 116. Changes in seismic frequency and energy at Nevado del Ruiz have been monitored by SGC for many years. Left: the cumulative number of daily VT, LP-VLP, TR, and HB seismic events, recorded between 1 January 2010 and 30 November 2020. The arrows highlight the days with the highest number of seismic events; the number and type of event is shown under the date. Right: The cumulative VT and HB seismic energy recorded between 1 January 2010 and 30 November 2020. The arrows highlight the days with the highest energy; the local magnitude of the event is shown below the date. SGC has adjusted the warning levels over time (bar across the bottom of each graph) according to changes in the slope of the curves. Courtesy of SGC (INFORME TÉCNICO – OPERATIVO DE LA ACTIVIDAD VOLCÁNICA, SEGMENTO VOLCÁNICO NORTE DE COLOMBIA – NOVIEMBRE DE 2020).

Activity during July-December 2020. Seismic energy increased during July compared to June 2020 with events localized around the Arenas crater. The depth of the seismicity varied from 0.3-7.8 km. Some of these signals were associated with small emissions of gas and ash, which were confirmed through webcams and by reports from officials of the Los Nevados National Natural Park (NNNP). The Washington VAAC reported a possible ash emission on 8 July that rose to 6.1 km altitude and drifted NW. On 21 July a webcam image showed an ash emission that rose to the same altitude and drifted W; it was seen in satellite imagery possibly extending 35 km from the summit but was difficult to confirm due to weather clouds. Short- to moderate-duration (less than 40 minutes) episodes of drumbeat seismicity were recorded on 5, 13, 17, and 21 July. SCG interprets this type of seismic activity as related to the growth of the Arenas crater lava dome. Primarily WNW drifting plumes of steam and SO2 were observed in the webcams daily. The gas was occasionally incandescent at night. The tallest plume of gas and ash reached 1,000 m above the crater rim on 30 July and was associated with a low-energy tremor pulse; it produced ashfall in parts of Manizales and nearby communities (figure 117).

Figure (see Caption) Figure 117. Images captured by a traditional camera (top) and a thermal camera (bottom) at Nevado del Ruiz showed a small ash emission in the early morning of 30 July 2020. Ashfall was reported in Manizales. The cameras are located 3.7 km W of the Arenas crater. Courtesy of SGC (Emisión de ceniza Volcan Nevado del Ruiz Julio 30 de 2020).

Seismicity increased in August 2020 with respect to July. Some of the LP and TR (tremor) seismicity was associated with small emissions of gas and ash, confirmed by web cameras, park personnel, and the Washington VAAC. The Washington VAAC received a report from the Bogota MWO of an ash emission on 1 August that rose to 6.1 km altitude and drifted NW; it was not visible in satellite imagery. Various episodes of short duration drumbeat seismicity were recorded during the month. The tallest steam and gas plume reached 1,800 m above the rim on 31 August. Despite the fact that in August the meteorological conditions made it difficult to monitor the surface activity of the volcano, three ash emissions were confirmed by SGC.

Seismicity decreased during September 2020 with respect to August. Some of the LP and TR (tremor) seismicity was associated with small emissions of gas and ash, confirmed by web cameras, park personnel and the Washington VAAC. The Washington VAAC reported an ash emission on 16 September that rose to 6.1 km altitude and drifted NW. A minor ash emission on 20 September drifted W from the summit at 5.8 km altitude. A possible emission on 23 September drifted NW at 6.1 km altitude for a brief period before dissipating. Two emissions were reported drifting WNW of the summit on 26 September at 5.8 and 5.5 km altitude. Continuous volcanic tremors were registered throughout September, with the higher energy activity during the second half of the month. One episode of drumbeat seismicity on 15 September lasted for 38 minutes and consisted of 25 very low energy earthquakes. Steam and gas plumes reached 1,800 m above the crater rim during 17-28 September (figure 118). Five emissions of ash were confirmed by the webcams and park officials during the month, in spite of difficult meteorological conditions; three of them occurred between 15 and 20 September.

Figure (see Caption) Figure 118. A dense plume of steam rose from Nevado del Ruiz in the morning of 17 September 2020. Courtesy of Gonzalo.

Seismicity increased during October with respect to September. A few of the LP and tremor seismic events were associated with small emissions of gas and ash, confirmed by web cameras, park personnel, and the Washington VAAC. The Washington VAAC issued advisories of possible ash emissions on 2, 6, 9, 11, 15, 17, 18, and 21 October. The plumes rose to 5.6-6.4 km altitude and drifted primarily W and NW. Steam plumes were visible most days of the month (figure 119). Only a few were visible in satellite data, but most were visible in the webcams. Several episodes of drumbeat seismicity were recorded on 13, 22-25, and 27 October, which were characterized by being of short duration and consisting of very low energy earthquakes. The tallest plume during the month rose about 2 km above the crater rim on 18 October. Ash emissions were recorded eight times during the month by SGC.

Figure (see Caption) Figure 119. A steam plume mixed with possible ash drifted SE from Nevado del Ruiz on 7 October 2020. Courtesy of vlucho666.

During November 2020, the number of seismic events decreased relative to October, but the amount of energy released increased. Some of the seismicity was associated with small emissions of gas and ash, confirmed by webcams around the volcano. The Washington VAAC reported ash emissions on 22 and 30 November; the 22 November event was faintly visible in satellite images and was also associated with an LP seismic event. They rose to 5.8-6.1 km altitude and drifted W. Various episodes of drumbeat seismicity registered during November were short- to moderate-duration, very low energy, and consisted of seismicity associated with rock fracturing (VT). Multiple steam plumes were visible from communities tens of kilometers away (figure 120).

Figure (see Caption) Figure 120. Multiple dense steam plumes were photographed from communities around Nevado del Ruiz during November 2020, including on 18 (top) and 20 (bottom) November. Top image courtesy of Jose Fdo Cuartas, bottom image courtesy of Efigas Oficial.

Seismic activity increased in December 2020 relative to November. It was characterized by continuous volcanic tremor, tremor pulses, long-period (LP) and very long-period (VLP) earthquakes. Some of these signals were associated with gas and ash emissions, one confirmed through the webcams. The Washington VAAC reported ash emissions on 5 and 7 December. The first rose to 5.8 km altitude and drifted NW. The second rose to 6.7 km altitude and drifted W. A single discrete cloud was observed 35 km W of the summit; it dissipated within six hours. Drumbeat seismic activity increased as well in December; the episode on 3 December was the most significant. Steam and gas emissions continued throughout the month; a plume of gas and ash reached 1,700 m above the summit on 20 December, and drifted NW.

Sentinel-2 satellite data showed at least one thermal anomaly inside the Arenas crater each month during August-December 2020, corroborating the seismic evidence that the dome continued to grow throughout the period (figure 121). Sulfur dioxide emissions were persistent, with many days every month recording DU values greater than two with the TROPOMI instrument on the Sentinel 5-P satellite (figure 122).

Figure (see Caption) Figure 121. Thermal anomalies at Nevado del Ruiz were recorded at least once each month during August-December 2020 suggesting continued growth of the dome within the Arenas crater at the summit. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 122. Sulfur dioxide emissions were persistent at Nevado del Ruiz during August-December 2020, with many days every month recording DU values greater than two with the TROPOMI instrument on the Sentinel 5-P satellite. Ecuador’s Sangay had even larger SO2 emissions throughout the period. Dates are at the top of each image. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Additional reports of activity during 2017. Activity appears to have continued during June-December 2017. Ash emissions were reported by the Bogota Meteorological Weather Office (MWO) on 13 May, and by SGC on 28 May. During June, some of the recorded seismic events were associated with minor emissions of ash; these were confirmed by webcams and by field reports from both the staff of SGC and the Los Nevados National Natural Park (PNNN). Ash emissions were confirmed in webcams by park officials on 3, 16, and 17 June. Gas emissions from the Arenas crater during July 2017 averaged 426 m above the crater rim, generally lower than during June. The emissions were mostly steam with small amounts of SO2. Emissions were similar during August, with most steam and gas plumes drifting NW. No ash emissions were reported during July or August.

SGC reported steam and gas plumes during September that rose as high as 1,650 m above the crater rim and drifted NW. On 21 September the Washington VAAC received a report of an ash plume that rose to 6.4 km altitude and drifted NNW, although it was not visible in satellite imagery. Another ash emission rising to 6.7 km altitude was reported on 7 October; weather clouds prevented satellite observation. An episode of drumbeat seismicity was recorded on 9 October, the first since April 2017. While SGC did not explicitly mention ash emissions during October, several of the webcam images included in their report show plumes described as containing ash and gas (figure 123).

Figure (see Caption) Figure 123. Plumes of steam, gas, and ash rose from Arenas crater at Nevado del Ruiz most days during October 2017. Photographs were captured by the webcams installed in the Azufrado Canyon and Cerro Gualí areas. Courtesy of SGC (INFORME DE ACTIVIDAD VOLCANICA SEGMENTO NORTE DE COLOMBIA, OCTUBRE DE 2017).

The Washington VAAC received a report from the Bogota MWO of an ash emission that rose to 6.1 km altitude and drifted NE on 8 November 2017. A faint plume was visible in satellite imagery extending 15 km NE from the summit. SGC reported that plumes rose as high as 2,150 m above the rim of Arenas crater during November. The plumes were mostly steam, with minor amounts of SO2. A diffuse plume of ash was photographed in a webcam on 24 November. SGC did not report any ash emissions during December 2017, but the Washington VAAC reported “a thin veil of volcanic ash and gases” visible in satellite imagery and webcams on 18 December that dissipated within a few hours. In addition to the multiple reports of ash emissions between May and December 2017, Sentinel-2 thermal satellite imagery recorded at least one image each month during June-December showing a thermal anomaly at the summit consistent with the slowly growing dome first reported in August 2015 (figure 124).

Figure (see Caption) Figure 124. Thermal anomalies from the growing dome inside Arenas crater at the summit of Nevado del Ruiz appeared at least once each month from June-December 2017. A strong anomaly was slightly obscured by clouds on 3 June (top left). On 2 August, a steam plume obscured most of the crater, but a small thermal anomaly is visible in its SE quadrant (top right). Strong anomalies on 30 November and 20 December (bottom) have a ring-like form suggestive of a growing dome. Atmospheric penetration rendering (bands 12, 11, 8A), courtesy of Sentinel Hub Playground.

Geologic Background. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Gonzalo (URL: https://twitter.com/chaloc22/status/1306581929651843076); Jose Fdo Cuartas (URL: https://twitter.com/JoseFCuartas/status/1329212975434096640); Vlucho666 (URL: https://twitter.com/vlucho666/status/1313791959954268161); Efigas Oficial (URL: https://twitter.com/efigas_oficial/status/1329780287920873472).

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Bulletin of the Global Volcanism Network - Volume 34, Number 09 (September 2009)

Managing Editor: Richard Wunderman

Anatahan (United States)

Quiet except for brief tremor in February 2009 and plume in June 2009

Kaba (Indonesia)

Increased seismicity and whitish vapor emissions

Koryaksky (Russia)

Continued ash emissions during May-September 2009

Pagan (United States)

Emission of a small plume in mid-April 2009

Reventador (Ecuador)

Lava flows seen and SO2 fluxes recorded during 16-17 September 2009

Rinjani (Indonesia)

More data relevant to eruptions during 2 May through at least 31 August 2009

St. Helens (United States)

Eruption ceased in late January 2008; quiet continues in late 2009

Turrialba (Costa Rica)

Non-eruptive in August 2009, but degassing and with widening cracks



Anatahan (United States) — September 2009 Citation iconCite this Report

Anatahan

United States

16.35°N, 145.67°E; summit elev. 790 m

All times are local (unless otherwise noted)


Quiet except for brief tremor in February 2009 and plume in June 2009

Our most recent report on Anatahan (BGVN 33:12) discussed sulfur dioxide emissions and steam plumes during 2008. This report covers activity between January and October 2009.

A team of research scientists from the University of Tokyo and Kyushu University visited the volcano during the week of 19 January. They worked with the Emergency Management Office of the Commonwealth of the Northern Mariana Islands (CNMI) to perform seismic station maintenance. The team observed no unusual volcanic phenomena. Seismic levels remained low, and no anomalies were observed in satellite imagery.

The U.S. Geological Survey (USGS) reported that seismic activity at Anatahan during the first half of 2009 was generally at background levels. On 11 February a brief episode of tremor occurred. A low level plume was observed in satellite images on 13 June, but there was no evidence that it contained ash. Nothing unusual was observed in satellite images throughout the rest of the week. According to the USGS, Anatahan was quiet as of 6 November.

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

Information Contacts: Dina Venezky, Volcano Hazards Program, U.S. Geological Survey, 345 Middlefield Road, MS 910, Menlo Park, CA 94025, USA (URL: http://volcanoes.usgs.gov/); Emergency Management Office, Commonwealth of the Northern Mariana Islands, PO Box 100007, Saipan, MP 96950, USA (URL: http://www.cnmihsem.gov.mp/).


Kaba (Indonesia) — September 2009 Citation iconCite this Report

Kaba

Indonesia

3.522°S, 102.615°E; summit elev. 1940 m

All times are local (unless otherwise noted)


Increased seismicity and whitish vapor emissions

Deep volcanic earthquakes, seismic tremor, and five small explosions with corresponding ash emission were reported from Kaba in August 2000 (BGVN 25:11). Since then, Kaba has been quiet, but even in its normal state it almost always emits whitish plumes 25-100 m high.

On 20 October 2009, the Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that seismic activity from Kaba increased in August and remained elevated into September and October. Inflation was also detected. When weather permitted, diffuse white plumes were seen rising ~ 25-50 m above the summit crater complex and drifting E. Based on the deformation and increased seismicity, CVGHM raised the Alert Level to 2 (on a scale of 1-4).

From January through August 2009, the frequency of deep volcanic earthquakes averaged 85 events per month, but in August the number of events rose to 257 per month. During August-September, whitish plumes remained similar to September-October. In September seismicity fluctuated but tended to increase. Earthquakes and total tremors recorded at Kaba's monitoring post are shown in table 2.

Table 2. Summary of Kaba seismic data recorded during 12 September-20 October 2009. Courtesy of CVGHM.

Dates (2009) Deep volcanic earthquakes (Count, Characteristics) Shallow volcanic earthquakes (Count, Characteristics) Notes
Beginning on 12 September 343 55 --
1-17 October 253. Max. amplitudes of 1-18 mm; S-wave minus P-wave arrival times ("S-P") of 0.2-3.5 s with signals lasting 4-35 s. 271. Max. amplitudes 0.5-15 mm, durations of 2.5-11 s. --
18 October 68. Max. amplitude of 1-19 mm; S-P times of 0.2-3 s, and a duration of 3.5-47 s. 67. Max. amplitudes 0.8-16 mm, durations of 2.5-13 s. --
19 October 50. Max. amplitudes of 0.5-18 mm; S-P 0.5-2 s, and a duration of 2-15 s. 127. Max. amplitudes 0.5-15 mm, durations of 2.5-10 s. Volcanic tremor registered during 0640-0900 local time; max. amplitudes 0.5-2 mm.
20 October 29. Max. amplitudes of 0.5-18 mm; S-P 0.5-2 seconds and a duration of 2-15 s. 21. Max. amplitudes 0.5-15 mm, durations of 2.5-10 s. Continuous tremor with amplitudes of 1-7 mm; the most prevalent amplitudes 1-3 mm. During clear weather, whitish plumes rose ~ 25 m.

Deformation measurements taken using an EDM (electronic distance measurement) method were as follows: Biring station, shorter by 10 cm; Voelsang station, longer by 0.4 cm; and Kaba station, shorter by 2 cm.

Measurements of the crater water temperature on 15 October showed a reading of 72°C, with a pH of 3.24. The sulfurous and associated solfatara areas recorded a temperature of around 106-107°C. There was no other activity in the area of the crater.

Geologic Background. Kaba, a twin volcano with Mount Hitam, has an elongated summit crater complex dominated by three large historically active craters trending ENE from the summit to the upper NE flank. The SW-most crater of Gunung Kaba, named Hidup (or Lama), is the largest. Most historical eruptions have affected only the summit area. They mostly originated from the central summit craters, although the upper-NE flank crater Kawah Vogelsang also produced explosions during the 19th and 20th centuries.

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


Koryaksky (Russia) — September 2009 Citation iconCite this Report

Koryaksky

Russia

53.321°N, 158.712°E; summit elev. 3430 m

All times are local (unless otherwise noted)


Continued ash emissions during May-September 2009

During March-18 April 2009 (BGVN 34:03) seismicity and volcanism continued at Karymsky, and ash plumes were detected for hundreds of kilometers. This report discusses the interval May-October 2009, with some discussion of earlier seismicity. The key conclusion for this new interval is that seismicity has not stopped and occasional, though smaller ash plumes continued.

In the mid-May 2009 volcanic and seismic activity decreased considerably. The active fumarole on the NW slope produced gas-steam plumes, but no longer contained appreciable ash (figure 8).

Figure (see Caption) Figure 8. Gas-steam emission seen on the NW side Koryaksky on 11 May 2009. The white snow on the volcano confirms the virtual absence of any ash in the plume. Photo by A. Socorenko.

On 2-3 June 2009, observers again saw small areas of snow that were dark gray, indicating some increased ash content. On 15-16 August 2009 instruments began to register a spasmodic volcanic tremor; seismicity increased, and on 17 August ash fell to the SW, forming a deposit 1 mm thick (figure 9).

Figure (see Caption) Figure 9. Ash plume from a vent on NW slope of Koryaksky. Snow on the slope covered fresh ashfall. Dark area around vent is due to local heating and melting of snow cover. Photo taken on 18 August 2009 by S. Chirkov.

Seismic analysis. Seliverstov (2009) analyzed seismicity for May 2008 to 10 June 2009, looking at events larger than Ks 4 (Class 4 earthquakes, roughly those larger than M ~ 1.2) and found a spatial and temporal pattern to this stronger seismicity. During March 2008 a prominent swarm of earthquakes was often centered at about 5-10 km depth. Smaller earthquakes were also seen around that time, several at ~ 12 km depth, and some at 15 km depth. This stronger seismicity then waned for several months until late June. During August 2008 to 10 June 2009, earthquakes were numerous, often centered near 5 km depth.

Figure 10 shows a representative set of hypocenters during 3 January 2009-6 November 2009. The pattern shown was similar to that seen during various months during 2008 through mid-2009. Other patterns during 2008 to mid-2009 included intervals where epicenters dipped, as noted in the analysis presented by Seliverstov (2009). Despite decreased volcanic activity, the elevated seismicity remained until at least 10 June 2009.

Figure (see Caption) Figure 10. Seismicity of Koryaksky (and Avachinsky, to the SE) recorded during May-October 2009. Map shows location and depths of earthquakes (white line is cross-section AB. Cross-section shows hypocenters within 20 km depth. Courtesy of the Kamchatka Branch of the Geophysical Service, Russian Academy of Sciences (KB GS RAS).

The number of earthquakes recorded within 10-15 km of the summit during January through October 2009 by the KB GS RAS peaked in April with 422 events, and again in August with 245 events. Otherwise, the interval commonly had monthly totals of 100-200 with the lowest during January (59 events) and October (37 events).

References. Seliverstov, N., 2009, The activity Koryaksky volcano, Kamchatka, Vestnik KRAUNC, Earth Science Series; Petropavlovsk-Kamchatsky, 2009, v. 13, p.7-9 [ISSN 1816-5524]. In Russian.

Geologic Background. The large symmetrical Koryaksky stratovolcano is the most prominent landmark of the NW-trending Avachinskaya volcano group, which towers above Kamchatka's largest city, Petropavlovsk. Erosion has produced a ribbed surface on the eastern flanks of the 3430-m-high volcano; the youngest lava flows are found on the upper W flank and below SE-flank cinder cones. Extensive Holocene lava fields on the western flank were primarily fed by summit vents; those on the SW flank originated from flank vents. Lahars associated with a period of lava effusion from south- and SW-flank fissure vents about 3900-3500 years ago reached Avacha Bay. Only a few moderate explosive eruptions have occurred during historical time, but no strong explosive eruptions have been documented during the Holocene. Koryaksky's first historical eruption, in 1895, also produced a lava flow.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far East Division, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/); Kamchatka Branch of the Geophysical Service of the Russian Academy of Sciences (KB GS RAS), Sergey Senukov, Russia (URL: http://www.emsd.ru/); Alexander Socorenko and Sergei Chirkov, IV&S FED RAS; Tokyo Volcanic Ash Advisory Center (VAAC), Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/).


Pagan (United States) — September 2009 Citation iconCite this Report

Pagan

United States

18.13°N, 145.8°E; summit elev. 570 m

All times are local (unless otherwise noted)


Emission of a small plume in mid-April 2009

Our most recent report on Pagan (BGVN 32:01) covered light ashfall and a small gas plume probably containing some ash during the first week of December 2006. We received no additional information regarding activity at Pagan until April 2009. The U.S. Geological Survey (USGS) does not currently have monitoring instruments on Pagan. Monitoring is by satellite and ground observers.

According to the Washington Volcanic Ash Advisory Center (VAAC), a plume from Pagan on 15 April consisting of intermittent puffs of steam rose to an altitude of 1.8 km and drifted about 37 km W. This observation was confirmed by a ship crew that noted a white plume "with some black" that same day.

On 16 April, the Washington VAAC reported that a narrow plume of unknown composition extended 85 km W from the volcano. According to the CNMI Emergency Management Office, fishermen reported that the plume was "thicker" on 15 April than on 16 April. Weather clouds obscured satellite views. The next day fishermen again reported a plume.

By 17 April, steaming had diminished. A passing pilot reported seeing no activity; however, the Washington VAAC noted a very faint plume extending 85 km NNW in satellite imagery.

Crew on a U.S. National Oceanic and Atmospheric Administration (NOAA) ship observed continuous emissions from the N crater during 21-22 April. Satellite imagery analyzed by the Washington VAAC showed a diffuse plume drifting 15 km W on 23 April. On 28 April, steam emissions had decreased.

Based on analyses of satellite imagery, the Washington VAAC reported that on 14 August a 2-hour-long thermal anomaly detected over Pagan was followed by a small emission. The emission, hotter than its surroundings, drifted NW and quickly dissipated.

No thermal hotspots on Pagan have been detected by MODIS during the last five years.

Geologic Background. Pagan Island, the largest and one of the most active of the Mariana Islands volcanoes, consists of two stratovolcanoes connected by a narrow isthmus. Both North and South Pagan stratovolcanoes were constructed within calderas, 7 and 4 km in diameter, respectively. North Pagan at the NE end of the island rises above the flat floor of the northern caldera, which may have formed less than 1,000 years ago. South Pagan is a stratovolcano with an elongated summit containing four distinct craters. Almost all of the recorded eruptions, which date back to the 17th century, have originated from North Pagan. The largest eruption during historical time took place in 1981 and prompted the evacuation of the sparsely populated island.

Information Contacts: Dina Venezky, Volcano Hazards Program, U.S. Geological Survey, 345 Middlefield Road, MS 910, Menlo Park, CA 94025, USA (URL: http://volcanoes.usgs.gov/); Emergency Management Office, Commonwealth of the Northern Mariana Islands, PO Box 100007, Saipan, MP 96950, USA (URL: http://www.cnmihsem.gov.mp/); Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Reventador (Ecuador) — September 2009 Citation iconCite this Report

Reventador

Ecuador

0.077°S, 77.656°W; summit elev. 3562 m

All times are local (unless otherwise noted)


Lava flows seen and SO2 fluxes recorded during 16-17 September 2009

Activity at Reventador between August 2008 and late April 2009 was a period of generally low seismicity (BGVN 34:03). During early November 2008 repeated small eruptions occurred with steam-and-ash plumes, Strombolian eruptions, and lava flows. This report continues coverage through October 2009, an interval that included new lava flows advancing ~ 500 m by mid-September 2009.

Based on analysis of satellite imagery, the Washington Volcanic Ash Advisory Center (VAAC) reported that on 1 May a thermal anomaly over Reventador occurred along with a possible low plume drifting W. The Instituto Geofísico-Escuela Politécnica Nacional (IG) reported to the VAAC the presence of lava and gas emissions and possible smoke from burning vegetation, but little to no ash.

On 15 May, the IG observed an ash emission, although neither an ash signature nor a thermal anomaly was detected in satellite imagery. On 26 May, a diffuse ash plume rose to an altitude of 6.4 km and drifted SW. Thermal anomalies were intermittently seen on satellite imagery.

On 21 July-3 August, tremor was sporadic. On 4 August, seismicity increased and periods of tremor frequently saturated the seismic stations. Thermal anomalies, detected in satellite imagery on 1 and 2 August, became more intense on 4, 5, and 10 August. On 6 August, a steam plume rose 1.2 km above the crater and drifted W. Incandescent blocks were ejected from the crater and fell onto the flanks. Thermal images taken from a location 7 km E of Reventador revealed a linear area of higher temperatures, confirming the presence of a new lava flow on the S flank. Incandescence in the crater was seen on 9 August. According to the Washington VAAC, based on information from the IG, an ash plume on 15 August rose to an altitude of 3.6 km and drifted NW.

Field observations on 16-17 September 2009. IG scientists visited Reventador during 16-17 September 2009; among their objectives was to map, sample, and collect thermal images of the new lava flows and to measure the sulfur dioxide (SO2) concentrations with a mobile DOAS.

The team noted that recent lava flows had descended the flanks in a SE to E direction, continuing the same pattern that had begun with the 2005 eruption (figure 31). A dome within the crater showed constant growth (figure 32). Gas was emitted to a height of less than 200 m and drifted mainly W. A small lava flow originating in the dome area had descended ~ 500 m from the cone's S flank.

Figure (see Caption) Figure 31. Panoramic view from the sequential camera of lava flows at Reventador. Courtesy of S. Vallejo.
Figure (see Caption) Figure 32. At Reventador, a photo taken on 16-17 September 2009 of the actively growing dome in the summit crater. Courtesy of J. Bourquin.

Thermal images and SO2 measurements were collected near the caldera, and lavas were sampled. SO2 flux measurements (table 4) were collected both by helicopter and by car (figure 33). A telescope for the SO2 measurements sat below the helicopter blades and those spinning blades may have interfered with the measurements. The values presented may thus underestimate the SO2 fluxes.

Table 4. Reventador SO2 data collected from helicopter on 16 and 17 September 2009. The transects in the first column are indicated on figure 33. Transect 34 measurements clearly indicated that the SO2 gas plume had divided (bifurcated) and the two plumes appear as 34a and 34b. For this transect, the SO2 fluxes were calculated separately for each lava plume segment, than added to get the total emission. Land-based measurements, transects 43 and 46, were collected S and W of the vent. Courtesy of IG.

Transect/Route Wind speed (m/s) Wind direction Data number Offset SO2 flux (t/d) Plume Width Traverse Length Intensity Limit
31 5 281 191 -28 811 1.9 km 52.2 km 7
34a 5 270 95 -1 1,425 3.6 km 22.2 km 7
34b 5 326 124 -8 795 2.5 km 49.2 km 7
34 Total -- -- 215 -- 2,220 -- -- --
35 5 337 84 -28 616 1.6 km 22.8 km 5
36 5 349 147 -16 557 2.1 km 30.2 km 8
43 5 202 471 -14 283 5.2 km 42.8 km 5
46 5 236 1222 -14 1,264 16 km 116 km 5
Figure (see Caption) Figure 33. Map of Reventador illustrating transects made (in colored version, each transect is in a different color). Transects 31 and 34 were conducted on 16 September; transects 35, 36, 43 and 46 were conducted on 17 September. Courtesy of IG.

Based on a pilot observation, the Washington VAAC reported that on 21 September a plume rose to an altitude of 7.6 km. An ash plume on 4 October drifted W. In both cases, ash was not seen in satellite imagery, although meteorological clouds were present. In the latter case, an occasional thermal anomaly was observed.

Thermal anomalies over the crater area were detected in MODIS satellite imagery on 6, 11, and 13 October. On 13 October, the OMI satellite sensor indicated that the SO2 concentration in the atmosphere near the volcano had increased. On 14 October, seismicity increased and harmonic tremor was detected. A seismic station located at ~ 2,600 m elevation on the NE flank of the cone detected rockfalls. Several people living in the area reported roaring noises and had observed slight incandescence from the crater during the previous few nights.

During an overflight on 16 October, scientists saw the lava dome and a lava flow on the NE flank (figure 34). Bluish gases were being emitted. According to a thermal camera, the incandescent parts in the crater were about 300°C. Other observers heard roaring noises and sounds resembling "cannon shots." Incandescent blocks were ejected from the crater, and steam and gas rose 100 m and drifted SW. Incandescent material was seen on the S flank.

Figure (see Caption) Figure 34. Aerial photo taken on the N side of Reventador on 16 October 2009 showing the lava dome amid weather clouds and some heavy steaming from the NE-flank lava flow. Courtesy of IG.

On 17 October, long period (LP) earthquakes and volcanic explosions lasting up to 10 hours were registered, incandescence on the S flank was noted, and noises similar to the previous day were again heard. A small gray plume was seen the next day. On 19 October, thermal anomalies were again detected on satellite imagery. During an overflight, blue gas plumes containing SO2 were seen (figure 35). The lava flow on the S flank occupied a large area and was divided into two branches.

Figure (see Caption) Figure 35. Photograph of the E side of Revantador's cone taken the morning of 19 October 2009. Note steam rising from dome summit and lava flows on volcano's flanks. Courtesy of IG.

According to the IG, on 21 October, steam-and-gas plumes with little to no ash rose 2-4 km above the crater and drifted in various directions. An explosion that day ejected incandescent material from the crater and blocks rolled down the flanks. On 22 October, a few explosions generated ash-and-steam plumes that rose 4 km. Observations during an overflight revealed a small lava flow on the N flank and a larger flow with four branches on the S flank (figure 36). Part of the lava dome base had disappeared and small spines were present, especially on the S side of the dome. Thermal images revealed that material in the crater was 400°C and the lava-flow fronts were 250°C. Cloudy weather prevented visual observations during 23-26 October. Roaring noises were heard on 25 October.

Figure (see Caption) Figure 36. Aerial photograph displaying the distribution of lava flows on the N side of Reventador's caldera on 22 October 2009. Courtesy of S. Vallejo.

Geologic Background. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Information Contacts: Geophysical Institute (IG), Escuela Politécnica Nacional, Apartado 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/); Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).


Rinjani (Indonesia) — September 2009 Citation iconCite this Report

Rinjani

Indonesia

8.42°S, 116.47°E; summit elev. 3726 m

All times are local (unless otherwise noted)


More data relevant to eruptions during 2 May through at least 31 August 2009

A series of eruptions at Rinjani began on 2 May 2009 (BGVN 34:06). The current report, provided by Alain Bernard, presents additional data regarding these eruptions, which continued through 31 August 2009.

Studies of Rinjani volcanic lake are part of a cooperative agreement between Indonesia and Belgium, a collaboration funded by the Commission Universitaire pour le Développement (CUD, the main Belgian development cooperation agency for universities). Geochemical and physical studies of the Segara Anak lake started in the framework of this collaborative effort during the summer of 2006. During the summer of 2008, investigators installed a monitoring station for continuous measurements of the lake's level and temperature, and for meteorological parameters.

The scientific teams involved in this study were (Indonesia) Akhmad Solikhin, Devy Syabahna and Syegi Kunrat of the Center of Volcanology and Geological Hazards Mitigation (CVGHM); (Belgium) Alain Bernard, Benjamin Barbier, Robin Campion, and Corentin Caudron of the Université Libre de Bruxelles (ULB), and Vincent Hallet and David Lemadec of the Facultés Universitaires Notre Dame de la Paix (FUNDP).

Segara Anak lake. The majestic Segara Anak lake filling the caldera of Rinjani covers an area of 11 km2. Prior to the 2009 eruption, the lake's volume was 1.02 km3. The lake-surface elevation is ~ 2 km (figures 11 and 12).

Figure (see Caption) Figure 11. Bathymetric map of Rinjani's Segara Anak lake made from 65 km of echo-sounder surveys conducted in 2007 and 2008. Maximum depth of the lake is 205 m. Courtesy of the CVGHM, ULB, and FUNDP study team.
Figure (see Caption) Figure 12. Topographic map of Rinjani caldera from Bakosurtanal-Indonesia (National Coordinator for Survey and Mapping Agency, Indonesia). Margins defining squares are 1 km long. "CTD" and "CTD-B" are locations of conductivity-temperature-depth profiles. "Meteo" is the site of the meteorological station monitoring air temperature, humidity, wind velocity, and net solar flux. The labels 51-54 are locations of hot springs discussed below. Courtesy of the CVGHM, ULB, and FUNDP study team.

The lake is neutral (pH: 7-8) and its chemistry dominated by chlorides and sulfates with a relatively high concentration of total-dissolved solids (TDS: 2,640 mg/L). This unusually high TDS value and lake surface temperatures (20-22°C), well above ambient temperatures (14-15°C) for this altitude, reflects a strong input of hydrothermal fluids. Numerous hot springs are located along the shore at the foot of the Barujari cone. Bathymetric profiles showed several areas with columns of gas bubbles escaping from the lake's floor.

Precursory signals of the May 2009 eruption. Changes in Segara Anak lake and the hot springs before the first 2 May 2009 eruption included significant anomalies in the temperature and chemistry of the hot springs.

During field work 10-14 April 2009, the researchers noted an increase in temperature and acidity of hot springs 53 and 54 (figures 13-14) compared to July. This increasing acidity was confirmed in the lab as the consequence of an increase in sulfate levels not observed during studies since 2004.

Figure (see Caption) Figure 13. Geochemistry of Rinjani's Segara Anak lake (from CTD locations, figure 12) and hot springs. NA signifies not analyzed. Courtesy of the CVGHM, ULB, and FUNDP study team.
Figure (see Caption) Figure 14. A plot of 2004 to 2009 sulfate (SO42-) ion concentration versus pH. Note the April 2009 increase in the acidity and sulfate contents of Rinjani's hot springs 53 and 54 (upper left). Courtesy of the CVGHM, ULB, and FUNDP study team.

The Fe-ion concentrations in spring 54, usually below detection limits, peaked at 120 mg/L. This change in chemistry produced a yellowish-brown coloration of the lake waters because of the precipitation of ferric hydroxide, Fe(OH)3 (figures 15-16). An ASTER image from 21 August 2009, processed to enhance the Fe(OH)3 precipitates, revealed a chemical plume close to where hot springs 53 and 54 injected water into the lake.

Figure (see Caption) Figure 15. The Rinjani lake shoreline seen at a point close to the hot spring 54 on 12 April 2009. The water has a brown color and the coating on the rocks is an amorphous ferric hydroxide that precipitated when hydrothermal fluids oxidized by mixing with the lake waters (yellow-brown in color). Rock discoloration reaches the height of the mans lower hand. Changes in lake level were a consequence of the rainy season. Photo by A. Bernard.
Figure (see Caption) Figure 16. A photo of Rinjani and Segara Anak Lake thought to have been taken on 26 April 2009 but certainly before the start of the eruption. A spectacular yellow-brown chemical precipitate floated on the lake's surface (at left). Copyrighted photo by Jim Chow.

A chemical plume of low pH and dissolved oxygen was observed at the lake surface extending up to several hundred meters away from hot spring 54. pH profiles as a function of depth recorded at several locations showed a clear acidification of Segara Anak lake especially at shallow depths (15-20 m) (figure 17). Rainfall in April 2009 caused a shallow zone of higher pH.

Figure (see Caption) Figure 17. Plot showing shifts of pH in Rinjani's caldera lake waters with depth. The 2009 profile was recorded in April 2009, and the 2008 profile, in July 2008. Line 2009b was drawn as an estimate of the curve without the rainfall event. Measurements made with an SBE Seacat 19-Plus profiler. Courtesy of the CVGHM, ULB, and FUNDP study team.

A slight lake surface temperature increase from 20°C in July 2008 to 22°C in early April 2009 was mostly attributed to meteorological effects. Large increases seen in lake level in January and February 2009 were the consequence of heavy rainfalls. Heating of the lake between August 2008 and April 2009 occurred mainly during periods with reduced heat loss to the atmosphere due to less wind.

A report of these field observations was made on 17 April to CVGHM, which prompted them to send another team to the volcano. The new team arrived at the summit of the volcano on 2 May 2009, the day the eruptions started.

Eruptive activity May-August 2009. The 2009 eruptions originated from the same vent of the October 2004 activity (figure 18), and was characterized by mild eruptions that produced a small lava flow and low altitude, ash-poor gas plumes (figure 19). Contrary to that reported in some newspapers, the 2009 eruption did not open a new vent.

Figure (see Caption) Figure 18. This July 2006 photo of Rinjani illustrates the new vent that opened on the NE slope of Gunung Baru in 2004 and then produced a short lava flow. The 2009 eruptive activity at Rinjani started from this same vent, producing a significant lava flow that entered the crater lake and built a delta. Photo by A. Bernard (July 2006).
Figure (see Caption) Figure 19. Eruption of Rinjani seen on 10 June 2009. The plume at this point was relatively small and lava proceeded N to enter the lake. Photo by R. Campion.

Alain Bernard sent a report by Robin Campion (ULB) who was on site June 2009. According to Campion, mild activity was observed from the SE rim during 9-11 June. Pressurized incandescent gas was released at a 1-2 second intervals from a vent located in the 2004 crater, on the S flank of Barujari. At variable intervals (10 seconds to 10 minutes), stronger gas jets ejected lava fragments to heights up to 100 m. Occasional ash ejections occurred from a second vent in the same crater. A third lower vent emitted a viscous lava flow that reached Segara Anak Lake. Contact between the lake and the lava delta resulted in a warm surface current (figure 20).

Figure (see Caption) Figure 20. A 10 June 2009 FLIR thermal camera image of Rinjani's Barujari cone and Segara Anak lake. A thermal plume of hot lake water was drifting from the lava entry points. Temperature scale is for lake waters. Photo by R. Campion.

Figure 21 shows an ASTER satellite image of Rinjani lake-surface temperatures. Increased discharge of the hot springs on the S flank of Barujari produced a distinct plume with an orange-red color. Weak winds carried the steam-and-gas plume (with low ash content) N and W at an altitude of 3-4 km. Activity did not vary during the 3-day observation period.

Figure (see Caption) Figure 21. ASTER satellite image of the N part of Rinjani's Segara Anak lake taken on 29 July 2009 (at 1446 UTC). Thermal infrared bands 13 and 14 processed with a split-window algorithm. Contours are in degrees C. Maximum temperature in the lake water was 57°C. Courtesy of the CVGHM, ULB, and FUNDP study team.

As of 31 August 2009, the eruption was still underway. At that point, the new lava flow covered an area of 0.65 km2 (figure 22). The shoreline had been significantly modified by the entry of lava into Segara Anak lake, and the lake surface area had been reduced by 0.46 km2 (figures 22 and 23).

Figure (see Caption) Figure 22. Rinjani seen in ASTER false color on 21 August 2009 (0235 UTC). The new lava covers an area of 650,000 m2 and significantly changed the shoreline. The inset shows the pre-eruption shoreline and the new lava margin (in red on colored versions). Courtesy of the CVGHM, ULB, and FUNDP study team.
Figure (see Caption) Figure 23. Rinjani, in a photo apparently taken on 4 August 2009, showing a new delta built into the lake. Brown waters from hot springs were still visible at the end of the lake and drifted over a large area of the lake. Courtesy of Arjo Vanderjagt.

According to Alain Bernard, updates on Rinjani's activity will be posted on the website of the Commission of Volcanic Lakes (CVL, see information contacts). Bernard sent additional figures describing Rinjani behavior as late as 27 September 2009.

Geologic Background. Rinjani volcano on the island of Lombok rises to 3726 m, second in height among Indonesian volcanoes only to Sumatra's Kerinci volcano. Rinjani has a steep-sided conical profile when viewed from the east, but the west side of the compound volcano is truncated by the 6 x 8.5 km, oval-shaped Segara Anak (Samalas) caldera. The caldera formed during one of the largest Holocene eruptions globally in 1257 CE, which truncated Samalas stratovolcano. The western half of the caldera contains a 230-m-deep lake whose crescentic form results from growth of the post-caldera cone Barujari at the east end of the caldera. Historical eruptions dating back to 1847 have been restricted to Barujari cone and consist of moderate explosive activity and occasional lava flows that have entered Segara Anak lake.

Information Contacts: Alain Bernard, Benjamin Barbier, Robin Campion, and Corentin Caudron, Université Libre de Bruxelles (ULB), Belgium (Commission of Volcanic lakes, URL: http://www.ulb.ac.be/sciences/cvl/rinjani/rinjani.html); Akhmad Solikhin, Devy Syabahna, and Syegi Kunrat, Center of Volcanology and Geological Hazards Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Vincent Hallet and David Lemadec, Facultés Universitaires Notre Dame de la Paix (FUNDP, URL: http://www.fundp.ac.be/); Bakosurtanal, Badan Koordinasi Survei dan Pemetaan Nasional (URL: http://www.bakosurtanal.go.id/); Jim Chow (URL: http://www.flickr.com/photos/11668976@N06/3486237730); Arjo Vanderjagt, Oude Boteringestraat 52, 9712 GL Groningen, The Netherlands (URL: http://www.flickr.com/photos/87453322@N00/3794836615).


St. Helens (United States) — September 2009 Citation iconCite this Report

St. Helens

United States

46.2°N, 122.18°W; summit elev. 2549 m

All times are local (unless otherwise noted)


Eruption ceased in late January 2008; quiet continues in late 2009

The eruptive episode that began with the volcano reawakening in October 2004 (BGVN 29:09) ended in late January or early February 2008. The activity included explosions containing ash that rose up to ~ 3 km above the crater and lava dome growth. Sherrod and others (2008) provide a comprehensive discussion of the 2004-2006 portion of the eruption. This report spans 28 November 2007 through October 2009.

A GPS receiver on the W part of the active spine recorded continued SW advance at a rate of 3-4 mm per day during September through November 2007. During 28 November-4 December 2007, small inflation-deflation events occurred, which the USGS Cascades Volcano Observatory (CVO) interpreted as dome-growth pulses. On 31 December 2007 aerial observers saw a new small, snow-free spine on top of the active lobe.

On 25 January 2008, a steam plume rose from the dome slightly above the crater rim. Though seismicity had persisted at low levels through mid-February 2008, very few earthquakes were recorded after late January. Locatable earthquakes were fewer than one per day, all under M 2.0. Ground tilt measurements showed an overall subsidence in the area of the new dome. A GPS receiver on the previously active spine settled about 2 cm per day on a southward path. During February, the daily ground-tilt events stopped and gas emissions were barely detectable.

Comparison of photographs taken by remote cameras during late January to mid-February 2008 showed no evidence of extrusion. Cynthia Gardner (CVO), in a personal communication, noted that dome growth stopped in late January or early February (January 27 +/- 10 days).

During March 2008, the most significant developments were a small, M 2.0 earthquake on 4 March and a very small earthquake swarm on 6 March. The latter started with a roughly M 1.2 event, followed by several smaller tremors over a seven-minute period. No tilt changes were associated with the swarm. On 14 March, the Pacific Northwest Seismic Network recorded four very small earthquakes located near the volcano. There were no tilt changes associated with this activity.

Radar imagery analyzed by Jet Propulsion Laboratory staff during late March 2008 showed that the E and W arms of Crater Glacier were touching, or close to touching, just N of the 1980s lava dome. From 30 May 2008 (figure 71) to 8 July 2008, the W arm of the glacier advanced ~ 20 m. By 8 July, the old and new lava domes in the crater were encircled by ice (figure 72). Further down slope glacier ice descended into the gullies that had been carved by erosion into the Pumice Plain. On 10 July, after nearly 5 months without signs of renewed activity, CVO lowered the Alert Level to Normal and the Aviation Color Code to Green.

Figure (see Caption) Figure 71. Aerial view of the St. Helens crater, as seen from the N. The two arms of the Crater Glacier had by 30 May 2008 fully encircled the dome. USGS photograph by Steve Schilling.
Figure (see Caption) Figure 72. Old and new lava domes (center and upper right respectively) in the St. Helens crater encircled by ice, as seen from the NW. USGS photograph taken on 5 August 2009 by Steve Schilling.

As of October 2009, earthquakes, volcanic gas emissions, and ground deformation had all fallen to levels observed prior to the onset of the eruption.

References. Lahusen, R.G., 2005, Acoustic flow monitor system?user manual: U.S. Geological Survey Open-File Report 02-429, 22 p.

Sherrod, D.R., Scott, W.E., and Stauffer, P.H., eds., 2008, A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006: U.S. Geological Survey, Professional Paper 1750, 856 p.

Geologic Background. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fujisan of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome. Mount St. Helens was formed during nine eruptive periods beginning about 40-50,000 years ago and has been the most active volcano in the Cascade Range during the Holocene. Prior to 2,200 years ago, tephra, lava domes, and pyroclastic flows were erupted, forming the older edifice, but few lava flows extended beyond the base of the volcano. The modern edifice consists of basaltic as well as andesitic and dacitic products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the north flank, and were witnessed by early settlers.

Information Contacts: Cascades Volcano Observatory (CVO), U.S. Geological Survey, 1300 SE Cardinal Court, Building 10, Suite 100, Vancouver, WA 98683-9589, USA (URL: https://volcanoes.usgs.gov/observatories/cvo/); Pacific Northwest Seismic Network, University of Washington, Dept. of Earth and Space Sciences, Box 351310, Seattle, WA 98195-1310, USA (URL: http://www.pnsn.org/); Hawai'i Institute of Geophysics and Planetology (HIGP) 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/).


Turrialba (Costa Rica) — September 2009 Citation iconCite this Report

Turrialba

Costa Rica

10.025°N, 83.767°W; summit elev. 3340 m

All times are local (unless otherwise noted)


Non-eruptive in August 2009, but degassing and with widening cracks

The Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA) continued monitoring the Turrialba non-eruptive interval of February 2008 through August 2009. As during the previous four months (BGVN 33:01), Turrialba continued to emit sulfurous gas from its central and W craters, and elsewhere, including some new cracks.

Activity during February-December 2008. During February 2008, the area around Turrialba affected by acid rain increased due to degassing. The degassing vents on the N, NW, W, and SW walls were rich in sublimated native sulfur. Gas-emission temperatures ranged from 72 to 132°C. Owing to prevailing winds, the vegetation most affected was on the N, NW, and SW flanks. The effects ranged from discoloration to death of various plant species. Residents in the area reported occasional nausea and irritation of the skin and eyes. On 22 February, local observers reported a gas plume up to ~ 2 km in height.

On the SE and SW walls of the central crater two cracks 2-3 cm wide and 100 m long continued to emit gases at ~ 90°C and produced sulfur deposits (figure 13). In stable atmospheric conditions gas columns often rose ~ 500 m above the crater. Rockslides sometimes covered emitting fumaroles, and new sulfur deposits tended to develop in these areas.

Figure (see Caption) Figure 13. Elongated cracks (red lines on colored version) mapped at Turrialba during in August 2009. From first being noticed in mid-2009 to being measured in August 2009, some cracks opened by as much as 12 cm. Courtesy of OVSICORI-UNA.

During 7-8 March 2008, gas sampling at the summit fumaroles determined the maximum temperature at the largest W wall vent was 278°C. Degassing vents were also noted at spots in the middle of the forest. In some cases emissions had killed all local vegetation.

On 7-8 March 2008, Erick Fernandez and Eliécer Duarte of OVSICORI, and the National University (UNA) took gas samples. The analysis, done by Jorge Andrés Diaz and Sergio Achí of the University of Costa Rica, revealed the presence of He at 80,000 ppm (parts per million), whereas the typical He concentration in the neighborhood of a volcano is 25 ppm.

OVSICORI-UNA reported continued degassing during August and September 2008. Multiple fumaroles and areas of sulfur deposition were noted in both the central and W craters. Fumarolic emissions on the S and SE flanks of the W crater continued to damage vegetation in that area.

On 23 September 2008, OVSICORI fieldwork confirmed a severe impact of acid-rain on areas that had been only mildly affected during the preceding 3 years of degassing. At least three sectors showed new impacts on vegetation and infrastructure, from the summit downhill ~ 3 km along the S and SE flanks. The upper sector, which includes the entire caldera and lower sectors to the E, S, and SE near the summit, had been severely burned during August and September. This area goes from the summit down to an elevation of ~ 2,900 m. By 23 September, weeds, dwarf vegetation, and trees had been completely burned; however in these areas some resistant species maintained some green and appeared seemingly viable. Along the external walls to the S of the W crater, plants had been burned down to the soil. Due to the removal of that natural coverage, erosion had cut extended radial gullies.

Between the elevations of 2,900 and 2,600 m, significant forest patches have been partially seared by extreme acidification, particularly the dense birch forests. Below 2,600 m elevation mild burns to the tree canopy and pasture areas were evident. The evidence of chemical burns due to the heavy gases are amplified along canyons and depressions. These conditions caused residents to voluntarily leave their farms in 2007.

Monitored SO2 emissions during the early part of 2008 had been ~ 750 metric tons per day (t/d). At the end of April 2008, an increase to ~ 1,000 t/d was noted, which then increased to ~ 2,000 t/d well into July. During the end of July the emissions declined to ~ 1,100 t/d. The increase in SO2 flux corresponded to increases in vegetation damage.

Activity during January-June 2009. In May 2009 OVSICORI reported ongoing fumarolic degassing during the preceding months from the central crater, from the N, NW, W, SW and S walls, from new vents on the S and SW walls, and other locations. Some locations continued to form sublimated sulfur deposits. The two cracks in the SE and SW walls had temperatures of ~ 87°C. The emissions in the W wall registered ~ 91°C and displayed sulfur deposits. In meteorologically quiet conditions, gas plumes were noted up to 500-600 m above the crater floor. All of these areas had experienced small landslides that occasionally covered some vents.

SO2 flux was variable during early 2009 (figure 14). The flux data were collected with a roughly consistent sun angle, between 0900 and 1100 in the morning on the SW flank. In the graph the SO2 flux varies between ~ 0 and ~ 2,000 t/d, the maximum flux occurred on 23 April.

Figure (see Caption) Figure 14. SO2 fluxes measured at Turrialba during April 2009 (with y-axis showing SO2 flux in metric tons per day and x-axis dates in the format, month/day/year). Courtesy of OVSICORI-UNA.

On 14 June 2009, OVSICORI-UNA reported that fumarolic activity from Turrialba had been observed all around the upper flanks of the active W crater. During the previous two months, the fumarolic activity was also accompanied by widening radial cracks (1.5 cm on average), 1-2 km tall gas-and-vapor plumes, and one sustained seismic swarm. Temperatures of fumarolic vents in the lower parts of the crater were between 120 and 160°C. The temperature of summit cracks was 94°C. By mid-June, dairy pastures and forests had been chemically burned as far away as 3.5 km NW and W. During the last week of August 2009, the W and NW lower flanks, sectors previously reported with moderate effects, showed acute burns, and yellow pastures within 3 to 4 km radius (figures 15, 16, and 17).

Figure (see Caption) Figure 15. Vegetation damage as of late August 2009 at Turrialba plotted on a shaded relief map by F. Robichaud. E. Duarte and others found that damage was generally within several kilometers of the volcano and in broader areas on the W flanks. The large dotted line indicates the boundary of detectible damage. Severe damage covered an irregular area, a strip both directly W of the active crater and a lobe to its SW as well. Courtesy of OVSICORI-UNA.
Figure (see Caption) Figure 16. Newly emerging fumaroles on Turrialba's upper NW flank and burns on vegetation, August 2009. Courtesy of OVSICORI-UNA.
Figure (see Caption) Figure 17. A view from Turrialba's seismic station PICA on the NW flank, showing active degassing from a variety of locations in August 2009. Left mid-ground shows plumes from the lowest fumaroles yet developed on this flank. Green grass is in the foreground, but most of the other foliage is brown to orange. Courtesy of OVSICORI-UNA.

Near the Toro Amarillo river (4 km E of the crater) chemical burning surrounds stands of trees. Such whitening effect had been previously reported at the end of 2007 for areas closer to the active crater, 1.5 km W (figure 18).

Figure (see Caption) Figure 18. An example of a zone with intense burns on grass at the foot of injured trees, damage attributed to acidic gases from Turrialba. The spot is near the Toro Amarillo river in late August 2009. Courtesy of OVSICORI-UNA.

Several elongated cracks were mapped just south of the W crater as well as 1 km downslope NW. One main crack, noticed during mid-2009 due to sulfur depositions on the surface, was opened by August in places as much as 12 cm. In late August 2009 it emitted gasses at 90°C. The crack trends E-W, in places intersecting a trail used to reach the summit's SW and W sides.

The last two years have caused residents to leave owing to the burned and dead pastures. Some commented on their apprehension related to the emergence of the lower fumaroles. Along the S side of the Irazú summit located 10 km SW of Turrialba's summit, mild burns have been observed on patches of birch, eucalyptus and pine. Lesser impact was reported last year in that same area.

False eruption report. The Washington VAAC received surface observations from an airport near the volcano erroneously indicating an eruption on the morning of 23 September 2009.

The VAAC decided to initially describe the activity as an eruption because it was the first time the airport had reported emissions, the volcano was known to have been degassing for some time, and early morning satellite imagery showed cloud cover, preventing good analysis. In addition, attempts to reach local volcanologists by telephone using contact numbers from the ICAO [International Civil Aviation Organization] handbook and the OVSICORI webpage were not successful. OVSICORI-UNA personnel reported a few hours later that the volcano had not erupted. As a result of the incident, the VAAC has obtained current contact numbers, including personal cell phones, for future use.

Geologic Background. Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive edifice covers an area of 500 km2. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.

Information Contacts: Eliécer Duarte, Erick Fernández, Vilma Barboza, S. Miranda, L. Ortiz, G. Chavez, Jorge Brenes, Thomás Marino, Javier Pacheco, Juan Segura, and Rodolfo van der Laat, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apdo. 2346-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Francois Robichaud, Université de Sherbrooke, 2500 boul. de l'Université, Sherbrooke, Québec J1K 2R1, Canada; Washington Volcanic Ash Advisory Center, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/).

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