6-6-6-6-6-6-6-6-6-6-6-6-6-6-6-6-6-6-6-6 From: "Kuhn, Sally" <KUHNS@xxxxxx> 6-6-6-6-6-6-6-6-6-6-6-6-6-6-6-6-6-6-6-6 Sally Kuhn Sennert - Weekly Report Editor (kuhns@xxxxxx) URL: https://volcano.si.edu/reports_weekly.cfm New Activity/Unrest: Klyuchevskoy, Central Kamchatka (Russia) | Tengger Caldera, Eastern Java (Indonesia) | Villarrica, Chile Ongoing Activity: Agung, Bali (Indonesia) | Aira, Kyushu (Japan) | Copahue, Central Chile-Argentina border | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Ibu, Halmahera (Indonesia) | Kadovar, Papua New Guinea | Karangetang, Siau Island (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Kerinci, Indonesia | Krakatau, Indonesia | Merapi, Central Java (Indonesia) | Nevados de Chillan, Chile | Rincon de la Vieja, Costa Rica | Sheveluch, Central Kamchatka (Russia) | Turrialba, Costa Rica 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 Klyuchevskoy | Central Kamchatka (Russia) | 56.056°N, 160.642°E | Summit elev. 4754 m KVERT reported that at 1030 on 9 April a small ash plume from Klyuchevskoy was identified in satellite images rising to altitudes of 3-3.5 km (10,000-11,500 ft) a.s.l. and drifting 20 km SW. The Aviation Color Code was raised to Yellow (the second lowest 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) http://www.kscnet.ru/ivs/kvert/index_eng.php Tengger Caldera | Eastern Java (Indonesia) | 7.942°S, 112.95°E | Summit elev. 2329 m PVMBG reported that at 0718 on 6 April ash plumes from Tengger Calderaâ??s Bromo cone rose 900 m above the crater rim and drifted SE. The Darwin VAAC reported that during 7-8 April ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted N and E, based on webcam images, satellite data, and ground-based observations. The Alert Level remained at 2 (on a scale of 1-4), and visitors were warned to stay outside of a 1-km radius of the crater. Geologic Summary. The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most active and most frequently visited volcanoes. Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/; Darwin Volcanic Ash Advisory Centre (VAAC) http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml Villarrica | Chile | 39.42°S, 71.93°W | Summit elev. 2847 m POVI reported an increase in the frequency of Strombolian explosions at Villarrica, with incandescent material ejected to 50 m above the crater rim during 7-8 April. Geologic Summary. Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks. Source: Proyecto Observación Villarrica Internet (POVI) http://www.povi.cl/ Ongoing Activity Agung | Bali (Indonesia) | 8.343°S, 115.508°E | Summit elev. 2997 m PVMBG reported that at 1331 on 4 April an explosion at Agung ejected incandescent material out of the crater and onto the flanks within a 2-3 km radius, mainly on the S flank. A dense gray ash plume rose 2 km above the crater rim and, based on satellite data, drifted W and S. Ashfall was reported in areas downwind including Telungbuana, Badeg, Besakih (7 km SW), Pempatan (8 km W), Teges, and Puregai. Roaring was heard at the observation post in Rendang (12 km NW). The Alert Level remained at 3 (on a scale of 1-4) with the exclusion zone set at a 4-km radius. Geologic Summary. Symmetrical Agung stratovolcano, Bali's highest and most sacred mountain, towers over the eastern end of the island. The volcano, whose name means "Paramount," rises above the SE caldera rim of neighboring Batur volcano, and the northern and southern flanks extend to the coast. The summit area extends 1.5 km E-W, with the high point on the W and a steep-walled 800-m-wide crater on the E. The Pawon cone is located low on the SE flank. Only a few eruptions dating back to the early 19th century have been recorded in historical time. The 1963-64 eruption, one of the largest in the 20th century, produced voluminous ashfall along with devastating pyroclastic flows and lahars that caused extensive damage and many fatalities. Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/; Darwin Volcanic Ash Advisory Centre (VAAC) http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml Aira | Kyushu (Japan) | 31.593°N, 130.657°E | Summit elev. 1117 m JMA reported that incandescence from Minamidake crater (at Aira Calderaâ??s Sakurajima volcano) was occasionally visible during 1-8 April. Two explosions on 7 April generated plumes that rose a maximum of 1.3 km above the crater rim and ejected material as far as 1.7 km. The Alert Level remained at 3 (on a 5-level scale). 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) http://www.jma.go.jp/jma/ Copahue | Central Chile-Argentina border | 37.856°S, 71.183°W | Summit elev. 2953 m On 5 April OVDAS-SERNAGEOMIN reported that seismicity at Copahue increased during 1-31 March, characterized by abundant volcano-tectonic earthquakes and increases in long-period and very-long-period earthquakes. In addition, the level of the lake water in El Agrio crater had dropped compared to previous months. The Alert Level was raised to Yellow (second highest level on a four-color scale); SERNAGEOMIN recommended no entry into a restricted area within 500 m of the crater. ONEMI raised the Alert Level to Yellow (the middle level on a three-color scale) for the municipality of Alto BiobÃo. Geologic Summary. Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the RÃo Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments. Source: Servicio Nacional de GeologÃa y MinerÃa (SERNAGEOMIN) http://www.sernageomin.cl/ Dukono | Halmahera (Indonesia) | 1.693°N, 127.894°E | Summit elev. 1229 m Based on satellite and wind model data, the Darwin VAAC reported that during 3-9 April ash plumes from Dukono rose as high as 2.1 km (7,000 ft) a.s.l. and drifted NE, E, SE, and S. The Alert Level remained at 2 (on a scale of 1-4), and visitors were 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. Sources: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml; Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ Ebeko | Paramushir Island (Russia) | 50.686°N, 156.014°E | Summit elev. 1103 m Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 29-31 March, 1 April, and 4 April that sent ash plumes up to 3.2 km (10,500 ft) a.s.l. Ash fell in Severo-Kurilsk on 31 March, the same day a thermal anomaly was identified in satellite images. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). 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) http://www.kscnet.ru/ivs/kvert/index_eng.php Ibu | Halmahera (Indonesia) | 1.488°N, 127.63°E | Summit elev. 1325 m The Darwin VAAC reported that on 28 March multiple ash plumes from Ibu were identified in satellite images drifting SE at an altitude of 2.1 km (7,000 ft) a.s.l. 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 active crater, and 3.5 km away on the N side. 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, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. 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. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998. Sources: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml; Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ Kadovar | Papua New Guinea | 3.608°S, 144.588°E | Summit elev. 365 m Based on satellite data and wind model data, the Darwin VAAC reported that on 9 April an ash plume from Kadovar rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted SE. Geologic Summary. The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. Kadovar is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. The village of Gewai is perched on the crater rim. A 365-m-high lava dome forming the high point of the andesitic volcano fills an arcuate landslide scarp that is open to the south, and submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. No certain historical eruptions are known; the latest activity was a period of heightened thermal phenomena in 1976. Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml Karangetang | Siau Island (Indonesia) | 2.781°N, 125.407°E | Summit elev. 1797 m Based on analyses of satellite imagery and model data, the Darwin VAAC reported that on 6 April a minor ash emission from Karangetang rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted SE. The Alert Level remained at 2 (on a scale of 1-4). Geologic Summary. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, north 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 in the historical record (Catalog of Active Volcanoes of the World: Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts has also produced pyroclastic flows. Sources: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.bom.gov.au/aviation/volcanic-ash/darwin-va-advisory.shtml; Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ Karymsky | Eastern Kamchatka (Russia) | 54.049°N, 159.443°E | Summit elev. 1513 m KVERT reported that an ash plume from Karymsky was visible in satellite images on 31 March drifting about 17 km S. Weather clouds obscured views during 1-6 April. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Geologic Summary. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php Kerinci | Indonesia | 1.697°S, 101.264°E | Summit elev. 3800 m PVMBG reported that at 1637 on 3 April a brownish ash plume rose 4.3 km above Kerinciâ??s crater rim and drifted NE, as noted by a ground-based observer. The Alert Level remained at 2 (on a scale of 1-4), and tourists were warned to remain outside of the 3-km exclusion zone. Geologic Summary. Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ Krakatau | Indonesia | 6.102°S, 105.423°E | Summit elev. 813 m PVMBG reported that during 1-7 April there were six explosions at Anak Krakatau detected by the seismic network. Foggy weather conditions prevented visual observations. The Alert Level remained at 3 (on a scale of 1-4), and residents were warned to remain outside of the 5-km radius hazard zone from the crater. Geologic Summary. The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ Merapi | Central Java (Indonesia) | 7.54°S, 110.446°E | Summit elev. 2910 m PVMBG reported that by 21 March the lava dome at Merapi had grown to an estimated volume of 472,000 cubic meters, based on analyses of drone footage. It remained relatively unchanged during 1-7 April, as most of the extruded lava fell into the upper parts of the SE-flank Gendol River drainage. Two block-and-ash flows traveled as far as 1 km down the Gendol drainage. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to remain outside of the 3-km exclusion zone. 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 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive 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 during historical time. Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://vsi.esdm.go.id/ Nevados de Chillan | Chile | 36.868°S, 71.378°W | Summit elev. 3180 m ONEMI and SERNAGEOMIN noted that on 5 April the pulsating, generally white, emissions from Nevados de Chillánâ??s Nicanor Crater were sometimes gray. Explosions was recorded at 0403 on 8 April and 0457 on 9 April, and were associated with long-period earthquake signals. A video posted on social media from the 9 April event showed incandescent material showering the flanks of the lava dome. The Alert Level remained at Orange, the second highest level on a four-color scale, and residents were reminded not to approach the crater within 3 km. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto, Coihueco, and San Fabián. Geologic Summary. The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, Cerro Blanco (Volcán Nevado), is located at the NW end of the group. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in elevation. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986 and eventually exceeded its height. Sources: Oficina Nacional de Emergencia-Ministerio del Interior (ONEMI) http://www.onemi.cl/; Servicio Nacional de GeologÃa y MinerÃa (SERNAGEOMIN) http://www.sernageomin.cl/ Rincon de la Vieja | Costa Rica | 10.83°N, 85.324°W | Summit elev. 1916 m OVSICORI-UNA reported that continuous emissions at Rincón de la Vieja were visible during 3-4 April rising 200 m above the crater rim. A small eruption was recorded at 1437. Geologic Summary. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge that was constructed within the 15-km-wide early Pleistocene GuachipelÃn caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of 1916-m-high Santa MarÃa volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A plinian eruption producing the 0.25 km3 RÃo Blanca tephra about 3500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater. Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/ Sheveluch | Central Kamchatka (Russia) | 56.653°N, 161.36°E | Summit elev. 3283 m KVERT reported that a thermal anomaly over Sheveluchâ??s lava dome was identified daily in satellite images during 29 March-6 April. Explosions on 5 April generated ash plumes that rose to 7-7.5 km (23,000-24,600 ft) a.s.l. and drifted about 550 km NW during 5-6 April. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Geologic Summary. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. 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 dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. 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 Turrialba | Costa Rica | 10.025°N, 83.767°W | Summit elev. 3340 m OVSICORI-UNA reported that minor ash emissions rose from Turrialba on 8 April. Geologic Summary. Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive edifice covers an area of 500 km2. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters. Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/ ============================================================== 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). ASU - http://www.asu.edu/ PSU - http://pdx.edu/ GVP - http://www.volcano.si.edu/ IAVCEI - http://www.iavcei.org/ To unsubscribe from the volcano list, send the message: signoff volcano to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxx. To contribute to the volcano list, send your message to: volcano@xxxxxxx. 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