The Weekly Volcanic Activity Report: February 27

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New activity/unrest was reported for 3 volcanoes from February 27 to March 5, 2019. Ongoing activity was reported for 12 volcanoes during the same period.

New activity/unrest: Bezymianny, Central Kamchatka (Russia) | Karymsky, Eastern Kamchatka (Russia) | Piton de la Fournaise, Reunion Island (France) 

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Ibu, Halmahera (Indonesia) | Karangetang, Siau Island (Indonesia) | Manam, Papua New Guinea | Merapi, Central Java (Indonesia) | Nevados de Chillan, Chile | Santa Maria, Guatemala | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Turrialba, Costa Rica

New activity/unrest

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 28 February-1 March. Strong gas-and-steam emissions continued to be visible. 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 22 and 24-26 February rising as high as 3.5 km (11,500 ft) a.s.l. and drifting 216 km E. A thermal anomaly was visible during 24-25 and 27-28 February. 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.

Piton de la Fournaise, Reunion Island (France)

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

OVPF reported that the fissure that opened 19 February at a site located at 1,800 m elevation at the foot of Piton Madoré, E of Piton de la Fournaise’s Dolomieu Crater, continued during 27 February-5 March. RSAM measurements showed fluctuating intensities though an overall upwards trend. Based on satellite images, the main flow front progressed slowly during 22-28 February, advancing only 300 m to 1,200 m elevation. A new lava flow emerged from an area near the cone and traveled NE; the more southern branches did not advance during 28 February-1 March. Scientists conducted fieldwork on 5 March and noted that the cone had grown to 100 m wide at the base, 25 m tall, and had a vent opening 50 m wide. High-temperature gas emissions rose from the vent, and Strombolian activity ejected material. White steam rose from the base of the cone, likely from the presence of lava tubes. The northernmost lava flow remained active.

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.

Ongoing activity

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 25 February-4 March. There were four events and seven explosive events. Plumes rose as high as 2.3 km, and material as ejected as far as 1.1 km from the crater. 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 and wind model data, ground observations, and notices from PVMBG, the Darwin VAAC reported that during 27 February-5 March ash plumes from Dukono rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted in multiple directions. On 28 February two plumes rising from the crater were visible; a northern plume was identified in satellite images and a southern plume rising to less than 1.5 km (5,000 ft) a.s.l. was reported by a ground observer. 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 22-26 February that sent ash plumes to 2.5 km (8,200 ft) a.s.l. Ash fell in Severo-Kurilsk during 23-26 February. 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.

Ibu, Halmahera (Indonesia)

1.488°N, 127.63°E, Summit elev. 1325 m

The Darwin VAAC reported that on 28 February an ash plume from Ibu was identified in satellite images drifting N 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.

Geological 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.

Karangetang, Siau Island (Indonesia)

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

PVMBG reported that during 25 February-5 March a low rate of lava effusion continued at Karangetang’s Kawah Dua (North Crater). White plumes rose as high as 500 m above the summit crater rims. The Darwin VAAC reported that on 27 February a pilot observed an ash plume rising to an altitude of 1.8 km (6,000 ft) a.s.l. and drifting SE. 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.

Manam, Papua New Guinea

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

The Darwin VAAC reported that on 1 and 5 March ash plumes from Manam were identified in satellite images rising to an altitude of 3 km (10,000 ft) a.s.l. and drifting SE, ESE, and E.

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 22 February-5 March the volume of the lava dome in Merapi’s summit crater had not changed since the last measurement of 466,000 cubic meters estimated on 21 February. 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 600-1,100 m down the Gendol drainage on 25 and 27 February, and on 2 March as many as 10 traveled as far as 2 km. Incandescent avalanches were visible at night. 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 2323 on 1 March and was associated with a long-period earthquake signal. The explosion ejected high-temperature incandescent material deposited in areas around the crater, and likely destroyed part 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.

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.

Santa Maria, Guatemala

14.757°N, 91.552°W, Summit elev. 3745 m

INSIVUMEH reported that during 1-5 March as many as four explosions per hour at Santa María’s Santiaguito lava-dome complex generated white plumes with ash that rose 500-700 m above the domes and drifted SE and SW. Avalanches of material descended the E and SE flanks of the lava dome. An explosion at 2155 on 4 March was heard in areas as far away as 10 km W, SW, S, and SE. The event ejected incandescent material 100 m high, produced ashfall around the volcano, and generated avalanches that traveled down the E and SE dome flanks reaching the base.

Geological summary: Symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

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 22 February-1 March. Strong gas-and-steam emissions contained variable amounts of ash on 21, 25, and 27 February, and rose 4-5 km (13,100-16,400 ft) a.s.l. and drifted 100 km SW and E. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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 22 February-1 March. Small events were occasionally recorded, generating plumes that rose as high as 900 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 an event at Turrialba at 1050 on 28 February generated a plume that rose 500 m above the crater rim and drifted SW. Some additional ash pulses were recorded that day. An event at 0444 on 1 March produced a plume that rose 200 m and drifted NE. A period of continuous emissions rising 200-300 m was recorded during 2-4 March; the plumes contained minor amounts of ash at least during 2-3 March.

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

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