The Weekly Volcanic Activity Report: July 22 - 28, 2020

The Weekly Volcanic Activity Report: July 22 - 28, 2020

New activity/unrest was reported for 3 volcanoes from July 22 to 28, 2020. During the same period, ongoing activity was reported for 9 volcanoes.

New activity/unrest: Copahue, Central Chile-Argentina border | Nishinoshima, Japan | Turrialba, Costa Rica.

Ongoing activity: Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Popocatepetl, Mexico | Reventador, Ecuador | Rincon de la Vieja, Costa Rica | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Villarrica, Chile.

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.

Note that many news agencies do not archive the articles they post on the Internet, and therefore the links to some sources may not be active. To obtain information about the cited articles that are no longer available on the Internet contact the source.

New activity/unrest

Copahue, Central Chile-Argentina border

37.856°S, 71.183°W, Summit elev. 2953 m

SERNAGEOMIN and SEGEMAR reported that elevated seismicity (continuous tremor) at Copahue was recorded on 16 July and accompanied by ash emissions observed by local residents. Sulfur dioxide emissions were anomalous on 4, 6, and 20 July; values were 2,100 and 1,713 tons per day on 2 and 4 July, respectively, on the high end of normal values. On 20 July residents of La Araucanía described an odor indicating hydrogen sulfide gas emissions. On 23 July the Alert Level was raised to Yellow (the second lowest level on a four-color scale). ONEMI raised a 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.

Nishinoshima, Japan

27.247°N, 140.874°E, Summit elev. 25 m

Based on satellite data, the Tokyo VAAC reported that during 22-28 July ash plumes from Nishinoshima rose to 2.4-5.2 km (8,000-17,000 ft) a.s.l. and drifted in multiple directions.

Geological summary: The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Another eruption that began offshore in 2013 completely covered the previous exposed surface and enlarged the island again. Water discoloration has been observed on several occasions since. The island is the summit of a massive submarine volcano that has prominent satellitic peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the sea surface 9 km SSE.

Turrialba, Costa Rica

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

OVSICORI-UNA reported that during 22-23 July white steam plumes from Turrialba contained a minor amount of ash on one occasion.

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.

Ongoing activity

Dukono, Halmahera (Indonesia)

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

Based on information from PVMBG and satellite data the Darwin VAAC reported that ash plumes from Dukono rose to 2.1-2.3 km (7,000-8,000 ft) a.s.l. and drifted N, NW, and W during 22-26 and 28 July. The Alert Level remained at a 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, Summit elev. 1103 m

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 17-24 July that sent ash plumes up to 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A thermal anomaly over the volcano was identified in satellite images each day; an ash cloud 11x13 km in size drifted 30 km SE on 22 July. 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.

Popocatepetl, Mexico

19.023°N, 98.622°W, Summit elev. 5393 m

CENAPRED reported that each day during 22-27 July there were 2-107 steam-and-gas emissions from Popocatépetl, some of which contained minor amounts of ash. Crater incandescence was visible most nights. Gas, steam, and ash plumes rose as high as 2 km above the crater rim and drifted NW, WSW, and SW. Minor ashfall was reported on 23 and 27 July in areas downwind, including in Tetela del Volcán (20 km SW), Ocuituco (24 km SW), Atlatlahucán (30 km WSW), Yecapixtla (20 km W), Yautepec (50 km WSW), and Jiutepec (60 km WSW), in the state of Morelos, as well as in Tlalmanalco (30 km NW), Juchitepec, Tepetlixpa (20 km W), Atlautla (17 km W), Ozumba (18 km W), and Ecatzingo (15 km SW), in the state of Mexico. Incandescent material was ejected a short distance from the crater on 25 July and was followed by minor ashfall in Ecatzingo, Atlautla, Tepetlixpa, and Juchitepec. Incandescent material was again ejected a short distance from the crater during 26-27 July. Explosions were recorded at 1135 on 27 July and 0511 on 28 July. Minor ashfall was reported in the municipalities of Tlalmanalco (30 km NW), Ayapango (22 km NW), Temamatla (32 km NW), Ecatepec, Valle de Chalco (44 km NW), Texcoco (60 km NNW), Tezoyuca (68 km NNW), Tepetlaoxtoc, Naucalpan (80 km NW), Atizapán (90 km NW), Huixquilucan (85 km NW), Nicolás Romero (95 km NW), and Tlalnepantla (80 km NW) in the state of México. The Alert Level remained at Yellow, Phase Two (middle level on a three-color scale).

Geological summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Reventador, Ecuador

0.077°S, 77.656°W, Summit elev. 3562 m

On 23 July IG reported that activity at Reventador remained high. A slight increase in surficial activity during the previous two weeks was characterized by ash emissions along with pyroclastic flows that descended the W, N, and NE flanks. Ash plumes rose 0.7-1.3 km above the crater rim and drifted several kilometers NW, W, and SW. Incandescent blocks preferentially rolled down the N and NE flanks, though sometimes material was ejected onto all of the flanks.

Geological summary: Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

Rincon de la Vieja, Costa Rica

10.83°N, 85.324°W, Summit elev. 1916 m

OVSICORI-UNA reported that periodic phreatic explosions at Rincón de la Vieja were recorded by the seismic network and webcams during 22-25 July. Sometimes the events were not visually confirmed due to weather conditions. Small eruptive events were recorded during 0700-0900 on 22 July, and during the first part of the day on 23 July; a minor steam plume was visible at 0536 on 23 July. An eruptive event at 0153 on 25 July produced a plume that rose 1 km 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 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 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 3,500 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.

Semeru, Eastern Java (Indonesia)

8.108°S, 112.922°E, Summit elev. 3657 m

PVMBG reported that white-and-gray ash plumes from Semeru rose 300-500 m above the summit and drifted S and W during 23-26 and 28 July. Weather conditions prevented visual observations on 22 and 27 July. 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.

Sheveluch, Central Kamchatka (Russia)

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

KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 17-24 July. 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 nighttime incandescence at Suwanosejima’s Ontake Crater was occasionally visible during 17-24 July. An explosion at 2247 on 22 July generated a gray plume that rose as high as 1.2 km above the crater rim and ejected large rocks as far as 300 m from the crater. The Tokyo VAAC reported that during 25-27 July ash plumes rose to 1.8-2.7 km (6,000-9,000 ft) a.s.l. (1-1.9 km above the crater rim) and drifted NW, N, NE. 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 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.

Villarrica, Chile

39.42°S, 71.93°W, Summit elev. 2847 m

ONEMI reported that during 1-15 July activity at Villarrica was characterized by nighttime crater incandescence, gas emission, and sporadic tephra emissions. SERNAGEOMIN reported that a long-period earthquake associated with a moderate explosion in the summit crater was recorded at 1807 on 25 July. The Alert Level remained at Yellow, the second lowest level on a four-color scale. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the municipalities of Villarrica, Pucón (16 km N), Curarrehue, and the commune of Panguipulli, and changed the exclusion zone for the public to a radius of 500 m around the crater.

Geological summary: Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.

Source: GVP


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