The Weekly Volcanic Activity Report: March 6 – 12, 2019

New activity/unrest was reported for 7 volcanoes from March 6 to 12, 2019. Ongoing activity was reported for 14 volcanoes during the same period.

New activity/unrest: Barren Island, Andaman Islands (India) | Bezymianny, Central Kamchatka (Russia) | Karymsky, Eastern Kamchatka (Russia) | Mayon, Luzon (Philippines) | Piton de la Fournaise, Reunion Island (France) | San Cristobal, Nicaragua | Tengger Caldera, Eastern Java (Indonesia).

Ongoing activity: Agung, Bali (Indonesia) | Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Karangetang, Siau Island (Indonesia) | Kerinci, Indonesia | Manam, Papua New Guinea | Merapi, Central Java (Indonesia) | Nevados de Chillan, Chile | Poas, Costa Rica | Sabancaya, Peru | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Turrialba, Costa Rica.

New activity/unrest

Barren Island, Andaman Islands (India)

12.278°N, 93.858°E, Summit elev. 354 m

Based on analysis of satellite imagery and wind data, the Darwin VAAC reported that on 7 March ash plumes from Barren Island rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted W and NW, and to an altitude of 1.2 km (4,000 ft) a.s.l. and drifted E and ESE.

Geological summary: Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S volcanic arc extending between Sumatra and Burma (Myanmar). It is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Bezymianny, Central Kamchatka (Russia)

55.972°N, 160.595°E, Summit elev. 2882 m

KVERT reported that a thermal anomaly over Bezymianny was identified in satellite images during 1-12 March. Strong gas-end-steam emissions continued to rise from the crater. Hot avalanches originating from the top of the lava dome were visible at night. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped 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.

Karymsky, Eastern Kamchatka (Russia)

54.049°N, 159.443°E, Summit elev. 1513 m

KVERT reported that ash plumes from Karymsky were identified in satellite images during 1 and 4-5 March rising as high as 3.5 km (11,500 ft) a.s.l. and drifting 90 km E. A thermal anomaly was also visible on those same days. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological 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.

Mayon, Luzon (Philippines)

13.257°N, 123.685°E, Summit elev. 2462 m

PHIVOLCS reported that during 6-11 March white steam plumes periodically emitted from Mayon drifted WNW, WSW, and SW, and crater incandescence was visible each night. As many as six volcanic earthquakes and two rockfalls per day were recorded by the seismic network. Phreatic events recorded at 0811 on 7 March and 0627 on 8 March generated grayish ash plumes that rose 500 and 300 m above the crater, respectively, and drifted SW. The Alert Level remained at 2 (on a 0-5 scale) and PHIVOLCS reminded residents to stay away from the 6-km-radius Permanent Danger Zone and the 7-km Extended Danger Zone on the SSW and ENE flanks.

Geological summary: Beautifully symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the Philippines' most active volcano. The structurally simple edifice has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. Historical eruptions date back to 1616 and 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 devastated populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Piton de la Fournaise, Reunion Island (France)

21.244°S, 55.708°E, Summit elev. 2632 m

During an overflight between 0700 and 0800 on 6 March tourists observed a new active fissure on the NW flank of Piton de la Fournaise’s Piton Madoré, 150 m upstream of the main vent. The fissure likely opened the day before during 0900 and 1900. The tourist report noted that a small cone had formed, and a lava flow was traveling N. In the morning of 7 March at least six new vents were visible, although weather conditions prevented OVPF volcanologists from confirming if they were along a new fissure. During fieldwork on 8 March volcanologists inspected the 5 March fissure and observed a small cone ejecting material up to 10 m above the rim. Lava from the W side flowed a few tens of meters, and a flow from the N side progressed E. The new vents that opened on 7 March were confirmed to be along an E-W trending fissure. The vents were active, each producing 50-m-high lava fountains. The report also noted that samples from the 5 March and 7 March vents had different compositions, though no other details were noted. Lava flows traveled to around 1,000 m elevation.

Satellite images showed sulfur dioxide plumes drifting 450-550 km E on 8 March. Lava flows rapidly progressed during 8-9 March; the lava emission rate was variable, ranging up to 25 cubic meters per second (based on satellite data), although since the new fissures opened the highest values (over 50 cubic meters per second) measured the past few days were approximately 10 times higher than the average values recorded during the 2017-2018 eruptions. By 0800 on 9 March the flow front was at an estimated elevation of 650-700 m. After a phase of intense surficial activity during 9-10 March, with lava fountains rising as high as 100 m, lava-flow emissions ceased around 0628 on 10 March and seismicity significantly decreased.

Geological summary: The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. 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 calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern 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 on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

San Cristobal, Nicaragua

12.702°N, 87.004°W, Summit elev. 1745 m

INETER reported that a low-energy explosion at San Cristóbal was detected by the seismic network at 1550 on 4 March. The event produced a gas-and-ash plume that rose 400 m above the crater rim and drifted SW.

Geological summary: The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km W of San Cristóbal; it and the eroded Moyotepe volcano, 4 km NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.

Tengger Caldera, Eastern Java (Indonesia)

7.942°S, 112.95°E, Summit elev. 2329 m

PVMBG reported that on 10 March an eruption at Tengger Caldera’s Bromo cone generated a white, brown, and gray ash plume that, according to a ground observer, rose 600 m and drifted SW. An event at 0600 on 11 March produced a dense gray-to-brown ash plume that rose 600 m and drifted S, SW, and W. The Alert Level remained at 2 (on a scale of 1-4).

Geological 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.

Ongoing activity

Agung, Bali (Indonesia)

8.343°S, 115.508°E, Summit elev. 2997 m

PVMBG reported that at 0452 on 4 March an event at Agung was recorded for just under three minutes and produced ashfall in Besakih (7 km SW) around 0615. No ash plume was visible although foggy conditions prevented views of the summit. An event that began at 0047 on 9 March lasted for 3 minutes and 50 seconds, and produced an ash plume that drifted E. The Alert Level remained at 3 (on a scale of 1-4) with the exclusion zone set at a 4-km radius.

Geological 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.

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Summit elev. 1117 m

JMA reported that incandescence from Minamidake crater (at Aira Caldera’s Sakurajima volcano) was occasionally visible during 4-11 March. Occasional small events and three explosions were detected during 8-11 March. Plumes rose as high as 1.9 km. The Alert Level remained at 3 (on a 5-level scale).

Geological 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.

Dukono, Halmahera (Indonesia)

1.693°N, 127.894°E, Summit elev. 1229 m

Based on satellite images, wind model data, and ground observations, the Darwin VAAC reported that during 5-9 and 11-12 March ash plumes from Dukono rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted WSW, SW, S, and SE. 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.

Geological 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.

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 1-2 and 5 March that sent ash plumes to 2.5 km (8,200 ft) a.s.l. Ash fell in Severo-Kurilsk on 1 and 5 March. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological 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.

Karangetang, Siau Island (Indonesia)

2.781°N, 125.407°E, Summit elev. 1797 m

PVMBG reported that during 4-10 March a low rate of lava effusion continued at Karangetang’s Kawah Dua (North Crater) as evident by avalanches in the Malabuhe River drainage on the NW flank. White plumes rose as high as 500 m above the rims of the summit craters during 4-12 March. The Darwin VAAC reported that on 7 March an ash plume rose to an altitude of 2.7 km (9,000 ft) a.s.l. and drifted SW. The Alert Level remained at 3 (on a scale of 1-4), and residents were warned to remain outside of the 2.5-km exclusion zone around the N and S craters, and additionally within 3 km WNW and 4 km NW.

Geological 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.

Kerinci, Indonesia

1.697°S, 101.264°E, Summit elev. 3800 m

PVMBG reported that at 1850 on 7 March a brown ash emission rose 150 m above the rim of Kerinci summit vent and drifted NE. Ash also drifted down the SE and E flanks. Another brown ash emission was observed at 1209 on 8 March rising 700 m and drifting W. Brown ash emissions at 1607 on 10 March and 0919 on 11 March rose 300 m and 500 m, respectively, and drifted NE. Seismicity was dominated by volcanic tremor during 7-11 March.

Geological 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.

Manam, Papua New Guinea

4.08°S, 145.037°E, Summit elev. 1807 m

The Darwin VAAC reported that during 5-6 March ash plumes from Manam rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted E based on satellite data and ground-based observations. A significant thermal anomaly was also visible in satellite images, and seismicity was elevated.

Geological summary: The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Merapi, Central Java (Indonesia)

7.54°S, 110.446°E, Summit elev. 2910 m

PVMBG reported that during 1-12 March white-and-gray emissions of variable density rose as high as 1 km above Merapi’s summit. The volume of the lava dome was 470,000 cubic meters on 5 March, as estimated from drone photographs, and relatively unchanged from the previous weeks. There were no apparent morphological changes; most of the extruded lava fell into the upper parts of the Gendol River drainage on the SE flank. Block-and-ash flows traveled 500-1,900 m down the Gendol drainage on 2, 3, and 7. 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.

Geological 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.

Nevados de Chillan, Chile

36.868°S, 71.378°W, Summit elev. 3180 m

ONEMI and SERNAGEOMIN reported that an explosive event at Nevados de Chillán’s Nicanor Crater was recorded at 0845 on 8 March and was associated with a long-period earthquake signal. The explosion ejected and deposited material in areas around the crater, mainly to the N, and produced a plume that rose 2.7 km above the crater rim. 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.

Geological 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.

Poas, Costa Rica

10.2°N, 84.233°W, Summit elev. 2708 m

OVSICORI-UNA reported that, although weather conditions often prevented visual observations of Poás during 7-8 and 10 March, gas plumes sometimes containing ash were observed rising as high as 500 m above the crater rim and drifting SW. A sulfur odor and ashfall were reported in Naranjo and Grecia (16 km SW).

Geological summary: The broad, well-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, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 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 the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Sabancaya, Peru

15.787°S, 71.857°W, Summit elev. 5960 m

Instituto Geofísico del Perú (IGP) and Instituto Geológico Minero y Metalúrgico (INGEMMET) reported that an average of 15 explosions per day occurred at Sabancaya during 4-10 March. Long-period seismic events were recorded, and hybrid earthquakes were infrequent and of low magnitude. Gas-and-ash plumes rose as high as 2.8 km above the crater rim and drifted 20 km SW, W, and NW. MIROVA detected four thermal anomalies, and on 3 March the sulfur-dioxide gas flux was high at 3,360 tons per day. The report noted that the public should not approach the crater within a 12-km radius.

Geological 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.

Sheveluch, Central Kamchatka (Russia)

56.653°N, 161.36°E, Summit elev. 3283 m

KVERT reported that a thermal anomaly over Sheveluch’s lava dome was identified daily in satellite images during 1-8 March. Strong gas-and-steam emissions containing variable amounts of ash rose to altitudes of 3.5-4 km (11,500-13,100 ft) a.s.l. and drifted about 50 km E on 1 March. On 9 March explosions generated ash plumes that rose 10-11.2 km (32,800-36,700 ft) a.s.l. and drifted 70 km NW and N, prompting KVERT to raise the Aviation Color Code to Red (the highest level on a four-color scale). Early on 10 March the Aviation Color Code was lowered to Orange. Ash plumes continued to rise from the crater, to an altitude of 8 km (26,200 ft) a.s.l., and drift 375 km N. Later that day gas-and-steam plumes with some ash rose as high as 4.5 km (14,800 ft) a.s.l. and drifted 15 km NE. On 11 March an ash plume rose as high as 4.7 km (15,400 ft) a.s.l. and drifted 70 km SE.

Geological 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.

Suwanosejima, Ryukyu Islands (Japan)

29.638°N, 129.714°E, Summit elev. 796 m

JMA reported that crater incandescence at Suwanosejima’s Ontake Crater was visible at night during 1-8 March. Small events were occasionally recorded, generating plumes that rose as high as 600 m above the crater rim. The Alert Level remained at 2 (on a 5-level scale).

Geological summary: The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Turrialba, Costa Rica

10.025°N, 83.767°W, Summit elev. 3340 m

OVSICORI-UNA reported that during 9-12 March plumes of gas sometimes containing small amounts of ash rose as high as 1 km above Turrialba’s crater rim.

Geological 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: GVP