Recently Published Bulletin Reports
Manam (Papua New Guinea) Few ash plumes during November-December 2022
Krakatau (Indonesia) Strombolian activity and ash plumes during November 2022-April 2023
Stromboli (Italy) Strombolian explosions and lava flows continue during January-April 2023
Nishinoshima (Japan) Small ash plumes and fumarolic activity during November 2022 through April 2023
Karangetang (Indonesia) Lava flows, incandescent avalanches, and ash plumes during January-June 2023
Ahyi (United States) Intermittent hydroacoustic signals and discolored plumes during November 2022-June 2023
Kadovar (Papua New Guinea) An ash plume and weak thermal anomaly during May 2023
San Miguel (El Salvador) Small gas-and-ash explosions during March and May 2023
Semisopochnoi (United States) Occasional explosions, ash deposits, and gas-and-steam plumes during December 2022-May 2023
Ebeko (Russia) Continued explosions, ash plumes, and ashfall during October 2022-May 2023
Home Reef (Tonga) Discolored plumes continued during November 2022-April 2023
Ambae (Vanuatu) New lava flow, ash plumes, and sulfur dioxide plumes during February-May 2023
Manam (Papua New Guinea) — July 2023 Cite this Report
Manam
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
Few ash plumes during November-December 2022
Manam is a 10-km-wide island that consists of two active summit craters: the Main summit crater and the South summit crater and is located 13 km off the northern coast of mainland Papua New Guinea. Frequent mild-to-moderate eruptions have been recorded since 1616. The current eruption period began during June 2014 and has more recently been characterized by intermittent ash plumes and thermal activity (BGVN 47:11). This report updates activity that occurred from November 2022 through May 2023 based on information from the Darwin Volcanic Ash Advisory Center (VAAC) and various satellite data.
Ash plumes were reported during November and December 2022 by the Darwin VAAC. On 7 November an ash plume rose to 2.1 km altitude and drifted NE based on satellite images and weather models. On 14 November an ash plume rose to 2.1 km altitude and drifted W based on RVO webcam images. On 20 November ash plumes rose to 1.8 km altitude and drifted NW. On 26 December an ash plume rose to 3 km altitude and drifted S and SSE.
Intermittent sulfur dioxide plumes were detected using the TROPOMI instrument on the Sentinel-5P satellite, some of which exceeded at least two Dobson Units (DU) and drifted in different directions (figure 93). Occasional low-to-moderate power thermal anomalies were recorded by the MIROVA (Middle InfraRed Observation of Volcanic Activity) system; less than five anomalies were recorded each month during November 2022 through May 2023 (figure 94). Two thermal hotspots were detected by the MODVOLC thermal alerts system on 10 December 2022. On clear weather days, thermal activity was also captured in infrared satellite imagery in both the Main and South summit craters, accompanied by gas-and-steam emissions (figure 95).
Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical basaltic-andesitic stratovolcano to its lower flanks. These valleys channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most observed eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.
Information Contacts: 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/); 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).
Krakatau (Indonesia) — July 2023 Cite this Report
Krakatau
Indonesia
6.1009°S, 105.4233°E; summit elev. 285 m
All times are local (unless otherwise noted)
Strombolian activity and ash plumes during November 2022-April 2023
Krakatau is located in the Sunda Strait between Java and Sumatra, Indonesia. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan cones and left only a remnant of Rakata. The post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former Danan and Perbuwatan cones; it has been the site of frequent eruptions since 1927. The current eruption period began in May 2021 and has recently consisted of explosions, ash plumes, and thermal activity (BGVN 47:11). This report covers activity during November 2022 through April 2023 based on information provided by the Indonesian Center for Volcanology and Geological Hazard Mitigation, referred to as Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), MAGMA Indonesia, the Darwin Volcanic Ash Advisory Center (VAAC), and several sources of satellite data.
Activity was relatively low during November and December 2022. Daily white gas-and-steam plumes rose 25-100 m above the summit and drifted in different directions. Gray ash plumes rose 200 m above the summit and drifted NE at 1047 and at 2343 on 11 November. On 14 November at 0933 ash plumes rose 300 m above the summit and drifted E. An ash plume was reported at 0935 on 15 December that rose 100 m above the summit and drifted NE. An eruptive event at 1031 later that day generated an ash plume that rose 700 m above the summit and drifted NE. A gray ash plume at 1910 rose 100 m above the summit and drifted E. Incandescent material was ejected above the vent based on an image taken at 1936.
During January 2023 daily white gas-and-steam plumes rose 25-300 m above the summit and drifted in multiple directions. Gray-to-brown ash plumes were reported at 1638 on 3 January, at 1410 and 1509 on 4 January, and at 0013 on 5 January that rose 100-750 m above the summit and drifted NE and E; the gray-to-black ash plume at 1509 on 4 January rose as high as 3 km above the summit and drifted E. Gray ash plumes were recorded at 1754, 2241, and 2325 on 11 January and at 0046 on 12 January and rose 200-300 m above the summit and drifted NE. Toward the end of January, PVMBG reported that activity had intensified; Strombolian activity was visible in webcam images taken at 0041, 0043, and 0450 on 23 January. Multiple gray ash plumes throughout the day rose 200-500 m above the summit and drifted E and SE (figure 135). Webcam images showed progressively intensifying Strombolian activity at 1919, 1958, and 2113 on 24 January; a gray ash plume at 1957 rose 300 m above the summit and drifted E (figure 135). Eruptive events at 0231 and 2256 on 25 January and at 0003 on 26 January ejected incandescent material from the vent, based on webcam images. Gray ash plumes observed during 26-27 January rose 300-500 m above the summit and drifted NE, E, and SE.
Low levels of activity were reported during February and March. Daily white gas-and-steam plumes rose 25-300 m above the summit and drifted in different directions. The Darwin VAAC reported that continuous ash emissions rose to 1.5-1.8 km altitude and drifted W and NW during 1240-1300 on 10 March, based on satellite images, weather models, and PVMBG webcams. White-and-gray ash plumes rose 500 m and 300 m above the summit and drifted SW at 1446 and 1846 on 18 March, respectively. An eruptive event was recorded at 2143, though it was not visible due to darkness. Multiple ash plumes were reported during 27-29 March that rose as high as 2.5 km above the summit and drifted NE, W, and SW (figure 136). Webcam images captured incandescent ejecta above the vent at 0415 and around the summit area at 2003 on 28 March and at 0047 above the vent on 29 March.
Daily white gas-and-steam plumes rose 25-300 m above the summit and drifted in multiple directions during April and May. White-and-gray and black plumes rose 50-300 m above the summit on 2 and 9 April. On 11 May at 1241 a gray ash plume rose 1-3 km above the summit and drifted SW. On 12 May at 0920 a gray ash plume rose 2.5 km above the summit and drifted SW and at 2320 an ash plume rose 1.5 km above the summit and drifted SW. An accompanying webcam image showed incandescent ejecta. On 13 May at 0710 a gray ash plume rose 2 km above the summit and drifted SW (figure 137).
The MIROVA (Middle InfraRed Observation of Volcanic Activity) graph of MODIS thermal anomaly data showed intermittent low-to-moderate power thermal anomalies during November 2022 through April 2023 (figure 138). Some of this thermal activity was also visible in infrared satellite imagery at the crater, accompanied by gas-and-steam and ash plumes that drifted in different directions (figure 139).
Geologic Background. The renowned Krakatau (frequently mis-named as Krakatoa) volcano lies in the Sunda Strait between Java and Sumatra. Collapse of an older edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of that volcano are preserved in Verlaten and Lang Islands; subsequently the Rakata, Danan, and Perbuwatan cones were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption caused more than 36,000 fatalities, most as a result of tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former Danan and Perbuwatan cones. Anak Krakatau has been the site of frequent eruptions since 1927.
Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.esdm.go.id/v1); 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).
Stromboli
Italy
38.789°N, 15.213°E; summit elev. 924 m
All times are local (unless otherwise noted)
Strombolian explosions and lava flows continue during January-April 2023
Stromboli, located in Italy, has exhibited nearly constant lava fountains for the past 2,000 years; recorded eruptions date back to 350 BCE. Eruptive activity occurs at the summit from multiple vents, which include a north crater area (N area) and a central-southern crater (CS area) on a terrace known as the ‘terrazza craterica’ at the head of the Sciara del Fuoco, a large scarp that runs from the summit down the NW side of the volcano-island. Activity typically consists of Strombolian explosions, incandescent ejecta, lava flows, and pyroclastic flows. Thermal and visual monitoring cameras are located on the nearby Pizzo Sopra La Fossa, above the terrazza craterica, and at multiple flank locations. The current eruption period has been ongoing since 1934 and recent activity has consisted of frequent Strombolian explosions and lava flows (BGVN 48:02). This report updates activity during January through April 2023 primarily characterized by Strombolian explosions and lava flows based on reports from Italy's Istituto Nazionale di Geofisica e Vulcanologia (INGV) and various satellite data.
Frequent explosive activity continued throughout the reporting period, generally in the low-to-medium range, based on the number of hourly explosions in the summit crater (figure 253, table 16). Intermittent thermal activity was recorded by the MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data (figure 254). According to data collected by the MODVOLC thermal algorithm, a total of 9 thermal alerts were detected: one on 2 January 2023, one on 1 February, five on 24 March, and two on 26 March. The stronger pulses of thermal activity likely reflected lava flow events. Infrared satellite imagery captured relatively strong thermal hotspots at the two active summit craters on clear weather days, showing an especially strong event on 8 March (figure 255).
Table 16. Summary of type, frequency, and intensity of explosive activity at Stromboli by month during January-April 2023; information from webcam observations. Courtesy of INGV weekly reports.
Month |
Explosive Activity |
Jan 2023 |
Typical Strombolian activity with spattering and lava overflows in the N crater area. Explosions were reported from 4 vents in the N area and 1-2 vents in the CS area. The average hourly frequency of explosions was low-to-medium (1-12 events/hour). The intensity of the explosions varied from low (less than 80 m high) to medium (less than 150 m high) in the N crater area and up to high (greater than 150 m high) in the CS crater area. |
Feb 2023 |
Typical Strombolian activity with spattering in the N crater area. Explosions were reported from 2-3 vents in the N area and 1-4 vents in the CS area. The average hourly frequency of explosions was low-to-medium (1-14 events/hour). The intensity of the explosions varied from low (less than 80 m high) to medium (less than 150 m high) in the N crater area and up to high (greater than 150 m high) in the CS crater area. |
Mar 2023 |
Typical Strombolian activity with spattering and lava overflows in the N crater area. Explosions were reported from 2-3 vents in the N area and 2-4 vents in the CS area. The average hourly frequency of explosions was low-to-medium (1-18 events/hour). The intensity of the explosions varied from low (less than 80 m high) to medium (less than 150 m high) in the N crater area and up to high (greater than 150 m high) in the CS crater area. |
Apr 2023 |
Typical Strombolian activity. Explosions were reported from 2 vents in the N area and 2-3 vents in the CS area. The average hourly frequency of explosions was low-to-high (1-16 events/hour). The intensity of the explosions varied from low (less than 80 m high) to medium (less than 150 m high) in both the N and CS crater areas. |
Activity during January-February 2023. Strombolian explosions were reported in the N crater area, as well as lava effusion. Explosive activity in the N crater area ejected coarse material (bombs and lapilli). Intense spattering was observed in both the N1 and N2 craters. In the CS crater area, explosions generally ejected fine material (ash), sometimes to heights greater than 250 m. The intensity of the explosions was characterized as low-to-medium in the N crater and medium-to-high in the CS crater. After intense spattering activity from the N crater area, a lava overflow began at 2136 on 2 January that flowed part way down the Sciara del Fuoco, possibly moving down the drainage that formed in October, out of view from webcams. The flow remained active for a couple of hours before stopping and beginning to cool. A second lava flow was reported at 0224 on 4 January that similarly remained active for a few hours before stopping and cooling. Intense spattering was observed on 11 and 13 January from the N1 crater. After intense spattering activity at the N2 crater at 1052 on 17 January another lava flow started to flow into the upper part of the Sciara del Fuoco (figure 256), dividing into two: one that traveled in the direction of the drainage formed in October, and the other one moving parallel to the point of emission. By the afternoon, the rate of the flow began to decrease, and at 1900 it started to cool. A lava flow was reported at 1519 on 24 January following intense spattering in the N2 area, which began to flow into the upper part of the Sciara del Fuoco. By the morning of 25 January, the lava flow had begun to cool. During 27 January the frequency of eruption in the CS crater area increased to 6-7 events/hour compared to the typical 1-7 events/hour; the following two days showed a decrease in frequency to less than 1 event/hour. Starting at 1007 on 30 January a high-energy explosive sequence was produced by vents in the CS crater area. The sequence began with an initial energetic pulse that lasted 45 seconds, ejecting predominantly coarse products 300 m above the crater that fell in an ESE direction. Subsequent and less intense explosions ejected material 100 m above the crater. The total duration of this event lasted approximately two minutes. During 31 January through 6, 13, and 24 February spattering activity was particularly intense for short periods in the N2 crater.
An explosive sequence was reported on 16 February that was characterized by a major explosion in the CS crater area (figure 257). The sequence began at 1817 near the S2 crater that ejected material radially. A few seconds later, lava fountains were observed in the central part of the crater. Three explosions of medium intensity (material was ejected less than 150 m high) were recorded at the S2 crater. The first part of this sequence lasted approximately one minute, according to INGV, and material rose 300 m above the crater and then was deposited along the Sciara del Fuoco. The second phase began at 1818 at the S1 crater; it lasted seven seconds and material was ejected 150 m above the crater. Another event 20 seconds later lasted 12 seconds, also ejecting material 150 m above the crater. The sequence ended with at least three explosions of mostly fine material from the S1 crater. The total duration of this sequence was about two minutes.
Short, intense spattering activity was noted above the N1 crater on 27 and 28 February. A lava overflow was first reported at 0657 from the N2 crater on 27 February that flowed into the October 2022 drainage. By 1900 the flow had stopped. A second lava overflow also in the N crater area occurred at 2149, which overlapped the first flow and then stopped by 0150 on 28 February. Material detached from both the lava overflows rolled down the Sciara del Fuoco, some of which was visible in webcam images.
Activity during March-April 2023. Strombolian activity continued with spattering activity and lava overflows in the N crater area during March. Explosive activity at the N crater area varied from low (less than 80 m high) to medium (less than 150 m high) and ejected coarse material, such as bombs and lapilli. Spattering was observed above the N1 crater, while explosive activity at the CS crater area varied from medium to high (greater than 150 m high) and ejected coarse material. Intense spattering activity was observed for short periods on 6 March above the N1 crater. At approximately 0610 a lava overflow was reported around the N2 crater on 8 March, which then flowed into the October 2022 drainage. By 1700 the flow started to cool. A second overflow began at 1712 on 9 March and overlapped the previous flow. It had stopped by 2100. Material from both flows was deposited along the Sciara del Fuoco, though much of the activity was not visible in webcam images. On 11 March a lava overflow was observed at 0215 that overlapped the two previous flows in the October 2022 drainage. By late afternoon on 12 March, it had stopped.
During a field excursion on 16 March, scientists noted that a vent in the central crater area was degassing. Another vent showed occasional Strombolian activity that emitted ash and lapilli. During 1200-1430 low-to-medium intense activity was reported; the N1 crater emitted ash emissions and the N2 crater emitted both ash and coarse material. Some explosions also occurred in the CS crater area that ejected coarse material. The C crater in the CS crater area occasionally showed gas jetting and low intensity explosions on 17 and 22 March; no activity was observed at the S1 crater. Intense, longer periods of spattering were reported in the N1 crater on 19, 24, and 25 March. Around 2242 on 23 March a lava overflow began from the N1 crater that, after about an hour, began moving down the October 2022 drainage and flow along the Sciara del Fuoco (figure 258). Between 0200 and 0400 on 26 March the flow rate increased, which generated avalanches of material from collapses at the advancing flow front. By early afternoon, the flow began to cool. On 25 March at 1548 an explosive sequence began from one of the vents at S2 in the CS crater area (figure 258). Fine ash mixed with coarse material was ejected 300 m above the crater rim and drifted SSE. Some modest explosions around Vent C were detected at 1549 on 25 March, which included an explosion at 1551 that ejected coarse material. The entire explosive sequence lasted approximately three minutes.
During April explosions persisted in both the N and CS crater areas. Fine material was ejected less than 80 m above the N crater rim until 6 April, followed by ejection of coarser material. Fine material was also ejected less than 80 m above the CS crater rim. The C and S2 crater did not show significant eruptive activity. On 7 April an explosive sequence was detected in the CS crater area at 1203 (figure 259). The first explosion lasted approximately 18 seconds and ejected material 400 m above the crater rim, depositing pyroclastic material in the upper part of the Sciara del Fuoco. At 1204 a second, less intense explosion lasted approximately four seconds and deposited pyroclastic products outside the crater area and near Pizzo Sopra La Fossa. A third explosion at 1205 was mainly composed of ash that rose about 150 m above the crater and lasted roughly 20 seconds. A fourth explosion occurred at 1205 about 28 seconds after the third explosion and ejected a mixture of coarse and fine material about 200 m above the crater; the explosion lasted roughly seven seconds. Overall, the entire explosive sequence lasted about two minutes and 20 seconds. After the explosive sequence on 7 April, explosions in both the N and CS crater areas ejected material as high as 150 m above the crater.
On 21 April research scientists from INGV made field observations in the summit area of Stromboli, and some lapilli samples were collected. In the N crater area near the N1 crater, a small cone was observed with at least two active vents, one of which was characterized by Strombolian explosions. The other vent produced explosions that ejected ash and chunks of cooled lava. At the N2 crater at least one vent was active and frequently emitted ash. In the CS crater area, a small cone contained 2-3 degassing vents and a smaller, possible fissure area also showed signs of degassing close to the Pizzo Sopra La Fossa. In the S part of the crater, three vents were active: a small hornito was characterized by modest and rare explosions, a vent that intermittently produced weak Strombolian explosions, and a vent at the end of the terrace that produced frequent ash emissions. Near the S1 crater there was a hornito that generally emitted weak gas-and-steam emissions, sometimes associated with “gas rings”. On 22 April another field inspection was carried out that reported two large sliding surfaces on the Sciara del Fuoco that showed where blocks frequently descended toward the sea. A thermal anomaly was detected at 0150 on 29 April.
Geologic Background. Spectacular incandescent nighttime explosions at Stromboli have long attracted visitors to the "Lighthouse of the Mediterranean" in the NE Aeolian Islands. This volcano has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent scarp that formed about 5,000 years ago due to a series of slope failures which extends to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.
Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy, (URL: http://www.ct.ingv.it/en/); 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).
Nishinoshima (Japan) — July 2023 Cite this Report
Nishinoshima
Japan
27.247°N, 140.874°E; summit elev. 100 m
All times are local (unless otherwise noted)
Small ash plumes and fumarolic activity during November 2022 through April 2023
Nishinoshima is a small island located about 1,000 km S of Tokyo in the Ogasawara Arc in Japan. The island is the summit of a massive submarine volcano that has prominent peaks to the S, W, and NE. Eruptions date back to 1973; the most recent eruption period began in October 2022 and was characterized by ash plumes and fumarolic activity (BGVN 47:12). This report describes ash plumes and fumarolic activity during November 2022 through April 2023 based on monthly reports from the Japan Meteorological Agency (JMA) monthly reports and satellite data.
The most recent eruptive activity prior to the reporting internal occurred on 12 October 2022, when an ash plume rose 3.5 km above the crater rim. An aerial observation conducted by the Japan Coast Guard (JCG) on 25 November reported that white fumaroles rose approximately 200 m above the central crater of a pyroclastic cone (figure 119), and multiple plumes were observed on the ESE flank of the cone. Discolored water ranging from reddish-brown to brown and yellowish-green were visible around the perimeter of the island (figure 119). No significant activity was reported in December.
During an overflight conducted by JCG on 25 January 2023 intermittent activity and small, blackish-gray plumes rose 900 m above the central part of the crater were observed (figure 120). The fumarolic zone of the E flank and base of the cone had expanded and emissions had intensified. Dark brown discolored water was visible around the perimeter of the island.
No significant activity was reported during February through March. Ash plumes at 1050 and 1420 on 11 April rose 1.9 km above the crater rim and drifted NW and N. These were the first ash plumes observed since 12 October 2022. On 14 April JCG carried out an overflight and reported that no further eruptive activity was visible, although white gas-and-steam plumes were visible from the central crater and rose 900 m high (figure 121). Brownish and yellow-green discolored water surrounded the island.
Intermittent low-to-moderate power thermal anomalies were recorded in the MIROVA graph (Middle InfraRed Observation of Volcanic Activity) during November 2022 through April 2023 (figure 123). A cluster of six to eight anomalies were detected during November while a smaller number were detected during the following months: two to three during December, one during mid-January 2023, one during February, five during March, and two during April. Thermal activity was also reflected in infrared satellite data at the summit crater, accompanied by occasional gas-and-steam plumes (figure 124).
Geologic Background. The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Multiple eruptions that began in 2013 completely covered the previous exposed surface and continued to enlarge the island. The island is the summit of a massive submarine volcano that has prominent peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the ocean 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); 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).
Karangetang (Indonesia) — July 2023 Cite this Report
Karangetang
Indonesia
2.781°N, 125.407°E; summit elev. 1797 m
All times are local (unless otherwise noted)
Lava flows, incandescent avalanches, and ash plumes during January-June 2023
Karangetang (also known as Api Siau), at the northern end of the island of Siau, Indonesia, contains five summit craters along a N-S line. More than 40 eruptions have been recorded since 1675; recent eruptions have included frequent explosive activity, sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters and collapses of lava flow fronts have produced pyroclastic flows. The two active summit craters are Kawah Dua (the N crater) and Kawah Utama (the S crater, also referred to as the “Main Crater”). The most recent eruption began in late November 2018 and has more recently consisted of weak thermal activity and gas-and-steam emissions (BGVN 48:01). This report updates activity characterized by lava flows, incandescent avalanches, and ash plumes during January through June 2023 using reports from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM, or the Center of Volcanology and Geological Hazard Mitigation), MAGMA Indonesia, the Darwin VAAC (Volcano Ash Advisory Center), and satellite data.
Activity during January was relatively low and mainly consisted of white gas-and-steam emissions that rose 25-150 m above Main Crater (S crater) and drifted in different directions. Incandescence was visible from the lava dome in Kawah Dua (the N crater). Weather conditions often prevented clear views of the summit. On 18 January the number of seismic signals that indicated avalanches of material began to increase. In addition, there were a total of 71 earthquakes detected during the month.
Activity continued to increase during the first week of February. Material from Main Crater traveled as far as 800 m down the Batuawang (S) and Batang (W) drainages and as far as 1 km W down the Beha (W) drainage on 4 February. On 6 February 43 earthquake events were recorded, and on 7 February, 62 events were recorded. White gas-and-steam emissions rose 25-250 m above both summit craters throughout the month. PVMBG reported an eruption began during the evening of 8 February around 1700. Photos showed incandescent material at Main Crater. Incandescent material had also descended the flank in at least two unconfirmed directions as far as 2 km from Main Crater, accompanied by ash plumes (figure 60). As a result, PVMBG increased the Volcano Alert Level (VAL) to 3 (the second highest level on a 1-4 scale).
Occasional nighttime webcam images showed three main incandescent lava flows of differing lengths traveling down the S, SW, and W flanks (figure 61). Incandescent rocks were visible on the upper flanks, possibly from ejected or collapsed material from the crater, and incandescence was the most intense at the summit. Based on analyses of satellite imagery and weather models, the Darwin VAAC reported that daily ash plumes during 16-20 February rose to 2.1-3 km altitude and drifted NNE, E, and SE. BNPB reported on 16 February that as many as 77 people were evacuated and relocated to the East Siau Museum. A webcam image taken at 2156 on 17 February possibly showed incandescent material descending the SE flank. Ash plumes rose to 2.1 km altitude and drifted SE during 22-23 February, according to the Darwin VAAC.
Incandescent avalanches of material and summit incandescence at Main Crater continued during March. White gas-and-steam emissions during March generally rose 25-150 m above the summit crater; on 31 March gas-and-steam emissions rose 200-400 m high. An ash plume rose to 2.4 km altitude and drifted S at 1710 on 9 March and a large thermal anomaly was visible in images taken at 0550 and 0930 on 10 March. Incandescent material was visible at the summit and on the flanks based on webcam images taken at 0007 and 2345 on 16 March, at 1828 on 17 March, at 1940 on 18 March, at 2311 on 19 March, and at 2351 on 20 March. Incandescence was most intense on 18 and 20 March and webcam images showed possible Strombolian explosions (figure 62). An ash plume rose to 2.4 km altitude and drifted SW on 18 March, accompanied by a thermal anomaly.
Summit crater incandescence at Main Crater and on the flanks persisted during April. Incandescent material at the S crater and on the flanks was reported at 0016 on 1 April. The lava flows had stopped by 1 April according to PVMBG, although incandescence was still visible up to 10 m high. Seismic signals indicating effusion decreased and by 6 April they were no longer detected. Incandescence was visible from both summit craters. On 26 April the VAL was lowered to 2 (the second lowest level on a 1-4 scale). White gas-and-steam emissions rose 25-200 m above the summit crater.
During May white gas-and-steam emissions generally rose 50-250 m above the summit, though it was often cloudy, which prevented clear views; on 21 May gas-and-steam emissions rose 50-400 m high. Nighttime N summit crater incandescence rose 10-25 m above the lava dome, and less intense incandescence was noted above Main Crater, which reached about 10 m above the dome. Sounds of falling rocks at Main Crater were heard on 15 May and the seismic network recorded 32 rockfall events in the crater on 17 May. Avalanches traveled as far as 1.5 km down the SW and S flanks, accompanied by rumbling sounds on 18 May. Incandescent material descending the flanks was captured in a webcam image at 2025 on 19 May (figure 63) and on 29 May; summit crater incandescence was observed in webcam images at 2332 on 26 May and at 2304 on 29 May. On 19 May the VAL was again raised to 3.
Occasional Main Crater incandescence was reported during June, as well as incandescent material on the flanks. White gas-and-steam emissions rose 10-200 m above the summit crater. Ash plumes rose to 2.1 km altitude and drifted SE and E during 2-4 June, according to the Darwin VAAC. Material on the flanks of Main Crater were observed at 2225 on 7 June, at 2051 on 9 June, at 0007 on 17 June, and at 0440 on 18 June. Webcam images taken on 21, 25, and 27 June showed incandescence at Main Crater and from material on the flanks.
MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed strong thermal activity during mid-February through March and mid-May through June, which represented incandescent avalanches and lava flows (figure 64). During April through mid-May the power of the anomalies decreased but frequent anomalies were still detected. Brief gaps in activity occurred during late March through early April and during mid-June. Infrared satellite images showed strong lava flows mainly affecting the SW and S flanks, accompanied by gas-and-steam emissions (figure 65). According to data recorded by the MODVOLC thermal algorithm, there were a total of 79 thermal hotspots detected: 28 during February, 24 during March, one during April, five during May, and 21 during June.
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. 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 (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.esdm.go.id/v1); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/); IDN Times, Jl. Jend. Gatot Subroto Kav. 27 3rd Floor Kuningan, Jakarta, Indonesia 12950, Status of Karangetang Volcano in Sitaro Islands Increases (URL: https://sulsel.idntimes.com/news/indonesia/savi/status-gunung-api-karangetang-di-kepulauan-sitaro-meningkat?page=all).
Ahyi (United States) — July 2023 Cite this Report
Ahyi
United States
20.42°N, 145.03°E; summit elev. -75 m
All times are local (unless otherwise noted)
Intermittent hydroacoustic signals and discolored plumes during November 2022-June 2023
Ahyi seamount is a large, conical submarine volcano that rises to within 75 m of the ocean surface about 18 km SE of the island of Farallon de Pajaros in the Northern Marianas. The remote location of the seamount has made eruptions difficult to document, but seismic stations installed in the region confirmed an eruption in the vicinity in 2001. No new activity was detected until April-May 2014 when an eruption was detected by NOAA (National Oceanic and Atmospheric Administration) divers, hydroacoustic sensors, and seismic stations (BGVN 42:04). New activity was first detected on 15 November by hydroacoustic sensors that were consistent with submarine volcanic activity. This report covers activity during November 2022 through June 2023 based on daily and weekly reports from the US Geological Survey.
Starting in mid-October, hydroacoustic sensors at Wake Island (2.2 km E) recorded signals consistent with submarine volcanic activity, according to a report from the USGS issued on 15 November 2022. A combined analysis of the hydroacoustic signals and seismic stations located at Guam and Chichijima Island, Japan, suggested that the source of this activity was at or near the Ahyi seamount. After a re-analysis of a satellite image of the area that was captured on 6 November, USGS confirmed that there was no evidence of discoloration at the ocean surface. Few hydroacoustic and seismic signals continued through November, including on 18 November, which USGS suggested signified a decline or pause in unrest. A VONA (Volcano Observatory Notice for Aviation) reported that a discolored water plume was persistently visible in satellite data starting on 18 November (figure 6). Though clouds often obscured clear views of the volcano, another discolored water plume was captured in a satellite image on 26 November. The Aviation Color Code (ACC) was raised to Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level (VAL) was raised to Advisory (the second lowest level on a four-level scale) on 29 November.
During December, occasional detections were recorded on the Wake Island hydrophone sensors and discolored water over the seamount remained visible. During 2-7, 10-12, and 16-31 December possible explosion signals were detected. A small area of discolored water was observed in high-resolution Sentinel-2 satellite images during 1-6 December (figure 7). High-resolution satellite images recorded discolored water plumes on 13 December that originated from the summit region; no observations indicated that activity breached the ocean surface. A possible underwater plume was visible in satellite images on 18 December, and during 19-20 December a definite but diffuse underwater plume located SSE from the main vent was reported. An underwater plume was visible in a satellite image taken on 26 December (figure 7).
Hydrophone sensors continued to detect signals consistent with possible explosions during 1-8 January 2023. USGS reported that the number of detections decreased during 4-5 January. The hydrophone sensors experienced a data outage that started at 0118 on 8 January and continued through 10 January, though according to USGS, possible explosions were recorded prior to the data outage and likely continued during the outage. A discolored water plume originating from the summit region was detected in a partly cloudy satellite image on 8 January. On 11-12 and 15-17 January possible explosion signals were recorded again. One small signal was detected during 22-23 January and several signals were recorded on 25 and 31 January. During 27-31 January a plume of discolored water was observed above the seamount in satellite imagery (figure 8).
Low levels of activity continued during February and March, based on data from pressure sensors on Wake Island. During 1 and 4-6 February activity was reported, and a submarine plume was observed on 4 February (figure 8). Possible explosion signals were detected during 7-8, 10, 13-14, and 24 February. During 1-2 and 3-5 March a plume of discolored water was observed in satellite imagery (figure 8). Almost continuous hydroacoustic signals were detected in remote pressure sensor data on Wake Island 2,270 km E from the volcano during 7-13 March. During 12-13 March water discoloration around the seamount was observed in satellite imagery, despite cloudy weather. By 14 March discolored water extended about 35 km, but no direction was noted. USGS reported that the continuous hydroacoustic signals detected during 13-14 March stopped abruptly on 14 March and no new detections were observed. Three 30 second hydroacoustic detections were reported during 17-19 March, but no activity was visible due to cloudy weather. A data outage was reported during 21-22 March, making pressure sensor data unavailable; a discolored water plume was, however, visible in satellite data. A possible underwater explosion signal was detected by pressure sensors at Wake Island on 26, 29, and 31 March, though the cause and origin of these events were unclear.
Similar low activity continued during April, May, and June. Several signals were detected during 1-3 April in pressure sensors at Wake Island. USGS suggested that these may be related to underwater explosions or earthquakes at the volcano, but no underwater plumes were visible in clear satellite images. The pressure sensors had data outages during 12-13 April and no data were recorded; no underwater plumes were visible in satellite images, although cloudy weather obscured most clear views. Eruptive activity was reported starting at 2210 on 21 May. On 22 May a discolored water plume that extended 4 km was visible in satellite images, though no direction was recorded. During 23-24 May some signals were detected by the underwater pressure sensors. Possible hydroacoustic signals were detected during 2-3 and 6-8 June. Multiple hydroacoustic signals were detected during 9-11 and 16-17 June, although no activity was visible in satellite images. One hydroacoustic signal was detected during 23-24 June, but there was some uncertainty about its association with volcanic activity. A single possible hydroacoustic signal was detected during 30 June to 1 July.
Geologic Background. Ahyi seamount is a large conical submarine volcano that rises to within 75 m of the ocean surface ~18 km SE of the island of Farallon de Pajaros in the northern Marianas. Water discoloration has been observed there, and in 1979 the crew of a fishing boat felt shocks over the summit area, followed by upwelling of sulfur-bearing water. On 24-25 April 2001 an explosive eruption was detected seismically by a station on Rangiroa Atoll, Tuamotu Archipelago. The event was well constrained (+/- 15 km) at a location near the southern base of Ahyi. An eruption in April-May 2014 was detected by NOAA divers, hydroacoustic sensors, and seismic stations.
Information Contacts: US Geological Survey, Volcano Hazards Program (USGS-VHP), 12201 Sunrise Valley Drive, Reston, VA, USA, https://volcanoes.usgs.gov/index.html; Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).
Kadovar (Papua New Guinea) — June 2023 Cite this Report
Kadovar
Papua New Guinea
3.608°S, 144.588°E; summit elev. 365 m
All times are local (unless otherwise noted)
An ash plume and weak thermal anomaly during May 2023
Kadovar is a 2-km-wide island that is the emergent summit of a Bismarck Sea stratovolcano. It 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 volcano, filling an arcuate landslide scarp open to the S. Submarine debris-avalanche deposits occur to the S of the island. The current eruption began in January 2018 and has comprised lava effusion from vents at the summit and at the E coast; more recent activity has consisted of ash plumes, weak thermal activity, and gas-and-steam plumes (BGVN 48:02). This report covers activity during February through May 2023 using information from the Darwin Volcanic Ash Advisory Center (VAAC) and satellite data.
Activity during the reporting period was relatively low and mainly consisted of white gas-and-steam plumes that were visible in natural color satellite images on clear weather days (figure 67). According to a Darwin VAAC report, at 2040 on 6 May an ash plume rose to 4.6 km altitude and drifted W; by 2300 the plume had dissipated. MODIS satellite instruments using the MODVOLC thermal algorithm detected a single thermal hotspot on the SE side of the island on 7 May. Weak thermal activity was also detected in a satellite image on the E side of the island on 14 May, accompanied by a white gas-and-steam plume that drifted SE (figure 68).
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: 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/); 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).
San Miguel (El Salvador) — June 2023 Cite this Report
San Miguel
El Salvador
13.434°N, 88.269°W; summit elev. 2130 m
All times are local (unless otherwise noted)
Small gas-and-ash explosions during March and May 2023
San Miguel in El Salvador is a broad, deep crater complex that has been frequently modified by eruptions recorded since the early 16th century and consists of the summit known locally as Chaparrastique. Flank eruptions have produced lava flows that extended to the N, NE, and SE during the 17-19th centuries. The most recent activity has consisted of minor ash eruptions from the summit crater. The current eruption period began in November 2022 and has been characterized by frequent phreatic explosions, gas-and-ash emissions, and sulfur dioxide plumes (BGVN 47:12). This report describes small gas-and-ash explosions during December 2022 through May 2023 based on special reports from the Ministero de Medio Ambiente y Recursos Naturales (MARN).
Activity has been relatively low since the last recorded explosions on 29 November 2022. Seismicity recorded by the San Miguel Volcano Station (VSM) located on the N flank at 1.7 km elevation had decreased by 7 December. Sulfur dioxide gas measurements taken with DOAS (Differential Optical Absorption Spectroscopy) mobile equipment were below typical previously recorded values: 300 tons per day (t/d). During December, small explosions were recorded by the seismic network and manifested as gas-and-steam emissions.
Gas-and-ash explosions in the crater occurred during January 2023, which were recorded by the seismic network. Sulfur dioxide values remained low, between 300-400 t/d through 10 March. At 0817 on 14 January a gas-and-ash emission was visible in webcam images, rising just above the crater rim. Some mornings during February, small gas-and-steam plumes were visible in the crater. On 7 March at 2252 MARN noted an increase in degassing from the central crater; gas emissions were constantly observed through the early morning hours on 8 March. During the early morning of 8 March through the afternoon on 9 March, 12 emissions were registered, some accompanied by ash. The last gas-and-ash emission was recorded at 1210 on 9 March; very fine ashfall was reported in El Tránsito (10 km S), La Morita (6 km W), and La Piedrita (3 km W). The smell of sulfur was reported in Piedra Azul (5 km SW). On 16 March MARN reported that gas-and-steam emissions decreased.
Low degassing and very low seismicity were reported during April; no explosions have been detected between 9 March and 27 May. The sulfur dioxide emissions remained between 350-400 t/d; during 13-20 April sulfur dioxide values fluctuated between 30-300 t/d. Activity remained low through most of May; on 23 May seismicity increased. An explosion was detected at 1647 on 27 May generated a gas-and-ash plume that rose 700 m high (figure 32); a decrease in seismicity and gas emissions followed. The DOAS station installed on the W flank recorded sulfur dioxide values that reached 400 t/d on 27 May; subsequent measurements showed a decrease to 268 t/d on 28 May and 100 t/d on 29 May.
Geologic Background. The symmetrical cone of San Miguel, one of the most active volcanoes in El Salvador, rises from near sea level to form one of the country's most prominent landmarks. A broad, deep, crater complex that has been frequently modified by eruptions recorded since the early 16th century caps the truncated unvegetated summit, also known locally as Chaparrastique. Flanks eruptions of the basaltic-andesitic volcano have produced many lava flows, including several during the 17th-19th centuries that extended to the N, NE, and SE. The SE-flank flows are the largest and form broad, sparsely vegetated lava fields crossed by highways and a railroad skirting the base of the volcano. Flank vent locations have migrated higher on the edifice during historical time, and the most recent activity has consisted of minor ash eruptions from the summit crater.
Information Contacts: Ministero de Medio Ambiente y Recursos Naturales (MARN), Km. 5½ Carretera a Nueva San Salvador, Avenida las Mercedes, San Salvador, El Salvador (URL: http://www.snet.gob.sv/ver/vulcanologia).
Semisopochnoi (United States) — June 2023 Cite this Report
Semisopochnoi
United States
51.93°N, 179.58°E; summit elev. 1221 m
All times are local (unless otherwise noted)
Occasional explosions, ash deposits, and gas-and-steam plumes during December 2022-May 2023
Semisopochnoi is located in the western Aleutians, is 20-km-wide at sea level, and contains an 8-km-wide caldera. The three-peaked Mount Young (formerly Cerberus) was constructed within the caldera during the Holocene. Each of these peaks contains a summit crater; the lava flows on the N flank appear younger than those on the S side. The current eruption period began in early February 2021 and has more recently consisted of intermittent explosions and ash emissions (BGVN 47:12). This report updates activity during December 2022 through May 2023 using daily, weekly, and special reports from the Alaska Volcano Observatory (AVO). AVO monitors the volcano using local seismic and infrasound sensors, satellite data, web cameras, and remote infrasound and lightning networks.
Activity during most of December 2022 was relatively quiet; according to AVO no eruptive or explosive activity was observed since 7 November 2022. Intermittent tremor and occasional small earthquakes were observed in geophysical data. Continuous gas-and-steam emissions were observed from the N crater of Mount Young in webcam images on clear weather days (figure 25). On 24 December, there was a slight increase in earthquake activity and several small possible explosion signals were detected in infrasound data. Eruptive activity resumed on 27 December at the N crater of Mount Young; AVO issued a Volcano Activity Notice (VAN) that reported minor ash deposits on the flanks of Mount Young that extended as far as 1 km from the vent, according to webcam images taken during 27-28 December (figure 26). No ash plumes were observed in webcam or satellite imagery, but a persistent gas-and-steam plume that might have contained some ash rose to 1.5 km altitude. As a result, AVO raised the Aviation Color Code (ACC) to Orange (the second highest level on a four-color scale) and the Volcano Alert Level (VAL) to Watch (the second highest level on a four-level scale). Possible explosions were detected during 21 December 2022 through 1 January 2023 and seismic tremor was recorded during 30-31 December.
During January 2023 eruptive activity continued at the active N crater of Mount Young. Minor ash deposits were observed on the flanks, extending about 2 km SSW, based on webcam images from 1 and 3 January. A possible explosion occurred during 1-2 January based on elevated seismicity recorded on local seismometers and an infrasound signal recorded minutes later by an array at Adak. Though no ash plumes were observed in webcam or satellite imagery, a persistent gas-and-steam plume rose to 1.5 km altitude that might have carried minor traces of ash. Ash deposits were accompanied by periods of elevated seismicity and infrasound signals from the local geophysical network, which AVO reported were likely due to weak explosive activity. Low-level explosive activity was also detected during 2-3 January, with minor gas-and-steam emissions and a new ash deposit that was visible in webcam images. Low-level explosive activity was detected in geophysical data during 4-5 January, with elevated seismicity and infrasound signals observed on local stations. Volcanic tremor was detected during 7-9 January and very weak explosive activity was detected in seismic and infrasound data on 9 January. Weak seismic and infrasound signals were recorded on 17 January, which indicated minor explosive activity, but no ash emissions were observed in clear webcam images; a gas-and-steam plume continued to rise to 1.5 km altitude. During 29-30 January, ash deposits near the summit were observed on fresh snow, according to webcam images.
The active N cone at Mount Young continued to produce a gas-and-steam plume during February, but no ash emissions or explosive events were detected. Seismicity remained elevated with faint tremor during early February. Gas-and-steam emissions from the N crater were observed in clear webcam images on 11-13 and 16 February; no explosive activity was detected in seismic, infrasound, or satellite data. Seismicity has also decreased, with no significant seismic tremor observed since 25 January. Therefore, the ACC was lowered to Yellow (the second lowest level on a four-color scale) and the VAL was lowered to Advisory (the second lowest level on a four-color scale) on 22 February.
Gas-and-steam emissions persisted during March from the N cone of Mount Young, based on clear webcam images. A few brief episodes of weak tremor were detected in seismic data, although seismicity decreased over the month. A gas-and-steam plume detected in satellite data extended 150 km on 18 March. Low-level ash emissions from the N cone at Mount Young were observed in several webcam images during 18-19 March, in addition to small explosions and volcanic tremor. The ACC was raised to Orange and the VAL increased to Watch on 19 March. A small explosion was detected in seismic and infrasound data on 21 March.
Low-level unrest continued during April, although cloudy weather often obscured views of the summit; periods of seismic tremor and local earthquakes were recorded. During 3-4 April a gas-and-steam plume was visible traveling more than 200 km overnight; no ash was evident in the plume, according to AVO. A gas-and-steam plume was observed during 4-6 April that extended 400 km but did not seem to contain ash. Small explosions were detected in seismic and infrasound data on 5 April. Occasional clear webcam images showed continuing gas-and-steam emissions rose from Mount Young, but no ash deposits were observed on the snow. On 19 April small explosions and tremor were detected in seismic and infrasound data. A period of seismic tremor was detected during 22-25 April, with possible weak explosions on 25 April. Ash deposits were visible near the crater rim, but it was unclear if these deposits were recent or due to older deposits.
Occasional small earthquakes were recorded during May, but there were no signs of explosive activity seen in geophysical data. Gas-and-steam emissions continued from the N crater of Mount Young, based on webcam images, and seismicity remained slightly elevated. A new, light ash deposit was visible during the morning of 5 May on fresh snow on the NW flank of Mount Young. During 10 May periods of volcanic tremor were observed. The ACC was lowered to Yellow and the VAL to Advisory on 17 May due to no additional evidence of activity.
Geologic Background. Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part. The three-peaked Mount Cerberus (renamed Mount Young in 2023) was constructed within the caldera during the Holocene. Each of the peaks contains a summit crater; lava flows on the N flank appear younger than those on the south side. Other post-caldera volcanoes include the symmetrical Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented eruptions have originated from Young, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone could have been recently active.
Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.gov/).
Ebeko
Russia
50.686°N, 156.014°E; summit elev. 1103 m
All times are local (unless otherwise noted)
Continued explosions, ash plumes, and ashfall during October 2022-May 2023
Ebeko, located on the N end of Paramushir Island in the Kuril Islands, consists of three summit craters along a SSW-NNE line at the northern end of a complex of five volcanic cones. Eruptions date back to the late 18th century and have been characterized as small-to-moderate explosions from the summit crater, accompanied by intense fumarolic activity. The current eruption period began in June 2022 and has recently consisted of frequent explosions, ash plumes, and thermal activity (BGVN 47:10). This report covers similar activity during October 2022 through May 2023, based on information from the Kamchatka Volcanic Eruptions Response Team (KVERT) and satellite data.
Activity during October consisted of explosive activity, ash plumes, and occasional thermal anomalies. Visual data by volcanologists from Severo-Kurilsk showed explosions producing ash clouds up to 2.1-3 km altitude which drifted E, N, NE, and SE during 1-8, 10, 16, and 18 October. KVERT issued several Volcano Observatory Notices for Aviation (VONA) on 7, 13-15, and 27 October 2022, stating that explosions generated ash plumes that rose to 2.3-4 km altitude and drifted 5 km E, NE, and SE. Ashfall was reported in Severo-Kurilsk (Paramushir Island, about 7 km E) on 7 and 13 October. Satellite data showed a thermal anomaly over the volcano on 15-16 October. Visual data showed ash plumes rising to 2.5-3.6 km altitude on 22, 25-29, and 31 October and moving NE due to constant explosions.
Similar activity continued during November, with explosions, ash plumes, and ashfall occurring. KVERT issued VONAs on 1-2, 4, 6-7, 9, 13, and 16 November that reported explosions and resulting ash plumes that rose to 1.7-3.6 km altitude and drifted 3-5 km SE, ESE, E, and NE. On 1 November ash plumes extended as far as 110 km SE. On 5, 8, 12, and 24-25 November explosions and ash plumes rose to 2-3.1 km altitude and drifted N and E. Ashfall was observed in Severo-Kurilsk on 7 and 16 November. A thermal anomaly was visible during 1-4, 16, and 20 November. Explosions during 26 November rose as high as 2.7 km altitude and drifted NE (figure 45).
Explosions and ash plumes continued to occur in December. During 1-2 and 4 December volcanologists from Severo-Kurilsk observed explosions that sent ash to 1.9-2.5 km altitude and drifted NE and SE (figure 46). VONAs were issued on 5, 9, and 16 December reporting that explosions generated ash plumes rising to 1.9 km, 2.6 km, and 2.4 km altitude and drifted 5 km SE, E, and NE, respectively. A thermal anomaly was visible in satellite imagery on 16 December. On 18 and 27-28 December explosions produced ash plumes that rose to 2.5 km altitude and drifted NE and SE. On 31 December an ash plume rose to 2 km altitude and drifted NE.
Explosions continued during January 2023, based on visual observations by volcanologists from Severo-Kurilsk. During 1-7 January explosions generated ash plumes that rose to 4 km altitude and drifted NE, E, W, and SE. According to VONAs issued by KVERT on 2, 4, 10, and 23 January, explosions produced ash plumes that rose to 2-4 km altitude and drifted 5 km N, NE, E, and ENE; the ash plume that rose to 4 km altitude occurred on 10 January (figure 47). Satellite data showed a thermal anomaly during 3-4, 10, 13, 16, 21, 22, and 31 January. KVERT reported that an ash cloud on 4 January moved 12 km NE. On 6 and 9-11 January explosions sent ash plumes to 4.5 km altitude and drifted W and ESE. On 13 January an ash plume rose to 3 km altitude and drifted SE. During 20-24 January ash plumes from explosions rose to 3.7 km altitude and drifted SE, N, and NE. On 21 January the ash plume drifted as far as 40 km NE. During 28-29 and 31 January and 1 February ash plumes rose to 4 km altitude and drifted NE.
During February, explosions, ash plumes, and ashfall were reported. During 1, 4-5 and 7-8 February explosions generated ash plumes that rose to 4.5 km altitude and drifted E and NE; ashfall was observed on 5 and 8 February. On 6 February an explosion produced an ash plume that rose to 3 km altitude and drifted 7 km E, causing ashfall in Severo-Kurilsk. A thermal anomaly was visible in satellite data on 8, 9, 13, and 21 February. Explosions on 9 and 12-13 February produced ash plumes that rose to 4 km altitude and drifted E and NE; the ash cloud on 12 February extended as far as 45 km E. On 22 February explosions sent ash to 3 km altitude that drifted E. During 24 and 26-27 February ash plumes rose to 4 km altitude and drifted E. On 28 February an explosion sent ash to 2.5-3 km altitude and drifted 5 km E; ashfall was observed in Severo-Kurilsk.
Activity continued during March; visual observations showed that explosions generated ash plumes that rose to 3.6 km altitude on 3, 5-7, and 9-12 March and drifted E, NE, and NW. Thermal anomalies were visible on 10, 13, and 29-30 March in satellite imagery. On 18, 21-23, 26, and 29-30 March explosions produced ash plumes that rose to 2.8 km altitude and drifted NE and E; the ash plumes during 22-23 March extended up to 76 km E. A VONA issued on 21 March reported an explosion that produced an ash plume that rose to 2.8 km altitude and drifted 5 km E. Another VONA issued on 23 March reported that satellite data showed an ash plume rising to 3 km altitude and drifted 14 km E.
Explosions during April continued to generate ash plumes. On 1 and 4 April an ash plume rose to 2.8-3.5 km altitude and drifted SE and NE. A thermal anomaly was visible in satellite imagery during 1-6 April. Satellite data showed ash plumes and clouds rising to 2-3 km altitude and drifting up to 12 km SW and E on 3 and 6 April (figure 48). KVERT issued VONAs on 3, 5, 14, 16 April describing explosions that produced ash plumes rising to 3 km, 3.5 km, 3.5 km, and 3 km altitude and drifting 5 km S, 5 km NE and SE, 72 km NNE, and 5 km NE, respectively. According to satellite data, the resulting ash cloud from the explosion on 14 April was 25 x 7 km in size and drifted 72-104 km NNE during 14-15 April. According to visual data by volcanologists from Severo-Kurilsk explosions sent ash up to 3.5 km altitude that drifted NE and E during 15-16, 22, 25-26, and 29 April.
The explosive eruption continued during May. Explosions during 3-4, 6-7, and 9-10 May generated ash plumes that rose to 4 km altitude and drifted SW and E. Satellite data showed a thermal anomaly on 3, 9, 13-14, and 24 May. During 12-16, 23-25, and 27-28 May ash plumes rose to 3.5 km altitude and drifted in different directions due to explosions. Two VONA notices were issued on 16 and 25 May, describing explosions that generated ash plumes rising to 3 km and 3.5 km altitude, respectively and extending 5 km E. The ash cloud on 25 May drifted 75 km SE.
Thermal activity in the summit crater, occasionally accompanied by ash plumes and ash deposits on the SE and E flanks due to frequent explosions, were visible in infrared and true color satellite images (figure 49).
Geologic Background. The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.
Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).
Home Reef
Tonga
18.992°S, 174.775°W; summit elev. -10 m
All times are local (unless otherwise noted)
Discolored plumes continued during November 2022-April 2023
Home Reef is a submarine volcano located in the central Tonga islands between Lateiki (Metis Shoal) and Late Island. The first recorded eruption occurred in the mid-19th century, when an ephemeral island formed. An eruption in 1984 produced a 12-km-high eruption plume, a large volume of floating pumice, and an ephemeral island 500 x 1,500 m wide, with cliffs 30-50 m high that enclosed a water-filled crater. Another island-forming eruption in 2006 produced widespread pumice rafts that drifted as far as Australia; by 2008 the island had eroded below sea level. The previous eruption occurred during October 2022 and was characterized by a new island-forming eruption, lava effusion, ash plumes, discolored water, and gas-and-steam plumes (BGVN 47:11). This report covers discolored water plumes during November 2022 through April 2023 using satellite data.
Discolored plumes continued during the reporting period and were observed in true color satellite images on clear weather days. Satellite images show light green-yellow discolored water extending W on 8 and 28 November 2022 (figure 31), and SW on 18 November. Light green-yellow plumes extended W on 3 December, S on 13 December, SW on 18 December, and W and S on 23 December (figure 31). On 12 January 2023 discolored green-yellow plumes extended to the NE, E, SE, and N. The plume moved SE on 17 January and NW on 22 January. Faint discolored water in February was visible moving NE on 1 February. A discolored plume extended NW on 8 and 28 March and NW on 13 March (figure 31). During April, clear weather showed green-blue discolored plumes moving S on 2 April, W on 7 April, and NE and S on 12 April. A strong green-yellow discolored plume extended E and NE on 22 April for several kilometers (figure 31).
Geologic Background. Home Reef, a submarine volcano midway between Metis Shoal and Late Island in the central Tonga islands, was first reported active in the mid-19th century, when an ephemeral island formed. An eruption in 1984 produced a 12-km-high eruption plume, large amounts of floating pumice, and an ephemeral 500 x 1,500 m island, with cliffs 30-50 m high that enclosed a water-filled crater. In 2006 an island-forming eruption produced widespread dacitic pumice rafts that drifted as far as Australia. Another island was built during a September-October 2022 eruption.
Information Contacts: Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).
Ambae
Vanuatu
15.389°S, 167.835°E; summit elev. 1496 m
All times are local (unless otherwise noted)
New lava flow, ash plumes, and sulfur dioxide plumes during February-May 2023
Ambae, also known as Aoba, is a large basaltic shield volcano in Vanuatu. A broad pyroclastic cone containing three crater lakes (Manaro Ngoru, Voui, and Manaro Lakua) is located at the summit within the youngest of at least two nested calderas. Periodic phreatic and pyroclastic explosions have been reported since the 16th century. A large eruption more than 400 years ago resulted in a volcanic cone within the summit crater that is now filled by Lake Voui; the similarly sized Lake Manaro fills the western third of the caldera. The previous eruption ended in August 2022 that was characterized by gas-and-steam and ash emissions and explosions of wet tephra (BGVN 47:10). This report covers a new eruption during February through May 2023 that consisted of a new lava flow, ash plumes, and sulfur dioxide emissions, using information from the Vanuatu Meteorology and Geo-Hazards Department (VMGD) and satellite data.
During the reporting period, the Alert Level remained at a 2 (on a scale of 0-5), which has been in place since December 2021. Activity during October 2022 through March 2023 remained relatively low and mostly consisted of gas-and-steam emissions in Lake Voui. VMGD reported that at 1300 on 15 November a satellite image captured a strong amount of sulfur dioxide rising above the volcano (figure 99), and that seismicity slightly increased. The southern and northern part of the island reported a strong sulfur dioxide smell and heard explosions. On 20 February 2023 a gas-and-ash plume rose 1.3 km above the summit and drifted SSW, according to a webcam image (figure 100). Gas-and-steam and possibly ash emissions continued on 23 February and volcanic earthquakes were recorded by the seismic network.
During April, volcanic earthquakes and gas-and-steam and ash emissions were reported from the cone in Lake Voui. VMGD reported that activity increased during 5-7 April; high gas-and-steam and ash plumes were visible, accompanied by nighttime incandescence. According to a Wellington VAAC report, a low-level ash plume rose as high as 2.5 km above the summit and drifted W and SW on 5 April, based on satellite imagery. Reports in Saratamata stated that a dark ash plume drifted to the WSW, but no loud explosion was heard. Webcam images from 2100 showed incandescence above the crater and reflected in the clouds. According to an aerial survey, field observations, and satellite data, water was no longer present in the lake. A lava flow was reported effusing from the vent and traveling N into the dry Lake Voui, which lasted three days. The next morning at 0745 on 6 April a gas-and-steam and ash plume rose 5.4 km above the summit and drifted ESE, based on information from VMGD (figure 101). The Wellington VAAC also reported that light ashfall was observed on the island. Intermittent gas-and-steam and ash emissions were visible on 7 April, some of which rose to an estimated 3 km above the summit and drifted E. Webcam images during 0107-0730 on 7 April showed continuing ash emissions. A gas-and-steam and ash plume rose 695 m above the summit crater at 0730 on 19 April and drifted ESE, based on a webcam image (figure 102).
According to visual and infrared satellite data, water was visible in Lake Voui as late as 24 March 2023 (figure 103). The vent in the caldera showed a gas-and-steam plume drifted SE. On 3 April thermal activity was first detected, accompanied by a gas-and-ash plume that drifted W (figure 103). The lava flow moved N within the dry lake and was shown cooling by 8 April. By 23 April much of the water in the lake had returned. Occasional sulfur dioxide plumes were detected by the TROPOMI instrument on the Sentinel-5P satellite that exceeded 2 Dobson Units (DU) and drifted in different directions (figure 104).
Geologic Background. The island of Ambae, also known as Aoba, is a massive 2,500 km3 basaltic shield that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone with numerous scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes (Manaro Ngoru, Voui, and Manaro Lakua) is located at the summit within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. That large central edifice is also called Manaro Voui or Lombenben volcano. Post-caldera explosive eruptions formed the summit craters about 360 years ago. A tuff cone was constructed within Lake Voui (or Vui) about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.
Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department (VMGD), Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory/); 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/); 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/); Copernicus Browser, Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/).
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Bulletin of the Global Volcanism Network - Volume 37, Number 12 (December 2012)
Managing Editor: Richard Wunderman
Akan (Japan)
Relatively quiet during 2009-2012
Kama'ehuakanaloa (United States)
Seismic swarms during 2001-2006
Krakatau (Indonesia)
September 2012 eruption ejects ash; lava flows reach the sea
Nyiragongo (DR Congo)
Bubbling lava lake visited by three groups during January 2011
Pagan (United States)
Ash, gas, and thermal emissions during 2011-2012
Tolbachik (Russia)
Seismicity precedes onset of dual fissure eruption in November 2012
Akan
Japan
43.384°N, 144.013°E; summit elev. 1499 m
All times are local (unless otherwise noted)
Relatively quiet during 2009-2012
Although Akan is the most active volcano on the island, little activity has been reported by JMA since November 2008; activity during 2008 was summarized in two previous Bulletins (BGVN 33:10 and 35:10). Since then quiet prevailed except for a few instances of tremor in 2009 and 2010 reported in Japan Meteorology Agency's (JMA) monthly summaries from September 2010 to November 2012. The caldera is located in Akan National Park on the island of Hokkaido, Japan (figure 11).
The Me-Akan volcano group, E of Lake Akan, is the only site of historical activity in Akan caldera. Me-Akan is composed of 9 overlapping cones; the main cone contains three prominent craters, the Akanuma crater, 96-1 crater, and "old crater" (figure 12).
JMA monitors the Akan complex, reporting eruptions, seismicity, and topographic change. A single seismic anomaly was discussed in the December 2010 monthly report (the latest report on Akan as of February 2013):
"Tremors with small amplitudes were observed four times from 12am to 10pm on 17 December [2010]. No remarkable changes in plume, infrasonic and tilt data were observed during the occurrence of these tremors. The previous tremor was observed on 18 March 2009. Seismic activity has returned to the background level, after a temporal increase of volcanic earthquakes with small amplitude during 17 December through 19 December. According to the observation by Kakioka Magnetic Observatory of JMA, geomagnetic total intensity at Meakandake [Akan] has been increasing since July 2009, which reflects the cooling process beneath the south slope of 96-1 crater, and its trend has been declining since July 2010. No remarkable changes in both plume activity and crustal deformation were observed."
Since the Me-Akan complex, part of a 13 X 24 km elongated caldera, lies within the Akan National Park (figure 13), JMA not only monitors the complex, but as well produced safety and evacuation procedures for the visitors. The JMA prepared both a hazard alert map (figure 14), and volcano hazard and evacuation procedure poster (figure 15). These are available at Lake Akan and Lake Kussharo-ko, hot springs, nature sites, and accommodations. Figures 14 and 15 meet the needs of those visitors unfamiliar with the nature of volcanoes, hot springs and calderas. In the form of a cartoon (infographics), the latter helps those with little or no knowledge of the Japanese language.
Geologic Background. Akan is a 13 x 24 km caldera located immediately SW of Kussharo caldera. The elongated, irregular outline of the caldera rim reflects its incremental formation during major explosive eruptions from the early to mid-Pleistocene. Growth of four post-caldera stratovolcanoes, three at the SW end of the caldera and the other at the NE side, has restricted the size of the caldera lake. Conical Oakandake was frequently active during the Holocene. The 1-km-wide Nakamachineshiri crater of Meakandake was formed during a major pumice-and-scoria eruption about 13,500 years ago. Within the Akan volcanic complex, only the Meakandake group, east of Lake Akan, has been historically active, producing mild phreatic eruptions since the beginning of the 19th century. Meakandake is composed of nine overlapping cones. The main cone of Meakandake proper has a triple crater at its summit. Historical eruptions at Meakandake have consisted of minor phreatic explosions, but four major magmatic eruptions including pyroclastic flows have occurred during the Holocene.
Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); Keiji Wada, Hokkaido University of Education, Hokumon-cho 9, Asahikawa 070-8621, Japan; Google Maps (URL: http://maps.google.com/); Secret-Japan.com (URL: http://www.secret-japan.com/).
Kama'ehuakanaloa (United States) — December 2012 Cite this Report
Kama'ehuakanaloa
United States
18.92°N, 155.27°W; summit elev. -975 m
All times are local (unless otherwise noted)
Seismic swarms during 2001-2006
Ken Rubin of the University of Hawaii provided some of the following information concerning Lōʻihi volcano, noting that there hasn't been much activity reported over the last 10 years. The ocean bottom seismometer (OBS) died several months after installation in mid-1996 because the cable connecting it to land was not armored and thus failed early after deployment. However, using available seismic data from the OBS and the Hawaiian Volcano Observatory (HVO) land network, Caplan-Auerbach and others (2001), were able to develop a more precise crustal velocity model so that seismic events at Lōʻihi recorded by the land stations at Kīlauea can now be precisely located. Unfortunately, only large events (probably >M 3 or M 4) are detected.
Several papers were published on Lōʻihi by Schipper and others (2010, 2011) looking at a reworked pyroclastic section of unknown age on the summit platform and making inferences on eruptive conditions (especially on the conditions of vesiculation and fragmentation). The samples for their studies were collected during the last known geological dives to the summit by Hawaii Undersea Research Laboratory (HURL) and NOAA in 2007.
Seismic swarms during 2001-2006. The Lōʻihi web site reported that a seismic swarm was detected at Lōʻihi's summit with earthquakes up to M 5.2 on 13 September 2001. Activity continued for a couple of weeks, with 4 events >M 4 at depths of 12-13 km. No >M 4 earthquakes were detected at Lōʻihi during 2002-2004. An M 4.3 earthquake occurred on 23 April 2005 at ~33 km depth beneath Lōʻihi, and earthquakes of M 5.1 and 5.4 occurred on 13 May and 17 July 2005, respectively, both at a depth of 44 km. The U.S. Geological Survey Advanced National Seismic System measured a small swarm of about 100 earthquakes (the largest 3 events were ~M 4, and between 12 and 28 km deep) that occurred beneath Lōʻihi on 7 December 2005. A more recent earthquake (estimated M 4.7) occurred on 18 January 2006, roughly midway between Lōʻihi and Pahala (on the S coast of the island of Hawaii).
References. Caplan-Auerbach, J., and Duennebier, F.K., 2001, Seismicity and Velocity Structure of Lōʻihi Seamount from the 1996 Earthquake Swarm, Bulletin of the Seismological Society of America, v. 91, no. 2, p. 178-190.
Rubin, K.H., Soule, S.A., Chadwick Jr., W.W., Fornari, D.J., Clague, D.A., Embley, R.W., Baker, E.T., Perfit, M.R., Caress, D.W., and Dziak, R.P., 2012, Volcanic eruptions in the deep sea, Oceanography, v. 25, no. 1, p. 142-157.
Schipper, C.I., White, J.D.L., and Houghton, B.F., 2010, Syn- and post-fragmentation textures in submarine pyroclasts from Lo`ihi Seamount, Hawai`i, Journal of Volcanology and Geothermal Research, v. 191, issues 3-4, p. 93-106.
Schipper, C.I., White, J.D.L., and Houghton, B.F., 2011, Textural, geochemical, and volatile evidence for a Strombolian-like eruption sequence at Lo`ihi Seamount, Hawai`i, Journal of Volcanology and Geothermal Research, v. 207, issues 1-2, p. 16-32.
Geologic Background. The Kama’ehuakanaloa seamount, previously known as Loihi, lies about 35 km off the SE coast of the island of Hawaii. This youngest volcano of the Hawaiian chain has an elongated morphology dominated by two curving rift zones extending north and south of the summit. The summit region contains a caldera about 3 x 4 km and exhibits numerous lava cones, the highest of which is about 975 m below the ocean surface. The summit platform also includes two well-defined pit craters, sediment-free glassy lava, and low-temperature hydrothermal venting. An arcuate chain of small cones on the western edge of the summit extends north and south of the pit craters and merges into the crests prominent rift zones. Seismicity indicates a magmatic system distinct from that of Kilauea. During 1996 a new pit crater formed at the summit, and lava flows were erupted. Continued volcanism is expected to eventually build a new island; time estimates for the summit to reach the ocean surface range from roughly 10,000 to 100,000 years.
Information Contacts: Lo`ihi Volcano website (URL: http://www.soest.hawaii.edu/GG/HCV/loihi.html); Ken Rubin, Department of Geology and Geophysics, School of Ocean and Earth Science and Technology (SOEST), University of Hawaii at Manoa, Honolulu, HI (URL: http://www/soest.hawaii.edu/GG); U.S. Geological Survey Earthquake Information Center (NEIC) (URL: https://earthquake.usgs.gov/neis); Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/).
Krakatau (Indonesia) — December 2012 Cite this Report
Krakatau
Indonesia
6.1009°S, 105.4233°E; summit elev. 285 m
All times are local (unless otherwise noted)
September 2012 eruption ejects ash; lava flows reach the sea
One of our previous reports on Krakatau (BGVN 36:08) discussed two eruption episodes, one spanning from 25 October 2010 to March 2011 and another beginning in August 2011 and continuing through the end of that report, around 1 October 2011. During the last two weeks of September 2011 volcanic earthquake swarms and diffuse emissions persisted. In November 2011, the photographer and guide Øystein Lund Andersen visited Krakatau and observed mild Strombolian explosions (BGVN 37:11).
This report summarizes behavior chiefly during 1 October 2011 through early October 2012. Eruptions around early September 2012 deposited ash on towns in Sumatra, and lava flows extended the shoreline of the island (Anak Krakatau) by ~100 m. The Alert Level was lowered after that and remained low into at least mid-January 2013. Figure 30 is an index map showing the location of the famous caldera Krakatau, located in the Sunda Strait (E of Sumatra and W of Java). The smaller feature Anak Krakatau grew to form an island well after the 1883 eruption and continues as the active center.
Activity during October 2011-early September 2012. The Alert Level was raised to 3 (on a scale of 1-4) on 30 September 2011, prohibiting visitors and residents from approaching within 2 km of the active crater. On 8 October 2011, a Jakarta Post article stated that activity at Krakatau was increasing; the number of seismic events on 6 October was 5,204; on 7 October, 5,543; and on 8 October, 5,883.
On 26 January 2012, CVGHM lowered the Alert Level from 3 to 2, noting that the number of tremor events had decreased significantly. The lowered Alert Level excluded visitors and residents from approaching within 1 km of the active crater.
During 1 June-1 September 2012, CVGHM's visual observations were often prevented by fog cover. When views were clear during June, observers saw occasional diffuse white plumes above the crater. In June, July, and August, the respective seismic events totaled 1,075, 807, and 2,335. Detailed seismicity during 1 June-2 September 2012 is cataloged in table 8.
Table 8. Type and occurrence of earthquakes and tremor at Krakatau during 1 June-2 September 2012; '-' indicates data not reported. Courtesy of CVGHM.
Date |
Deep volcanic |
Shallow volcanic |
Local tectonic |
Distant tectonic |
Harmonic tremor |
"Hot air blast" tremor |
Seismic tremor |
Jun 2012 |
63 |
837 |
1 |
5 |
17 |
152 |
-- |
Jul 2012 |
80 |
679 |
11 |
6 |
-- |
31 |
-- |
Aug 2012 |
165 |
1436 |
9 |
6 |
139 |
547 |
34 |
1-2 Sep 2012 |
7 |
79 |
-- |
-- |
-- |
15 |
20 |
Seismicity increased on 2 September 2012. CVGHM recorded continuous tremor, and a Strombolian eruption ejected lava 200-300 m above the crater. At times, residents heard booming sounds that rattled windows. On 3 September, the Darwin Volcanic Ash Advisory Centre (VAAC) reported that ash plumes rose to altitudes of 2.4-4.3 km and drifted 35-95 km N. The Jakarta Globe (citing the state news agency Antara News) reported that a dense ash plume had drifted N, reaching a number of areas in Lampung (the most southerly province of Sumatra), and blanketing Lampung's capital, Bandar Lampung (~75 km NNW of Krakatau; figure 31), with a thin layer of ash.
Ashfall on 2 September prompted officials to recommend that residents and tourists wear masks outside and not venture within 3 km of the volcano. The Jakarta Post indicated that government officials planned to distribute 680,000 masks to residents in a number of affected districts in anticipation of further Krakatau explosions. According to Antara News, less intense tremor continued on 4 September. A satellite image acquired by NASA's Earth Observatory on 4 September showed fresh lava flows descending Anak Krakatau's SE flank, extending the shoreline by about 100 m (figure 32).
September 2012 eruption and visit by Volcano Discovery. A Volcano Discovery group toured Krakatau during the first several days of September 2012 and observed what they noted was the largest explosion there in ten years. They noted that seismic activity (recorded by CVGHM) peaked on 2 September, with a day of continuous explosions and lava descending the volcano's E and W flanks. Photos showed lava entering the sea (figure 33).
The Volcano Discovery group noted that the eruption had altered part of the S and W crater rim, splitting the rim into two parts. They saw an abundance of lava bombs on the volcano's flanks in the forest, indicating the force of the explosions. The group indicated that by 5 September, activity had greatly diminished and incandescence from the crater was absent. On 6 September, Krakatau was calm with limited seismic activity reported by the observatory.
On 8 September, the Jakarta Post also reported that seismic activity had greatly diminished during the previous two days. However, this news account noted that residents in Bandar Lampung still reported ashfall. The article also stated that ash from the eruption had damaged volcano-monitoring equipment.
2012 visits by Øystein Lund Andersen. As indicated in our previous report on Krakatau (BGVN 37:11), the photographer and guide Øystein Lund Andersen has visited Krakatau multiple times and his website contains good descriptions and photos of the volcano during these visits. The following describes his observations during 2012.
On 8 January 2012, during a 3-hour visit, Andersen observed no Strombolian activity, in contrast with his observation on 13 November 2011. On his next visit, during 12-14 February, he reported medium to heavy venting from the crater and fumarolic activity that was more intense than the activity during January. He noted continuous steam-and-gas emissions that rose 100-500 m and incandescence at night, but no eruptions.
During a visit on 6-7 April 2012, Andersen noticed that the S part of the crater was illuminated at night. He further reported that on 7 April, Krakatau started to produce small eruptions from the S part of the crater, the same side as the growing lava dome.
During 6-8 May, Andersen noted that activity at Krakatau had decreased somewhat in the previous several weeks. Steam plumes reached a height of 100-200 m and seemed less intense than during his visit in April. He noted incandescence at night, but it was less intense that the previous month. Andersen reported on 7 April: "footage taken by Pierre Fortine showed no sign of any lava dome, but the red glow that is often clearly visible at night from Verlaten, Lang, or Rakata are in fact multiple glowing vents (some of them were gas vents that were burning) and red hot material surrounding them. The lava dome that people have claimed to observe [through] February to April may have been destroyed during the last small eruptions that I reported of in April. Shallow earthquake data recorded by the Krakatau Volcano Observatory in Pasauran (PVMG) shows that the level of activity remains on the relative same level as last month."
During 2-3 June, he reported that activity had decreased since April and May. He stated that incandescence was almost non-observable, and steam plumes only rose 50-100 m on this visit (compared to 200 m in May), and were at times non-existent.
On 3 September 2012, Andersen wrote that he had heard continuous booming noises half way from Java, and that large booming sounds could be heard in the villages of Carita and Anyar (or Anyer), neighboring villages on the W coast of Java, about 50 km ESE of the volcano. As he approached the volcano, he noted a high plume from the main vent and the ejection of lava bombs to heights of up to 300 m. An area on the SE shore also emitted a large steam plume. According to Andersen: "The local crew/guides who joined our group looked very surprised and worried, as we all noticed these major changes. I first thought this was the result of new geothermal activity, but first realized later that this was in fact a new lava flow." According to Andersen, the lava flow had extended the seashore on the E side by up to 100 m, and the E and W part of the crater walls had experienced a partial collapse (figure 34).
On a visit during 6-7 October 2012, Andersen observed no activity other than a weak and irregular steam plume and, at night, "some small spots of glowing lava, near and on the lava flow on the western flank." On this visit, he studied the new lava flow. He reported that the lava had flowed down both the W and E sides of the volcano, leaving deep scars on both flanks. According to Andersen, news accounts had reported the lava flow on the E flank, but few had noted the one on the W flank, which was significant, although not as great as the one on the E flank.
Geologic Background. The renowned Krakatau (frequently mis-named as Krakatoa) volcano lies in the Sunda Strait between Java and Sumatra. Collapse of an older edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of that volcano are preserved in Verlaten and Lang Islands; subsequently the Rakata, Danan, and Perbuwatan cones were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption caused more than 36,000 fatalities, most as a result of tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former Danan and Perbuwatan cones. Anak Krakatau has been the site of frequent eruptions since 1927.
Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); 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/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov and http://eo1.gsfc.nasa.gov/); The Jakarta Post (URL: http://www2.thejakartapost.com); Antara News (URL: http://www.antaranews.com/en/); Volcano Discovery (URL: http://www.volcanodiscovery.com); Indonesia Destination & Travel Information Guide (URL: http://baliwww.com); Øystein Lund Andersen (URL: http://www.oysteinlundandersen.com/).
Nyiragongo (DR Congo) — December 2012 Cite this Report
Nyiragongo
DR Congo
1.52°S, 29.25°E; summit elev. 3470 m
All times are local (unless otherwise noted)
Bubbling lava lake visited by three groups during January 2011
This report discusses observations of Nyiragongo made in January 2011. As noted in BGVN 35:09, a 14-24 June 2010 expedition into the crater showed that Nyiragongo's lava lake was continuously active and had risen since the last extensive eruption that inundated central Goma in January 2002.
Similar activity was confirmed during visits by three groups to the crater during 9-12 January, 16-26 January, and 20-23 January 2011, with observations of a continuously active lava lake, lava fountains reaching several meters high, and gas emissions (figures 48 and 49; dozens more images appear on the websites noted in the Information Contacts subsection). One group described the lava lake as "boiling so lively and quick-tempered, like cream of wheat in a pot at the highest heat setting."
On 20 January 2011, the topography of the interior of the crater remained the same as in mid-June 2010 (figure 50). The surface of the lava lake was then between 3,010 m and 3,020 m elevation. Convection of the lava lake surface and disruptions in the cooled surface that produced fountains and gas emissions were observed at differing intensities. The symbols in figure 50 correspond to those of figure 45 in our previous report, thus preserving terminology (BGVN 35:09). The observers recognized three upper terraces from the previous figure (α, β, and γ) but not all are visible in figure 50.
Geologic Background. The Nyiragongo stratovolcano 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 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 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: Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); Marc Szeglat, Vulkane.net (URL: http://vulkane.net/); Christoph Weber, VHDL, Muehlweg 11, 74199 Untergruppenbach, Germany (URL: http://www.volcanic-hazards.de/).
Pagan (United States) — December 2012 Cite this Report
Pagan
United States
18.13°N, 145.8°E; summit elev. 570 m
All times are local (unless otherwise noted)
Ash, gas, and thermal emissions during 2011-2012
Our last report described gas-and-steam plumes in October and November 2010 that rose from Pagan's active cone located on the N side of the island (BGVN 35:12). After that, the Volcanic Alert Level and Aviation Color Code were reduced from Advisory (Yellow) to Unassigned on 22 February 2011. The Alert was raised again to Advisory ("Volcano is exhibiting signs of elevated unrest above known background level") on 23 April 2011 where it remained level through the end of 2012.
In this report, we tabulate and briefly comment on advisories from the Washington Volcanic Ash Advisory Center (VAAC) that reported Pagan's gas emissions, occasional ash plumes, and thermal anomalies. Reports of activity were also contributed by observers from other islands and a passing research vessel. We also share the results from the ash transport and dispersion model, PUFF, for the 30 January 2012 ash emission. MODVOLC thermal alerts were triggered several times during this reporting period, mainly in late 2012. Clear images from satellites and the International Space Station are also included in this report.
The primary methods of monitoring Pagan are satellite remote sensing and visual observations from the Emergency Management office (based in Saipan), local residents of the islands, and mariners. Pagan lacks ground-based geophysical instrumentation dedicated to volcano monitoring. During this reporting period, the closest operating seismometers were located over 155 km away on the islands of Sarigan, Anatahan, Rota, and Saipan (figure 11).
Activity during 2011. With the exception of a diffuse steam-and-gas plume observed on 24 January 2011, no unusual activity at Pagan volcano had been detected in satellite imagery during January-March.
On 23 April, a Northern Mariana Islands status report noted that a NOAA research vessel in the vicinity of Pagan reported incandescence at the summit of the volcano at night. Satellite image observations were obscured by clouds during that time.
Between 27 June and 1 September, the Washington VAAC reported that emissions were visible from Pagan (table 3). Gas and possible ash were noted based on satellite imagery from MTSAT (Multifunctional Transport Satellites), meteorological centers, and Global Forecast System (GFS) Winds. GFS is a model developed by NOAA's National Centers for Environmental Prediction. Ash emissions appeared in satellite imagery on 1 September during an event that produced a plume that rose 2.4 km above sea level (a.s.l.). That day, the Saipan Emergency Management Center also reported that gases and ash were visible.
Northern Mariana Islands status reports noted that low-level gas-and-steam plumes with possible fine ash were detected in satellite imagery (as well as noted by observers on the island) on 7 July and during 26 August-2 September 2011. From 28 October to 2 December, status reports noted satellite observations of a persistent gas-and-steam plume drifting from the island.
Activity during 2012. During 2012, the Washington VAAC released periodic notices describing emissions from Pagan; these reports were primarily during January, April, July, November, and December (table 3). The tallest plumes rose 3 km a.s.l. with various drift directions (S, E, SSW, N, and NW). The Marianas Emergency Management Center reported local observations of ashfall on the island on 9 July 2012.
PUFF volcanic ash transport and dispersion simulations. The results from a volcanic ash tracking model were available for the 30 January 2012 ash event (figure 12). Simulations from the PUFF model provided the extent of ash for a plume with starting conditions determined by the Washington VAAC; the time of the eruption, reported plume heights, drift direction and speed were required for the model. "The intent of PUFF is to show the position of eruption clouds when satellite image observations are not available, and to use satellite observations, when available, to validate or improve simulations (Searcy and others, 1998)." The model is frequently used for ash events within the N Pacific air traffic region and assists the Alaska Volcano Observatory (AVO, a joint program of the United States Geological Survey, USGS, the Geophysical Institute of the University of Alaska Fairbanks, UAFGI, and the State of Alaska Division of Geological and Geophysical Surveys, ADGGS) and other agencies.
The simulation for the 30 January 2012 ash event began at 1050 UTC and showed that, by 1450 UTC, ash had drifted E in a narrow band with a maximum altitude of 3.048 km. This result correlates well with satellite observations reported by the Washington VAAC at 1041 (table 3); after that time, the Washington VAAC reported that ash was possible but not detectable during the time period that the Puff model forecasted ash extending further E.
The PUFF model was recently expanded to include an interface with Google Earth. Ash dispersion results can be viewed in Google Earth including the plume start time, altitude and simulation length, two-dimensional maps of ash with time stamps (color coded by altitude), and the three-dimensional ash cloud. This interface also allows selection by ash particle so the user can view its location, its volcanic origin, the elapsed time since the eruption began, and altitude (in km and feet a.s.l.) (Webley and others, 2008).
Thermal anomaly detection in 2012. Hotspots from the summit region were detected by the MODIS instrument (onboard the Terra and Aqua satellites) during 2012. The MODVOLC hotspot alerting system recorded six significant thermal anomalies between 6 August and 11 December (figure 13). Thermal anomalies appeared at least once per month between October and December 2012 suggesting clear viewing conditions during times of elevated activity (table 3).
A view of Pagan from the International Space Station. On 6 March 2012, an astronaut on the International Space Station photographed Pagan Island during spectacular viewing conditions (figure 14). With a digital camera, the entire extent of the island was captured as well as a persistent white plume drifting from the summit area. Some clouds had gathered around the southern region of the island (a narrow peninsula of older volcanic centers), but the main features of the island were easy to distinguish. Historical lava flows appeared dark brown and black within the large (5.5 km wide), circular caldera (a feature that dominates the N end of the island) (Trusdell and others, 2006). The youngest lava flows date from 1981, however, lavas from an eruption during 1872-1873 reached the N shoreline; note the black region in contrast with the vegetated shoreline at the right-hand side of the photo.
MODIS satellite images: May and October 2012. On 7 May, the MODIS instrument on the Terra satellite acquired a clear image of Pagan Island with a conspicuous plume of gas and steam drifting W (figure 15). The plume's blue tint suggested the presence of sulfur dioxide. According to NASA's Earth Observatory, the Ozone Monitoring Instrument (OMI) on the Aura satellite detected elevated levels of SO2 just W of the volcano several hours after this image was acquired. The USGS reported that minor steam-and-gas plumes were observed in partly cloudy satellite images during 4-11 May.
According to NASA's Earth Observatory, a satellite image acquired on 16 October showed a steam-and-gas plume drifting WNW (figure 16). Scattered clouds filled much of the view but the island was mostly cloud-free with a plume trailing into the denser bands of clouds.
References. Searcy, C., Dean, K., and Stringer, W., 1998. PUFF: A high-resolution volcanic ash tracking model, Journal of Volcanology and Geothermal Research, 80, pp. 1-16.
Trusdell, F.A., Moore, R.B., and Sako, M.K., 2006. Preliminary Geologic Map of Mount Pagan Volcano, Pagan Island, Commonwealth of the Northern Mariana Islands, U.S. Geological Survey Open-File Report 2006-1386 (URL: http://pubs.usgs.gov/of/2006/1386/).
Webley, P.W., Dean, K., Bailey, J.E., Dehn, J., and Peterson, R., 2008. Automated forecasting of volcanic ash dispersion utilizing Virtual Globes, Natural Hazards, 51, 2, pp. 345-361.
Geologic Background. Pagan Island, the largest and one of the most active of the Mariana Islands volcanoes, consists of two stratovolcanoes connected by a narrow isthmus. Both North and South Pagan stratovolcanoes were constructed within calderas, 7 and 4 km in diameter, respectively. North Pagan at the NE end of the island rises above the flat floor of the northern caldera, which may have formed less than 1,000 years ago. South Pagan is a stratovolcano with an elongated summit containing four distinct craters. Almost all of the recorded eruptions, which date back to the 17th century, have originated from North Pagan. The largest eruption during historical time took place in 1981 and prompted the evacuation of the sparsely populated island.
Information Contacts: Emergency Management Office of the Commonwealth of the Northern Mariana Islands (EMO-CNMI) and USGS Volcano Hazards Program, PO Box 100007, Saipan, MP 96950, USA (URL: http://www.cnmihsem.gov.mp/, http://volcanoes.usgs.gov/nmi/activity/); Frank Trusdell, Hawaiian Volcano Observatory, PO Box 51, Hawaii National Park, HI, 96718-0051; 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/); Hawai`i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System (MODVOLC), 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/); Peter Webley, University of Alaska Fairbanks Geophysical Institute, 909 Koyukuk Drive, Fairbanks, AK, 99775, USA (URL: http://www.gi.alaska.edu/); NASA Earth Observatory, NASA Goddard Space Flight Center (URL: http://earthobservatory.nasa.gov/).
Tolbachik (Russia) — December 2012 Cite this Report
Tolbachik
Russia
55.832°N, 160.326°E; summit elev. 3611 m
All times are local (unless otherwise noted)
Seismicity precedes onset of dual fissure eruption in November 2012
Nearly 36 years after its last eruption, the largest basaltic eruption in Kamchatka during historic times (1975/76 eruptions; CSLP 51-75; SEAN 01:07, 01:08), Tolbachik (figure 1) began erupting again on 27 November 2012 following almost three weeks of episodic volcanic tremor. The eruption emerged as two fissures along the W side of Tolbachinsky Dol (a lava plateau along the SW flank of Tolbachik), in the same area as the northern vents of the 1975/76 eruptions. The eruption produced both effusive lava flows and explosions that generated low-level ash-bearing plumes.
This report mainly summarizes Kamchatkan Volcanic Eruption Response Team (KVERT) daily and weekly reports and information releases concerning the ongoing (as of early February 2013) Tolbachik fissure eruption.
Seismicity preceding 27 November 2012 eruption. Episodic tremor was recorded at Tolbachik during 7-10, 18, and 26 November 2012; KVERT noted a distinct difference between these episodes of tremor and discrete events that had occurred over "many years" prior. Shallow volcanic earthquakes began on 26 November, increasing in number to ~267 through 27 November. The Aviation Color Code was raised from Green to Yellow (on a scale increasing from Green-Yellow-Orange-Red) on 27 November. In a daily report discussing activity on 27 November, KVERT reported that shallow events, possibly indicating ash explosions, had occurred during 1715-2000. The Kamchatka Branch of the Geophysical Service of the Russian Academy of Sciences (KB GS RAS) reported a strong seismic event at 1752 that day. Informed by KB GS RAS, the Tokyo Volcanic Ash Advisory Center (VAAC) posted a volcanic ash advisory at 1837 (table 1). The ash explosions prompted KVERT to raise the Aviation Color Code to Orange. Continuos tremor occurred for the rest of the day, indicating possible lava flows.
Table 1. Summary of Tokyo VAAC volcanic ash (VA) advisories for Tolbachik during November 2012-January 2013. Plume heights are reported in km above sea level (a.s.l.); '-' indicates data not reported. Note that the fissures are at approximately 1,600-1,700 m elevation, and not at the summit (3,682 m elevation), thus complicating plume height estimates. Yelizovo Airport is indicated as a data source by its airport code, UHPP. All times are local (UTC - 12 hours). Courtesy of Tokyo VAAC.
Date |
Time |
Plume Altitude (km) |
Drift Direction |
Remarks (data source) |
27 Nov 2012 |
1837 |
6.1 |
-- |
Eruption reported at 1715 (KB GS RAS) |
27 Nov 2012 |
2313 |
10.05 |
NNW |
Eruption (KB GS RAS) |
29 Nov 2012 |
1003 |
3.95 |
N |
VA reported (UHPP) |
29 Nov 2012 |
1500 |
3.65 |
SE |
VA reported (KVERT) |
29 Nov 2012 |
1746 |
3.95 |
SE |
Continuing emissions (satellite imagery) |
29 Nov 2012 |
2355 |
3.95 |
SE |
Continuing emissions (satellite imagery) |
30 Nov 2012 |
0600 |
3.95 |
N |
Continuing emissions (satellite imagery) |
30 Nov 2012 |
1152 |
-- |
-- |
VA dissipated on imagery (satellite imagery) |
30 Nov 2012 |
1634 |
NVA reported (UHPP) |
03 Dec 2012 |
2138 |
4.25 |
NW |
VA reported (UHPP) |
05 Dec 2012 |
1221 |
4.25 |
SE |
VA reported (KVERT) |
07 Dec 2012 |
1431 |
4.25 |
SW |
VA reported (KVERT) |
13 Dec 2012 |
1139 |
3.05 |
NE |
VA reported (KVERT) |
13 Dec 2012 |
1232 |
4.55 |
E |
VA reported (UHPP) |
14 Dec 2012 |
1209 |
3.05 |
NE |
VA reported (KVERT) |
27 Dec 2012 |
1126 |
5.2 |
SE |
VA reported (UHPP) |
07 Jan 2013 |
1145 |
3.65 |
NE |
VA reported (KVERT) |
07 Jan 2013 |
1202 |
4.25 |
NE |
VA reported (KVERT) |
Observations reveal two fissure vents. By the early morning of 28 November 2012, observers in Kozyrevsk (~40 km NW) and Lazo (~50 km SW) had reported periodic incandescence from Tolbachik during the night. Later that morning, observers in the same locations reported ash explosions and lava flows in the area of the northern vents of the 1975/76 eruptions, along the W side of Tolbachinsky Dol.
The first available photograph of the eruption showed that lava was issuing through two fissures (figure 2). Ashfall 4-cm-deep was reported in Krasny Yar (~60 km NNW) by midday on 28 November (figure 3). According to a KVERT information release, the Aviation Color Code was raised to Red for a brief period on 29 November, but this was not reflected in the daily reports; the Aviation Color Code remained Orange for the remainder of the reporting interval.
KVERT reported on 28 November that the N and S fissures were located 4-5 km and 6-7 km S of Plosky Tolbachik, respectively. Plosky Tolbachik is a shield volcano with nested summit calderas that makes up the E half of Tolbachik; the W portion of Tolbachik is the sharply-peaked Ostry Tolbachik stratovolcano (figures 1 and 4). At that time, Strombolian activity (figure 5) was observed at 4-5 vents in the N fissure and 2-3 vents in the S fissure; the very fluid lavas (figure 6) were flowing, often in 'lava rivers', to the W side of Tolbachinsky Dol (figure 7), and KVERT noted a large thermal anomaly over the N part of Tolbachinsky Dol (figure 8). Observers reported booming noises and vibrating windowpanes.
On 29 November, seismicity declined, and KVERT characterized the eruption as effusive; renewed seismicity occurred the next day, and a gas-and-steam plume with small amounts of ash rising to ~3 km was reported. Lava flows from the N fissure destroyed two scientific base camps located ~10 km from Tolbachik.
Cinder cones grow on S fissure; new fumarole. A KVERT weekly report issued on 6 December 2012 noted that cinder cones were growing on the S fissure, and that lava effused from the S fissure had flowed up to 20 km away by 7 December. A fumarole was observed at the bottom of the Plosky Tolbachik caldera on 8 December (figure 9); this was the first fumarole observed in the caldera in ~30 years. On 9 December KVERT daily reports began stating that the effusion of lava was continuing from the S fissure, no longer mentioning the N fissure.
By the end of December, KVERT reported that five cinder cones were growing on the S fissure (e.g. figure 10); by 10 January 2013, however, KVERT reported only four cinder cones on the S fissure.
As of early February 2013, the eruption continued to produce very fluid lava flows, four growing cinder cones, gas-and-steam plumes with variable ash contents that often reached ~4 km a.s.l. and drifted in various directions, and daily thermal alerts above Tolbachinsky Dol. Two examples of eruptive products from the eruption are shown in figure 11.
Geologic Background. The massive Tolbachik volcano is located at the southern end of the Kliuchevskaya volcano group. The massif is composed of two overlapping, but morphologically distinct, volcanoes. The flat-topped Plosky Tolbachik shield volcano with its nested Holocene calderas up to 3 km in diameter is located east of the older and higher sharp-topped Ostry Tolbachik stratovolcano. The summit caldera at Plosky Tolbachik was formed in association with major lava effusion about 6,500 years ago and simultaneously with a major southward-directed sector collapse of Ostry Tolbachik. Long rift zones extending NE and SSW of the volcano have erupted voluminous basaltic lava flows during the Holocene, with activity during the past two thousand years being confined to the narrow axial zone of the rifts. The 1975-76 eruption originating from the SSW-flank fissure system and the summit was the largest historical basaltic eruption in Kamchatka.
Information Contacts: Kamchatkan Volcanic Eruption Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Tokyo Volcanic Ash Advisory Center (VAAC), Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Kamchatka Branch of the Geophysical Service of the Russian Academy of Sciences (KB GS RAS), Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Yelizovo Airport (UHPP), Petropavlovsk-Kamchatsky, Kamchatka Krai, Russia; NASA Earth Observatory, NASA Goddard Space Flight Center (URL: http://earthobservatory.nasa.gov/); NASA Jet Propulsion Laboratory, California Institute of Technology (URL: http://www.jpl.nasa.gov/); Wikipedia (URL: http://www.wikipedia.org/).