1-1-1-1-1-1-1-1-1-1-1-1-1-1 From: "Kuhn, Sally" <KUHNS@xxxxxx> Smithsonian / USGS Weekly Volcanic Activity Report 2-8 August 2023 Sally Sennert - Weekly Report Editor (kuhns@xxxxxx) URL: https://urldefense.com/v3/__https://volcano.si.edu/reports_weekly.cfm__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssMT2fGZB$ <https://urldefense.com/v3/__https://volcano.si.edu/reports_weekly.cfm__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9TqZf1ZI$> New Activity/Unrest: Bagana, Bougainville (Papua New Guinea) | Poas, Costa Rica | Shishaldin, Fox Islands (USA) | Ulawun, New Britain (Papua New Guinea) Ongoing Activity: Aira, Kyushu (Japan) | Dukono, Halmahera | Ebeko, Paramushir Island (Russia) | Fagradalsfjall, Iceland | Great Sitkin, Andreanof Islands (USA) | Karangetang, Sangihe Islands | Katmai, Alaska | Klyuchevskoy, Central Kamchatka (Russia) | Lewotolok, Lembata Island | Mayon, Luzon (Philippines) | Merapi, Central Java | Piton de la Fournaise, Reunion Island (France) | Sabancaya, Peru | Semeru, Eastern Java | Semisopochnoi, Aleutian Islands (USA) | Sheveluch, Central Kamchatka (Russia) | Ubinas, Peru The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Wednesday, these reports are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week, but rather a summary of activity at volcanoes that meet criteria discussed in detail in the "Criteria and Disclaimers" section. Carefully reviewed, detailed reports about recent activity are published in issues of the Bulletin of the Global Volcanism Network. Note that many news agencies do not archive the articles they post on the Internet, and therefore the links to some sources may not be active. To obtain information about the cited articles that are no longer available on the Internet contact the source. New Activity/Unrest Bagana | Bougainville (Papua New Guinea) | 6.137°S, 155.196°E | Summit elev. 1855 m The Darwin VAAC reported that an intense thermal anomaly over Bagana was identified in satellite images during 30-31 July. Ash emissions rose to 2.4 km (8,000 ft) a.s.l. and drifted WSW on 30 July. The VAAC received a ground report from RVO describing localized emissions at 0900 on 31 July. Ash was not identified in satellite images, though weather clouds obscured views. Geologic Summary. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides. Source: Darwin Volcanic Ash Advisory Centre (VAAC) https://urldefense.com/v3/__http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssEP2CJWR$ <https://urldefense.com/v3/__http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9HMEo1DQ$> Poas | Costa Rica | 10.2°N, 84.233°W | Summit elev. 2697 m OVSICORI-UNA reported that a small phreatic eruption at Poás occurred at 0153 on 2 August at the W part of the crater lake, ejecting material about 20 m above the water. At 1655 on 5 August a phreatic eruption from three areas of the lake ejected sediment and steam 50-100 m above the lake. At least two eruptive pulses were seen. Fumarolic degassing and lake convection were visible during 2-8 August. Geologic Summary. The broad vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the complex stratovolcano extends to the lower N flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, last erupted about 7,500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since an eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water. Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) https://urldefense.com/v3/__http://www.ovsicori.una.ac.cr/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssONAgDCS$ <https://urldefense.com/v3/__http://www.ovsicori.una.ac.cr/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw97NojduQ$> Shishaldin | Fox Islands (USA) | 54.756°N, 163.97°W | Summit elev. 2857 m AVO reported that the effusive and explosive eruption at Shishaldin continued during 1-8 August. Low-level ash emissions rose to below 3 km (10,000 ft) a.s.l. and drifted over 90 km N during 1-2 August. Seismicity was low but punctuated by a few episodes of volcanic tremor associated with the ash emissions. Elevated surface temperatures were consistent with cooling lava over a few days but had begun to increase and were visible though moderate weather cloud cover during 2-3 August; the increasing temperatures were consistent with lava effusion. Seismic tremor began to steadily increase at around 1036 on 3 August. Explosive activity about 20 hours later was detected using infrasound and seismic data. An ash cloud was visible in a satellite image at 0520 on 4 August rising to 7.6 km (25,000 ft) a.s.l. and drifting 60-75 km NE. Pilots saw and reported the plume at 0836. By 0900 the plume had risen to 9 km (30,000 ft) a.s.l., prompting AVO to raise the Aviation Color Code to Red (the highest color on a four-color scale) and the Volcano Alert Level to Warning (the highest level on a four-level scale) at 1017. The National Weather Service issued a Significant Meteorological Information (SIGMET) statement for the ash cloud and a Special Weather Statement warned of possible trace amounts of ash on marine waters downwind of Shishaldin. Seismic tremor levels peaked at 1400 and then sharply declined at 1500 to slightly elevated levels; the plume was sustained during the period of high tremor and drifted N and NE. AVO lowered the Volcano Alert Level to Watch and the Aviation Color Code to Orange at 1955. Seismic tremor levels were low. Ash emissions were possibly continuing but they could not be confirmed due to meteorological clouds cover. Elevated surface temperatures observed in satellite data during 5-8 August were consistent with cooling lava. Seismicity has remained low with a few daily local earthquakes. Geologic Summary. The symmetrical glacier-covered Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. It is the westernmost of three large stratovolcanoes in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." Constructed atop an older glacially dissected edifice, it is largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the W and NE sides at 1,500-1,800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of Strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century. A steam plume often rises from the summit crater. Source: US Geological Survey Alaska Volcano Observatory (AVO) https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssMh2T5bK$ <https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9Dhkngug$> Ulawun | New Britain (Papua New Guinea) | 5.05°S, 151.33°E | Summit elev. 2334 m Rabaul Volcano Observatory (RVO) reported that small, diffuse, white plumes rose from Ulawunâ??s summit during 27 July-4 August when there were extended periods of good visibility from the webcam in Ulamona (11-12 km NW). Seismicity fluctuated at moderate levels and was dominated by volcanic tremor; RSAM values ranged from 380 to 800. The Alert Level was lowered to Stage 1 (the lowest level on the four-level scale) on 31 July. Overall, RSAM showed a slow and erratic upward trend during 15 July-4 August and corresponded to an increase in volcanic tremor amplitudes. RVO warned that minor eruptive activity may occur if the trend continued and that ash emissions had previously occurred at similar RSAM levels. Geologic Summary. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the N coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1,000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater. Source: Rabaul Volcano Observatory (RVO) https://urldefense.com/v3/__https://webdev.datec.net.pg/geohazards/category/volcanoes/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssJRdMrot$ <https://urldefense.com/v3/__https://webdev.datec.net.pg/geohazards/category/volcanoes/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9Pt44eCw$> Ongoing Activity Aira | Kyushu (Japan) | 31.593°N, 130.657°E | Summit elev. 1117 m JMA reported ongoing activity at both Minamidake Crater and Showa Crater (Aira Calderaâ??s Sakurajima volcano) during 31 July-7 August. Nighttime incandescence at Minamidake was occasionally observed. Sulfur dioxide emissions measured during a field visit on 3 August averaged 1,800 tons per day. An eruptive event at Showa at 0542 on 4 August produced an ash plume that rose 1 km above the crater rim and drifted N, and ejected blocks 400 m from the crater. An explosion at the same crater at 2150 produced an ash plume that rose 2.3 km above the crater rim and drifted NW, and ejected blocks as far as 800 m from the vent. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 2 km away from both craters. Geologic Summary. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76. Source: Japan Meteorological Agency (JMA) https://urldefense.com/v3/__http://www.jma.go.jp/jma/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssAY4fTun$ <https://urldefense.com/v3/__http://www.jma.go.jp/jma/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9TBMtbGA$> Dukono | Halmahera | 1.693°N, 127.894°E | Summit elev. 1229 m PVMBG reported that the eruption at Dukono was ongoing during 2-8 August. Dense white-and-gray plumes rose as high as 450 m above the summit and drifted in multiple directions on all days except 3 August when only white plumes were reported. The Alert Level remained at Level 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone. Geologic Summary. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssG2uY_Zh$ <https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9_jClpVo$> Ebeko | Paramushir Island (Russia) | 50.686°N, 156.014°E | Summit elev. 1103 m KVERT reported that moderate explosive activity at Ebeko was ongoing during 27 July-3 August. According to volcanologists in Severo-Kurilsk (Paramushir Island, about 7 km E), explosions during 27 July and 2-3 August generated ash plumes that rose as high as 3.5 km (11,500 ft) a.s.l and drifted to the NE and SE. Thermal anomalies were identified in satellite images on 29 July; weather clouds obscured views on other days. The Aviation Color Code remained at Orange (the third level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted. Geologic Summary. The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssLCZ8FaF$ <https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9M9ln8ec$> Fagradalsfjall | Iceland | 63.895°N, 22.258°W | Summit elev. 250 m At 1706 on 5 August IMO lowered the Aviation Color Code for Fagradalsfjall to Yellow (the second level on a four-color scale), noting that the eruption had declined during the previous few days and very minor activity at the crater was visible in webcam images. Tremor had decreased during the previous 36 hours and reached background levels by 1500 on 5 August. Gas plumes had typically risen 1-2 km above the vent, though on 1 August plumes rose more than 2.5 km, and according to news articles, a notable amount of fume rose from the vent on 4 August. The crater had become deeper and smaller by 4 August. Activity was last seen on 5 August and a thermal anomaly in the crater was last identified in satellite images on 6 August. Geologic Summary. Although the Fagradalsfjall fissure swarm has previously been considered a split or secondary swarm of the KrýsuvÃkâ??Trölladyngja volcanic system, as of September 2022 Icelandic volcanologists managing the Catalogue of Icelandic Volcanoes made the decision to identify it as a distinct separate system. The recent eruptions and related reports have been reassigned here, and other content will be prepared and adjusted as appropriate. Sources: Icelandic Meteorological Office (IMO) https://urldefense.com/v3/__http://en.vedur.is/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssGELuKPC$ <https://urldefense.com/v3/__http://en.vedur.is/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9OHuL3DE$> ; Icelandic National Broadcasting Service (RUV) https://urldefense.com/v3/__https://www.ruv.is/english/2023-08-04-smoke-rises-crater-falls-lava-slows-389194__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssGA5LSAt$ <https://urldefense.com/v3/__https://www.ruv.is/english/2023-08-04-smoke-rises-crater-falls-lava-slows-389194__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9hIFdeHs$> ; Icelandic National Broadcasting Service (RUV) https://urldefense.com/v3/__https://www.ruv.is/frettir/innlent/2023-08-08-kaflaskil-i-eldgosinu-a-reykjanesskaga-389400__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssP5-Jouj$ <https://urldefense.com/v3/__https://www.ruv.is/frettir/innlent/2023-08-08-kaflaskil-i-eldgosinu-a-reykjanesskaga-389400__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9GJa9PLE$> Great Sitkin | Andreanof Islands (USA) | 52.076°N, 176.13°W | Summit elev. 1740 m AVO reported that slow lava effusion continued at Great Sitkin during 1-8 August, producing a thick flow in the summit crater. The eastern lobe continued to advance into glacial ice surrounding the crater, causing the ice to deform and crack, based on a 1 August satellite image. Seismicity remained slightly elevated throughout the week. Weather clouds often obscured satellite and webcam views, though a clear image showed no unusual activity during 5-6 August and an image showed diffuse steaming from the lava surface during 6-7 August. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale). Geologic Summary. The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century. Source: US Geological Survey Alaska Volcano Observatory (AVO) https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssMh2T5bK$ <https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9Dhkngug$> Karangetang | Sangihe Islands | 2.781°N, 125.407°E | Summit elev. 1797 m PVMBG reported that dense white gas-and-steam plumes from Karangetang were visible rising as high as 250 m and drifting multiple directions on most days during 2-8 August. Webcam images published in the reports showed incandescence at the summit and from material on the flanks of Main Crater (S crater). According to a news source, lava avalanches traveled more than 1-1.5 km SW down the Batang, Timbelang, and West Beha drainages. Lava flows in drainages on the S and SW flanks were active; the flow in the Batuawang was 1.5 km long, the flow in Kahetang was more than 1.8 km long, and the flow in Keting was 2.1 km long. Gray clouds sometimes accompanied lava flow activity. Incandescent material was sometimes ejected up to 25 m above the summit. During the end of the week 104 people were evacuated from the Tatahadeng and Tarorane villages, located within a 2.5-km radius of the crater, to evacuation centers and remained there at least through 9 August. Incandescence at the dome in the N crater continued to be visible. The Alert Level remained at 3 (on a scale of 1-4) and the public were advised to stay 2.5 km away from Main Crater with an extension to 3.5 km on the S and SE flanks. Geologic Summary. 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. Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssG2uY_Zh$ <https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9_jClpVo$> ; Antara News https://urldefense.com/v3/__https://www.antaranews.com/berita/3674019/pvmbg-erupsi-efusif-karangetang-masih-terjadi__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssM5L1foV$ <https://urldefense.com/v3/__https://www.antaranews.com/berita/3674019/pvmbg-erupsi-efusif-karangetang-masih-terjadi__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9ZrsBHtY$> ; Antara News https://urldefense.com/v3/__https://www.antaranews.com/berita/3662289/pvmbg-ada-1189-kali-gempa-guguran-gunung-karangetang-dalam-sepekan__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssDQLm_7D$ <https://urldefense.com/v3/__https://www.antaranews.com/berita/3662289/pvmbg-ada-1189-kali-gempa-guguran-gunung-karangetang-dalam-sepekan__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9Og-invI$> ; Antara News https://urldefense.com/v3/__https://www.antaranews.com/berita/3674016/bpbd-sebut-39-kk-masih-mengungsi-dari-awan-panas-guguran-karangetang__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssP9unH_C$ <https://urldefense.com/v3/__https://www.antaranews.com/berita/3674016/bpbd-sebut-39-kk-masih-mengungsi-dari-awan-panas-guguran-karangetang__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9JLxD5cE$> Katmai | Alaska | 58.28°N, 154.963°W | Summit elev. 2047 m AVO reported that beginning at about 1430 on 4 August, strong SE winds in the vicinity of Katmai and the Valley of Ten Thousand Smokes dispersed unconsolidated ash up to 1.8 km (6,000 ft) a.s.l. to the NW. The ash was originally deposited during the Novarupta-Katmai eruption in 1912. The Volcano Alert Level remained at Normal (the lowest level on a four-level scale) and the Aviation Color Code remained at Green (the lowest level on a four-color scale). Geologic Summary. Katmai was initially considered to be the source of the Valley of Ten Thousand Smokes ash flow in 1912. However, the 3 x 4 km caldera of 1912 is now known to have formed as a result of the voluminous eruption at nearby Novarupta volcano. Prior to 1912 this compound stratovolcano had four NE-SW-trending summits, most of which were truncated by caldera collapse in that year. Two or more large explosive eruptions took place during the late Pleistocene. Most of the two overlapping pre-1912 Katmai volcanoes are Pleistocene, but Holocene lava flows from a flank vent descend the SE flank of the SW edifice into the Katmai River canyon. The steep walled young caldera has a jagged rim that rises 500-1,000 m above the caldera floor and contains a 250-m-deep, still-rising lake. Lake waters have covered a small post-collapse lava dome (Horseshoe Island) that was seen on the caldera floor at the time of the initial ascent to the caldera rim in 1916. Source: US Geological Survey Alaska Volcano Observatory (AVO) https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssMh2T5bK$ <https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9Dhkngug$> Klyuchevskoy | Central Kamchatka (Russia) | 56.056°N, 160.642°E | Summit elev. 4754 m KVERT reported that the explosive Strombolian eruption at Klyuchevskoy continued during 28 July-3 August and a daily bright thermal anomaly was identified in satellite images. Lava advanced down the Apakhonchich drainage on the SE flank. The Aviation Color Code remained at Yellow (the second level on a four-color scale). Geologic Summary. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssLCZ8FaF$ <https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9M9ln8ec$> Lewotolok | Lembata Island | 8.274°S, 123.508°E | Summit elev. 1431 m PVMBG reported that the eruption at Lewotolok continued during 2-8 August. Daily white steam-and-gas plumes rose as high as 400 m above the summit and drifted W and NW. On 7 August white-and-gray plumes rose as high as 200 m and drifted W and NW. Incandescent material being ejected above the summit was visible in a few of the webcam images posted during the week. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay at least 2 km away from the summit crater. Geologic Summary. The Lewotolok (or Lewotolo) stratovolcano occupies the eastern end of an elongated peninsula extending north into the Flores Sea, connected to Lembata (formerly Lomblen) Island by a narrow isthmus. It is symmetrical when viewed from the north and east. A small cone with a 130-m-wide crater constructed at the SE side of a larger crater forms the volcano's high point. Many lava flows have reached the coastline. Eruptions recorded since 1660 have consisted of explosive activity from the summit crater. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssG2uY_Zh$ <https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9_jClpVo$> Mayon | Luzon (Philippines) | 13.257°N, 123.685°E | Summit elev. 2462 m PHIVOLCS reported that the eruption at Mayon continued during 2-8 August, with slow lava effusion from the summit crater feeding flows on the S, SE, and E flanks. The length of the lava flow in the Mi-Isi (S) drainage remained at 2.8 km, the flow in the Basud (E) drainage remained at 600 m long, and the flow in the Bonga (SE) drainage was 3.4 km long. Collapses at the lava dome and from the lava flows produced incandescent rockfalls and pyroclastic density currents (PDCs, or pyroclastic flows) that descended the Mi-Isi, Bonga, and Basud drainages as far as 4 km. Each day seismic stations recorded 66-225 rockfall events, 1-9 PDC events, and 44-272 low-frequency volcanic earthquakes. Sulfur dioxide emissions were reported on most days, averaging between 969 and 3,465 tonnes per day, with the highest value recorded on 2 August. There was a total of 27 emissions of short, dark ash plumes (called â??ashingâ?? by PHIVOLCS) during 1-4 August. Daily seismicity during 3-8 August included 10-197 tremor events, each with durations of 1-18 minutes. A short-lived (35 seconds) ejection of lava at 0442 on 6 August was accompanied by seismic and infrasound signals. The Alert Level remained at 3 (on a 0-5 scale) and residents were reminded to stay away from the 6-km-radius Permanent Danger Zone (PDZ). PHIVOLCS recommended that civil aviation authorities advise pilots to avoid flying close to the summit. Geologic Summary. Symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the most active volcano of the Philippines. The steep upper slopes are capped by a small summit crater. Recorded eruptions since 1616 CE range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often damaged populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns. Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS) https://urldefense.com/v3/__http://www.phivolcs.dost.gov.ph/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssDmC2PRp$ <https://urldefense.com/v3/__http://www.phivolcs.dost.gov.ph/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw954VtvvI$> Merapi | Central Java | 7.54°S, 110.446°E | Summit elev. 2910 m BPPTKG reported that the eruption at Merapi (on Java) continued during 28 July-3 August and seismicity remained at elevated levels. The SW lava dome produced a total of 194 lava avalanches that descended the SW flank; 12 traveled as far as 1.6 km down the upper part of the Boyong drainage and 182 traveled as far as 2 km down the upper Bebeng drainage. One earthquake signal indicating a pyroclastic flow was recorded by the seismic network. Morphological changes to the SW lava dome were due to continuing collapses of material. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 3-7 km away from the summit based on location. Geologic Summary. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities. Source: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG) https://urldefense.com/v3/__http://www.merapi.bgl.esdm.go.id/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssJ6XnE2x$ <https://urldefense.com/v3/__http://www.merapi.bgl.esdm.go.id/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw90nH-F8Q$> Piton de la Fournaise | Reunion Island (France) | 21.244°S, 55.708°E | Summit elev. 2632 m OVPF reported that the eruption at Piton de la Fournaise was ongoing during 1-8 August, though weather conditions often obscured views. The amplitude of volcanic tremor (an indicator of lava and gas emissions) was relatively stable during the week. The active cone located on the upper part of Grandes Pentes, SE of Enclos Fouqué, at approximately 1,720 m a.s.l. continued to produce minor spattering. Lava flows traveled mainly through tubes but incandescence from breakout flows were occasionally visible in semi-clear views; flows were visibly active 1.2-2 km from the cone during 2-3 August. The Alert Level remained at 2-1, signifying an â??ongoing eruptionâ?? inside the Enclos Fouqué caldera. Geologic Summary. 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. Source: Observatoire Volcanologique du Piton de la Fournaise (OVPF) https://urldefense.com/v3/__http://www.ipgp.fr/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssHHBasgF$ <https://urldefense.com/v3/__http://www.ipgp.fr/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9Y43SjSc$> Sabancaya | Peru | 15.787°S, 71.857°W | Summit elev. 5960 m Instituto GeofÃsico del Perú (IGP) reported that the eruption at Sabancaya continued during 31 July-6 August with a daily average of 19 explosions. Gas-and-ash plumes rose as high as 2.3 km above the summit and drifted in multiple directions. Three thermal anomalies from the lava dome in the summit crater were detected using satellite data. Minor inflation was detected near the Hualca Hualca sector (4 km N). The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 12 km radius. Geologic Summary. Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750. Source: Instituto GeofÃsico del Perú (IGP) https://urldefense.com/v3/__http://www.igp.gob.pe/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssCgX19jd$ <https://urldefense.com/v3/__http://www.igp.gob.pe/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9fklL_Dc$> Semeru | Eastern Java | 8.108°S, 112.922°E | Summit elev. 3657 m PVMBG reported that eruptive activity continued at Semeru during 2-8 August. White-and-gray or gray-to-brown ash plumes that were sometimes dense rose as high as 1 km above the summit and drifted in multiple directions during 2-3, 5, and 7-8 August. The Alert Level remained at 3 (third highest on a scale of 1-4). The public was warned to stay at least 5 km away from the summit in all directions, 13 km from the summit to the SE, 500 m from the banks of the Kobokan drainage as far as 17 km from the summit, and to avoid other drainages including the Bang, Kembar, and Sat, due to lahar, avalanche, and pyroclastic flow hazards. Geologic Summary. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssG2uY_Zh$ <https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9_jClpVo$> Semisopochnoi | Aleutian Islands (USA) | 51.93°N, 179.58°E | Summit elev. 1221 m AVO reported that the last time possible explosions were detected at Semisopochnoiâ??s Mount Young in monitoring data was 25 April and the last ash emission occurred on 5 May. Since then, earthquake activity has been low and steaming from the N crater continued. On 3 August the Volcano Alert Level was lowered to Normal (the lowest level on a four-level scale) and the Aviation Color Code was lowered to Green (the lowest color on a four-color scale). Geologic Summary. Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part. The three-peaked Mount Cerberus (renamed Mount Young in 2023) was constructed within the caldera during the Holocene. Each of the peaks contains a summit crater; lava flows on the N flank appear younger than those on the south side. Other post-caldera volcanoes include the symmetrical Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented eruptions have originated from Young, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone could have been recently active. Source: US Geological Survey Alaska Volcano Observatory (AVO) https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssMh2T5bK$ <https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9Dhkngug$> Sheveluch | Central Kamchatka (Russia) | 56.653°N, 161.36°E | Summit elev. 3283 m KVERT reported that the eruption at Sheveluch continued during 27 July-3 August. Intense fumarolic activity was visible at the active dome, and daily thermal anomalies were identified in satellite images. An ash plume was visible in satellite images drifting 82 km E on 28 July. The Aviation Color Code remained at Orange (the third level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted. Geologic Summary. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka's largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes occur on its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssLCZ8FaF$ <https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9M9ln8ec$> Ubinas | Peru | 16.355°S, 70.903°W | Summit elev. 5672 m Instituto GeofÃsico del Perú (IGP) and Instituto Geológico Minero y Metalúrgico (INGEMMET) reported that the eruption at Ubinas continued during 31 July-7 August. According to IGP a daily average of 115 volcano-tectonic earthquakes indicating rock fracturing and 124 long-period earthquakes signifying the movement of gas and magma 31 July-6 August. In addition, there were four seismic signals associated with explosive events (mainly on 1 and 6 August) and 6-9 daily hours of seismic signals related to ash emissions. At 2110 on 1 August a major explosion produced an ash plume that rose as high as 5.4 km above the crater rim and ejected blocks as far as 3 km from the crater onto the SW, S, and SE flanks. The ash plume drifted 30 km E, SE, S, SW, and W, causing ashfall in the districts of Ubinas (6 km SE) and Chojata (19 km ESE). Ash-and-gas emissions rose as high as 2 km and drifted in multiple directions on the other days of the week. Ashfall was reported within a 15-km radius. An explosion at 0009 on 6 August produced a gas-and-ash plume that rose 1.4 km and drifted SE and E, causing ashfall in Ubinas and Chojata and other areas within a 30-km radius. INGEMMET noted that sulfur dioxide emissions were low on 7 August, averaging 400 tons per day. The Alert Level remained at Orange (the third level on a four-color scale) and the public was warned to stay 4 km away from the crater. Geologic Summary. A small, 1.4-km-wide caldera cuts the top of Ubinas, Perú's most active volcano, giving it a truncated appearance. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3,700 years ago extend 10 km from the volcano. Widespread Plinian pumice-fall deposits include one of Holocene age about 1,000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions. Sources: Instituto GeofÃsico del Perú (IGP) https://urldefense.com/v3/__http://www.igp.gob.pe/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssCgX19jd$ <https://urldefense.com/v3/__http://www.igp.gob.pe/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9fklL_Dc$> ; Instituto Geológico Minero y Metalúrgico (INGEMMET) https://urldefense.com/v3/__http://www.ingemmet.gob.pe/__;!!IKRxdwAv5BmarQ!YOrKurKMNQ0OFr5KromHWVxwEdtrJPFAP7AMr4l1BfAOe-RXTDRIPtrlhurp-CDRAJ-8g8IssHKEW-Ot$ <https://urldefense.com/v3/__http://www.ingemmet.gob.pe/__;!!IKRxdwAv5BmarQ!aDoQ3V6cqoKBS6iujBRRt-uLMP0ULeqtr340I1XGXtvWaWKmARCDrJ8J5VEuOr0FiKw9sIzdqOc$> 1-1-1-1-1-1-1-1-1-1-1-1-1-1 ============================================================== Volcano Listserv is a collaborative venture among Arizona State University (ASU), Portland State University (PSU), the Global Volcanism Program (GVP) of the Smithsonian Institution's National Museum of Natural History, and the International Association for Volcanology and Chemistry of the Earth's Interior (IAVCEI). 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