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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 38, Number 01 (January 2013)

Managing Editor: Richard Wunderman

Akita-Komagatake (Japan)

Short lived plume rising to 50 m observed on 14 December 2011

Dona Juana (Colombia)

Seismic swarm in 2010 and monitoring efforts

Heard (Australia)

Satellite imagery reveals lava flows in December 2012

Huila, Nevado del (Colombia)

Dome growth and displaced glacier in 2009; decreasing activity during 2010-2012

Izu-Oshima (Japan)

Non-eruptive May 2010 surface deformation from inferred deep instrusion

Kikai (Japan)

Steam plumes rose to 800 m duing latter half of 2012

Kuchinoerabujima (Japan)

Increased seismicity, 11 December 2011-5 January 2012

San Cristobal (Nicaragua)

Ash eruption during 25-28 December 2012



Akita-Komagatake (Japan) — January 2013 Citation iconCite this Report

Akita-Komagatake

Japan

39.761°N, 140.799°E; summit elev. 1637 m

All times are local (unless otherwise noted)


Short lived plume rising to 50 m observed on 14 December 2011

The Japanese Meterological Agency (JMA) reported that a short-lived plume rose to 50 m above Akita-Komaga-take on 14 December 2011 and was recorded by a camera located to the N of Me-dake's summit.

Aerial observations were conducted in cooperation with the Japan Ground Self Defense Force on 13 December. Areas of snow melt corresponded to geothermal areas that had been previously identified. No new geothermal areas were found.

An M 2.6 earthquake on 27 December at 1234 local time occurred ~2 km W of Me-dake, with a maximum JMA Seismic Intensity of 1 in Senboku-city, Akita Prefecture. The JMA Seismic Intensity scale, used in Japan and Taiwan is classified into 10 categories; 0 to 4, 5 weak, 5 strong, 6 weak, 6 strong, and 7. The seismicity around the area had temporarily increased, but then returned to baseline levels. No volcanic activity related to this seismicity was observed.

JMA reported no activity at Akita-Komaga-take in 2012.

Geologic Background. Two calderas partially filled by basaltic cones cut the summit of Akita-Komagatake volcano. The larger southern caldera is 1.5 x 3 km wide and has a shallow sloping floor that is drained through a narrow gap cutting the SW caldera rim. On its northern side is a smaller more circular 1.2-km-wide caldera whose rim is breached widely to the NE. The two calderas were formed following explosive eruptions at the end of the Pleistocene, between about 13,500 and 11,600 years ago. Two cones, Medake and Kodake, occupy the NE corner of the southern caldera, whose long axis trends NE-SW. The Onamedake cone within the northern caldera has produced lava flows to the north and east; it has a 100-m-wide summit crater. Small-scale historical eruptions have occurred from cones and fissure vents inside the southern caldera. The temperatures of geothermal areas increased beginning in 2005, and some fumarolic plumes were observed in 2011-12.

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/en).


Dona Juana (Colombia) — January 2013 Citation iconCite this Report

Dona Juana

Colombia

1.5°N, 76.936°W; summit elev. 4137 m

All times are local (unless otherwise noted)


Seismic swarm in 2010 and monitoring efforts

Doña Juana, a volcano in repose, is located ~50 km NE of Pasto, the provincial capital where the local Instituto Colombiano de Geología y Minería (INGEOMINAS) volcanic and seismic observatory is based (figure 1). In this report we discuss monitoring efforts that began as early as 2004, highlight elevated seismicity detected in mid-2010, and describe the relatively new national park which encompasses Doña Juana and two other volcanic centers (Petacas and Ánimas). Petacas is ~19 km NE of Doña Juana and Ánimas, 12.5 km NE. Ánimas lacks a clear Holocene age; however, Ánimas is an important landmark in this report because the recent seismicity is often found proximal to this volcano. Listed as a Quaternary volcanic center, Ánimas can be found in the "Preliminary List of Pleistocene Volcanoes" section of the Volcanoes of the World 3rd edition (Siebert and others, 2010).

Figure (see Caption) Figure 1. This map of instrumentation from 2012 shows the monitoring network for Doña Juana with telemetered locations for the observatory in Pasto (red circle). Triangles are short period seismic stations (red triangles correspond to INGEOMINAS stations and the pink triangle is part of the National Seismic Network of Colombia (RSNC)), the orange hexagon is a broadband seismic station, green circles are electronic tiltmeters, and green squares are repeater stations for telemetry. The volcanic centers of Doña Juana and Galeras are labeled with yellow text. Courtesy of INGEOMINAS.

Aerial observations and field investigations. Aerial observations had been collected since 2004 in collaboration with the Colombian Air Force (FAC). Overflights during clear conditions provided views of the lava domes and exposures of bare rock where high elevation and frequent rockfalls limit vegetation (figure 2). Remote sensing images of the region also captured the variations in vegetation and distribution of scree slopes (figure 3).

Figure (see Caption) Figure 2. This SE looking photo of Doña Juana was taken during aerial surveys on 12 March 2007. The town of La Cruz appears in the foreground, ~13 km W of the volcanic edifice (on the skyline). Courtesy of INGEOMINAS.
Figure (see Caption) Figure 3. This false-color ASTER image of Doña Juana from 9 September 2010 provided a clear view of the sharp boundaries between heavy vegetated outer flanks (red) and the scrub-covered dome complex (green). Within the central dome area a pale region is attributed to scree from rockfalls. The lowlands, where agriculture dominates the topography, can be distinguished by the pale pink to white regions. Courtesy of NASA.

During 13-21 September 2006, INGEOMINAS led field investigations around Doña Juana. Four scientists focused on the area's stratigraphy and composition of volcanic deposits for development of a future hazard map as well as enhancing the knowledge of the volcano's eruptive history.

Monitoring stations. Three seismic stations were online in 2008: Lava, Florida, and Páramo (figure 4). The Páramo tiltmeter was also online in 2008. In 2009 two additional stations were online; La Cruz seismic station was installed in April and La Florida electronic tiltmeter was installed in June. In 2011, geochemical monitoring began at hot springs within 7 km of the edifice.

Figure (see Caption) Figure 4. The telemetered monitoring network for Doña Juana in 2012 included seismic and electronic tiltmeter instruments. Regular monitoring efforts also included measurements at hot springs (see text). Names of the two volcanic centers Doña Juana and Ánimas and the local communities are highlighted in green. The largest nearby community is the town of La Cruz, ~13 km NNW of the volcanic edifice. Volcán Ánimas is the nearest volcanic center to Doña Juana (~12.5 km NE); however, there has been no documented Holocene volcanism from this site. Courtesy of INGEOMINAS.

As of December 2012, the monitoring network consisted of four seismic stations, with radio repeaters linked to the Pasto network, and two electronic tiltmeters.

Hot spring investigations. INGEOMINAS routinely monitored six thermal springs located ~7 km N and SW from the summit (figure 4). There were three visits during 2011 (August, October, and December) and a visit in April 2012. Temperature and pH monitoring as well as geochemical analysis were the main goals for these investigations.

In their online April 2012 technical bulletin, INGEOMINAS noted that bicarbonate (HCO3) concentrations varied at all monitoring sites, and highest values were consistent between the Tajumbina (1,276-1,436 mg/L) and Ánimas II (1,159-1,229 mg/L) sites. Of all sites, Ánimas I showed an increase since August 2011 in both temperature (41.2°C to 55.3°C) and pH (6.5 to 6.83).

In April 2012, INGEOMINAS discovered a new hot spring location, Ánimas III. This site was within 1 km of Ánimas I, and at the time of sampling, had a neutral pH (7.02) and a lower temperature (56.6°C) compared to the neighboring Ánimas I and Ánimas II sites.

Seismicity. INGEOMINAS reported trends in local seismicity during 2009-2012 in technical bulletins available online. Limited seismicity was detected in 2009 and an abrupt change appeared in early 2010 (figure 5). Combined seismicity (volcano-tectonic, tremor, long period, hybrid, and a category noted as "VOL") tallied for 2010 produced an average of 241 events per month. INGEOMINAS assigned earthquakes to the "VOL" category if they did not meet the criteria of other earthquake types but could be distinguished by fracturing signals proximal to the volcanic edifice. Volcano-tectonic (VT) earthquakes occurred more frequently than other types, occurring on average 107 times per month.

Figure (see Caption) Figure 5. Monthly earthquakes detected with the Doña Juana seismic network during 2009-2012. The number of earthquakes represents a sum of volcano-tectonic, tremor, long period, hybrid, and 'VOL' (see text) events per month. Bar color alternates from red to blue to distinguish years. Courtesy of INGEOMINAS.

Seismicity peaked in August 2010 owing to three VT swarms. That month the various earthquakes totaled more than 675 events. These were low-magnitude earthquakes (M 0-2.7) with relatively shallow depths (7-10 km below the summit).

The calculated locations of earthquakes were available for events during 2010-2012 (table 1). During this time period, epicenters were frequently dispersed between Doña Juana and Ánimas except for the mid-2010 activity and during January-February 2011. This record of information highlights the significance of August 2010 when VT earthquakes were clustered ~7 km NE of Doña Juana, slightly closer to the older volcanic edifice Ánimas (figure 6).

Table 1. During June 2010-December 2012, earthquake detection was sufficient for calculating magnitudes and locations. During several months (January-May 2010, June and October 2011, and September and November 2012) no locations were determined. "Notes" refer to epicenter characteristics such as clustering locations; "dispersed" events are those that occurred at various depths and distances from the volcanic centers. Courtesy of INGEOMINAS.

Month Total Located Magnitude Depth (km below summit) Notes
Jun 2010 68 0.1-2.6 5-10 ~5 km SW of Ánimas
Jul 2010 14 0.2-1.5 6-10 ~5 km SW of Ánimas
Aug 2010 130 0-2.7 7-10 ~5 km SW of Ánimas
Sep 2010 34 0.2-2.1 1-11 ~5 km SW of Ánimas
Oct 2010 10 0.6-2.7 ~7 dispersed
Nov 2010 5 1.1-2.3 3-6 dispersed
Dec 2010 7 0.2-1.8 4-10 dispersed
Jan 2011 59 0.1-3.1 3-14; 6-8 ~8 km SW of Ánimas; many earthquakes clustered at 6-8 km depth
Feb 2011 1 1.2 7 2 km SW of Ánimas
Mar 2011 7 0.5-2.1 15-50 between Doña Juana and Ánimas
Apr 2011 2 -- 5.7-6.5 between Doña Juana and Ánimas
May 2011 2 0.4, 1.7 8, 11 dispersed
Jun 2011 -- -- -- --
Jul 2011 9 0.3-1.1 6-12 some clustering near Ánimas
Aug 2011 7 -- 4-15 between Doña Juana and Ánimas
Sep 2011 1 0.7 4 between Doña Juana and Ánimas
Oct 2011 -- -- -- --
Nov 2011 9 0.3-1.5 3-8 between Doña Juana and Ánimas
Dec 2011 2 0.9, 1.7 4-6 between Doña Juana and Ánimas
Jan 2012 16 0.3-1.5 1-19 between Doña Juana and Ánimas
Feb 2012 5 0.9-1.7 2-8 between Doña Juana and Ánimas
Mar 2012 2 0.8, 1.3 7 between Doña Juana and Ánimas
Apr 2012 5 0.4-1.3 0-18 dispersed
May 2012 7 0.5-1.4 3-9.5 dispersed
Jun 2012 20 0-2.3 1-14 dispersed
Jul 2012 13 0.7-1.9 1-14 dispersed
Aug 2012 6 0.2-1.9 0-14.5 SW of Doña Juana
Sep 2012 -- -- -- --
Oct 2012 4 0.7-1.3 0-20 SW of Doña Juana
Nov 2012 -- -- -- --
Dec 2012 2 1.1, 0.7 2, 20 ~10 km S of Doña Juana
Figure (see Caption) Figure 6. Volcano-tectonic seismicity during August 2010 was characterized by a swarm located between Doña Juana and Ánimas volcano; ~8 km NE of Doña Juana. Courtesy of INGEOMINAS.

Colombia's 52nd Natural National Park. In 2007, the Doña Juana-Cascabel Volcanic Complex Natural National Park was created both by the Ministry of Environmental, Housing and Territorial Development and the Colombian Natural National Parks (figure 7). This included Doña Juana, Ánimas, and Petacas volcano (located ~19 km NE of Doña Juana) within the 65,858 hectares of preserved land. Within this densely forested region, a series of streams and waterfalls was locally known as El Cascabel. The park was developed to protect diverse flora and fauna, including numerous endangered species such as the Andean condor, the Moor tapir, the spectacled bear, and puma; approximately 11% of the park includes alpine terrain.

Figure (see Caption) Figure 7. This map of biomes includes the Doña Juana-Cascabel Volcanic Complex Natural National Park and surrounding region. Doña Juana is located in the SW portion of the park. Shaded areas indicate low-elevation Amazon through high-elevation Andean environments. The park boundary is indicated by a heavy black line; populated areas are shaded light pink, road systems are represented by gray lines, and major towns are labeled. This map appears in the 2008-2013 Management Plan of PNN CVDJ-C (2008).

References. Department of the Environment, Housing and Territorial Development Special Administration Unit of the system of Natural National Parks (UAESPNN), 2008, Doña Juana-Cascabel Volcanic Complex Natural National Park (PNN CVDJ-C) Management Plan 2008-2013, Popayán, Colombia, July 2008.

Siebert L., Simkin T., and Kimberly P., 2010, Volcanoes of the World, 3rd edition, University of California Press, Berkeley, 558 p.

Geologic Background. The forested Doña Juana stratovolcano contains two calderas, breached to the NE and SW. The summit of the andesitic-dacitic volcano is comprised of a series of post-caldera lava domes. The older caldera, open to the NE, formed during the mid-Holocene, accompanied by voluminous pyroclastic flows. The younger caldera contains the active central cone. The only historical activity took place during a long-term eruption from 1897-1906, when growth of a summit lava dome was accompanied by major pyroclastic flows.

Information Contacts: Instituto Colombiano de Geologia y Mineria (INGEOMINAS), Observatorio Vulcanológico y Sismológico de Pasto, Pasto, Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html); WWF Colombia (URL: http://www.wwf.org.co/?109882/Nuevo-Parque-Nacional-Natural-en-el-piedemonte-Andino-Amazonico-colombiano); Doña Juana-Cascabel Volcanic Complex National Natural Park (URL: http://www.parquesnacionales.gov.co/).


Heard (Australia) — January 2013 Citation iconCite this Report

Heard

Australia

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

All times are local (unless otherwise noted)


Satellite imagery reveals lava flows in December 2012

We received an informal report from Matt Patrick (Hawaiian Volcano Observatory) on a new eruptive episode at Big Ben volcano, Heard Island (figure 16). He noted that MODVOLC thermal alerts reappeared at Heard in September 2012 after a four year hiatus (the last eruptive episode ended on 2 March 2008; BGVN 33:01), suggesting the start of a new eruptive episode at the volcano. Since Heard Island is unsettled and extremely isolated, monitoring of the volcano is possibly primarily through satellite imagery (Patrick, 2013).

Figure (see Caption) Figure 16. A contour map (interval = 200 m) showing the partly ice-covered Heard Island. At the time of map preparation, the brown areas were ice free. Produced and issued in January 2000 by the Australian Antarctic Data Centre, Department of the Environment and Heritage, Commonwealth of Australia.

EO-1 Advanced Land Imager images collected through late 2012 and early 2013 confirm that eruptive activity resumed around September 2012, in the form of a low-level effusive style eruption similar to its other recent eruptions (figures 17 and 18). Patrick noted that the vent crater had enlarged significantly over the four years following the end of the last eruptive phase, March 2006-March 2008.

Figure (see Caption) Figure 17. A series of images documenting the summit crater and subsequent lava advances at Mawson Peak, Heard Island from 3 July 2012 to 5 January 2013. The Earth Observing-1 (EO-1) satellite's Advanced Land Imager (ALI) Band 1 (panchromatic) images (10-m-pixel size) acquired several clear images on 3 July, 9 September, 13 October, 15 and 28 December 2012, and 5 January 2013. North is to the top of the photos. In the first three images the 200-m diameter crater at the summit of Mawson Peak is easily visible, and there is no evidence of activity outside of the crater. Courtesy of Matt Patrick.
Figure (see Caption) Figure 18. EO-1 ALI Band 10-3-2 RGB composites (30-m-pixel size) of the same series of images as in figure 17 (3 July 2012 to 5 January 2013). North is to the top of the photos. The red is the shortwave infrared band (Band 10, 2 microns); red pixels indicate high temperatures suggesting hot lava surfaces. As in figure 17, the 3 July 2012 image shows that the summit crater was cold, with no evidence of lava inside. However, the 9 September 2012 image clearly shows that elevated temperatures (and presumably lava) had appeared in the crater, consistent with the appearance of MODVOLC thermal alerts later that month. Therefore, this eruptive episode appears to have started around September. Courtesy of Matt Patrick.

The 15 December 2012 image in figure 17 shows that a short lava flow from the summit was emplaced on the SW flank. The flow was ~420 m long and had two lobes. By 28 December, a flow consisting of two lobes (presumably the same flow as in the 15 December image) had reached 770 m SW of the summit crater. In the 5 January 2013 image this flow was 780 m long and had changed little over the previous week.

Figure 18 shows that the 9 September and 13 October 2012 images suggested active lava contained with the summit crater. The 15 and 28 December 2012 images showed elevated temperatures on the lava flow SW of the summit, suggesting it was active over this interval, which was consistent with the observed elongation of the flow in the visible images. Fewer high-temperature pixels in the 5 January 2013 image and the meager advancement observed in the visible images, suggested that the flow had stalled by this point.

Overall, the activity as of mid-March 2013 had consisted of lava within the crater and a lava flow of at least 770 m long emplaced SW of the crater. This low-level effusive activity is consistent with the previous three eruptive episodes observed in satellite images at Heard Island (Patrick and Smellie, in review). These three episodes, May 2000-November 2001 (BGVN 25:11, 26:02, 26:03, and 28:01), June 2003-July 2004 (BGVN 29:12), and March 2006-March 2008 (BGVN 31:05, 31:11, 32:03, 32:06, 33:01, and 35:09), each lasted 1-2 years. On this basis, Patrick suggested that this new eruptive episode may persist for a similar duration. MODVOLC thermal alerts were measured nearly continuously from 21 September 2012 through 24 February 2013.

References. Patrick, M., 2013, A new eruptive episode at Big Ben Volcano, Heard Island, informal communication to BGVN, 23 February 2013.

Patrick, M.R., and Smellie, J.L., in review, A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000-2010, Antarctic Science, in review in 2013.

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

Information Contacts: Matt Patrick, Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/); Australian Antarctic Data Centre, Department of the Environment and Heritage, Commonwealth of Australia (URL: https://data.aad.gov.au/database/mapcat/heard/heard_island.gif); MODVOLC, 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/).


Nevado del Huila (Colombia) — January 2013 Citation iconCite this Report

Nevado del Huila

Colombia

2.93°N, 76.03°W; summit elev. 5364 m

All times are local (unless otherwise noted)


Dome growth and displaced glacier in 2009; decreasing activity during 2010-2012

Lava dome emplacement occurred at Nevado del Huila's Pico Central (central peak) in late 2008, and was accompanied by seismic unrest and significant sulfur dioxide (SO2) emissions (BGVN 37:10). Extrusion continued between November 2008 and November 2009. Ash plumes were frequently observed by webcameras during late 2008 to December 2009, and satellite imagery reviewed by the Washington Volcanic Ash Advisory Center (VAAC) detected intermittent ash emissions between October 2009 and April 2011. From January 2009 to December 2012, the Instituto Colombiano de Geología y Minería (INGEOMINAS) reported persistent emissions from the lava dome and dramatic changes to the perched glacier as the lava dome expanded across the E and W flanks. Activity generally decreased in November 2010 through 2012.

In this report, we focus on the time period of December 2008-December 2012 and also discuss monitoring efforts overseen by INGEOMINAS with collaborators such as the Colombian Air Force (FAC), the Washington VAAC, and the Sulfur Dioxide Group's Ozone Monitoring Instrument (OMI). The following subsections review webcamera and aerial observations, thermal-camera imaging, satellite images of volcanic plumes, seismicity, SO2 measurements (DOAS, Flyspec, and OMI), acoustic flow monitoring, and new tilt data. The local monitoring network was expanded during this reporting period, adding two infrasound monitoring stations in 2009 and 2012, two webcameras in 2010 and 2012, and instrumentation at the Caloto site that included a broadband seismometer and an electronic tilt station in 2012.

Web-camera observations. From December 2008 to December 2009, the Tafxnú web-camera (located ~15 km S of the volcanic edifice) frequently recorded gas-and-ash plumes rising higher than 2,000 m above the active dome (figure 26). In 2009, plumes (frequently ash-and-gas, but in some cases gas without ash) rose to maximum heights above the dome as follows: 1,000-2,000 m in June; 1,000-2,500 m in November; and 2,000-5,000 m in December.

Figure (see Caption) Figure 26. On 6 and 9 November 2009, summit activity from Nevado del Huila was observed by INGEOMINAS' N-looking Tafxnú web-camera. Accelerated dome growth was noted by INGEOMINAS that month (discussed in text below), and they annotated this image to circle the location of incandescence and summit activity. Note that these images have been altered from the originals; GVP staff increased the brightness and contrast in order to better distinguish the peaks of the Huila complex. (Top images) Incandescence on 6 November was absent at 0331 (left image) but appeared at 0333 within the green circled region (right image). INGEOMINAS suggested this incandescence resulted from dome collapse events exposing hot rock. The darker peak centered in the foreground is Pico Sur, while the active Pico Central is located higher and to the right of that peak in these images. (Bottom images) Plumes of ash and gas drifting NW from Pico Central were observed on 9 November at 0652 (left image) and 0653 (right image). The green circled region in the left-hand image corresponds to the same location circled in the image from 0333 on 6 November. Two water droplets on the camera lens created the local circular distortions. Courtesy of INGEOMINAS.

An additional camera was brought online in July 2010, located in the town of Maravillas (~10 km SE). A third camera, located at the Caloto site (~4 km SSW of the active dome) came online in July 2012 (figures 27 and 28).

Figure (see Caption) Figure 27. This composite image shows, at left, a map view of the three Nevado del Huila webcamera locations and the extent of their viewsheds. Photos at right show camera installation sites. The newest monitoring station (Caloto) was installed on 19 May 2012 on the SW flank. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 28. A map of monitoring stations for Nevado del Huila from June 2012 included locations of webcameras and seismic, geochemical, and geophysical instruments. The summit of Pico Central is located approximately beneath the text BUCB. Note that yellow and black lines represent major and minor roads, respectively, and blue lines represent rivers. Courtesy of INGEOMINAS.

Observations of dome growth and summit activity during 2009-2010. With support from the Colombian Air Force (FAC) during 2009-2012, INGEOMINAS monitored dome growth and geomorphological changes at Huila by conducting aerial observations with helicopters.

During February 2009 and June-December 2009, INGEOMINAS reported numerous episodes of tremor that were likely associated with ash emissions, but cloud cover and nightfall sometimes precluded direct observations. Notable ash plumes were observed on 11 February, 23 July, 3 August, 16-23 October, and 3, 9, 12, 13 and 15 November; ashfall was noted by observers on all days except 11 February. A crack that had formed along the N face of Pico Central in 2007 continued to steam during this time period.

During three overflights conducted in January 2009, INGEOMINAS determined that the Pico Central lava dome had grown since November 2008. With repeat aerial photography, scientists calculated a total dome volume of 52 x 106 m3 with dimensions of 1,000 m N-S and 250 m E-W. The fresh dome rock continuously degassed (figure 29). Tafxnú webcamera images also showed that gas emissions frequently rising above Pico Central were often blue-colored. Due to continued unrest at Nevado del Huila (note that this name is shortened to 'Huila' during the remainder of this report), especially seismicity and active dome growth at Pico Central, INGEOMINAS maintained Orange Alert (Alert Level II; the second highest Alert Level on a 4-color scale from Green/IV-Yellow/III-Orange/II-Red/I) during January-February 2009.

Figure (see Caption) Figure 29. On 28 January 2009, the FAC facilitated observations of Nevado del Huila's growing lava-dome. In this view, the SW flank (centered) emitted a small gas column. This image highlights the zone of active lava dome growth (outlined in yellow) and the perimeter of the crater (outlined in orange). Courtesy of FAC and INGEOMINAS.

On 11 February 2009, a small pulse of tremor was accompanied by an ash plume discharged at Pico Central which was captured by the Taxfnú webcamera during 0745-0751. During that time period, INGEOMINAS noted a small pulse of tremor. On 23 February, an INGEOMINAS passenger on a commercial aircraft saw diffuse gas escaping from both the crater that hosts the dome and from the N-flank crack. During March, the webcamera frequently showed degassing from the crater and the lava dome. Clear conditions enabled observers on commercial flights to observe a white plume rising from Pico Central in the morning of 10 March. INGEOMINAS noted that both seismicity and remote observations of dome growth indicated decreased activity since February. Accordingly, on 31 March 2009, INGEOMINAS reduced the Alert Level to Yellow (II).

Aerial observations in April highlighted the presence of ash covering the S glacier, confirming the ongoing eruption. Elevated temperatures were concentrated at the extreme high and low points of the dome and degassing continued from the higher-elevation portion of the crater (figure 30).

Figure (see Caption) Figure 30. Photos taken on 19 April 2009 showed Nevado del Huila's active dome and the adjacent ash-covered and locally disturbed glacier. (top) In this visible-light view, the active lava dome has extended down the SW flank of Pico Central (yellow line). Cloud cover obscures the upper peaks of Pico Central (left) and Pico Sur (right). The glacier around Pico Central is difficult to distinguish due to ash cover and cracking attributed to dome emplacement. (bottom) This image is a close-up of the lava dome's SW flank with a forward-looking infrared (FLIR) camera which disclosed higher thermal flux from the dome's upper and lower regions. Gas emissions had been more concentrated from the higher region of the dome, however, the bright glow in this image may also be due to the reflective cloud-cover seen in the visible-spectrum image (top). Courtesy of FAC and INGEOMINAS.

During May and June 2009, the dome's surface continued to produce thermal anomalies, and dome growth was inferred based on the observable fragmentation of dome rock and a wider distribution of fresh material. INGEOMINAS noted that the color of the extruded material in the higher region of the dome had changed to a red-brown color (earlier dome rock was distinctively gray).

On 23 July ashfall was reported at the local military base in Santo Domingo and José Jair Cuspian (Caloto). They reported ashfall in the NW sector of the volcanic edifice. INGEOMINAS reported that this ash event coincided with a pulse of tremor registered that day at 0442.

On 3 August there was a pulse of tremor at 0036 and INGEOMINAS received reports of ashfall in the municipalities of Toribío and Santander de Quilichao (~30 km and ~50 km W of the edifice, respectively). Aerial observations on 16 August established that the crater had grown wider.

During September 2009 there were no major changes observed via webcam. On 16 and 23 October, reports of widespread ashfall came from various municipalities of N Cauca, Valle del Cauca, and in the foothills around the volcano (departments of Cauca, Valle, Tolima, and Huila) (figure 31). There were also reports of sulfur odors from the most proximal communities.

Figure (see Caption) Figure 31. An ash plume from Nevado del Huila's newly-formed crater and fumarolic sites was observed from aircraft on 23 October 2009. (top) A dark curtain of ash ("Cortina de cenizas") drifted SE from Pico Central that day; the plume height was ~1,000 m above the crater. The Washington VAAC reported ash in satellite images at 1015 that day, and noted that the ash plume rose to 6 km altitude, was ~46 km long, and drifting SE at 5 m/s. (bottom) A closer view of the W flank highlights gas-and-ash plumes rising from the upper crater (orange outline) while isolated sites released white plumes, including the site on the N flank of Pico Central (at left) where steam from a fissure had been observed consistently since November 2007. The accumulation of newly erupted material was typically observed from the upper region of the dome (circled in blue); the extent of the dome is outlined with yellow. Ashfall had covered the snow and glaciers of Huila; however, cracks in the glacier remained visible as jagged black and white lines, particularly on Pico Sur (right-hand edge of photo). Courtesy of FAC and INGEOMINAS.

At 0541 on 16 October 2009, the webcamera captured images of an ash plume rising in pulses from Pico Central and drifting E. Accordingly, the Alert Level was raised from Yellow (III) to Orange (II), where it stayed until 5 January 2010. An overflight on 23 October provided views of both intense fumarolic activity from the dome and a column of ash that reached up to 1,000 m above the crater. The summit and glaciers were covered by ashfall, lava extrusion was continuing from the upper region of the crater, and there were thermal anomalies where gas emissions were concentrated. An 11-minute-long episode of tremor that began at 0200 on 28 October was thought to signify dome rock extrusion.

Based on observations during overflights on 30 October and 2 November, INGEOMINAS calculated that the dome volume had increased by ~9 x 106 m3 since the previous estimate in January 2009. Aerial observers saw ash emitted in pulses.

Rapid dome growth occurred in November as witnessed during five aerial investigations (2, 4, 6, 10, and 25 November). On 3 November, an explosion was heard and ashfall was reported by the communities of Inzá, Mosoco, Jambaló y Belalcázar, and other communities SW of the volcano. New layers of ash had accumulated around the summits of Huila, often appearing brown-red as opposed to the gray material deposited in previous months (figure 32). A weekly INGEOMINAS report announced that by 10 November 2009, the dome volume had increased by ~16 x 106 m3 since the previous estimate, more than doubling the amount of growth that had occurred during January-October 2009.

Figure (see Caption) Figure 32. Aerial photos from November 2009 documented rapid changes on Nevado del Huila's Pico Central. (top) On 4 November INGEOMINAS observed additional ejecta surrounding the lava dome and elevated ash emissions. In this photo of the S face of Pico Central, steam and ash rise from the crater, and brown-red ash and blocks cover the glacier that surrounds the active dome. Dome rock extends from the center of Pico Central to lower elevations on the W flank. (bottom) This view of Nevado del Huila's SE flank on 25 November 2009 reveals the increased size of the lava dome which towers above Pico Sur, the rugged-looking peak centered in this view. Ash covered snow and glacial ice surrounds the immediate region of the dome while plumes of gas drift westerly. The dark gray, rounded peak to the lower left is Cerro Negro, the location of a seismic station that remained offline during this reporting period. Courtesy of FAC and INGEOMINAS.

Gas emissions were observed by the webcamera at Tafxnú and during four overflights in December 2009; however, fumarolic activity dropped during the first week of December. Aerial observations determined that 2008 dome rock was being covered by 2009 lava that contained fewer large blocks; the 2008 dome material was distinctively more gray and blocky. During an overflight on 29 December, clear weather allowed INGEOMINAS scientists to observe minor dome collapse events, new cracks in the glacier along the lower E dome contact, and additional dome rock extending down the E flank.

In January 2010, dome growth continued and notably expanded the dome E by ~50 m, further displacing portions of the Pico Central glacier. Gray ash continued to be deposited in the area, covering the glacier surfaces. White plumes were observed this month during overflights and from the webcamera. On 5 January, INGEOMINAS reduced the Alert Level from Orange (II) to Yellow (III); this status was maintained until 15 June 2010.

On 22 February 2010, scientists on board an FAC helicopter noted displaced glacial ice, some steaming along the dome edge, and the surface textures of the 2008 and 2009 lava domes persisted (blocky vs. smaller clast sizes, respectively; figure 33). Based on aerial observations, INGEOMINAS calculated a total dome volume of at least 70 x 106 m3.

Figure (see Caption) Figure 33. During an overflight on 22 February 2010, Nevado del Huila's active dome, displaced ice, and gas emissions were visible. Fresh volcanic material clearly began to extend W and E, divided by the long axis of the Huila complex. (Top) An aerial view of Pico Central's S-facing peak where the active dome was shedding material to the W and E. (Middle) Degassing dome rock is visible along the W flank. The blocky gray rock centered in this region was attributed to 2008 lava extrusion. (Bottom) New dome rock is in contact with the fragmented glacial ice on the E flank, and dome steaming is visible along the margin. Courtesy of FAC and INGEOMINAS.

INGEOMINAS reported that on 12 April additional ash had accumulated on the glacier and lava extrusion was continuing. Columns of gas continued to be emitted from the surface of the new dome, at the contact of 2008 and 2009 lava, and from the crack that had formed in 2007 on the N flank of Pico Central.

No overflights were conducted in June, however the Alert Level was raised to Orange (II) due to increased seismicity, primarily hybrid earthquakes and SO2 emissions (see seismic and SO2 discussion below). INGEOMINAS suggested that the marked increase in hybrid earthquakes may have been linked with the ascent of new magmatic material within the volcanic edifice.

In July, degassing continued and intermittent, small ash emissions were observed toward the end of the month by the ground-based cameras Tafxnú and Maravillas. By 16 July, INGEOMINAS reduced the Alert Level to Yellow (III), due to the reduction in seismicity and SO2 flux, where it remained through August. The Washington VAAC reported possible ash plumes drifting from Huila during 28-30 of July but an absence of such plumes during August.

A 19 August flight revealed that snow had accumulated on the dome. INGEOMINAS noted that some episodes of tremor were likely related to the process of lava dome extrusion and these conditions did not show wide variations in August. Minor ash emissions were reported toward the end of the month. The Maravillas camera detected incandescence on 26 and 29 August, possibly from hot rockfalls from the lava dome.

A pulse of tremor on 30 August at 0635 coincided with ash emissions also observed by the Tafxnú camera. In the afternoon that day, people in the town of Toribío (~30 km W) noted an ash plume. There was also a report that the Símbola River changed color due to the presence of ash. The VAAC noted a hotspot at the summit in satellite images on 31 August.

During September, webcameras imaged plumes of gas as well as gray and reddish-colored emissions attributed to volcanic ash. These plumes were not visible in satellite imagery; however, the Washington VAAC released two notices on 9 September in response to reports from INGEOMINAS that ground-based observations included continuous emissions of gases and some ash.

During the first week of September, the Maravillas webcamera and local populations observed incandescence from the active dome; INGEOMINAS attributed the activity to hot rockfalls on the dome. On 9 September, INGEOMINAS raised the Alert Level to Orange (II); seismicity (particularly energetic tremor) and frequent incandescence were considerations for this announcement. On 9 September, both webcameras captured images of ash and incandescence. On 10 September, drumbeat earthquakes (earthquake signatures related to dome extrusion) had appeared in the seismic records. The last time that drumbeat earthquakes had been detected from Huila was in November 2008 (BGVN 37:10). By 21 September, INGEOMINAS announced that 1,799 drumbeat earthquakes had been detected over the past 13 days.

An overflight on 15 September determined that conditions at the dome were continuing to change; extrusion continued from the highest part of the dome (near the contact with the crater wall). They also observed a debris flow containing rocks and ice that had originated from the edge of the dome and had traveled ~1.5 km down the E flank (figure 34). By the end of the month, gas emissions continued and incandescence was observed by the webcameras.

Figure (see Caption) Figure 34. On 15 September 2010 INGEOMINAS observed debris flows along the E flank of Nevado del Huila. (top) Snow had visibly collected on the active dome that continued to degass and displace the glacier. Near the dome, the glacier was notably fragmented and discolored due to overlying debris and ash. (bottom) This view is a closeup of the area below the fragmented glacier on Huila's E flank. The extent of the debris flow is visible as a 1.5 km long trace of gray material that had incorporated blocks of ice and rocks. Courtesy of FAC and INGEOMINAS.

Aerial observations on 29 September, 1 October, and 4 November confirmed ongoing dome growth. On 1 October, the VAAC reported ash drifting from the summit. On 12 October, INGEOMINAS reduced the Alert Level to Yellow (III); they stated that conditions appeared to have stabilized, in particular local seismicity and gas-and-ash emissions. The webcameras continued to capture images of white gas emissions during the second week of October. White plumes and some incandescence were visible in October. Thermal images from 4 November found that the W-central dome's temperature was 250°C. On 11 November the Washington VAAC reported ash drifting from the summit.

Observations during January-December 2011. The webcameras continued to record images of white plumes rising from the Pico Central dome throughout 2011. Aerial observations during the year noted frequent gas emissions and infrequent ash plumes. During an overflight on 25 January, a FLIR camera detected temperatures up to 90°C from various locations on the dome (figure 35). During an overflight on 29 March, observers noted degassing and odors of sulfur.

Figure (see Caption) Figure 35. In these photo pairs taken during an overflight on 25 January 2011, INGEOMINAS measured surface temperatures of Nevado del Huila's lava dome. (top) These photos are centered on the E flank of Huila. The thermal image is zoomed in on the brown-colored lava dome that continued to steam and degass, forming a small plume rising above Pico Central. For the dome, the minimum ("BAJA") and maximum ("ALTA") temperatures were less than 30 and 68.3°C, respectively. (bottom) These photos are viewing the S-facing Pico Central with the lava dome (centered). Gas emissions were rising from the highest region of the dome and the minimum and maximum temperatures were less than 30 and 80.6°C, respectively. Courtesy of FAC and INGEOMINAS.

On 19 April, the Washington VAAC reported that an ash plume was detected in enhanced multispectral imagery at 0315. The plume was drifting NNW from Huila. The announcement included a note that the ash plume did not appear to be the result of an explosive event. Later that day, after sunrise, INGEOMINAS confirmed that low seismicity was detected, a white plume was visible, but ash emissions were absent.

Aerial observations on 26 April included intense degassing from the NW side of the lava dome; the emissions were gray. A thermal camera detected temperatures of the dome in the range of 78-83°C. The glacier also appeared to have further deformed since the last aerial observations in March.

In May, degassing was observed with the webcameras on days where weather conditions permitted clear views. On 6 and 20 June, scientists confirmed that degassing continued during an overflight; they also observed the accumulation of snow on the lava dome as well as on the surrounding glacier. On 20 June, notable rockfalls were visible from the lava dome that contributed to scree along the dome's lower edges.

Degassing continued to appear in clear webcamera views and during overflights in June-July and September-December. Aerial observers on 22 October saw snow avalanches on the Pico Norte glacier and intense steaming from the upper regions of the dome.

Observations during January-December 2012. Throughout 2012, INGEOMINAS recorded observations of the dome based primarily on webcamera images. No major changes were noted in the weekly and monthly online reports; pervasive steaming and white plumes were frequently observed throughout the year by the two webcameras (Tafxnú and Maravillas). INGEOMINAS maintained Yellow Alert (III) during 2012.

One overflight was conducted by INGEOMINAS in 2012. On 14 January 2012, scientists observed the usual degassing and noted that snow had collected on the dome and glacier. That day's clear viewing conditions allowed detailed observations of the lava dome texture and INGEOMINAS attributed the spiny texture of the dome to late-stage extrusion (figure 36).

Figure (see Caption) Figure 36. On 14 January 2012, clear conditions provided aerial views of Nevado del Huila's lava dome texture. (top) This view of the dome's SE face is centered on the part of the lava dome that had started to accumulate snow cover. Steaming was visible from some regions of the dome but a strong plume was not visible during this overflight. (bottom) INGEOMINAS noted that the higher region of the dome had distinguishable spines that may have formed recently. Courtesy of FAC and INGEOMINAS.

Declining seismicity during January-August 2009. During 2009, four seismometers (two broadband and two short-period stations) were maintained by INGEOMINAS. Ash emissions in October 2009 temporarily disabled the short-period Verdún 2 station, located ~5 km N of the active dome. The Cerro Negro short-period station, closest to the active dome, was not operating during this reporting period (2009-2012). In general, three to four seismic stations were operating during 2009-2012.

In 2009, a total of nine earthquakes were large enough for people nearby to feel shaking; these events had magnitudes between 2.8 and 4.8 with focal depths between 6.2 and 12 km. The epicenters were 3-25 km away from the closest seismic station, CENE, which was located ~3 km S of Pico Central. INGEOMINAS highlighted these earthquakes in their monthly technical bulletins.

From January to September 2009, INGEOMINAS reported a decreasing trend in seismicity. In particular, volcano-tectonic (VT) and long period (LP) earthquakes were becoming less frequent on a monthly basis (figure 37). INGEOMINAS described VT earthquakes as resulting from rock-fracturing events, and LP earthquakes from fluid transport processes within the volcanic edifice. Large daily counts of LP earthquakes generally became less frequent over time. Low levels of tremor, hybrid events, and superficial activity (rockfalls and explosions) were detected throughout this time interval.

Figure (see Caption) Figure 37. Nevado del Huila's seismicity, in particular VT, LP, and tremor earthquakes, decreased overall during January-August 2009. In this plot, the number of events were tallied per day and plotted over time. The legend in the upper right-hand corner lists terminology in Spanish that relates to these conventions: VT (red), LP (yellow), hybrid (orange), explosions (red with black outlines), tremor (blue), and surface activity such as rockfalls (green). Explosions were detected during this time period, but are difficult to read from this plot. Explosions were detected mainly in June and July; see previous subsection "Observations of dome growth and summit activity during 2009-2010" for descriptions of explosive activity. Courtesy of INGEOMINAS.

Clustered epicenters in 2009. Beginning in January 2009, INGEOMINAS described a clustering of seismicity notable in distinct regions of the volcanic edifice. These consisted of three regions, the SW sector, the SE sector, and beneath the central edifice (Pico Central). This pattern was particularly clear in June, October, and December. The June 2009 map of seismicity appears in figure 38. The deepest earthquakes (8-12 km) tended to occur S of the edifice while shallow events were distributed throughout the area. Several deep and distal earthquakes occurred each month with depths between 10-20 km and epicenters up to 25 km from the edifice; these events have been attributed to regional faults.

Figure (see Caption) Figure 38. A map with cross-sections plotting epicenters and hypocenters of volcano-tectonic and hybrid earthquakes during June 2009 at Nevado del Huila. Three zones of clustered activity took place beneath the volcanic edifice (dashes lines). Note the yellow bar for scale (10 km) and the yellow text labeling five seismic stations (marked with blue squares). Four stations were operating; Cerro Negro (CENE) was offline during this reporting period. The active summit area of Pico Central is ~3 km N of the CENE station. Courtesy of INGEOMINAS.

Peaks in seismicity and ash emissions between October 2009 and May 2010. INGEOMINAS reported an abrupt increase in seismicity in October 2009. The occurrence of VT, LP, hybrid, and tremor events had more than doubled since September. On 12 October, a swarm of VT events was detected (figure 39). During the onset of elevated seismicity, INGEOMINAS reported ash emissions during 17-21 October and the Washington VAAC released reports of ash observations from satellite imagery on 16 October.

Figure (see Caption) Figure 39. Seismicity from January 2009 through May 2010 detected from Nevado del Huila included notable peaks in LP earthquakes. In their May 2010 report, INGEOMINAS noted that tremor had been recorded continuously throughout January-May. The legend in the upper left-hand corner lists VT (red), LP (yellow), hybrid (orange), explosions (red with black outlines), tremor (blue), and surface activity such as rockfalls (green). Explosions were detected during this time period, but are difficult to read from this plot. Courtesy of INGEOMINAS.

The appearance of volcanic ash in satellite images was periodically reported by the Washington VAAC from October through mid-November 2009. Aided by the web-camera Tafxnú, INGEOMINAS reported observations of ash plumes frequently occurring through November.

The Washington VAAC reported that, after 15 November 2009, volcanic ash was no longer visible in satellite images. In their monthly technical report, INGEOMINAS noted seismic signals suggesting ash emissions in December 2009, and visual observations of white plumes from the summit that were inferred to be gas-rich. As seen on figure 39, LP events peaked dramatically during 9-10 December when signals characterized as drumbeats were detected (see BGVN 37:10 for additional descriptions of drumbeat earthquakes). INGEOMINAS suggested the onset of drumbeat earthquakes was associated with the extrusion of new material to the surface and growth of the lava dome.

INGEOMINAS reported an average of 995 LP earthquakes per month during January-March 2010. VT events tallied on a monthly basis averaged 239 during that same time interval, suggesting an absence of discernible major changes in the volcanic system since the drumbeat earthquake swarm in December 2009. Tremor was detected more frequently over time and from February to May an average increase of 37 events per month was recorded.

As seen at the right on figure 39, during April-May 2010, very high LP seismicity returned. LP earthquakes peaked in May, with a total of 5,141 events. During April-May, the Washington VAAC released advisories in response to possible ash plumes from Huila, however, they did not detect ash due to frequent cloud cover, and because numerous reports indicated eruptions at night, when satellite instruments offer fewer means of detecting ash.

An ML 3.8 earthquake shook the towns of Toéz and Tálaga (15 km SSW and 22 km S respectively) at 0708 on 23 May. These towns are located SW of Pico Central. The earthquake was located 8.13 km SW of Pico Central and was 7.2 km deep (relative to the elevation of the active crater).

Seismicity and ash observations during June-December 2010. In June, direct observations of ash plumes were rare due to weather conditions; however, the Washington VAAC reported ash visible in satellite imagery on 2 June 2010. While LP seismicity remained low in early June 2010, hybrid seismicity emerged from background levels (figure 40). During January-May, typically 3-34 hybrid earthquakes were detected per month. By 14 June, more than 200 hybrid events were occurring per day; however, by 24 June, hybrid earthquakes had decreased to less than 50 events per day. Hybrid earthquakes, events INGEOMINAS attributes to the combined mechanisms of fluid transport and rock fractures, rarely dominate Huila's seismic records.

Figure (see Caption) Figure 40. Seismicity from Nevado del Huila during 2010 included peaks of LP, VT, and tremor episodes. The legend in the upper left-hand corner lists VT (red), LP (yellow), hybrid (orange), explosions (red with black outlines), tremor (blue), and surface activity such as rockfalls (green). Explosions were detected during this time period, but are difficult to read from this plot. Courtesy of INGEOMINAS.

As seen on figure 40, during August-November 2010, elevated tremor persisted (630-2,576 episodes per month). LP seismicity peaked in May and then twice between September and December. For the tallest peak (September 2010), counts reached more than 1,000 events per day.

On 3 December at 2054 a felt M 3.4 earthquake within the Páez River drainage centered 6.2 km S of Pico Central had a relatively shallow focal depth of 5.2 km (as measured beneath the crater). Another felt earthquake was reported by residents in the Belalcázar-Cauca area on 29 December. This ML 2.9 event occurred at 2106 with a focal depth of 8 km, located 8.5 km SW of Pico Central. This earthquake lacked any noticeable effect on the stability of the volcanic system.

Seismicity in 2011. In 2011, INGEOMINAS noted that both LP earthquakes and tremor were decreasing over time (figure 41). Tremor persisted at low levels. In June VT and LP earthquakes notably increased to 434 and 623 events, respectively, but returned to background levels during the following month.

Figure (see Caption) Figure 41. This plot of Nevado del Huila's seismicity during January-December 2011 shows a general decline in seismicity. This plot excludes VT earthquakes, highlighting instead the daily count of LP, hybrid, and tremor events. Courtesy of INGEOMINAS.

In November 2011, several moderate earthquakes (M≤4) struck near Huila. In particular, three events had magnitudes 2.8, 3.2, and 4.0. For example, on 26 November, inhabitants of Mesa de Toéz felt an M 4.0 event whose epicenter was 8.5 km SW of Pico Central with a depth of 7.4 km (as measured below the crater). VT epicenters in November were widely distributed throughout the edifice and local region (figure 42). Depths of these earthquakes were within the range of past VT earthquakes (0-12 km). Persistent seismicity SW of Huila also continued in November.

Figure (see Caption) Figure 42. A map and cross-sections showing Nevado del Huila's VT epicenters during November 2011. The active dome is ~3 km N of CENE. INGEOMINAS noted four areas where seismicity was clustered (yellow shaded ovals). Note that the largest highlighted region has been an area of persistent seismicity throughout the year (for example, see figure 38). Seismic stations are marked with blue squares and labels (DIAB, VER2, CENE, BUCO, and MARA). Courtesy of INGEOMINAS.

Seismicity in 2012. The low-level seismicity observed in the last months of 2011 continued through 2012. In a comparison with 2011, the average number of events per year was remarkably reduced in 2012 (VT, LP, and tremor); hybrid earthquakes, however, were the exceptions. The average for hybrid earthquakes per month was slightly higher in 2012 (table 4). Hybrid earthquakes were quite variable in number during 2011, ranging from 0 to 60 per month.

Table 4. Monthly counts for volcanic-tectonic, long period, tremor, and hybrid events detected at Nevado del Huila during 2011-2012. More event types and data appear in INGEOMINAS online reports. Courtesy of INGEOMINAS.

Month Volcanic-tectonic Long-period Tremor Hybrid
Jan 2011 284 388 220 2
Feb 2011 217 1,064 154 15
Mar 2011 217 876 168 13
Apr 2011 168 634 152 0
May 2011 136 729 220 0
Jun 2011 434 623 128 60
Jul 2011 165 416 77 25
Aug 2011 143 491 51 32
Sep 2011 137 304 27 8
Oct 2011 110 371 50 13
Nov 2011 176 219 32 2
Dec 2011 164 195 32 34
2011 Avg: 196 526 109 17
 
Jan 2012 155 245 27 28
Feb 2012 111 159 12 18
Mar 2012 145 200 27 21
Apr 2012 154 244 19 21
May 2012 87 200 34 13
Jun 2012 121 183 11 18
Jul 2012 109 208 14 16
Aug 2012 118 178 15 30
Sep 2012 93 172 5 14
Oct 2012 168 257 18 23
Nov 2012 171 205 9 14
Dec 2012 158 227 26 32
2012 Avg: 133 207 18 21

The wide distribution of epicenters noted in November and December 2011 persisted during January-February 2012, but fewer earthquakes were detected during these months. From March through December, significant clustering was absent, although, in October some events appeared concentrated along Huila's N-S axis.

The largest earthquake in 2012 occurred in March; a 3.8 earthquake shook the town of Toribio (in Cauca) at 0248 on 15 March. The epicenter was 1.8 km E of Pico Central with a focal depth of approximately 3.2 km. Seismicity that month was slightly higher than February (table 4). Throughout the year, VT earthquakes were typically less than M 2.6.

Infrasound monitoring 2009-2012. Augmenting seismic monitoring efforts, an infrasound station installed at the Diablo monitoring site (located ~5 km NNW of the active dome) became operational in July 2009. An additional acoustic monitoring system was installed at the Caloto station (located ~3.7 km from the active dome) in May 2012. Data collected with infrasonic microphones complements seismic instrumentation and can be analyzed with similar techniques. The method has also detected distant explosions from volcanoes such as Sakura-jima, Japan (BGVN 20:08), Fuego, Guatemala (BGVN 36:06), and Stromboli, Italy (BGVN 26:07).

Sulfur dioxide emissions during 2009-2012. INGEOMINAS conducted routine sulfur dioxide (SO2) gas monitoring with differential optical absorption spectroscopy (DOAS) equipment from January 2009 through December 2012. With this mobile scanner, INGEOMINAS conducted traverses along the Pan-American Highway between the cities of Calí and Popayán (figure 43).

Figure (see Caption) Figure 43. On 14 and 24 August 2010, INGEOMINAS technicians traversed routes along the Pan-American Highway with mobile DOAS equipment to measure Nevado del Huila's SO2 gas fluxes. These images include color-coded line segments that correspond to high and low concentrations (red and blue, respectively). The approximate locations of the plume have been shaded to correspond with the locations of high SO2 flux. The plots shows the wavelength on the x-axis and concentration-pathlength (ppm-m) on the y-axis. (Top) This image includes the mapped route between the towns of Santander de Quilichao and Villarrica where the gas plume was scanned on 14 August. The wind speed was 10.8 m/s, wind direction was 294°, and SO2 flux was 28.2 kg/s (1,441 t/d). (Bottom) This image includes the results from 24 August when field technicians traversed routes between Pescador and Villarrica. SO2 flux was 23.3 kg/s (2,020 t/d); wind speed and direction were not reported. Courtesy of INGEOMINAS.

Scanning DOAS systems at fixed locations were operating during 2009-2012. During October 2009, elevated SO2 emissions were detected by the Calí and Santander de Quilichao stations (figure 44). In September 2009, a station was operating in Manantial (~53 km W of Huila).

Figure (see Caption) Figure 44. During 7 January 2009-27 November 2012, INGEOMINAS measured the SO2 flux from Nevado del Huila in a series of numbered campaigns (x-axis). A total of 137 values were reported from three detection methods, scan DOAS stations (corresponding to numbers 33 and 35 dating from October 2009, and 55-57 dating from June 2010), FLYSPEC (numbers 118-122 dating from May 2012, and 128 and 129 dating from August 2012), and mobile DOAS (all other values). Red and blue highlighting distinguishes the datasets from each year. SO2 detection was conducted several times each month and the maximum value from each measurement was reported. Courtesy of INGEOMINAS.

Wind velocity has a strong bearing on the computed SO2 flux. In their December 2011 technical bulletin, INGEOMINAS discussed the variability in windspeed and direction, including the Weather Research and Forecasting (WRF) modeling system used for calculations during 2011 (figure 45). The WRF was public domain software available online and was developed in order to provide atmospheric simulations based on numerical modeling.

Figure (see Caption) Figure 45. INGEOMINAS released the source of their windspeed data used for SO2 flux calculations in their December 2011 technical report. (top) This plot shows the datapoints used throughout 2011 for windspeed values determined by the WRF Model. (bottom) These images show a map of the expected aerial extent of the gas plume, a series of photos showing plume conditions during the SO2 surveys, and a table of the measurements from three surveys in December. Courtesy of INGEOMINAS.

In May and August 2012, INGEOMINAS reported the results from FLYSPEC (a portable UV spectrometer) surveys and discussed the variations observed in SO2 flux. They emphasized that SO2 fluxes were low, a finding consistent with previous measurements during this post-crisis period (dome growth had ceased by November 2009). They also mentioned that seismicity had been low in May 2012, particularly in those events related to fluid motion (LP earthquakes, for example).

Flux calculations required wind speed data from the WRF models and daily forecasts from the Institute of Hydrology, Meteorology, and Environmental Studies (IDEAM), Colombia. Wind speeds in the range of 6-12 m/s during 8-29 May 2012 were applied to SO2 flux calculations.

Elevated SO2 emissions from Huila were detected almost daily by the OMI spectrometer during 2009-2012. The AURA satellite maps SO2 in the atmospheric column using ultraviolet solar backscatter. A flux can be estimated for the OMI spectrometer data by looking at the total mass of SO2 measured and the time it took to accumulate. On this basis, INGEOMINAS compared peaks in SO2 flux detected during traverses with DOAS (mobile and scanning) with OMI data for October 2009 (figure 46).

Figure (see Caption) Figure 46. In October 2009, elevated SO2 flux was detected from Nevado del Huila by three remote sensing techniques. (Top) The plotted values show combined datasets from mobile DOAS, OMI, and scan DOAS. (Bottom) The OMI spectrometer on the AURA satellite detected 9.95 kt of SO2 on 20 October 2009 (left) during its pass at 2414-2417 local time (coverage area of 368,974 km2, recording a maximum value of 43.3 Dobson Units (DU)). On 26 October 2009 (right) it detected 7.79 kt of SO2 during its pass at 2337-2340 local time (coverage area of 314,303 km2, recording a maximum value of 31.12 DU). Courtesy of INGEOMINAS and Simon Carn, Michigan Technological University and Joint Center for Earth Systems Technology, University of Maryland Baltimore County.

Lahar investigations. INGEOMINAS maintained seven early warning systems to warn of downstream flooding in vulnerable municipalities such as Belalcázar. At sites within the drainages of the Páez and Símbola rivers, flow monitoring with geophones has continued since October 2006, employing equipment installed by the INGEOMINAS Popayan Observatory in collaboration with the Nasa Kiwe Corporation (CNK). CNK is a relief group that has been active in this area of Colombia since the 1994 earthquake and resultant landslides that devastated the Cauca and Huila regions, including communities along the Páez river (BGVN 19:05). Those events also damaged the Tierradentro archaeological sites, a UNESCO World Heritage Site since 1995.

Following Huila's 2007 lahars (BGVN 33:01), Worni and others (2012) conducted fieldwork and reconstructed events in order to model future lahars for mitigation purposes. The researchers argued that large-volume lahars (tens to hundreds of millions of cubic meters) require targeted studies. The authors noted that "in 1994, 2007, and 2008, Huila volcano produced lahars with volumes of up to 320 million m3." To constrain the dimensions of simulated flows, they used inundation depths, travel duration, and observations of flow deposits from the April 2007 events and applied the two programs LAHARZ and FLO-2D for lahar modeling.

LAHARZ was developed by USGS scientists in order to provide a deterministic inundation forecasting tool; this program was designed to run in a Geographic Information System (GIS) environment (Schilling, 1998; Iverson and others, 1998). "For user-selected drainages and user-specified lahar volumes, LAHARZ can delineate a set of nested lahar-inundation zones that depict gradations in hazard in a manner that is rapid, objective, and reproducible" (Schilling, 1998). Worni and others (2012) presented results from the semi-empirical LAHARZ models along with physically-based results from FLO-2D (FLO-2D Software I, 2009) in order to forecast future inundation areas with specified flow volumes (figure 47). The authors concluded that, despite local deviations, the two models produced reasonable inundation depths (differing by only 10%) and encouraged future investigations that could address sources of uncertainty such as the effects of sediment entrainment that would cause dynamic changes in lahar volumes.

Figure (see Caption) Figure 47. Results are shown from two modeling programs to understand lahar hazards from Nevado del Huila, FLO-2D (top three images) and LAHARZ (bottom three images), for the specified flow volumes. Note the modeled effects on the Belalcázar region (located ~20 km S of Huila). Three scenarios are presented based on lahar flow volumes of 3 x 108, 6 x 108, and 10 x 108 m3. Image from Worni and others (2012).

Deformation monitoring during 2009-2012. An electronic tilt station was operating in July 2009, located at the Diablo monitoring site ~6.26 km NW of Pico Central (4.1 km above sea level). Telemetered data from a new electronic tilt station became available in May 2012; the station was located in the town of Caloto, located ~4 km SSW of Pico Central (4.2 km above sea level). Data from Diablo and Caloto was presented in the monthly technical bulletins posted online by INGEOMINAS.

After seven months of calibrations, INGEOMINAS developed an initial baseline for the new tilt data. The N and E components of Caloto recorded minor fluctuations during this time period. The trend of the E component was generally stable while the N component detected a gradual excursion during 17 June-25 September 2012.

References. FLO-2D Software I, 2009, FLO-2D User's Manual. Available at: www.flo-2d.com.

Iverson, R.M., Schilling, S.R, and Vallance, J.W., 1998, Objective delineation of areas at risk from inundation by lahars, Geological Society of America Bulletin, v. 110, no. 8, pg. 972-984.

Schilling, S.P, 1998, LAHARZ: GIS programs for automated mapping of lahar-inundation hazard zones, U.S. Geological Survey Open-File Report 98-638, 80 p.

Worni, R., Huggle, C., Stoffel, M., and Pulgarín, B., 2012, Challenges of modeling current very large lahars at Nevado del Huila Volcano, Colombia, Bulletin of Volcanology, 74: 309-324.

Geologic Background. Nevado del Huila, the highest peak in the Colombian Andes, is an elongated N-S-trending volcanic chain mantled by a glacier icecap. The andesitic-dacitic volcano was constructed within a 10-km-wide caldera. Volcanism at Nevado del Huila has produced six volcanic cones whose ages in general migrated from south to north. The high point of the complex is Pico Central. Two glacier-free lava domes lie at the southern end of the volcanic complex. The first historical activity was an explosive eruption in the mid-16th century. Long-term, persistent steam columns had risen from Pico Central prior to the next eruption in 2007, when explosive activity was accompanied by damaging mudflows.

Information Contacts: Instituto Colombiano de Geologia y Mineria (INGEOMINAS), Observatorio Vulcanológico y Sismológico de Popayán, Popayán, Colombia; Washington Volcanic Ash Advisory Center (VAAC), NOAA Science Center Room 401, 5200 Auth road, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Ozone Monitoring Instrument (OMI), Sulfur Dioxide Group, Joint Center for Earth Systems Technology, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA (URL: https://so2.gsfc.nasa.gov/); Nasa Kiwe Corporation (CNK) (URL: http://www.nasakiwe.gov.co/index.php); Weather Research Forecasting (WRF) (URL: http://www.wrf-model.org/index.php).


Izu-Oshima (Japan) — January 2013 Citation iconCite this Report

Izu-Oshima

Japan

34.724°N, 139.394°E; summit elev. 758 m

All times are local (unless otherwise noted)


Non-eruptive May 2010 surface deformation from inferred deep instrusion

Oshima is an active volcano located on the northern tip of the Izu-Bonin volcanic arc. Our last report of activity at Oshima (BGVN 21:08) enumerated a flurry of shallow low-frequency earthquakes beneath the top and W flank of the volcano that started on 5 August 1996.

Since those relatively benign events, the Japan Meteorological Agency (JMA) had not observed any subsequent events worthy of note until May 2010 when land surface inflation was detected. The inflation was registered by a strainmeter, a Global Positioning System (GPS) network (run by the Geospatial Information Authority of Japan, GSI), and a tiltmeter network (run by the National Research Institute for Earth Science and Disaster Prevention, NIED).

In July 2010 seismicity in the shallow parts of and around Oshima began to increase. (High seismicity synchronous with inflation of the edifice was seen earlier, including in 2004 and 2007). These events were considered to be due to magma intrusion into the deeper part of the volcano. There were no remarkable changes in surface phenomenon. In September, the inflation that was detected in May began declining. Seismicity in the shallow parts of and around Oshima continued at a low level with some small earthquakes which temporally increased in the western offshore areas of Oshima on 22 December 2010.

The earthquakes increased in frequency again on 9 February 2011. GPS and strainmeter measurements indicated contraction since January, but the trend reversed to show inflation in October 2011. Seismicity remained at a low level. Very low level gas emissions were sometimes observed by a camera positioned on the NW summit. Based on a field survey on 28 October, no remarkable change in surface phenomena was observed.

No remarkable activity has been noted since October 2011. Throughout the noted activity, JMA held the Alert Level at 1.

Geologic Background. Izu-Oshima volcano in Sagami Bay, east of the Izu Peninsula, is the northernmost of the Izu Islands. The broad, low stratovolcano forms an 11 x 13 km island and was constructed over the remnants of three dissected stratovolcanoes. It is capped by a 4-km-wide caldera with a central cone, Miharayama, that has been the site of numerous historical eruptions. More than 40 cones are located within the caldera and along two parallel rift zones trending NNW-SSE. Although it is a dominantly basaltic volcano, strong explosive activity has occurred at intervals of 100-150 years throughout the past few thousand years. Historical activity dates back to the 7th century CE. A major eruption in 1986 produced spectacular lava fountains up to 1600 m height and a 16-km-high eruption column; more than 12,000 people were evacuated from the island.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/).


Kikai (Japan) — January 2013 Citation iconCite this Report

Kikai

Japan

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

All times are local (unless otherwise noted)


Steam plumes rose to 800 m duing latter half of 2012

Kikai is a 17 x 20 km mostly submarine caldera as close as ~40 km from the S margin of the island of Kyushu (see figure 1 in BGVN 37:07; also see Shinohara and others, 2002, for 16 journal articles devoted to this volcano. Maeno, 2008, offers an online overview). A few areas on the caldera rim lie above water (figure 2). Mild-to-moderate emissions have often occurred at the dome called Iwo-dake (alternately spelled Iodake, figure 2). Table 4 summarizes the seismicity and steam plume observations for July-December 2012, an interval of calm, absence of tremor, and low hazard status.

Figure (see Caption) Figure 2. A shaded-relief, contour map of Kikai caldera that labels three islands on the N caldera rim, Satsuma Iwo-jima, Showa Iwo-jima, and Take-shima. Satsuma Iwo-jima contains the highest point of the complex (704 m elevation). On that island, the cones Iwo-dake (a rhyolitic volcano) and Inamura-dake (a basaltic volcano) both reflect post-caldera volcanism focused along or just inside the caldera's wall (the shaded, scalloped line trending NE across the island). The island Showa Iwo-jima emerged during the caldera's last major eruptions, during 1934-1935, starting with floating pumices and including late-stage lava emissions that helped armor the island and allowed it to erode only modestly during the subsequent decades of breaking waves. The caldera floor chiefly resides 300-500 m below sea level but it also contains some post-eruptive cones. From Fukashi Maeno (2008).

Table 4. Monthly summary of seismicity and plume observations at Kikai during July-December 2012. All reported plumes were described as white. Data courtesy of JMA.

Month Earthquakes per month Maximum steam plume height (m above Iwo-dake crater rim)
Jul 2012 238 800
Aug 2012 187 300
Sep 2012 193 500
Oct 2012 219 700
Nov 2012 168 400
Dec 2012 -- --

We last reported on Kikai activity through mid-2012 (BGVN 37:07) covering generally small steam plumes and monthly seismicity of up to ~200 earthquakes per month through June 2012. This report is a compilation of subsequent monthly reports of volcanic activity through December 2012 from Japan Meteorological Agency (JMA) monthly reports. The Alert Level remained constant at Level 2 (on a scale of 1-5: 2 = "Do not approach the crater"), before being downgraded to Level 1 in December 2012.

Between July and September 2012, plume emissions at the Iwo-dake summit crater continued (table 4). Weak incandescence was recorded at night with a high-sensitivity camera on 22 July, 28 August, 6 November and 22-24 November. Seismic activity remained at low levels. No unusual ground deformation was observed in GPS data through December 2012.

An aerial observation conducted by the Japan Maritime Self-Defense Force (JMSDF) on 11 September 2012 revealed white plumes rising from Iwo-dake's summit crater and flanks.

The results of a field survey conducted from 17-20 November 2012 showed no remarkable change in white fumes from Iwo-dake. Infrared images also found that the temperature distribution had remained essentially unchanged. Aerial monitoring conducted by the Japan Coast Guard (JCG) on 25 November 2012 revealed the presence of brown and green discolored water around the eastern coast (similar findings as a previous survey) as well as patterns of steaming similar to those observed during the field survey. SO2 emissions during 17-20 November 2012 were measured to be ~400 tons/day; a previous survey conducted in July 2012 yielded an estimated flux of ~500 tons/day.

References. Shinohara, H., Iguchi, M., Hedenquist, J.W., and Koyaguchi, T., 2002, Preface to special volume, Earth, Planets and Space 54 (3), pp. 173-174.

Maeno, F, 2008, Geology and eruptive history of Kikai Caldera, Earthquake Research Institute, University of Tokyo (URL: http://www.eri.u-tokyo.ac.jp/fmaeno/kikai/kikaicaldera.html); accessed 23 February 2013.

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

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); MODVOLC, 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/).


Kuchinoerabujima (Japan) — January 2013 Citation iconCite this Report

Kuchinoerabujima

Japan

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

All times are local (unless otherwise noted)


Increased seismicity, 11 December 2011-5 January 2012

Since a small eruption in 1980, Kuchinoerabu-jima experienced numerous periods of elevated seismicity, with volcanic earthquakes and tremor detected at least through December 2009 (BGVN 35:11). The volcano is located in the Ryukyu Island arc, off Japan's SW coast (figure 4).

Figure (see Caption) Figure 4. A map of the major volcanoes of Japan. Kuchinoerabu-jima is at the lower left. Courtesy of USGS/CVO.

Recent monthly reports of volcanic activity from the Japan Meteorological Agency (JMA) translated into English resumed in October 2010. The only recent English-translated JMA report on Kuchinoerabu-jima available online through December 2012 was in January 2012. We know of no other recent report on this volcano's seismic activity; therefore, this report summarizes seismicity between December 2011 and January 2012.

According to JMA, seismicity increased to a relatively high level immediately after 11 December 2011, but then decreased on 5 January 2012. On 20 January 2012, the Alert Level was lowered from 2 to 1; JMA noted that the possibility of an eruption was minimal.

During the December 2011-January 2012 period, no significant change in plume activity was observed, and plume heights remained below 100 m above the crater. According to a field survey on 11 January, infrared images (compared to images obtained in December 2011) showed no significant change in temperature distribution either at the summit or on the W slope of Shin-dake (also refered to as Shin-take), the youngest and most active cone.

Field surveys found that sulfur dioxide levels were 50 and 100 metric tons/day on 12 and 13 January 2012, respectively, which were lower than those recorded in December 2011 (200 metric tons/day on 9 December 2011).

According to JMA, continuous GPS measurements have established a baseline across Shin-dake, collecting data since September 2010. Shin-dake's rate of change in surface deformation at the stations has been slowing since September 2011.

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

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/).


San Cristobal (Nicaragua) — January 2013 Citation iconCite this Report

San Cristobal

Nicaragua

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

All times are local (unless otherwise noted)


Ash eruption during 25-28 December 2012

Our last report highlighted monitoring efforts at San Cristóbal and the explosive eruption that began on 8 September 2012 (BGVN 37:08). By 16 September 2012, seismicity and emissions had decreased; however, the Instituto Nicaragüense de Estudios Territoriales (INETER) announced in late December 2012 that volcanic activity had re-started. In this report, we cover the time period of 25-31 December when seismicity, explosions, and gas-and-ash emissions were reported.

At 2000 on 25 December 2012, observers noted a series of gas-and-ash explosions from the summit. The wind carried the fine- to sand-sized ash SW. Several hours prior to this activity, INETER had reported that seismicity was elevated but sulfur dioxide emissions (SO2) were relatively low compared to measurements from previous days.

During the early hours of the morning on 26 December, winds dispersed fine ash NW, W, and SW. Sand-size ash was fell on the W and SW flanks (figure 28). Civil Defense authorities from the municipality of Chinandega reported an ash plume up to 500 m above the summit and described the event as a "moderate eruption" similar to the 8 September 2012 event.

Figure (see Caption) Figure 28. A view S toward San Cristóbal with an ash plume drifting westerly on 26 December 2012. The lower hills to the right are part of El Chonco, an older volcanic edifice. Photograph by Hector Retamal, AFP, Getty Images.

On 26 December, government officials reported to Reuters that local inhabitants were evacuating. Rosario Murillo, a government spokeswoman, called on residents within a 3 km radius of the volcano to leave the area; some families had already self-evacuated.

By 1000 that day, INETER reported that seismicity had increased, and that they had received reports from Civil Defense stating that an eruption of fine ash rose to ~2,500 m above the crater. By the early afternoon, four major seismic events were detected and interpreted as explosions at the summit. Ashfall from these events primarily affected an area within a 5-6 km radius of the summit: El Viejo, Las Rojas, Banderas, Abraham Rugama, and those communities north of Chinandega's urban limit Grecia (particularly two communities called ##1 and ##4; see figure 19 in BGVN 36:12 for major town locations).

In their second communication on 26 December, INETER suggested that local inhabitants protect their water sources from ashfall, particularly those communities W, SW, and S of the volcano. They also announced that grazing lands would be closed in those regions due to the quantity of ash that had fallen. Research at Raupehu, New Zealand, and elsewhere has found that grazing animals can suffer damage to their teeth and poisoning due to elevated sulfur and fluorine if they consume ash-covered plants (Cronin and others, 2003). Precautions were also recommended for young children who could be adversely affected by inhaling fine ash. INETER noted that aviation traffic had been alerted to the presence of ash in the region.

The Washington Volcanic Ash Advisory Center (VAAC) detected ash from San Cristóbal during 26-28 December. Emissions were ongoing during that time period; plumes rose 2.4-4.3 km a.s.l. and drifted approximately W over the Pacific Ocean as far as 670 km WNW from the summit (figure 29).

Figure (see Caption) Figure 29. The aerial extent of observed volcanic ash from San Cristóbal was concentrated in three discrete regions mainly offshore of Central America at 0430 on 28 December 2012. The red polygons were developed by the VAAC as geospatial files (KML) for display in Google Earth. Courtesy of Washington VAAC and Google Earth.

INETER reported to local news agencies that 7 of the 13 municipalities of Chinandega were affected by ashfall by 27 December. Visibility was greatly reduced within the urban city of Chinandega. Emissions continued from the summit and reached 200 m above the crater rim in the morning. At the time of their second online notice, a plume of fine ash was visible rising up to 500 m above the crater, and small-to-moderate sized explosions of gas and ash continued.

On 28 December, the minister of Agriculture and Forestry told the local news agency, La Jornada, that while 2 millimeters of ash had fallen in some areas around the volcanic edifice, the farming areas should not be adversely affected since most of the crops had already been harvested. The public utility company, ENACAL, conducted investigations into water quality for the region.

News agencies reported that up to 20 km of highway was affected by ashfall along the Pan-American Highway between Honduras and Nicaragua. Vehicles opted to use headlights due to reduced visibility. La Jornada reported that a total of 268 people had left the area of San Cristóbal by 28 December and 68 were evacuated by the national humanitarian agency (Nicaraguan Humanitarian Rescue Unit, UHR).

INETER reported that small to moderate sized explosions had occurred in the morning of 28 December and a significant increase in SO2 flux was detected. This announcement included warnings regarding eye, skin, and respiratory irritation due to volcanic gases. There were also recommendations regarding ash removal from roofs and structures. Ash was distributed NW, W, and SW from the volcano and satellite images detected ash extending across the Pacific Ocean following the regional airstream offshore of El Salvador.

After an explosion of ash and gas at 1100 on 28 December, emissions throughout the day were ash-poor. Seismicity also decreased that day and, by 29 December, explosions had ceased and diffuse gas emissions continued. In their online bulletin, INETER reported that, as of 31 December, no ash explosions had been detected over the past two days. Gas emissions continued from the summit but SO2 levels had returned to normal.

Volcanic hazards map for San Cristóbal. A map of volcanic hazards was available on the INETER website for the region of San Cristóbal (figure 30). Volcanic ballistics, lahars, landslides, lava flows, and tephrafall were assessed and likely impacted areas were delineated. The tephrafall region corresponded to the prevailing winds and correlated well with ash-effected regions during the December 2012 events.

Figure (see Caption) Figure 30. Volcanic hazards from San Cristóbal include ejecta, lahars, landslides, and lava flows. This map was released in April 2006 and developed to show the aerial extent of potential events. Densely populated regions are yellow, road systems are black, and rivers are blue; additional color regions correspond to hazards listed in the key (in Spanish). The brown circle has a radius of 5 km and encompasses the main volcanic edifice indicating the maximum expected extent of ballistics (volcanic bombs for example); the two tan regions indicate the extent of possible tephra fall (where lighter shading indicates a medium-level risk zone and darker is higher-level risk); red regions follow major drainages where lahars and landslides could occur; the region shaded pink encompasses the areas most likely effected by future lava flows. Courtesy of INETER.

Reference. Cronin, S.J., Neall, V.E., Lecointre, J.A., Hedley, M.J., and Loganathan, P., 2003, Environmental hazards of fluoride in volcanic ash: a case study from Ruapehu volcano, New Zealand, Journal of Volcanology and Geothermal Research, 121, 271-291.

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

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); Washington Volcanic Ash Advisory Center (VAAC), 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/); La Jornada (URL: http://www.lajornadanet.com/diario/archivo/2012/diciembre/28/1.php); La Prensa de Nicaragua (URL: http://www.laprensa.com.ni/2012/12/27/ambito/128746/imprimir); Reuters.

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