The Weekly Volcanic Activity Report: September 2 - 8, 2020

The Weekly Volcanic Activity Report: September 2 - 8, 2020

New activity/unrest was reported for 2 volcanoes from September 2 to 8, 2020. During the same period, ongoing activity was reported for 12 volcanoes.

New activity/unrest: Kavachi, Solomon Islands | Sinabung, Indonesia.

Ongoing activity: Aira, Kyushu (Japan) | Cleveland, Chuginadak Island (USA) | Copahue, Central Chile-Argentina border | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Karymsky, Eastern Kamchatka (Russia) | Makushin, Fox Islands (USA) | Rincon de la Vieja, Costa Rica | Sangay, Ecuador | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan).

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 23:00 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.

New activity/unrest

Kavachi, Solomon Islands

8.991°S, 157.979°E, Elevation -20 m

Satellite data showed discolored water around Kavachi possibly beginning in early September; by 7 September discolored plumes in the water were visible E of the submarine cone.

Geological summary: Named for a sea-god of the Gatokae and Vangunu peoples, Kavachi is one of the most active submarine volcanoes in the SW Pacific, located in the Solomon Islands south of Vangunu Island about 30 km N of the site of subduction of the Indo-Australian plate beneath the Pacific plate. Sometimes referred to as Rejo te Kvachi ("Kavachi's Oven"), this shallow submarine basaltic-to-andesitic volcano has produced ephemeral islands up to 1 km long many times since its first recorded eruption during 1939. Residents of the nearby islands of Vanguna and Nggatokae (Gatokae) reported "fire on the water" prior to 1939, a possible reference to earlier eruptions. The roughly conical edifice rises from water depths of 1.1-1.2 km on the north and greater depths to the SE. Frequent shallow submarine and occasional subaerial eruptions produce phreatomagmatic explosions that eject steam, ash, and incandescent bombs. On a number of occasions lava flows were observed on the ephemeral islands.

Sinabung, Indonesia

3.17°N, 98.392°E, Elevation 2460 m

PVMBG reported that white plumes rose as high as 600 m above Sinabung’s summit and drifted in multiple directions on most days during 2-8 September. At 0513 on 5 September an eruption produced a gray ash plume that rose at least 800 m and drifted NNE. Emissions were brown and white on 6 September. The Alert Level remained at 3 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions to 5 km on the SE sector and 4 km in the NE sector.

Geological summary: Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Elevation 1117 m

JMA reported that 12 eruptive events at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) during 31 August-7 September produced plumes that rose as high as 1.7 km above the crater rim. The daily sulfur dioxide emission rate was 1,400 tons/day on 31 August. 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.

Cleveland, Chuginadak Island (USA)

52.825°N, 169.944°W, Elevation 1730 m

AVO lowered both the Volcano Alert Level and the Aviation Color Code for Cleveland to Unassigned on 3 September, noting a lack of unrest over the past few months. A short-lived explosion was recorded on 1 June; satellite images showed no signs of elevated temperatures nor surficial changes in the summit crater since then.

Geological summary: The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks. This volcano is located within the Aleutian Islands, a UNESCO Biosphere Reserve property.

Copahue, Central Chile-Argentina border

37.856°S, 71.183°W, Elevation 2953 m

SERNAGEOMIN reported continuing activity at Copahue during 16-31 August. Webcams recorded gas-and-ash plumes rising as high as 1.7 km, sometimes associated with nighttime crater incandescence. The plumes drifted in multiple directions as far as 4.3 km N, 9 km NE, 8 km E, 4 km SE, 4 km SW, 9 km W, and 4.4 km NW. Sulfur dioxide emissions were high, averaging 2,641 tonnes per day (ranging from 2,029 to 3,253 tonnes per day), with a high value of 4,627 on 27 August. The Alert Level was remained at Yellow (the second lowest level on a four-color scale). ONEMI maintained the Yellow Alert (the middle level on a three-color scale) for residents of the Alto Biobío municipality and access to an area within 1 km of El Agrio Crater was restricted to the public.

Geological 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 Río 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.

Dukono, Halmahera (Indonesia)

1.693°N, 127.894°E, Elevation 1229 m

Based on satellite and wind model data, and information from PVMBG, the Darwin VAAC reported that during 2-8 September ash plumes from Dukono rose 2.1 km (7,000 ft) a.s.l. and drifted NW, W, and SW. 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 27-28 and 30-31 August, and 1-2 September. Ash plumes rose up to 3 km (10,000 ft) a.s.l. and drifted N, NE, SE, and S. 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.

Karymsky, Eastern Kamchatka (Russia)

54.049°N, 159.443°E, Elevation 1513 m

KVERT reported that explosions at Karymsky were last recorded on 29 July. A thermal anomaly was weak for most of August and undetectable after 21 August. The Aviation Color Code was lowered to Green (the lowest level on a four-color scale) on 3 September.

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.

Makushin, Fox Islands (USA)

53.891°N, 166.923°W, Elevation 1800 m

Seismicity at Makushin returned to background levels after steadily declining for almost three months following a sequence of earthquakes about 10 km E of the summit at a depth of 8 km that had started on 15 June. AVO lowered the Aviation Color Code and Volcano Alert Level remained at Green and Normal, respectively, on 8 September.

Geological summary: The ice-covered, 1800-m-high Makushin volcano on northern Unalaska Island west of the town of Dutch Harbor is capped by a 2.5-km-wide caldera. The broad, domical structure of Makushin contrasts with the steep-sided profiles of most other Aleutian stratovolcanoes. Much of the volcano was formed during the Pleistocene, but the caldera (which formed about 8000 years ago), Sugarloaf cone on the ENE flank, and a cluster of about a dozen explosion pits and cinder cones at Point Kadin on the WNW flank, are of Holocene age. A broad band of NE-SW-trending satellitic vents cuts across the volcano. The composite Pakushin cone, with multiple summit craters, lies 8 km to the SW of Makushin. Frequent explosive eruptions have occurred during the past 4000 years, sometimes accompanied by pyroclastic flows and surges. Geothermal areas are found in the summit caldera of Makushin and on the SE and eastern flanks of the volcano. They represent the largest and most investigated high-temperature geothermal resources in Alaska. Small-to-moderate explosive eruptions have been recorded at Makushin since 1786.

Rincon de la Vieja, Costa Rica

10.83°N, 85.324°W, Elevation 1916 m

OVSICORI-UNA reported that on 3 September geologists observed Rincón de la Vieja from the summit and noted that the acid lake in the main crater had a low water level, was actively convecting, and exhibited strong gas emissions. The temperature of the lake was 60 degrees Celsius. Vigorous fumaroles on the inner W wall of the crater were 120 degrees Celsius. At 0559 on 8 September an eruption produced a plume that rose 500 m above the crater rim.

Geological 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 Guachipelín 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 María 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 Río 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.

Sangay, Ecuador

2.005°S, 78.341°W, Elevation 5286 m

IG reported a high level of activity at Sangay during 2-8 September. Seismicity was characterized by high levels of explosions, harmonic tremor, long-period earthquakes, and signals indicating emissions. Weather clouds often prevented visual observations of the volcano, but the Washington VAAC and IG webcams recorded daily ash plumes that rose 600-1,500 m above the summit and drifted NW, W, and S. Lahars were periodically generated by heavy rains. On 2 September pyroclastic flows descended the SE flank.

Geological summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Semeru, Eastern Java (Indonesia)

8.108°S, 112.922°E, Elevation 3657 m

PVMBG reported that at 0541 on 8 September an ash plume from Semeru rose 400 m above the summit and drifted S. The Alert Level remained at 2 (on a scale of 1-4).

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.

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 daily during 28 August-4 September. 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, Elevation 796 m

JMA reported periodic nighttime incandescence at Suwanosejima’s Ontake Crater during 28 August-4 September, and there was a total of 11 eruptions. An eruption at 0234 on 4 September generated a grayish white ash plume that rose 1.3 km above the crater rim before entering weather clouds. 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.

Source: GVP

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