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).

Figure 93. Distinct sulfur dioxide plumes were captured, rising from Manam based on data from the TROPOMI instrument on the Sentinel-5P satellite on 16 November 2022 (top left), 6 December 2022 (top right), 14 January 2023 (bottom left), and 23 March 2023 (bottom right). Plumes generally drifted in different directions. Courtesy of the NASA Global Sulfur Dioxide Monitoring Page.

Figure 94. Occasional low-to-moderate power thermal anomalies were detected at Manam during November 2022 through May 2023, as shown in this MIROVA graph (Log Radiative Power). Only three anomalies were detected during late November, one in early December, two during January 2023, one in late March, four during April, and one during late May. Courtesy of MIROVA.

Figure 95. Infrared (bands B12, B11, B4) satellite images show a consistent thermal anomaly (bright yellow-orange) in both the Main (the northern crater) and South summit craters on 10 November 2022 (top left), 15 December 2022 (top right), 3 February 2023 (bottom left), and 24 April 2023 (bottom right). Gas-and-steam emissions occasionally accompanied the thermal activity. Courtesy of Copernicus Browser.

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 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.

Figure 135. Webcam images of a strong, gray ash plume (left) and Strombolian activity (right) captured at Krakatau at 0802 on 23 January 2023 (left) and at 2116 on 24 January 2023 (right). Courtesy of PVMBG and MAGMA Indonesia.

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.

Figure 136. Webcam image of a strong ash plume rising above Krakatau at 1522 on 28 March 2023. Courtesy of PVMBG and MAGMA Indonesia.

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).

Figure 137. Webcam image of an ash plume rising 2 km above the summit of Krakatau at 0715 on 13 May 2023. Courtesy of PVMBG and MAGMA Indonesia.

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).

Figure 138. Intermittent low-to-moderate power thermal anomalies were detected at Krakatau during November 2022 through April 2023, based on this MIROVA graph (Log Radiative Power). Courtesy of MIROVA.

Figure 139. A thermal anomaly (bright yellow-orange) was visible at Krakatau in infrared (bands B12, B11, B4) satellite images on clear weather days during November 2022 through May 2023. Occasional gas-and-steam and ash plumes accompanied the thermal activity, which drifted in different directions. Images were captured on 25 November 2022 (top left), 15 December 2022 (top right), 27 January 2023 (bottom left), and 12 May 2023 (bottom right). Courtesy of Copernicus Browser.

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, 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).

Figure 253. Explosive activity persisted at Stromboli during January through April 2023, with low to medium numbers of daily explosions at the summit crater. The average number of daily explosions (y-axis) during January through April (x-axis) are broken out by area and as a total, with red for the N area, blue for the CS area, and black for the combined total. The data are smoothed as daily (thin lines) and weekly (thick lines) averages. The black squares along the top represent days with no observations due to poor visibility (Visib. Scarsa). The right axis indicates the qualitative activity levels from low (basso) to highest (altissimo) with the green highlighted band indicating the most common level. Courtesy of INGV (Report 17/2023, Stromboli, Bollettino Settimanale, 18/04/2023 - 24/04/2023).

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.

Figure 254. Intermittent thermal activity at Stromboli was detected during January through April 2023 and varied in strength, as shown in this MIROVA graph (Log Radiative Power). A pulse of activity was captured during late March. Courtesy of MIROVA.

Figure 255. Infrared (bands B12, B11, B4) satellite images showing persistent thermal anomalies at both summit crater on 1 February 2023 (top left), 23 March 2023 (top right), 8 March 2023 (bottom left), and 27 April 2023. A particularly strong thermal anomaly was visible on 8 March. Courtesy of Copernicus Browser.

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.

Figure 256. Webcam images of the lava flow development at Stromboli during 17 January 2023 taken by the SCT infrared camera. The lava flow appears light yellow-green in the infrared images. Courtesy of INGV (Report 04/2023, Stromboli, Bollettino Settimanale, 16/01/2023 - 22/01/2023).

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.

Figure 257. Webcam images of the explosive sequence at Stromboli on 16 February 2023 taken by the SCT and SCV infrared and visible cameras. The lava appears light yellow-green in the infrared images. Courtesy of INGV (Report 08/2023, Stromboli, Bollettino Settimanale, 13/02/2023 - 19/02/2023).

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.

Figure 258. Webcam images of the lava overflow in the N1 crater area of Stromboli on 23 March 2023 taken by the SCT infrared camera. The lava appears light yellow-green in the infrared images. The start of the explosive sequence was also captured on 25 March 2023 accompanied by an eruption plume (e) captured by the SCT and SPT infrared webcams. Courtesy of INGV (Report 13/2023, Stromboli, Bollettino Settimanale, 20/03/2023 - 26/03/2023).

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.

Figure 259. Webcam images of the explosive sequence at Stromboli during 1203-1205 (local time) on 7 April 2023 taken by the SCT infrared camera. Strong eruption plumes are visible, accompanied by deposits on the nearby flanks. Courtesy of INGV (Report 15/2023, Stromboli, Bollettino Settimanale, 03/04/2023 - 09/04/2023).

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 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.

Figure 119. Aerial photo of gas-and-steam plumes rising 200 m above Nishinoshima on 25 November 2022. Reddish brown to brown and yellowish-green discolored water was visible around the perimeter of the island. Courtesy of JCG via JMA (monthly reports of activity at Nishinoshima, November 2022).

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.

Figure 120. Aerial photo of a black-gray ash plume rising approximately 900 m above the crater rim of Nishinoshima on 25 January 2023. White fumaroles were visible on the E slope of the pyroclastic cone. Dense brown to brown discolored water was observed surrounding the island. Photo has been color corrected. Courtesy of JCG via JMA (monthly reports of activity at Nishinoshima, January, 2023).

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.

Figure 121. Aerial photo of white gas-and-steam plumes rising 900 m above Nishinoshima on 14 April 2023. Brown and yellow-green discolored water is visible around the perimeter of the island. Photo has been color corrected. Courtesy of JCG via JMA (monthly reports of activity at Nishinoshima, April, 2023).

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).

Figure 123. Intermittent low-to-moderate thermal anomalies were detected at Nishinoshima during November 2022 through April 2023, according to this MIROVA graph (Log Radiative Power). A cluster of anomalies occurred throughout November, while fewer anomalies were detected during the following months. Courtesy of MIROVA.

Figure 124. Infrared (bands B12, B11, B4) satellite images show a small thermal anomaly at the summit crater of Nishinoshima on 9 January 2023 (left) and 8 February 2023 (right). Gas-and-steam plumes accompanied this activity and extended S and SE, respectively. Courtesy of Copernicus Browser.

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 (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).

Figure 60. Photos of the eruption at Karangetang on 8 February 2023 that consisted of incandescent material descending the flanks (top left), ash plumes (top right and bottom left), and summit crater incandescence (bottom right). Courtesy of IDN Times.

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.

Figure 61. Webcam image of summit incandescence and lava flows descending the S, SW, and W flanks of Karangetang on 13 February 2023. Courtesy of MAGMA Indonesia.

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.

Figure 62. Webcam image of intense summit incandescence and incandescent avalanches descending the flanks of Karangetang on 18 March 2023. Photo has been color corrected. Courtesy of MAGMA Indonesia.

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.

Figure 63. Webcam image showing incandescent material descending the flanks of Karangetang on 19 May 2023. Courtesy of MAGMA Indonesia.

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.

Figure 64. Strong thermal activity was detected during mid-February 2023 through March and mid-May through June at Karangetang during January through June 2023, as recorded by this MIROVA graph (Log Radiative Power). During April through mid-May the power of the anomalies decreased, but the frequency at which they occurred was still relatively high. A brief gap in activity was shown during mid-June. Courtesy of MIROVA.

Figure 65. Incandescent avalanches of material and summit crater incandescence was visible in infrared satellite images (bands 12, 11, 8A) at both the N and S summit crater of Karangetang on 17 February 2023 (top left), 13 April 2023 (top right), 28 May 2023 (bottom left), and 7 June 2023 (bottom right), as shown in these infrared (bands 12, 11, 8A) satellite images. The incandescent avalanches mainly affected the SW and S flanks. Sometimes gas-and-steam plumes accompanied the thermal activity. Courtesy of Copernicus Browser.

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 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.

Figure 6. A clear, true color satellite image showed a yellow-green discolored water plume extending NW from the Ahyi seamount (white arrow) on 21 November 2022. Courtesy of Copernicus Browser.

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).

Figure 7. Clear, true color satellite images showed yellow-green discolored water plumes extending NE and W from Ahyi (white arrows) on 1 (left) and 26 (right) December 2022, respectively. Courtesy of Copernicus Browser.

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).

Figure 8. True color satellite images showed intermittent yellow-green discolored water plumes of various sizes extending N on 5 January 2023 (top left), SE on 30 January 2023 (top right), W on 4 February 2023 (bottom left), and SW on 1 March 2023 (bottom right) from Ahyi (white arrows). Courtesy of Copernicus Browser.

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 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).

Figure 67. True color satellite images showing a white gas-and-steam plume rising from Kadovar on 28 February 2023 (left) and 30 March 2023 (right) and drifting SE and S, respectively. Courtesy of Copernicus Browser.

Figure 68. Infrared (bands B12, B11, B4) image showing weak thermal activity on the E side of the island, accompanied by a gas-and-steam plume that drifted SE from Kadovar on 14 May 2023. Courtesy of Copernicus Browser.

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 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.

Figure 32. Webcam image of a gas-and-ash plume rising 700 m above San Miguel at 1652 on 27 May 2023. Courtesy of MARN.

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 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.

Figure 25. Webcam image of a gas-and-steam plume rising above Semisopochnoi from Mount Young on 21 December 2022. Courtesy of AVO.

Figure 26. Webcam image showing fresh ash deposits (black color) at the summit and on the flanks of Mount Young at Semisopochnoi, extending up to 1 km from the N crater. Image was taken on 27 December 2022. Image has been color corrected. Courtesy of AVO.

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, 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).

Figure 45. Photo of an ash plume rising to 2.7 km altitude above Ebeko on 26 November 2022. Photo has been color corrected. Photo by L. Kotenko, IVS FEB RAS.

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.

Figure 46. Photo of an explosive event at Ebeko at 1109 on 2 December 2022. Photo has been color corrected. Photo by S. Lakomov, IVS FEB RAS.

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.

Figure 47. Photo of a strong ash plume rising to 4 km altitude from an explosive event on 10 January 2023 (local time). Photo by L. Kotenko, IVS FEB RAS.

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.

Figure 48. Photo of an ash cloud rising to 3.5 km altitude at Ebeko on 6 April 2023. The cloud extended up to 12 km SW and E. Photo has been color corrected. Photo by L. Kotenko, IVS FEB RAS.

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).

Figure 49. Infrared (bands B12, B11, B4) and true color satellite images of Ebeko showing occasional small thermal anomalies at the summit crater on 4 October 2022 (top left), 30 April 2023 (bottom left), and 27 May 2023 (bottom right). On 1 November (top right) ash deposits (light-to-dark gray) were visible on the SE flank. An ash plume drifted NE on 30 April, and ash deposits were also visible to the E on both 30 April and 27 May. Courtesy of Copernicus Browser.

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 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).

Figure 31. Visual (true color) satellite images showing continued green-yellow discolored plumes at Home Reef (black circle) that extended W on 28 November 2022 (top left), W and S on 23 December 2022 (top right), NW on 13 March 2023 (bottom left), and E and NE on 22 April 2023 (bottom right). Courtesy of Copernicus Browser.

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, 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.

Figure 99. Satellite image of the strong sulfur dioxide plume above Ambae taken on 15 November 2022. The Dobson Units (DU) exceeded 12. Courtesy of VMGD.

Figure 100. Webcam image of a gas-and-ash plume rising above Ambae at 1745 on 20 February 2023. The plume drifted SSW. Courtesy of VMGD.

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).

Figure 101. Webcam image showing a gas-and-ash plume rising 5.4 km above the summit of Ambae at 0745 on 6 April 2023. Courtesy of VMGD.

Figure 102. Webcam image showing a gas-and-ash plume rising 695 m above the summit of Ambae at 0730 on 19 April 2023. Courtesy of VMGD.

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).

Figure 103. Satellite images showing both visual (true color) and infrared (bands B12, B11, B4) views on 24 March 2023 (top left), 3 April 2023 (top left), 8 April 2023 (bottom left), and 23 April 2023 (bottom right). In the image on 24 March, water filled Lake Voui around the small northern lake. A gas-and-steam plume drifted SE. Thermal activity (bright yellow-orange) was first detected in infrared data on 3 April 2023, accompanied by a gas-and-ash plume that drifted W. The lava flow slowly filled the northern part of the then-dry lake and remained hot on 8 April. By 23 April, the water in Lake Voui had returned. Courtesy of Copernicus Browser.

Figure 104. Images showing sulfur dioxide plumes rising from Ambae on 26 December 2022 (top left), 25 February 2023 (top right), 23 March 2023 (bottom left), and 5 April 2023 (bottom right), as detected by the TROPOMI instrument on the Sentinel-5P satellite. These plumes exceeded at least 2 Dobson Units (DU) and drifted in different directions. Courtesy of the NASA Global Sulfur Dioxide Monitoring Page.

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/).

Situated on Halmahera Island in northern Indonesia, Dukono released an ash plume 5 December 2006. The Moderate Resolution Imaging Spectroradiometer (MODIS) flying onboard NASA's Terra satellite captured the 5 December plume (figure 3) drifting E away from meteorological clouds. NASA affiliate Jesse Allen has interpreted the plume as ash bearing.

Figure 3. Inferred ash plume of Dukono volcano streaming E and then S on 5 December 2006. NASA image created by Jesse Allen, Earth Observatory, using data provided courtesy of the MODIS Rapid Response team.

As of early 2007, the Darwin Volcanic Ash Advisory Center (VAAC) reported that plumes from Dukono were visible on satellite imagery several times during 2006, and once in January 2007 (see table 3). Satellite images suggested modest successive plumes with ash concentrations varying from diffuse to dense.

Table 3. Summary of plumes reported from Dukono, January 2006-January 2007. Courtesy of the Darwin VAAC.

Thermal anomalies were detected by MODIS (table 4) on 13 December 2006 and then on four days in February 2007. These were the first anomalies detected by the MODVOLC system since October 2004 (BGVN 31:06).

Table 4. Thermal anomalies at Dukono based on MODIS-MODVOLC retrievals and processing from October 2004 through February 2007. Courtesy of Hawai'i Institute of Geophysics and Planetology Thermal Alerts System.

Geologic Background. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, have occurred since 1933. During a major eruption in 1550 CE, a lava flow filled in the strait between Halmahera and the N-flank Gunung Mamuya cone. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

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 Center (VAAC), Bureau of Meteorology, Darwin, Australia (URL: http://www.bom.gov.au/); Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).

This report extends reporting of the Observatoire Volcanologique du Piton de la Fournaise (OVPF) and covers the period from 28 July 2006 to 22 February 2007.

At 0400 on [20 July] a tremor recorded by the Bory seismic station was interpreted as the start of an eruption. Subsequent observation noted a fissure had opened between 2,380 m and 2,250 m elevation on the SW flank. A lava flow went down E of Rivals crater. At 0540 a second 50-m long fissure opened at the 2,150 m elevation on the S flank between Rivals crater and "Ch?teau Fort" that began building a small cone, and producing a 2-km-long lava flow.

Fifteen days after the initial eruption began on 20 July, activity at the cone which was slowly developing at 2,150 m elevation on the S flank almost ceased; however it continued to emit a visible plume and the OVPF reported "a considerable" degasification. The eruption, which had started on 20 July, stopped at 2300 local time on 14 August. The total lava output was estimated to be 2-3 x 10⁶ m³.

On 30 August, a small seismic event occurred at 1000 hours, and a summit eruption started from the SSE edge of Dolomieu Crater at 1135. A fissure opened on the crater floor, and a large portion of the crater floor was covered with lava by the afternoon. A second fissure opened just outside of the crater and produced a lava flow on the E flank. On 9 Oct, a second vent, formed about 100 m SW of the first one, which was still active.

The eruption continued through the middle of October, within the Dolomieu Crater. A new cone about 20-25 m high was formed in the SE part of Dolomieu, and lava flows up to 10 m thick filled up 75% of the crater floor. The E part of the crater was filled up to the rim and lava flowed over and down the flank for hundreds of meters.

Between 25-26 November a hornito grew in the center of Dolomieu crater. After 27 November, a new overflow of the Dolomieu crater started and a 4 to 5 m diameter lava tube drained lava to the Piton de la Fournaise east flank and fed a ~ 2.5 km long lava flow that passed south of crater Jean, but did not reach the "Grandes Pentes."

As of 14 December, OVPF reported that the eruption, which had started on August 30, was continuing (then 3.5 months). A second 25-m-high crater, named Piton Moinama, formed within Dolomieu about 100 m SSW of the first crater, Piton Wouandzani. Abundant lava flows totally covered Dolomieu crater floor again with a 10-30 m deep and reached the eastern border of the crater. Several small lava flows overflowed the rim but never reached more than 100-200 m long.

On 22 December, tremor signals increased, and a third eruptive vent opened on the evening of 27 December between Piton Wouandzani and the Piton Moinama. On 2 January 2007 OVPDLF reported that the eruption of Piton de la Fournaise that began on 30 August 2006 was believed to have ceased on 1 January.

On 18 February, after a "seismic event" that began at 1611, and which lasted only a few minutes, the summit inclinometers indicated strong inflation. A new eruptive phase began at 1638 that afternoon. The exact location of the eruption was not determined; however, the signals recorded at the observatory most probably place it at the summit. The cessation of volcanic tremor the next day at 0155 marked the end of the eruption. A fissure that crossed Dolomieu crater from the west was seen during an aerial observation on 18 February.

On 19 February, seven small (M 0.7) seismic tremors were recorded at the summit. On 22 February, a fissure was observed halfway up the E side of the summit cone.

Geologic Background. Piton de la Fournaise is a massive basaltic shield volcano on the French island of Réunion in the western Indian Ocean. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three scarps formed at about 250,000, 65,000, and less than 5,000 years ago by progressive eastward slumping, leaving caldera-sized embayments open to the E and SE. Numerous pyroclastic cones are present on the floor of the scarps and their outer flanks. Most recorded eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest scarp, which is about 9 km wide and about 13 km from the western wall to the ocean on the E side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures outside the scarps.

Information Contacts: Thomas Staudacher, Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr/ovpf/observatoire-volcanologique-piton-de-fournaise); Serge Gélabert, 85, rue juliette Dodu, 97400 Saint-Denis, Ile de La Réunion, France.

Oliver Hyvernaud twice notified the Bulletin of Notice to Mariners reports of discolored sea water observed on 4 October and 15 November 2006 at about 24°17'N, 141°29'E. Both warnings referred to the same general location, encompassing an area of ocean 93 km SSW of Iwo Jima. In reality, the two positions noted below are ~ 1.3 km apart, perhaps overlapping each other. The warnings were as follows:

1) Discolored water with submarine volcanic activity reported within 1,700 m of 24°17.5' N, 141°29.4 E at 0400 UTC on 4 October 2006 [ref. Notice to Mariners, 14 October 2006 (no. 41), HYDROPAC Warning 1921/06(97) North Pacific, issued 1009 UTC on 4 October 2006].

2) Discolored water with submarine volcanic activity reported within 2,000 m of 24°17.1' N, 141°28.8 E at 0236 UTC on 15 November 2006 [ref. Notice to Mariners, 2 December 2006 (no. 48), HYDROPAC Warning 2225/06(97) North Pacific, issued 1133 UTC on 16 November 2006]

For the locations given for warnings 1 and 2, the respective deviations from coincidence with Fukutoku-Okanoba (at the coordinates given above) are 1.4 and 0.8 km. That seamount frequently produces discolored seawater and is known to erupt on occasions as well, and is thus the probable source for the discolored water.

According to the Japan Meteorological Agency, observations on 15 November 2006 by the Japan Maritime Self Defense Force and aerial observations on 21 November 2006 by the Japan Coast Guard revealed areas of discolored water on the sea surface above the volcano. Those cases seemed to be caused by volcanic activities.

Geologic Background. Fukutoku-Oka-no-ba is a submarine volcano located 5 km NE of the island of Minami-Ioto. Water discoloration is frequently observed, and several ephemeral islands have formed in the 20th century. The first of these formed Shin-Ioto ("New Sulfur Island") in 1904, and the most recent island was formed in 1986. The volcano is part of an elongated edifice with two major topographic highs trending NNW-SSE, and is a trachyandesitic volcano geochemically similar to Ioto.

Information Contacts: Olivier Hyvernaud, Laboratoire de Géophysique, BP 640 Pamatai, Tahiti, French Polynesia; Notice to Mariners, National Geospatial-Intelligence Agency, National Ocean Service, and U.S. Coast Guard, Office of Corporate Relations, Public Affairs Division, MS D-54, 4600 Sangamore Road, Bethesda, MD 20816-5003, USA (URL: http://www.nga.mil/portal/site/maritime/); Japan Meteorological Agency, 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/).

Karthala, in the Comoros Islands (figure 28), was a scene of elevated seismicity from October 2006 to January 2007. The last time an eruption of Karthala caused significant damage was in the 1970s when it destroyed a village S of the capital, Moroni. Presently, Karthala is monitored using seismic and ground deformation surveys. The seismic activity that began 28 May 2006 (BGVN 31:07) appeared to have been a singular event. Renewed seismicity on 29 October 2006 prompted authorities to warn island residents that one of the two volcanoes on the main island of Grand Comore (Karthala or La Grille) could erupt within the next few weeks.

Figure 28. Map illustrating the regional setting of Karthala volcano in the Comoros Islands with comments relevant to the January 2007 crisis. Courtesy of ReliefWeb, a part of the United Nations Office for the Coordination of Humanitarian Affairs - Integrated Regional Information Networks (IRIN).

Following earthquakes (which measured M 4 and larger on the Richter scale) that occurred on 12 January 2007, authorities again alerted the local population about hazards due to Karthala and activated a National Emergency Preparedness Plan. According to news reports, Hamidi Soule Saadi, director of the Karthala Volcano Observatory (KVO), warned that magma and gas were trapped inside the mountain.

According to a 15 January news article obtained from the ReliefWeb News, scientists from the KVO reported that an eruption occurred during the evening of 12 January. The news article noted Moroni residents observing jets of red flames above the summit (on the night of 12-13 January). A low eruptive tremor was detected 13 January and was accompanied by a number of M 4 earthquakes. An ash plume was observed above the volcano. Aerial observers on 15 January saw a lava lake forming within the crater.

The KVO said there was no immediate risk of a lava flow, and that there were three scenarios to consider: (1) seismic activity could decrease, reflecting diminished volcanic activity; (2) cracks or fissures could occur on the flanks, resulting in lava flowing down the side of the mountain; or (3) seismicity could intensify and increase lava production, which could flow over the crater rim. On 18 January, the volcano shook twice more but the tremors seemed to be weakening.

No evacuations of the island's 300,000 people occurred during the elevated seismicity; however, frightened residents were sleeping outside on football fields and in their gardens, fearing collapse of their homes. UN Resident Coordinator in the Comoros, Giuseppina Mazza, later reported that "There are now fewer earthquakes and their intensity has reduced, the population is not panicking."

The IRIN news article noted that volcanic activity is common to Grande Comoro Island. Karthala erupted twice in 2005, affecting 40,000 people in April and 175,000 more in November. After an eruption on 28 May 2006 (BGVN 32:07), volcanic dust and debris covered large areas of the island. Volcanic ash contaminated water supplies, raising concerns about the health of people and livestock, along with its effects on agriculture.

According to the UN Office for the Coordination of Humanitarian Affairs (OCHA), since the 12 January volcanic activity, the authorities kept the hazard status at "red alert" and "have activated the national emergency response preparedness plan. They established a crisis management cell (CMC) which includes government departments, UN agencies, the Comoros Red Crescent Society, as well as local NGOs and diplomatic missions ... [and the] partners are reviewing preparedness arrangements."

Geologic Background. The southernmost and largest of the two shield volcanoes forming Grand Comore Island (also known as Ngazidja Island), Karthala contains a 3 x 4 km summit caldera generated by repeated collapse. Elongated rift zones extend to the NNW and SE from the summit of the Hawaiian-style basaltic shield, which has an asymmetrical profile that is steeper to the S. The lower SE rift zone forms the Massif du Badjini, a peninsula at the SE tip of the island. Historical eruptions have modified the morphology of the compound, irregular summit caldera. More than twenty eruptions have been recorded since the 19th century from the summit caldera and vents on the N and S flanks. Many lava flows have reached the sea on both sides of the island. An 1860 lava flow from the summit caldera traveled ~13 km to the NW, reaching the W coast to the N of the capital city of Moroni.

Information Contacts: Hamidi Soule Saadi, Karthala Volcano Observatory (KVO), Observatoire Volcanologique du Karthala, Centre National de Documentation et de la Recherche Scientifique des Comores, BP 169 Moroni, République Fédérale Islamique des Comores; Giuseppina Mazza, UN Resident Coordinator in Comoros, BP 648, Moroni, Comoros; Hamidou Nassor, Université de la Réunion, BP 7151, 15 Avenue, René Cassin, 97715 Saint-Denis, La Réunion, France; United Nations Office for the Coordination of Humanitarian Affairs?Integrated Regional Information Networks (IRIN), 3rd Floor, Sandton 2146, PO Box 1617, Parklands, 2121, Johannesburg, Republic of South Africa; Reuters.

After more than 17-years in quiescence, Macdonald seamount entered into a short phase of hydroacoustic activity starting at 1400 UTC on 13 October 2005. The seamount is ~ 6,000 km S of Honolulu, Hawaii (figure 2). When hydroacoustic activity has been of sufficient amplitude and duration, it has often been inferred to suggest submarine eruptions. In this case the signals were relatively weak and of modest duration, indicating seismic swarms without a clear association with volcanism.

Figure 2. Shaded view of seafloor topography for the Cook-Austral island chains (see upper inset for location). Map projection is made along direction of the present motion of Pacific plate (which moves from right to the left). White lines correspond to crustal magnetic anomalies, and their corresponding ages, in millions of years (Ma), are in white numerals. Black diamonds represent places where K-Ar or Ar/Ar ages are known. These ages, in Ma, are printed in black. From A. Bonneville (undated, post-2002 website, see References below).

Over five days the Polynesian Seismic Network (RSP for Réseau Sismique Polynésien) recorded 423 small- and medium-amplitude T-wave events from the seamount (figure 3). The best inland seismic station recording the event was at East Tuamotu, ~ 750 km from Macdonald. The ground response there was in the range of 50-300 nanometers.

Figure 3. A plot of the cumulative number and amplitude of T-wave events from Macdonald seamount during 13-17 October 2005. The x-axis shows the date. The y-axis scale is on the right and indicates the cumulative number of events (for the curve labeled Nb), which ultimately totaled 423. The y-axis scale is on the left and gives the amplitudes of ground motion for each of the 423 events (diamonds, some of which may be superimposed). Courtesy of Dominique Reymond and Olivier Hyvernaud, Laboratoire de Géophysique, CEA/DASE/LDG, Tahiti.

According to Robert Dziak, hundreds of medium to large amplitude T-wave events were also recorded on the NOAA/PMEL hydrophone array in the eastern Equatorial Pacific located some 2,200 km away from Macdonald. There was an absence of Pn and Sn seismic phases (the P- and S-wave phases that propagate at the base of ocean crust along the Moho discontinuity) suggesting the swarm was composed of comparatively low-magnitude events. Accordingly, geophysicists from both the RSP and NOAA/PMEL all interpreted the activity as a modest seismic swarm.

Many of the October 2005 T-wave signals were well located, with an error ellipse of less than 1 km in diameter. The strongest signals were seen on Tahiti, Rangiroa, and parts of the East Tuamotu networks; and consequently, these yielded the smaller error ellipses. The weakest T waves were seen on parts of the East Tuamotu network, resulting in the large NE-trending error ellipses.

The signals stopped at 0700 UTC on 17 October 2005. Dominique Reymond and Olivier Hyvernaud of the RSP were not aware of any witnessed eruptive signs or any detected hydroacoustic activity at or near Macdonald following the 2005 episode through 2006.

Additional research. Our previous reports on Macdonald seamount discussed activity during the 1980s, most recently during January 1989 (SEAN 14:01). Since then, several papers have shed light on the region (including Stoffers and others, 1989; McNutt and others, 1997; Sleep, 1997). McNutt and others (1997) presented high-resolution swath bathymetry in the Southern Austral islands, and noted more than one lone seamount in the area of Macdonald.The seamounts at Macdonald were morphologically distinct from their neighbors to the W along the Austral island chain in both their tall form and their slopes, which curved concave-upward.

References. Bonneville, A., (undated-post 2002), The Cook-Austral volcanic chain, URL: http://www.mantleplumes.org/Cook-Austral.html.

McNutt, M.K., Caress, D.W. Reynolds, J., Jordahl1, K.A., and Duncan, R.A., 1997, Failure of plume theory to explain midplate volcanism in the southern Austral islands: Nature, v. 389, p. 479-482.

Sleep, N., 1997 (2 October), Earth Science: The puzzle of the South Pacific: Nature, v. 389, p. 439-440.

Stoffers, P., Botz1, R., Cheminée, J-L., Devey, C.W., Froger, V., Glasby, G.P., Hartmann, M., Hékinian, R., Kögler, F., Laschek, D., Larqué, P., Michaelis, W., M?he1, R.K., Puteanus, D., and Richnow, H.H., 1989, Geology of Macdonald Seamount region, Austral Islands: Recent hotspot volcanism in the south Pacific: Journal Marine Geophysical Researches, v. 11, no. 2/June, p. 101-112.

Geologic Background. Discovered by the detection of teleseismic waves in 1967, Macdonald seamount (also known as Tamarii seamount) rises from a depth of about 1,800 m to within 27 m of the ocean surface at the eastern end of the Austral Islands. The basaltic submarine volcano marks the site of a hotspot that was the source of the Austral-Cook island chain. The summit, named after volcanologist Gordon Macdonald, consists of a flat plateau about 100 x 150 m wide with an average depth of about 40 m. The summit plateau is capped with spatter cones that form steep-sided pinnacles. Most eruptions have been seismically detected, but in 1987 and 1989 pumice emission was observed from research vessels. Pumice rafts observed in the South Pacific in 1928 and 1936 may also have originated here.

Information Contacts: Dominique Reymond and Olivier Hyvernaud, Laboratoire de Géophysique, Commissariat a l'Energie Atomique, CEA/DASE/LDG, PO Box 640, Papeete, Tahiti, French Polynesia; Robert P. Dziak, Oregon State University, 2115 SE OSU Drive Newport OR 97365, USA.

According to Dominique Reymond and Olivier Hyvernaud (affiliates of Laboratoire de Geophysique, in Saint Martin d' Heres, France), activity at Monowai from 2005-2006 was remarkable because of the more than 1,650 events recorded as hydroacoustic waves (also called T-phase waves or T-waves) on the Polynesian Seismic Network (Réseau Sismique Polynésien, or RSP). Such waves are generated by submarine earthquakes and/or volcanic eruptions that can be monitored at great distances via seismic stations close to the shore and/or by hydrophones. The amplitudes of T-waves are related to the strength or intensity of submarine volcanism at the seamount.

The T-wave activity after 2002 appeared in two main stages (figure 17). The initial stage extended from early 2003 to August 2004, followed by a period of repose that lasted until March 2005. A second stage of T-wave activity then continued until July 2006, followed by another six months of quiet. Reymond and Hyvernaud noted that individual T-wave swarms typically had durations varying between 1 day and 3 weeks.

Figure 17. Cumulative number of events recorded by the RSP for Monowai from 1 November 2002 to 31 December 2006. Courtesy of Dominique Reymond and Olivier Hyvernaud.

It appears that another cycle started 12 December 2006 (figure 17), continuing at least until the end of the month. The average number of events from the end of 2002 until the end of 2006 was about 950 per year. In the last two years (2005-2006), a slightly lower rate of 825 events per year was measured (figure 18).

Figure 18. Cumulative number of T-waves at Monowai recorded by the RSP over the period 2005-2006, with dates indicating the start and end of each swarm. The duration of the swarms varied between 1 day and 3 weeks. Courtesy of Dominique Reymond and Olivier Hyvernaud.

The amplitudes of T-waves recorded during 2005-2006 at the TVO seismic station in Tahiti never reached 1/3 of the amplitude that was recorded on 24 May 2002. It was that day when amplitudes of 350 nm were reached (figure 19). The average values for T-wave amplitudes during the period shown in figure 19 are in the 5-50 nm range.

Figure 19. Amplitude (in nanometers of ground motion) for Monowai T-waves recorded at the TVO station over the last 4 years (2002-2006). While the average values are in the range of 5- 50 nm, only one exceptional value of 350 nm was recorded on 24 May 2002 (BGVN 27:05). Courtesy of Dominique Reymond and Olivier Hyvernaud.

Geologic Background. Monowai, also known as Orion seamount, is a basaltic stratovolcano that rises from a depth of about 1,500 to within 100 m of the ocean surface about halfway between the Kermadec and Tonga island groups, at the southern end of the Tonga Ridge. Small cones occur on the N and W flanks, and an 8.5 x 11 km submarine caldera with a depth of more than 1,500 m lies to the NNE. Numerous eruptions have been identified using submarine acoustic signals since it was first recognized as a volcano in 1977. A shoal that had been reported in 1944 may have been a pumice raft or water disturbance due to degassing. Surface observations have included water discoloration, vigorous gas bubbling, and areas of upwelling water, sometimes accompanied by rumbling noises. It was named for one of the New Zealand Navy bathymetric survey ships that documented its morphology.

Information Contacts: Dominique Reymond and Olivier Hyvernaud, Laboratoire de Géophysique, Commissariat a l'Energie Atomique, CEA/DASE/LDG, PO Box 640, Papeete, Tahiti, French Polynesia.

Jacques Durieux, the United Nations manager for Volcano Risk Reduction for the Goma Volcano Observatory (GVO), reported that at about 2000 on 26 October 2006 the observatory began to record sustained seismic activity. The activity took place in the Virunga area, located in the central part of Western arm of the East African rift valley. The swarm of long-period earthquakes was located around Nyamuragira and persisted for a month, through 1700 on 27 November 2006. The volcano was the scene of several seismic swarms in middle and late 2005 (BGVN 31:01).

GVO observed the beginning of a new eruption at 2000 on 27 November 2006 (figure 26). Seen from ~ 30 km S of the volcano in Goma, the eruption site appeared to be located on the S flank; intense red glow suggested typical lava fountains and lava flows.

Figure 26. Aerial photograph of Nyamuragira in vigorous eruption with fire fountains venting along a broad linear zone, as seen from above the city of Goma. The photo was taken 27 November 2006 at 2300, one hour after the beginning of the eruption. Copyrighted photo provided by J. Durieux.

The local security situation prevented closer field observations. GVO was attempting to organize helicopter overflights to collect more information for updates. One concern was that foraging animals could fall ill after eating ash-coated vegetation. In assessing the situation, authorities considered Goma to be safe from any potential lava flows as Mount Nyiragongo would serve as a buffer.

Based on satellite imagery, the Toulouse VAAC reported that during 29 November-2 December 2006 emissions produced ash plumes to altitudes of 3-6.1 km. Those plumes drifted W and NW. By mid-morning on 2 December, ash plumes were no longer reported.

Besides ash and possible lava, the volcano also released extensive sulfur dioxide (SO₂), a feature of this volcano that has been mentioned repeatedly in the literature (see some references below). The Ozone Monitoring Instrument (OMI) on NASA's Aura satellite tracked the emission of this gas from the volcano from 28 November to 4 December 2006 (figure 27). The SO₂ gas was most concentrated around the eruption site and thinned as it moved away. The plume first traveled W, then curved along an arc progressing in a clockwise direction toward the NE and then E. It remained clearly detectable over NW India, a distance of ~ 9,000 km.

Figure 27. OMI measurements for 28 November-4 December 2006 looking at SO2 emitted by Nyamuragira. OMI (which is basically a spectrometer) measured the atmospheric column daily, assessing the region between the satellite and the surface of the Earth, and this graphic depicts the average values of SO2 thickness-concentration product during the multi-day interval. The thickness-concentration products are shown on a logarithmic color scale which utilizes Dobson Units (DU) [(1 milli-atm-cm = 1 DU = 10 ppm at STP (0°C, 1,013.25 hPa). If all SO2 in the air column were flattened into a thin layer at the Earth's surface at a temperature of 0°C, one Dobson Unit would make a layer of SO2 0.01 millimeters thick.] On the colored version of this figure, the greatest concentrations appear in red and the smallest concentrations appear in pale pinkish-lavender. Courtesy of NASA Earth Observatory and Simon Carn.

The latest eruption of Nyamuragira was its 15th since 1980. Table 2 shows OMI's estimated SO₂ loadings during 28 November to 4 December 2006 as computed by Simon Carn. Carn also presented daily OMI images (like figure 27) during the same date range as table 2.

Table 2. Daily SO₂ flux at Nyamuragira, measured by OMI during 28 November to 4 December 2006. Courtesy of Simon Carn.

References. Carn, S.A., Bluth, G.J.S., and Head, E., (in progress), Virunga Volcanic SO₂ Emissions Research (ViSOR) project (discussed at URL: http://userpages.umbc.edu/~scarn/virunga/).

Carn, S.A., 2004, Eruptive and passive degassing of sulfur dioxide at Nyiragongo volcano (D.R. Congo): the 17 January 2002 eruption and its aftermath: Acta Vulcanologica, v. 14-15, p. 75-86.

Carn, S.A., and Bluth, G.J.S., 2003, Prodigious sulfur dioxide emissions from Nyamuragira volcano, D.R. Congo: Geophys. Res. Lett., v. 30, no. 23, p. 2211, doi:10.1029/2003GL018465.

Bluth, G.J.S, and Carn, S.A., (in progress), Exceptional sulphur degassing from Nyamuragira volcano, 1979-2005: Int. J. Remote Sensing.

Tedesco, D., Vaselli, O., Papale, P., Carn, S.A., Voltaggio, M., Sawyer, G.M., Durieux, J., Kasereka, M., and Tassi, F., (in progress), The January 2002 Eruption of Nyiragongo volcano, Democratic Republic of Congo: J. Geophys. Res.

Geologic Background. Africa's most active volcano, Nyamulagira (also known as Nyamuragira), is a massive high-potassium basaltic shield about 25 km N of Lake Kivu and 13 km NNW of the steep-sided Nyiragongo volcano. The summit is truncated by a small 2 x 2.3 km caldera that has walls up to about 100 m high. Documented eruptions have occurred within the summit caldera, as well as from the numerous flank fissures and cinder cones. A lava lake in the summit crater, active since at least 1921, drained in 1938, at the time of a major flank eruption. Recent lava flows extend down the flanks more than 30 km from the summit as far as Lake Kivu; extensive lava flows from this volcano have covered 1,500 km2 of the western branch of the East African Rift.

Information Contacts: Jacques Durieux, Observatoire Volcanologique de Goma, Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo; NASA, Earth Observatory Natural Hazards website (URL: http://earthobservatory.nasa.gov/NaturalHazards); Simon Carn, Joint Center for Earth Systems Technology (JCET), University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD, USA (URL: https://jcet.umbc.edu/); Toulouse Volcanic Ash Advisory Center (VAAC), Météo-France, 42 Avenue Gaspard Coriolis, F-31057 Toulouse cedex, France (URL: http://www.meteo.fr/vaac/).

Jim Luhr, director of our volcano program since 1995, passed away unexpectedly in his sleep on 1 January 2007. He was 53 years of age, and died of complications from influenza. He leaves behind his wife Karen Prestegaard, a professor at the University of Maryland, and their two school-aged daughters.

One of Jim's legacies is the greatly expanded public access to Smithsonian volcano data resulting from his promotion of the growth of our widely used website. In the mid-1990s, he helped create a new exhibit hall exposing millions of visitors each year to displays with significant emphasis on geophysics, plate tectonics, and volcanology (giving visitors electronic access to geologic and geophysical information).

Jim acted as chief editor of the graphically stunning book Earth. He also co-edited the book "Paricutín: The Volcano Born in a Mexican Cornfield," an outgrowth of his many detailed field and laboratory studies of Mexican volcanoes. Jim was well known for his work on the petrology of young volcanic rocks and the atmospheric impact of eruptions.

[Notice from BGVN 31:11] With deep regret we announce that Jim Luhr passed away unexpectedly and peacefully in his sleep on 1 January 2007 at the age of 53. He directed the Smithsonian's Global Volcanism Program during 1995 through 2006, and in that role helped elevate both this Bulletin and its younger sister publication, the Smithsonian / USGS Weekly Volcanic Activity Report. Jim was well-known for well-crafted, multifaceted analytical studies of his beloved Mexican volcanoes.

Geologic Background. Obituary notices for volcanologists are sometimes written when scientists are killed during an eruption or have had a special relationship with the Global Volcanism Program.

Information Contacts:

At 1800 on 4 December 2006 scientists from the Hawaiian Volcano Observatory (HVO) and Emergency management Office (EMO) were advised by Pagan residents of ashfall at their camp. They continued to report light ashfall (through an unreported date), with up to a centimeter per day accumulating 3 km SW of the summit and a plume rising about 60 m above the vent. There were no felt earthquakes or noise from the volcano, but occasional sulfur smells wafted through the camp.

Visible satellite imagery interpreted by the Washington VAAC showed a small gas plume, possibly with minor ash, at 0733 on 5 December. Cloud cover made satellite observations difficult, but during 5-6 December plumes could be distinguished extending as far as 185 km W. A Terra MODIS image on 6 December (figure 6) showed the plume near the island to be light brown in color, indicating ash content. A serpentine-shaped plume at 0833 on 7 December extended 140 km WSW from the island. Later that day, at 1300, a faint narrow plume could still be seen to a distance of about 300 km W. The last visible imagery that showed an ash plume was at 1633 on 8 December; the plume was very narrow and at low altitudes.

Figure 6. Terra MODIS image showing a light brown ash plume blowing W from Pagan, 6 December 2006. Courtesy of NASA Earth Observatory and the MODIS Rapid Response Team at Goddard Space Flight Center.

Although significant eruptive activity seemed to have ended on 8 December, observations from the International Space Station revealed a plume on 11 January 2007 (figure 7). The very diffuse plume was most likely steam. There were no reports of ash plumes from the island or warnings to aviators based on satellite data after 8 December 2006.

Figure 7. Photograph showing a thin plume extending SW from Pagan on 11 January 2007. [Astronaut photograph ISS014-E-11872 was acquired with a Kodak 760C digital camera using a 180 mm lens.] Courtesy of NASA Earth Observatory, the ISS Crew Earth Observations experiment, and the Image Science & Analysis Laboratory, Johnson Space Center.

Eruption during 1993-94. The eruption that began around mid-January 1993 (BGVN 18:03) continued through at least 30 April 1994 (figure 8). Fieldwork by USGS and EMO scientists during April and May 1994 was not previously reported in the Bulletin. Trusdell and others (2006) noted that following the eruption in 1981 (SEAN 06:04), "Intermittent light ejection of chiefly phreatic ash continued until 1996, with maximum post-1981 accumulation estimated at as much as 1-2 m on the source cone."

Figure 8. Ash plume erupting from Pagan, 30 April 1994. View is to the S. Courtesy of Frank Trusdell, USGS.

References. Sako, M.K., Trusdell, F.A., Koyanagi, R.Y., Kojima, G., and Moore, R.B., 1995, Volcanic investigations in the Commonwealth of the Northern Mariana islands, April to May 1994: U. S. Geological Survey Open-File Report 94-705, 57 p.

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, 32 p.

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), PO Box 100007, Saipan, MP 96950, USA (URL: http://www.cnmihsem.gov.mp/); U.S. Geological Survey, Hawaiian Volcano Observatory (HVO), PO Box 51, Hawaii National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/nmi/activity/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/).

Growth of the lava dome at Soputan began in 1991 (BGVN 16:06), eventually overtopping the crater rim and generating rockfalls to distances of 2-4 km downslope. Phreatic eruptions since that time have been triggered during the rainy season, and ash explosions have been frequent since 2000. An eruption and dome collapse in July 2005 sent a pyroclastic flow to a distance of 3 km from the summit. The nearest residents are at a distance of 8 km, so none of these events created hazards to the local population. Following pyroclastic avalanches and Strombolian activity in late December 2005 (BGVN 31:04), the Centre of Volcanology and Geological Hazard Mitigation (CVGHM) did not report further activity at Soputan until December 2006.

Lava dome volume in early December 2006 was reported to be 34 million cubic meters. Rockfall signals from the lava dome typically occur at a rate of about 75 per day, but the number of these events increased to 153 on 11 December, and remained high over the next two days: 120 on 12 December and 126 on the 13th. Volcanic tremor amplitude also increased on 11 December. Although thick fog hampered observations, "white smoke" was seen rising 25-30 m above the summit. At 1400 on 14 December a "thunderous" eruption was heard at the CVGHM observation post 8 km from the summit. Gray ash plumes rising 250 m above the summit caused ashfall within a 15-km radius. On 15 December the Alert Level was raised from 2 to 3 (on a scale of 1-4) due to this increase in activity.

A precautionary aviation advisory was issued by the Darwin VAAC on 18 December based on information from the CVGHM. A few hours later a plume was detected on an MTSAT image taken at 1933. The high-level eruption may have reached an altitude of 12 km altitude with the plume extending 37 km to the W.

Geologic Background. The Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano is the only active cone in the Sempu-Soputan volcanic complex, which includes the Soputan caldera, Rindengan, and Manimporok (3.5 km ESE). Kawah Masem maar was formed in the W part of the caldera and contains a crater lake; sulfur has been extracted from fumarolic areas in the maar since 1938. Recent eruptions have originated at both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Diponegoro 57, Bandung, Jawa Barat 40122, Indonesia (URL: http://vsi.esdm.go.id/); Jenny Farlow, Darwin Volcanic Ash Advisory Centre, Bureau of Meteorology, Australia (URL: http://www.bom.gov.au/info/vaac/).

On 26 September 2006, the Philippine Institute of Volcanology and Seismology (PHILVOLCS) announced ongoing seismic unrest at Taal (a low lying caldera ~ 45 km S of Manila). The Main Crater Seismic Station recorded 29 volcanic earthquakes during the 24 hours after 0600 on 25 September 2006. Five (5) of these occurred at 0233, 0234, 0242, 0247, and 0249 and were felt at Intensities II to III by residents on Volcano Island (figure 7 and 8). These earthquakes were accompanied by rumbling sounds. Initial computations showed epicenters generally dispersed toward northerly locations in the vicinity of Daang Kastila (NE), Tibag (N), Tablas (NE), Mataas na Gulod (NE), and Panikihan (NW).

Figure 7. A map of Taal volcano indicating the location of components of the monitoring network (seismic stations, telemetry repeater stations, reflector, and various kinds of survey and measuring points). Volcano island (the large island in the N-central part of the caldera lake) is the site of all historical eruptions. Contour interval is 100 m. Courtesy of PHIVOLCS.

Figure 8. Photograph taken from the top of the N topographic margin of Taal, looking S across Lake Taal and Volcano Island, 28 May 2001. The topographic high on the far side of the lake is Mt. Macolod. Copyrighted photograph by Franck Landais (provided by Panoramio.com).

This seismic activity was notably higher than usual, which during quiet periods is generally only five or less events detected in 24 hours. Surface thermal observations, however, did not indicate significant change in the thermal and steam emission manifestations in the Main Crater Lake area. The increase in seismicity reflected a low-level episode of unrest. However, there is still no indication of an impending eruption.

Taal manifested a sustained moderate level of seismic activity since 18 November 2006, characterized by occasional large amplitude volcanic earthquakes. During one 24-hour period, 10 volcanic earthquakes were detected. Ground deformation surveys conducted during 28 November-6 December 2006 revealed the edifice inflated 14.0 mm, suggesting possible magma intrusion. The Main Crater lake water became more acidic since 12 September 2006, and the newly formed mud geyser, which is now merged with the Crater Lake due to increase in water level, continues to be very active. The increasing acidity and hydrothermal activity are probably caused by the injection of hot gases and fluids coming from below the crater floor.

According to PHIVOLCS in its Taal Volcano Advisory of 14 December 2006, the above observations indicated a significant increase in activity although no eruption is imminent. Alert Level 1 continued, making the Main Crater off-limits to the public because of the chance of sudden steam explosions and high toxic gas concentrations.

Geologic Background. Taal is one of the most active volcanoes in the Philippines and has produced some powerful eruptions. The 15 x 20 km Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 km2 surface lies only 3 m above sea level. The maximum depth of the lake is 160 m, with several submerged eruptive centers. The 5-km-wide Volcano Island in north-central Lake Taal is the location of all observed eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones. Powerful pyroclastic flows and surges have caused many fatalities.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), University of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph); Panoramio.com, Calle Rosa Zaragoza 8, 03360 Callosa de Segura (Alicante), Spain (URL: http://www.panoramio.com/photo/40914).

Indonesian volcanologists with the Center of Volcanology and Geological Hazard Mitigation (CVGHM) (previously known by other names, including the Volcanological Survey of Indonesia) maintain an observation post and seismic network at Talang. After intermittent activity during September 2001 (BGVN 26:10) until June 2002 (BGVN 27:06), there was no additional reported activity until 2005 and 2006.

Activity during April 2005. On 12 April 2005 an eruption at Talang during 0340-0600 produced an ash plume that rose to ~ 1 km above the crater. About 4 mm of ash fell in the village of Bukit Sileh, NE of the crater. On the afternoon of 10 April observers had noted a "grey ash cloud" rising ~ 100 m, followed the next day by a diffuse white cloud around the summit. Volcanologist Dalipa, who heads the Batu Bajanjang observation post, told The Jakarta Post that there had been five large eruptions and hundreds of small eruptions before 1200 on 12 April that caused ashfall as far as 10 km away. He added that between the evening of 12 April and 0600 the next morning there were only six small eruptions.

An infrared image (GOES-9) taken at 0425 on 12 April 2005, analyzed by the Darwin VAAC, showed the eruption plume. There was a weak ash signature in the small cloud for a couple of hours before it became difficult to track. Plume height was estimated to be 7.5 km because the upper part of the cloud went NW, and winds below that were more or less westerly. The height of the cloud would have been difficult to see from the ground during the peak activity before dawn.

Simon Carn reported that the Ozone Monitoring Instrument (OMI) on EOS/Aura detected an SO₂ plume from Talang on 12 April at 1402, and possible much weaker emissions on 13 April. The plume on 12 April extended roughly ESE towards central Sumatra, so was presumably at a lower elevation than the upper part of the ash cloud imaged earlier by the Darwin VAAC. The preliminary estimated SO₂ mass was around 1,000 metric tons. Weak emissions were reported several days prior to the 12 April event, but OMI data only showed SO₂ emissions from nearby Kerinci volcano.

A local government official told news media on 14 April that 25,150 residents from five villages in Lembang Jaya and Gunung Talang districts, located within a 5-km radius from the danger zone, had been evacuated. Winds were reportedly carrying ash downslope along with volcanic gases.

On 13 April volcanic and seismic activity decreased in comparison to the previous day. A "white-gray ash plume" rose 250 m from three points inside Kawah Mati crater, and white gas was emitted from Gabuo Atas crater. There was a decrease in the number of deep volcanic, shallow volcanic, and explosion earthquakes. By 0600 on 14 April the only reported activity was a diffuse "white ash" plume rising 250-300 m above the crater. However, news media quoting a government geologist reported that Talang "sent out fresh clouds of dust and continued to rumble" on 15 April.

By 17 April, activity had decreased and volcanologists lowered the hazard status to 3 (on a scale of 1-4). People were permitted to return their homes near the volcano, but no one could enter within 1 km of the summit. Due to a continued decrease in seismicity during 24-28 April (less than 10 volcanic events per day), the Alert Level was dropped to 2 on 28 April. Due to the hazards of minor phreatic eruptions, unstable land, and toxic gases, the area within a 1-km radius of the crater remained closed.

Activity during July 2005. Small phreatic eruptions occurred on 2 and 3 July 2005. The eruptions occurred at the main crater and a crater on the S slope. Ash columns reached 300-500 m above the volcano and caused 0.5-1 mm of ashfall around Kampung Batu, 2 km S of the summit. On the N slope, the Gabuo Atas, Gabuo Bawah, and Kapundan Panjang craters emitted "white-brown steam" to low altitudes. The temperature of Batu Bajanjang hotspring, located below the summit, was 41.9-61.3°C. The hazard status remained unchanged at Alert level 2 (on a scale of 1-4).

Increased seismicity on 18 July prompted an change in the Alert Level to 3. During 15-18 July, the seismic network recorded 93 deep volcanic earthquakes, one low-frequency tremor, and three "felt shocks" around the N slope of the crater. Minor phreatic activity occurred at the S and N slope craters, with dark gray ash plumes rising 0.5-1.5 km above the crater on 18 July.

Activity during September 2006. Increasing seismicity and gas emissions led to the hazard status being raised to Alert Level 3 on 9 September 2006. The next day "brownish smoke" was being emitted to heights of 250 m. The daily number of volcanic earthquakes and tremor fluctuated over the next few months, reaching a high of 33 events on 23 November. After that date seismicity showed a decreasing trend through late January 2007. Weak gas emissions continued during this period from both South Crater and Main Crater. Due to the lowered levels of activity, the hazards status was once again dropped to Alert Level 2 on 27 January.

Geologic Background. Talang, which forms a twin volcano with the extinct Pasar Arbaa volcano, lies ESE of the major city of Padang and rises NW of Dibawah Lake. Talang has two crater lakes on its flanks; the largest of these is 1 x 2 km wide Danau Talang. The summit exhibits fumarolic activity, but which lacks a crater. Historical eruptions have mostly involved small-to-moderate explosive activity first documented in the 19th century that originated from a series of small craters in a valley on the upper NE flank.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation, Diponegoro 57, Bandung, Jawa Barat 40122, Indonesia (URL: http://vsi.esdm.go.id/); Andrew Tupper, Darwin Volcanic Ash Advisory Centre, Bureau of Meteorology, Australia (URL: http://www.bom.gov.au/info/vaac/); Simon Carn, Joint Center for Earth Systems Technology (JCET), University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA; Agence France-Presse (AFP) (URL: http://www.afp.com/english/home/); Indahnesia.com (URL: http://news.indahnesia.com/); The Jakarta Post, Indonesia (URL: http://www.thejakartapost.com/); Associated Press (URL: http://www.ap.org/).