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 23-29 April 2025 Sally Sennert - Weekly Report Editor (kuhns@xxxxxx) URL: https://volcano.si.edu/reports_weekly.cfm <https://urldefense.com/v3/__https://volcano.si.edu/reports_weekly.cfm__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHxyEyLhQg$> New Activity/Unrest: Bezymianny, Russia | Bulusan, Philippines | Home Reef, Tonga | Klyuchevskoy, Russia | Poas, Costa Rica | Ulawun, Papua New Guinea Ongoing Activity: Ahyi, United States | Aira, Japan | Ambae, Vanuatu | Ambrym, Vanuatu | Atka Volcanic Complex, United States | Dukono, Indonesia | Etna, Italy | Fuego, Guatemala | Gaua, Vanuatu | Great Sitkin, United States | Ibu, Indonesia | Kanlaon, Philippines | Lewotobi, Indonesia | Lewotolok, Indonesia | Lopevi, Vanuatu | Marapi, Indonesia | Nevado del Ruiz, Colombia | Sangay, Ecuador | Semeru, Indonesia | Sheveluch, Russia | Yasur, Vanuatu 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 Bezymianny | Russia | 55.972°N, 160.595°E | Summit elev. 2882 m The Kamchatkan Volcanic Eruption Response Team (KVERT) reported increased activity at Bezymianny and tall ash plumes on 23 April. A large thermal anomaly was visible in satellite images for several days during 17-24 April. Incandescent avalanches continued to descend the flanks. Ash clouds from the avalanches rose 4 km (13,100 ft) a.s.l. and drifted 36 km W on 20 April, rose 2.5-3 km (8,200-9,800 ft) a.s.l. and drifted 45 km WSW on 21 April, and rose up to 4 km and drifted 35 km W on 22 April. At about 0145 on 23 April eruptive activity produced a dense ash plume that rose to 9 km (29,500 ft) a.s.l. An ash cloud, 10 x 10 km in dimension, was visible in satellite images drifting NNW. At 0351 the Aviation Color Code was raised to Red (the highest level on a four-color scale). Hot avalanches continued to descend the flanks and gas-and-steam emissions were visible. Ash was not visible in subsequent images; at 0600 on 23 April the Aviation Color Code was lowered to Orange. A stronger explosive eruption began later that day at 2310 and produced an ash plume that rose 11 km (36,100 ft) a.s.l. Satellite images showed a 36 x 26 km ash cloud drifting NNE. At 2348 the Aviation Color Code was raised to Red. The period of increased activity ended at around 0300 on 24 April. Ashfall was reported in the villages of Atlasovo, Lazo, and Milkovo. According to Kamchatka Volcanological Station (Volkstat) pyroclastic flows descended the flanks. KVERT noted that at 0510 a satellite images showed an ash cloud at altitudes of 7-7.5 km (23,000-24,600 ft) a.s.l. that was covered 110 x 175 km and had reached about 320 km SW of the volcano. At 0600 the Aviation Color Code was lowered to Orange. Dates are reported in UTC; specific events are in local time where noted. Geologic Summary. The modern Bezymianny, much smaller than its massive neighbors Kamen and Kliuchevskoi on the Kamchatka Peninsula, was formed about 4,700 years ago over a late-Pleistocene lava-dome complex and an edifice built about 11,000-7,000 years ago. Three periods of intensified activity have occurred during the past 3,000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large open crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater. Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php <https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzAFv2McA$> ; Kamchatka Volcanological Station http://volkstat.ru/ <https://urldefense.com/v3/__http://volkstat.ru/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHxAs_m3zg$> Bulusan | Philippines | 12.769°N, 124.056°E | Summit elev. 1535 m The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported increased activity at Bulusan on 27 April and a phreatic eruption on 28 April. Seismicity had increased on 12 April and continued to be elevated, prompting a special report to be issued on 21 April. On 27 April there were 53 volcanic earthquakes detected by the seismic network. Detection of strong tremor and infrasound signals started at 0354 on 28 April and lasted about 29 minutes. Local government officials reported rumbling sounds towards the end of that period in the barangays of Cogon, Bacolod, and Patag (Irosin) and in Añog and Rangas (Juban). Monitoring data indicated a phreatic eruption started about 15 minutes later, which continued during 0436-0500. A voluminous ash-and-gas plume rose 4.5 km above the crater rim and drifted generally W and SW. A small-volume pyroclastic density current descended the SW flank as far as 3 km and produced an ash cloud based on a Disaster Response Operations Monitoring and Information Center (DROMIC) report. Ashfall up to 1 mm thick was reported in Cogon, Tinampo, Omagom, Gulang-Gulang, and Bolos (Irosin), in Puting Sapa, Buraburan, and Guruyan (Juban), and in Tula-tula Sur, Caditaan, Cadandanan, Siuton, Salvacion, and Busay (Magallanes). A sulfur odor was reported in Cogon. A total of 86 volcanic earthquakes were recorded through 2000 and continuous gas emissions at the summit continued at least through 2030. The Alert Level was raised to 1 (the second lowest level on a scale of 0-5). The public was reminded not to enter the 4-km-radius Permanent Danger Zone (PDZ) and to be vigilant within the 2-km Extended Danger Zone (EDZ) on the SE flank. A second phreatic eruption began at 1943 on 29 April and lasted about 77 minutes based on seismic and infrasound data. Weather clouds obscured views of the ash-and-gas cloud, though it likely drifted SW based on the locations of 19 communities affected by ashfall. Ashfall from trace amounts to depths around 1 cm was reported in Cogon, Tinampo, Monbon, Bolos, Gulang-Gulang, Gabao, Bulawan, and Macawayan (Irosin), in Zone 7, Somagongsong, Beguin, Aquino, San Francisco, Calomagon, Inararan, Cadandanan, Dolos, and Polot (Bulan), and in Guruyan (Juban). Rumbling was heard in Cogon and Bagsangan (Irosin). According to the Office of Civil Defense, at around 2100 there were 59 families in Cogon that evacuated to two shelters. Supplies, including hygiene kits and N95 masks, were delivered to residents and local governments were receiving support to clean up the ashfall. PHIVOLCS noted that by 2000 the seismic network had recorded a total of 54 volcanic earthquakes that day. Prior to the eruption, sulfur dioxide emissions averaged 548 tonnes per day (t/d), higher than the baseline of less than 200 t/d. The DROMIC report issued at 1800 on 30 April stated that 211 people (65 families) were in two shelters. Additionally, two people were staying with relatives or friends. Geologic Summary. Luzon's southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. It lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded since the mid-19th century. Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS) http://www.phivolcs.dost.gov.ph/ <https://urldefense.com/v3/__http://www.phivolcs.dost.gov.ph/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHyvkWP4kg$> ; Office of Civil Defense https://www.ocd.gov.ph/index.php <https://urldefense.com/v3/__https://www.ocd.gov.ph/index.php__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzr5niPUQ$> ; Disaster Response Operations Monitoring and Information Center (DROMIC) https://dromic.dswd.gov.ph/ <https://urldefense.com/v3/__https://dromic.dswd.gov.ph/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHyRi2wt3A$> Home Reef | Tonga | 18.992°S, 174.775°W | Summit elev. -10 m The Tonga Geological Services reported continuing activity at Home Reef. Satellite imagery from 4 April captured a series of small low-level ash plumes generated by explosions. Surface changes at the vent, including new tephra deposits and lava textures, were identified in a 5 April satellite image. A satellite image from 11 April indicated that the vent had the same dimensions as previously reported, 125 m N-S and 110 m W-E. The dome in the vent had grown, mainly to the SW, and spalled or ejected material that rolled down to the shoreline. In both 11 and 26 April images steam plumes rose from the vent and water around the island was discolored. Moderate thermal anomalies were detected by the Middle InfraRed Observation of Volcanic Activity (MIROVA) system during 8-28 April. A sulfur dioxide emission was identified in a 22 April satellite image. Ash emissions were visible in satellite data at around 1400 on 26 April, prompting Tonga Geological Services to raise the Aviation Color Code to Orange (the second highest level on a four-level scale) that same day. According to the Wellington VAAC intermittent, low-level ash plumes were visible in satellite images during 26-27 and 29 April rising 0.9-1.2 km (3,000-4,000 ft) a.s.l. and drifting W and NW. The Maritime Alert Level remained at Orange (the third level on a four-level scale), and mariners were advised to stay at least 2 nautical miles (3.7 km) away from the island. The Alert Level for residents of Vavaâ??u and Haâ??apai remained at Green (the first level on a four-level scale). Geologic Summary. 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. Sources: Tonga Geological Services, Government of Tonga https://www.facebook.com/tongageologicalservice <https://urldefense.com/v3/__https://www.facebook.com/tongageologicalservice__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHym0l0c1w$> ; Wellington Volcanic Ash Advisory Center (VAAC) http://vaac.metservice.com/ <https://urldefense.com/v3/__http://vaac.metservice.com/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHyixgEpLA$> Klyuchevskoy | Russia | 56.056°N, 160.642°E | Summit elev. 4754 m The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that a thermal anomaly at Klyuchevskoy was identified in satellite images during 18-22 April. A new Strombolian eruption began on 20 April. Weather clouds obscured views during 23-25 April. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted. Geologic Summary. Klyuchevskoy is the highest and most active volcano on the Kamchatka Peninsula. Since its origin about 6,000 years ago, this symmetrical, basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during approximately the past 3,000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 and 3,600 m elevation. Eruptions recorded since the late 17th century have resulted in frequent changes to the morphology of the 700-m-wide summit crater. These eruptions over the past 400 years 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) http://www.kscnet.ru/ivs/kvert/index_eng.php <https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzAFv2McA$> Poas | Costa Rica | 10.2°N, 84.233°W | Summit elev. 2697 m The Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) reported frequent explosions and ash-and-gas plumes at Poás during 23-29 April. Seismicity, specifically background tremor, had decreased on 17 April and remained at stable levels with increases related to eruptive events during 21-23 April. The number of long-period events increased, and occasional periods of harmonic tremor began to be recorded on 21 April. Analysis of ash showed an increased proportion of juvenile material. Inflation continued to be detected. Eruptive events at 0529 and at 0744 on 23 April generated ash-and-gas plumes that rose at least 3 km and 1 km above the crater rim, respectively. Each event lasted about five minutes. The plumes drifted SW and NE, causing ashfall in areas downwind including Belén, Alajuela (20 km S), Palmares (27 km SW), San Rafael, and San Pedro de Poás (14 km S). During 23-24 April significant and almost continuous gas-and-steam plumes with some ash rose from the crater and drifted mainly SW. Incandescence at the vents was visible at night. A small, one-minute-long eruptive event at 0107 on 24 April produced a plume that rose 1 km above the crater rim and drifted NE. Ballistics around 250 degrees Celsius were ejected to the E. A larger event was recorded at around 2030. A period of moderate-to-intense activity began at 2312 on 25 April and intensified at 2322; an ash-and-gas plume rose 1 km above the crater rim and drifted W. Incandescent material, about 300 degrees Celsius, was ejected from the vents onto the crater floor and cooled quickly. Activity was again intense during 0230-0420 on 26 April based on seismic data. During 0500-0600 hot blocks were observed being ejected from Boca C. Ash-and-gas plumes rose a few hundred meters to 1 km above the crater rim and drifted in variable directions. Almost continuous gas-and-steam emissions from both Boca A and Boca C during 27-28 April rose as high as 1 km above the crater rim. The emissions were punctuated by pulses of ash that rose 500 m and drifted in variable directions on 27 April and small eruptive pulses on 28 April that ejected incandescent material from the vents. Sulfur dioxide emissions were 2,000-10,000 tons per day. Overnight during 28-29 April almost continuous emissions rose 300 m from both vents and drifted SW; the emissions contained a smaller amount of ash than during recent days. The volcanoâ??s Alert Level remained at 3 (the second highest level on a four-level scale) and the Aviation Color Code remained at Orange (the second highest color on a four-color scale). 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) http://www.ovsicori.una.ac.cr/ <https://urldefense.com/v3/__http://www.ovsicori.una.ac.cr/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzk_INGhw$> Ulawun | Papua New Guinea | 5.05°S, 151.33°E | Summit elev. 2334 m The Rabaul Volcano Observatory (RVO) reported that activity at Ulawun was low during 7-25 April. Summit emissions were white and had variable densities. On some days there were no emissions. Brief low rumbling sounds were heard during 15-16 and 19 April. In general seismicity was low, though slightly higher that background (RSAM values of 100-200). Data from the seismic station (UULA), 2.8 km from the summit on the lower WSW flank, was characterized by both low- and high-frequency volcanic earthquakes, with low-frequency earthquakes being the dominant signal. Brief surges in seismicity activity occasionally occurred and consisted of changes from discrete low- and high-frequency earthquakes to low-level, continuous volcanic tremors that lasted between several minutes and less than few hours. The Alert Level was at Stage 1 (the lowest level of a four-stage scale). 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) Ongoing Activity Ahyi | United States | 20.42°N, 145.03°E | Summit elev. -75 m Unrest at Ahyi Seamount may have continued during 18-25 April. Signals coming from the direction of Ahyi were identified in data from underwater pressure sensors near Wake Island (about 2,270 km E of Ahyi) on 18 and 20 April. No signs of activity at the oceanâ??s surface were identified in satellite images. The Aviation Color Code remained at Yellow (the second lowest level on a four-color scale) and the Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale). Geologic Summary. 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. Source: US Geological Survey https://www.usgs.gov/ <https://urldefense.com/v3/__https://www.usgs.gov/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHw_GFeS0Q$> Aira | Japan | 31.5772°N, 130.6589°E | Summit elev. 1117 m The Japan Meteorological Agency (JMA) reported ongoing eruptive activity at Minamidake Crater (Aira Calderaâ??s Sakurajima volcano) during 21-28 April. Nightly crater incandescence was visible at Minamidake Crater in webcam images, and very small eruptive events were recorded during 25-28 April. An eruptive event at 1803 on 21 April generated an ash plume that rose 1.6 km above the crater rim. The Alert Level remained at 3 (on a 5-level scale), and the public was warned to stay 2 km away from both the Minimadake and Showa craters. Geologic Summary. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim and built an island that was joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4,850 years ago, after which eruptions took place at Minamidake. Frequent eruptions since the 8th century have deposited ash on the city of Kagoshima, located across Kagoshima Bay only 8 km from the summit. The largest recorded eruption took place during 1471-76. Source: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/ <https://urldefense.com/v3/__http://www.jma.go.jp/jma/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHxqaFBXIQ$> Ambae | Vanuatu | 15.389°S, 167.835°E | Summit elev. 1496 m On 24 April the Vanuatu Meteorology and Geohazards Department (VMGD) reported that steam and/or gas emissions from the active vents at Ambae were visible in webcam images during 1-4, 7, 11, and 19 April. Sulfur dioxide emissions were detected in satellite data during 1-8, 10, and 21 April. Seismic data also confirmed ongoing unrest. The Alert Level remained at 2 (on a scale of 0-5), and the public was warned to stay outside of the Danger Zone, defined as a 2-km radius around the active vents in Lake Voui, and away from drainages during heavy rains. Geologic Summary. 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. Source: Vanuatu Meteorology and Geohazards Department (VMGD) http://www.geohazards.gov.vu/ <https://urldefense.com/v3/__http://www.geohazards.gov.vu/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHw9rYAeRw$> Ambrym | Vanuatu | 16.25°S, 168.12°E | Summit elev. 1334 m On 24 April the Vanuatu Meteorology and Geohazards Department (VMGD) reported ongoing fumarolic activity at Ambrym from both Benbow and Marum craters based on webcam images. Seismic data confirmed ongoing unrest. A low-level thermal anomaly was identified in satellite data on 9 April indicative of increased surface temperatures. The Alert Level remained at 2 (on a scale of 0-5). VMGD warned the public to stay outside of Permanent Danger Zone A, defined as a 1-km radius around Benbow Crater and a 2-km radius around Marum Crater, and to stay 500 m away from the ground cracks created by the December 2018 eruption. Geologic Summary. Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides Arc. A thick, almost exclusively pyroclastic sequence, initially dacitic then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major Plinian eruption with dacitic pyroclastic flows about 1,900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations. Source: Vanuatu Meteorology and Geohazards Department (VMGD) http://www.geohazards.gov.vu/ <https://urldefense.com/v3/__http://www.geohazards.gov.vu/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHw9rYAeRw$> Atka Volcanic Complex | United States | 52.331°N, 174.139°W | Summit elev. 1518 m A small, short-lived explosion from the summit of Korovin, one of the volcanoes at the Atka volcanic complex, was detected at 1034 on 25 April, prompting the Alaska Volcano Observatory (AVO) to raise the Volcano Alert Level to Advisory (the second lowest level on a four-level scale) and the Aviation Color Code to Yellow (the second lowest color on a four-color scale). High weather clouds obscured views at the time of the explosion, preventing confirmation of the event in satellite observations. Similar past events at the Atka complex did not result in ash emissions of noticeable ashfall. No further activity was detected during 26-29 April; seismicity was low and weather clouds obscured webcam and satellite views. Geologic Summary. The Atka Volcanic Complex consists of a central shield and Pleistocene caldera and four notable volcanic cones. A major explosive dacitic eruption accompanied formation of the caldera about 500,000 to 300,000 years ago; approximately half of the caldera rime remains, open towards the NW. The Sarichef cone, ~5 km ESE of the caldera rim, retains a symmetrical profile, unlike most other heavily eroded features outside the caldera to the S and W. The Kliuchef stratovolcano grew within the caldera and exhibits five eruptive vents striking NE, including two at the summit, that have been active in the Holocene. A 700-m-diameter crater 1 km NE of the summit may have been the source vent for a large 1812 CE eruption. Hot springs and fumaroles are located on the flanks of Kliuchef and in a glacial valley to the SW. The most frequently active volcano of the complex is Korovin, at the NE tip of Atka Island about 5 km N of Kliuchef. An 800-m-diameter crater on the SE side of the summit contains a deep circular pit that sometimes contains a crater lake thought to be the source of phreatic ash explosions. The smaller Konia cone, slightly offset to the E, lies between Kliuchef and Korovin. Most of the lava flows in the complex are basaltic, though some dacitic flows are also present. Source: US Geological Survey Alaska Volcano Observatory (AVO) https://avo.alaska.edu/ <https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHwu9ySGwQ$> Dukono | Indonesia | 1.6992°N, 127.8783°E | Summit elev. 1273 m The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Dukono continued during 23-29 April. White-and-gray ash plumes rose 600-1,100 m above the crater rim and drifted E on most days; no plumes were visible on 24 April. The Alert Level remained at Level 2 (on a scale of 1-4) and the public was warned to stay 4 km away from the Malupang Warirang Crater. Geologic Summary. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, have occurred since 1933. During a major eruption in 1550 CE, a lava flow filled in the strait between Halmahera and the N-flank Gunung Mamuya cone. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ <https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzUkZBAgw$> Etna | Italy | 37.748°N, 14.999°E | Summit elev. 3357 m The Sezione di Catania - Osservatorio Etneo (INGV) reported continuing activity at Etna during 21-27 April, characterized by Strombolian activity with lava overflows at SE Crater and gas emissions at Bocca Nuova Crater, NE Crater, and Voragine. Strombolian activity at SE Crater began at 2000 on 22 April that involved at least three vents and was followed by lava overflowing onto the SE flank. At 2145 a second lava flow descended the S flank. The activity ceased at around 0300 on 23 April. Satellite data from 27 April was used to map the flows. The SE-flank flow covered an area of about 34,000 square meters and was about 700 m long, reaching 2,940 m elevation. The S-flank flow covered about 6,000 square meters and was about 200 m long, reaching 3,170 m elevation. Geologic Summary. Mount Etna, towering above Catania on the island of Sicily, has one of the world's longest documented records of volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank. Source: Sezione di Catania - Osservatorio Etneo (INGV) http://www.ct.ingv.it/ <https://urldefense.com/v3/__http://www.ct.ingv.it/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHwngga_6w$> Fuego | Guatemala | 14.4748°N, 90.8806°W | Summit elev. 3799 m The Instituto Nacional de SismologÃa, VulcanologÃa, MeteorologÃa e HidrologÃa (INSIVUMEH) reported a few explosions and the ejection of incandescent material at Fuego during 22-29 April. White steam-and-gas plumes rose as high as 100 m above the summit during the week. At night a few incandescent blocks occasionally collapsed and formed minor avalanches. During 23-24 April there were 1-3 weak explosions reported. Additional weak explosions during 27-28 April took place 6-8 times per hour, producing faint rumbling sounds and ash plumes that rose just over 800 m above the summit and drifted up to 15 km SW. Incandescent material was observed at night being ejected 100-200 m above the summit. Avalanches of material descended the flanks, reaching vegetated areas. Four weak explosions accompanied by weak rumbling was recorded during 28-29 April. Geologic Summary. Volcán Fuego, one of Central America's most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows. Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/ <https://urldefense.com/v3/__http://www.insivumeh.gob.gt/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzOQn79OQ$> Gaua | Vanuatu | 14.281°S, 167.514°E | Summit elev. 729 m On 24 April the Vanuatu Meteorology and Geohazards (VMGD) reported that unrest continued at Gaua. Sulfur dioxide emissions were identified in satellite images during 2-3 and 6-8 April, and steam and/or gas emissions from the vent were visible in images on 17 April. A low-level thermal anomaly was identified in satellite images on 4, 11, and 19 April, indicative of increased surface temperatures. The Alert Level remained at 2 (on a scale of 0-5) and the public was warned to stay away from the main cone. Geologic Summary. The roughly 20-km-diameter Gaua Island, also known as Santa Maria, consists of a basaltic-to-andesitic stratovolcano with an 6 x 9 km summit caldera. Small vents near the caldera rim fed Pleistocene lava flows that reached the coast on several sides of the island; littoral cones were formed where these lava flows reached the ocean. Quiet collapse that formed the roughly 700-m-deep caldera was followed by extensive ash eruptions. The active Mount Garet (or Garat) cone in the SW part of the caldera has three pit craters across the summit area. Construction of Garet and other small cinder cones has left a crescent-shaped lake. The onset of eruptive activity from a vent high on the SE flank in 1962 ended a long period of dormancy. Source: Vanuatu Meteorology and Geohazards Department (VMGD) http://www.geohazards.gov.vu/ <https://urldefense.com/v3/__http://www.geohazards.gov.vu/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHw9rYAeRw$> Great Sitkin | United States | 52.076°N, 176.13°W | Summit elev. 1740 m The Alaska Volcano Observatory (AVO) reported that slow lava effusion continued to feed a thick flow in Great Sitkinâ??s summit crater during 23-29 April. Small daily earthquakes were detected by the seismic network. Weather clouds often obscured satellite and webcam views of the volcano. The Volcano Alert Level remained at Watch (the third level on a four-level scale) and the Aviation Color Code remained at Orange (the third color on a four-color scale). Geologic Summary. The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an older edifice and produced a submarine debris avalanche. Deposits from this and an even older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Eruptions have been recorded since the late-19th century. Source: US Geological Survey Alaska Volcano Observatory (AVO) https://avo.alaska.edu/ <https://urldefense.com/v3/__https://avo.alaska.edu/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHwu9ySGwQ$> Ibu | Indonesia | 1.488°N, 127.63°E | Summit elev. 1325 m The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that the eruption at Ibu continued during 23-29 April. Dense gray ash plumes rose 400-700 m above the summit and drifted E and NE on most days. Eruptive events were recorded by the seismicity network on 24 and 26 April, though weather conditions prevented visual observations. Nighttime crater incandescence was visible in some webcam images. The Alert Level remained at 3 (the second highest level on a four-level scale) and the public was advised to stay 4 km away from the active crater and 5 km away from the N crater wall opening. Geologic Summary. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and a smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ <https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzUkZBAgw$> Kanlaon | Philippines | 10.4096°N, 123.13°E | Summit elev. 2422 m The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported continuing eruptive activity at Kanlaon during 22-28 April. The seismic network recorded 7-36 daily volcanic earthquakes and one period of volcanic tremor (10 minutes long) on 28 April. Daily sulfur dioxide emissions ranged from 1,693 to 2,736 tonnes per day. Gas-and-steam emissions generally rose 150-400 m above the crater rim and drifted WNW, W, and SW. There was one ash emission on 28 April that lasted 10 minutes long based on the seismic signal. The ash-and-gas plume rose 200 m and drifted SW. The Alert Level remained at 3 (on a scale of 0-5); the public was warned to stay 6 km away from the summit and pilots were warned not to fly close to the volcano. Geologic Summary. Kanlaon volcano (also spelled Canlaon) forms the highest point on the Philippine island of Negros. The massive andesitic stratovolcano is covered with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The largest debris avalanche known in the Philippines traveled 33 km SW from Kanlaon. The summit contains a 2-km-wide, elongated northern caldera with a crater lake and a smaller but higher active vent, Lugud crater, to the south. Eruptions recorded since 1866 have typically consisted of phreatic explosions of small-to-moderate size that produce minor local ashfall. Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS) http://www.phivolcs.dost.gov.ph/ <https://urldefense.com/v3/__http://www.phivolcs.dost.gov.ph/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHyvkWP4kg$> Lewotobi | Indonesia | 8.542°S, 122.775°E | Summit elev. 1703 m The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity at Lewotobi Laki-laki continued during 23-29 April. Gray or gray-to-black ash plumes rose 500 m above the summit, to as high as 4 km above the summit, and drifted multiple directions during 24-28 April. Though the view was often obscured due to weather or volcanic plumes, incandescence around the upper flanks was visible in a webcam image at 0215 on 25 April. At 2115 on 27 April an eruptive event generated a dense gray as plume that rose 4 km above the summit and drifted N and NE. A corresponding webcam images showed trails of incandescent material on the upper flanks. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 6 km away from the center of Laki-laki. Geologic Summary. The Lewotobi edifice in eastern Flores Island is composed of the two adjacent Lewotobi Laki-laki and Lewotobi Perempuan stratovolcanoes (the "husband and wife"). Their summits are less than 2 km apart along a NW-SE line. The conical Laki-laki to the NW has been frequently active during the 19th and 20th centuries, while the taller and broader Perempuan has had observed eruptions in 1921 and 1935. Small lava domes have grown during the 20th century in both of the summit craters, which are open to the north. A prominent cone, Iliwokar, occurs on the E flank of Perampuan. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ <https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzUkZBAgw$> Lewotolok | Indonesia | 8.274°S, 123.508°E | Summit elev. 1431 m The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that an eruption at Lewotolok was ongoing during 23-29 April. White steam-and-gas plumes rose as high as 100 m above the summit of the cone and drifted E and SE. Nighttime webcam images showed incandescent material being ejected above the summit. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 2 km away from the vent and 2.5 km away on the S, SE, and W flanks. Geologic Summary. The Lewotolok (or Lewotolo) stratovolcano occupies the eastern end of an elongated peninsula extending north into the Flores Sea, connected to Lembata (formerly Lomblen) Island by a narrow isthmus. It is symmetrical when viewed from the north and east. A small cone with a 130-m-wide crater constructed at the SE side of a larger crater forms the volcano's high point. Many lava flows have reached the coastline. Eruptions recorded since 1660 have consisted of explosive activity from the summit crater. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ <https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzUkZBAgw$> Lopevi | Vanuatu | 16.507°S, 168.346°E | Summit elev. 1413 m On 24 April the Vanuatu Meteorology and Geohazards Department (VMGD) reported that during the previous month seismic data confirmed continuing unrest at Lopevi. Small fumarolic steam plumes were continuously emitted at the summit crater based on webcam images from 1, 19, and 20 April. Low-level thermal anomalies were identified in satellite images on 6 and 20 April, indicative of increased surface temperatures. The Alert Level remained at 2 (on a scale of 0-4). Geologic Summary. The small 7-km-wide conical island of Lopevi, known locally as Vanei Vollohulu, is one of Vanuatu's most active volcanoes. A small summit crater containing a cinder cone is breached to the NW and tops an older cone that is rimmed by the remnant of a larger crater. The basaltic-to-andesitic volcano has been active during historical time at both summit and flank vents, primarily along a NW-SE-trending fissure that cuts across the island, producing moderate explosive eruptions and lava flows that reached the coast. Historical eruptions at the 1413-m-high volcano date back to the mid-19th century. The island was evacuated following major eruptions in 1939 and 1960. The latter eruption, from a NW-flank fissure vent, produced a pyroclastic flow that swept to the sea and a lava flow that formed a new peninsula on the western coast. Source: Vanuatu Meteorology and Geohazards Department (VMGD) http://www.geohazards.gov.vu/ <https://urldefense.com/v3/__http://www.geohazards.gov.vu/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHw9rYAeRw$> Marapi | Indonesia | 0.38°S, 100.474°E | Summit elev. 2885 m The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that eruptive activity from Verbeek Crater at Marapi (on Sumatra) continued during 23-29 April. Dense gray ash plumes rose 350-1,000 m above the summit and drifted N during 25 and 27-28 April. Two more eruptive events were recorded on 28 April but not visually observed due to weather conditions. The Alert Level remained at 2 (on a scale of 1-4) and the public was warned to stay 3 km away from the active crater. Geologic Summary. Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2,000 m above the Bukittinggi Plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ <https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzUkZBAgw$> Nevado del Ruiz | Colombia | 4.892°N, 75.324°W | Summit elev. 5279 m The Servicio Geológico Colombianoâ??s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 22-28 April. Seismic data indicated that events associated with fluid movement increased in both number and intensity compared to the previous week. Some of the seismic events were associated with pulsating ash emissions; webcam images confirmed these ash emissions, including some with higher-temperature ejecta. Gas-and-steam plumes rose as high as 1.8 km above the summit and drifted NNE, N, and NNW; the highest plume, a gas-and-ash emission that rose as high as 2 km above the summit, occurred at 2251 on 26 April. Seismicity associated with rock fracturing stayed at similar levels compared to the previous week. The earthquakes were mainly located below Arenas Crater and the NE, E, S, and SW flanks within 5 km at depths of 1-8 km. Low-energy thermal anomalies on the crater floor were identified in satellite data, though weather clouds often obscured views. Sulfur dioxide emissions detected in satellite data continued to be significant. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater, not to spend long periods of time on the Murillo-Cerro Gualà Road, and to avoid drainages in the high-threat zones. Geologic Summary. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption. Source: Servicio Geológico Colombiano (SGC) https://www2.sgc.gov.co/volcanes/index.html <https://urldefense.com/v3/__https://www2.sgc.gov.co/volcanes/index.html__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHxeQQCiXA$> Sangay | Ecuador | 2.005°S, 78.341°W | Summit elev. 5286 m The Instituto GeofÃsico-Escuela Politécnica Nacional (IG-EPN) reported high levels of eruptive activity at Sangay during 21-29 April. The seismic network recorded 124-258 daily explosions. Several ash-and-gas plumes were observed rising more than 4 km above the summit during 22-24 April, as high as 3 km above the summit during 24-25 April, and up to 1.7 km above the summit during the rest of the week; weather clouds sometimes obscured views during the last half of the week and almost completely obscured views during 21-22 and 26-27 April. The ash-and-gas plumes drifted mainly NW, W, and SW. Minor ashfall was reported in the province of Chimborazo during 22-25 April, and especially in the parish of Cebadas and in Utucun, Rayoloma, and Pueblo Cebadeño during 23-24 April. Nighttime crater incandescence was visible. On most nights several incandescent avalanches were observed descending the SE flank as far as 1 km below the summit. Incandescent material was ejected 100 m above the summit during 23-24 April. SecretarÃa de Gestión de Riesgos (SGR) maintained the Alert Level at Yellow (the second highest level on a four-color scale). Geologic Summary. The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within the open calderas of two previous edifices which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been eroded by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an eruption was in 1628. Almost continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex. Sources: Instituto GeofÃsico-Escuela Politécnica Nacional (IG-EPN) http://www.igepn.edu.ec/ <https://urldefense.com/v3/__http://www.igepn.edu.ec/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHxpMTNc8Q$> ; SecretarÃa de Gestión de Riesgos (SGR) http://www.gestionderiesgos.gob.ec/ <https://urldefense.com/v3/__http://www.gestionderiesgos.gob.ec/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHxthaaTUA$> Semeru | Indonesia | 8.108°S, 112.922°E | Summit elev. 3657 m The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported that activity continued at Semeru during 23-29 April, with multiple daily eruptive events recorded by the seismic network. White-and-gray ash plumes rose 300-900 m above the summit and drifted in multiple directions. Incandescence at the summit was visible in 24 and 26 April webcam images. The Alert Level remained at 2 (the second lowest level on a scale of 1-4). The public was warned to stay at least 5 km away from the summit in all directions, 13 km from the summit to the SE, 500 m from the banks of the Kobokan drainage as far as 17 km from the summit, and to avoid other drainages including the Bang, Kembar, and Sat, due to lahar, avalanche, and pyroclastic flow hazards. Geologic Summary. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ <https://urldefense.com/v3/__http://vsi.esdm.go.id/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzUkZBAgw$> Sheveluch | Russia | 56.653°N, 161.36°E | Summit elev. 3283 m The Kamchatkan Volcanic Eruption Response Team (KVERT) reported that lava extrusion may have continued at Sheveluchâ??s â??300 years of RASâ?? dome on the SW flank of Old Sheveluch and at the Young Sheveluch dome during 17-24 April. Thermal anomalies over the domes were identified in satellite images during 20-21 April; weather clouds obscured views on the other days. The Aviation Color Code remained at Orange (the second highest 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) http://www.kscnet.ru/ivs/kvert/index_eng.php <https://urldefense.com/v3/__http://www.kscnet.ru/ivs/kvert/index_eng.php__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHzAFv2McA$> Yasur | Vanuatu | 19.532°S, 169.447°E | Summit elev. 361 m On 24 April the Vanuatu Meteorology and Geohazards Department (VMGD) reported that activity at Yasur continued at a level of â??major unrest,â?? as defined by the Alert Level 2 status (on a scale of 0-5). Satellite and webcam images indicated that explosions continued, producing emissions of gas, steam, and/or ash. Sulfur dioxide gas emissions were identified in satellite images during 1-8, 11-12, 15, 17-19, and 21-22 April, and low-level thermal anomalies were identified during 1, 3, 5, 7, 12, 16, 18-19, and 21 April. Seismic data confirmed continuing volcanic activity with explosions that were occasionally strong. The report warned that ejected material from explosions could fall in and around the crater. The public was reminded to not enter the restricted area within 600 m around the boundaries of the Permanent Exclusion Zone, defined by Danger Zone A on the hazard map. Geologic Summary. Yasur has exhibited essentially continuous Strombolian and Vulcanian activity at least since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island in Vanuatu, this pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide open feature associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century. Source: Vanuatu Meteorology and Geohazards Department (VMGD) http://www.geohazards.gov.vu/ <https://urldefense.com/v3/__http://www.geohazards.gov.vu/__;!!IKRxdwAv5BmarQ!dxaSCQ2EjSGUv9pkcqq0lLdOsrN8ZUo6P63uckwWqmbuj0uLfq2wOiTJNuSahjF_2DlxEOtFF53cNXAfqHw9rYAeRw$> 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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