The Weekly Volcanic Activity Report: March 25 - 31, 2020

The Weekly Volcanic Activity Report: March 25 - 31, 2020

New activity/unrest was reported for 3 volcanoes from March 25 - 31, 2020. During the same period, ongoing activity was reported for 15 volcanoes.

New activity/unrest: Kerinci, Indonesia | Reykjanes, Iceland | Semeru, Eastern Java (Indonesia).

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Ibu, Halmahera (Indonesia) | Karangetang, Siau Island (Indonesia) | Klyuchevskoy, Central Kamchatka (Russia) | Merapi, Central Java (Indonesia) | Nevados de Chillan, Chile | San Miguel, El Salvador | Semisopochnoi, United States | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Stromboli, Aeolian Islands (Italy) | Suwanosejima, Ryukyu Islands (Japan) | Yasur, Vanuatu.

New activity/unrest

Kerinci, Indonesia

1.697°S, 101.264°E, Elevation 3800 m

The Darwin VAAC reported that on 25 March an ash plume from Kerinci rose to 4.3 km (14,000 ft) a.s.l. and drifted WSW based on information from PVMBG. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 3-km exclusion zone.

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. This volcano is located within the Tropical Rainforest Heritage of Sumatra, a UNESCO World Heritage property.

Reykjanes, Iceland

63.85°N, 22.566°W, Elevation 140 m

There were more than 6,000 earthquakes recorded beneath the Reykjanes peninsula as of 26 March, making this period of unrest the largest seismic crisis ever recorded in this part of the country since digital monitoring started in 1991, according to IMO. The seismicity occurred across three main volcanic systems: Eldey, Reykjanes-Svartsengi, and Krýsuvík. Uplift continued to be detected in the Thorbjorn area totaling about 70-80 mm; the deformation rate was lower than in January and February. Deformation modeling suggested that recent inflation was caused by a second magmatic intrusion at a depth of 3-4 km in an area W of Thorbjorn, close to the intrusion that occurred at the beginning of the year. GPS data suggested a small deformation pattern detectable over a regional area, far beyond the Thorbjorn area.

Geological summary: The Reykjanes volcanic system at the SW tip of the Reykjanes Peninsula, where the Mid-Atlantic Ridge rises above sea level, comprises a broad area of postglacial basaltic crater rows and small shield volcanoes. The submarine Reykjaneshryggur volcanic system is contiguous with and is considered part of the Reykjanes volcanic system, which is the westernmost of a series of four closely-spaced en-echelon fissure systems that extend diagonally across the Reykjanes Peninsula. Most of the subaerial part of the system (also known as the Reykjanes/Svartsengi volcanic system) is covered by Holocene lavas. Subaerial eruptions have occurred in historical time during the 13th century at several locations on the NE-SW-trending fissure system, and numerous submarine eruptions dating back to the 12th century have been observed during historical time, some of which have formed ephemeral islands. Basaltic rocks of probable Holocene age have been recovered during dredging operations, and tephra deposits from earlier Holocene eruptions are preserved on the nearby Reykjanes Peninsula. This volcano is located within the Reykjanes, a UNESCO Global Geopark property.

Semeru, Eastern Java (Indonesia)

8.108°S, 112.922°E, Elevation 3657 m

PVMBG reported that during 23-29 March white plumes rose 100 m above Semeru’s summit. Incandescent material was ejected 20 m above the Jonggring-Seloko Crater. Incandescent material from the ends of lava flows descended 200-500 m, reaching a maximum distance of 750 m from the crater. The Alert Level remained at 2 (on a scale of 1-4), and the public was reminded to stay outside of the general 1-km radius from the summit and 4 km on the SSE flank.

Geological 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. This volcano is located within the Bromo Tengger Semeru-Arjuno, a UNESCO Biosphere Reserve property.

Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Elevation 1117 m

JMA reported that during 23-30 March incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible nightly. Twelve eruptive events were recorded along with three explosions during 23-27 March. An eruption at 1041 on 27 March produced an ash plume that rose 1.8 km above the crater rim and ejected material 800-1,100 m away from the crater. The Alert Level remained at 2 (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, Elevation 1229 m

Based on satellite and wind model data, the Darwin VAAC reported that during 25-31 March ash plumes from Dukono rose to 1.8-2.3 km (7,000-8,000 ft) a.s.l. and drifted in multiple directions. The Alert Level remained at 2 (on a scale of 1-4), and the public was 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, Elevation 1103 m

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 24-25 March that sent ash plumes up to 2.5 km (8,200 ft) a.s.l. Ash plumes drifted NE and W. 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, Elevation 1325 m

PVMBG reported that at 1730 on 26 March, at 0642 on 28 March, and at 0855 on 29 March gray ash plumes rose 600 m above Ibu’s summit and drifted W and N. The Darwin VAAC stated that on 30 March an ash plume rose to 2.1 km (7,000 ft) a.s.l. and drifted NE based on satellite images and weather models. 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, Elevation 1797 m

PVMBG reported that during 23-29 March lava continued to effuse from Karangetang’s Main Crater (S), traveling as far as 1.8 km down the Nanitu, Pangi, and Sense drainages on the SW and W flanks. Sometimes dense white plumes rose up to 75 m above the summit; foggy weather occasionally prevented observations. Incandescence from both summit craters was visible at night. The Alert Level remained at 2 (on a scale of 1-4).

Geological summary: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi island. 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 have produced pyroclastic flows.

Klyuchevskoy, Central Kamchatka (Russia)

56.056°N, 160.642°E, Elevation 4754 m

KVERT reported that Strombolian activity at Klyuchevskoy was visible during 20-27 March, and a bright thermal anomaly was identified in satellite images those same days. Vulcanian activity was visible on 20 and 25 March; ash plumes drifted as far as 180 km E and NE at altitudes of 5.5-6 km (18,000-19,700 ft) a.s.l. on those same days. The Aviation Color Code remained at Orange.

Geological 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. This volcano is located within the Volcanoes of Kamchatka, a UNESCO World Heritage property.

Merapi, Central Java (Indonesia)

7.54°S, 110.446°E, Elevation 2910 m

BPPTKG reported that beginning at 1056 on 27 March a seven-minute-long eruption at Merapi produced an ash plume that rose 5 km above the crater rim and pyroclastic flows that descended the SSE flank as far as 2 km. The ash plume drifted mainly SW and caused ashfall within 20 km, particularly in areas to the W and including the Mungkid subdistrict and in Banyubiru Village. The report noted that there were no clear precursors for the eruption. Eruptions at 2146 on 27 March and at 0521 the next day generated ash plumes that rose 1 km and 2 km, respectively. Each lasted about 2 minutes and 40 seconds based on the seismic data. Minor ashfall was noted in areas within 5 km, especially to the W, including Krinjing subdistrict. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to stay 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, Elevation 3180 m

The Buenos Aires VAAC reported that during 25 and 29-31 March ash plumes from Nevados de Chillán rose to altitudes of 3.7-5.5 km (12,000-18,000 ft) a.s.l. and drifted SE.

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.

San Miguel, El Salvador

13.434°N, 88.269°W, Elevation 2130 m

SNET stated that during 30-31 March the seismic network at San Miguel recorded a period of increased seismicity characterized by continuous, low-frequency, tremor-type signals. RSAM values were between 90 and 116 units, lower than the normal values of 150, at a seismic station located on the upper N flank.

Geological summary: The symmetrical cone of San Miguel volcano, one of the most active in El Salvador, rises from near sea level to form one of the country's most prominent landmarks. The unvegetated summit rises above slopes draped with coffee plantations. A broad, deep crater complex that has been frequently modified by historical eruptions (recorded since the early 16th century) caps the truncated summit, also known locally as Chaparrastique. Radial fissures on the flanks of the basaltic-andesitic volcano have fed a series of historical lava flows, including several erupted during the 17th-19th centuries that reached beyond the base of the volcano on the N, NE, and SE sides. The SE-flank flows are the largest and form broad, sparsely vegetated lava fields crossed by highways and a railroad skirting the base of the volcano. The location of flank vents has migrated higher on the edifice during historical time, and the most recent activity has consisted of minor ash eruptions from the summit crater.

Semisopochnoi, United States

51.93°N, 179.58°E, Elevation 1221 m

AVO reported that seismicity at Semisopochnoi remained elevated during 25-31 March and no surface activity was observed on most days, though weather clouds often prevented visual confirmation. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geological summary: Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is 1221-m-high Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part. The three-peaked 774-m-high Mount Cerberus volcano was constructed during the Holocene within the caldera. Each of the peaks contains a summit crater; lava flows on the northern flank of Cerberus appear younger than those on the southern side. Other post-caldera volcanoes include the symmetrical 855-m-high Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented historical eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone within the caldera could have been active during historical time. This volcano is located within the Aleutian Islands, a UNESCO Biosphere Reserve property.

Sheveluch, Central Kamchatka (Russia)

56.653°N, 161.36°E, Elevation 3283 m

KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 20-27 March. A gas-and-steam plume containing some ash drifted 45 km N on 25 March. 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.

Shishaldin, Fox Islands (USA)

54.756°N, 163.97°W, Elevation 2857 m

AVO reported elevated seismicity at Shishaldin during 25-31 March characterized by continuous low-level tremor. Steam-and-gas plumes rising from the summit crater were occasionally recorded by the webcam and identified in satellite images. Weakly- to- moderately elevated surface temperatures were identified in satellite images during 29-30 March. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.

Geological summary: The beautifully symmetrical Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steam plume often rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the W and NE sides at 1,500-1,800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of Strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century. This volcano is located within the Aleutian Islands, a UNESCO Biosphere Reserve property.

Stromboli, Aeolian Islands (Italy)

38.789°N, 15.213°E, Elevation 924 m

INGV reported that during 23-29 March activity at Stromboli was characterized by ongoing explosive activity mainly from three vents in Area N (north crater area) and at least three vents in Area C-S (south-central crater area). Lava effused from the northern-most vent located on the edge of Area N for about four hours, beginning at 1856 on 28 March, and traveled down the Sciara del Fuoco all the way to the coast. Variable-intensity explosions from Area N occurred at a rate of 8-13 events per hour and ejected lapilli and bombs 80-150 m above the vents. Ejected tephra fell onto the flanks and some blocks rolled down the Sciara del Fuoco to the coast. Explosions from Area C-S occurred at a rate of 6-10 events per hour and ejected coarse material mixed with ash to heights less than 150 m above the vents.

Geological summary: Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium. This volcano is located within the Isole Eolie (Aeolian Islands), a UNESCO World Heritage property.

Suwanosejima, Ryukyu Islands (Japan)

29.638°N, 129.714°E, Elevation 796 m

JMA reported that during 19-27 March incandescence from Suwanosejima’s Ontake Crater was visible nightly. One explosion was recorded on 23 March and eruptive events were detected during 23-24 March; ringing sounds were noted in a village 4 km SSW. Gray-white plumes rose 700 m above the crater rim on 24 March. 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.

Yasur, Vanuatu

19.532°S, 169.447°E, Elevation 361 m

On 27 March the Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported that activity at Yasur continued to be elevated with ongoing ash and/or gas emissions. The Alert Level remained at 2 (on a scale of 0-4). VMGD reminded residents and tourists that hazardous areas were near and around the volcanic crater, within a 395-m-radius permanent exclusion zone, and that volcanic ash and gas could reach areas impacted by trade winds.

Geological summary: ​Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity 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, this mostly unvegetated 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, horseshoe-shaped caldera 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: GVP

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