The Weekly Volcanic Activity Report: July 14 - 20, 2021

The Weekly Volcanic Activity Report: July 14 - 20, 2021

New activity/unrest was reported for 2 volcanoes from July 14 - 20, 2021. During the same period, ongoing activity was reported for 14 volcanoes.

New activity/unrest: Suwanosejima, Ryukyu Islands (Japan) | Taal, Luzon (Philippines).

Ongoing activity: Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Fuego, Guatemala | Karymsky, Eastern Kamchatka (Russia) | Krysuvik-Trolladyngja, Iceland | Lewotolok, Lembata Island (Indonesia) | Merapi, Central Java (Indonesia) | Nevado del Ruiz, Colombia | Sangay, Ecuador | Santa Maria, Guatemala | Semisopochnoi, Aleutian Islands (USA) | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Whakaari/White Island, North Island (New Zealand).

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

Suwanosejima, Ryukyu Islands (Japan)

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

JMA reported that five explosions at Suwanosejima's Ontake Crater during 12-19 July ejected bombs as far as 400 m from the crater. Crater incandescence was visible on some nights and ashfall was occasionally reported in Toshima village (4 km SSW). An explosion at 2330 on 12 July produced an ash plume that rose 3.6 km. The Alert Level remained at 3 and the public was warned to stay 2 km away from the crater.

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.

Taal, Luzon (Philippines)

14.002°N, 120.993°E, Summit elev. 311 m

PHIVOLCS reported that unrest at Taal continued during 13-20 July. Daily plumes of steam and sulfur dioxide gas rose 0.9-2.1 km from the lake and drifted in multiple directions. Sulfur dioxide emissions averaged 1,142-6,574 tonnes/day. Two tremor events, at 1018 and 1038 on 20 July, were felt at Intensity I by residents of Pira-piraso in the NE sector of Volcano Island. The DROMIC report stated that 3,839 people were in evacuation centers or private residences by 20 July. The Alert Level remained at 3 (on a scale of 0-5) and PHIVOLCS reminded the public that the entire Taal Volcano Island is a Permanent Danger Zone (PDZ) and to not enter the high-risk barangays of Agoncillo and Laurel. Activities on Taal Lake were strictly prohibited.

Geological summary: Taal is one of the most active volcanoes in the Philippines and has produced some of its most powerful historical eruptions. Though not topographically prominent, its prehistorical eruptions have greatly changed the landscape of SW Luzon. The 15 x 20 km Talisay (Taal) caldera is largely filled by Lake Taal, whose 267 km2 surface lies only 3 m above sea level. The maximum depth of the lake is 160 m, and several eruptive centers lie submerged beneath the lake. The 5-km-wide Volcano Island in north-central Lake Taal is the location of all historical eruptions. The island is composed of coalescing small stratovolcanoes, tuff rings, and scoria cones that have grown about 25% in area during historical time. Powerful pyroclastic flows and surges from historical eruptions have caused many fatalities.

Ongoing activity

Dukono, Halmahera (Indonesia)

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

Based on satellite and wind model data, the Darwin VAAC reported that during 13-19 July ash plumes from Dukono rose to 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted NW, N, NE, and ESE. 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, Summit elev. 1103 m

According to volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, explosions during 10-14 July produced ash plumes that rose as high as 3 km (10,000 ft) a.s.l. and drifted E. A thermal anomaly was identified in satellite images on 10 and 12 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.

Fuego, Guatemala

14.473°N, 90.88°W, Summit elev. 3763 m

INSIVUMEH reported that 5-15 explosions per hour were recorded during 13-20 July at Fuego, generating ash plumes as high as 1.1 km above the crater rim and shock waves that often rattled buildings around the volcano. Ash plumes mostly drifted 10-20 km NW, W, and SW and caused daily ashfall in several areas downwind, including Morelia (9 km SW), Panimaché I and II (8 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), Finca Palo Verde, Sangre de Cristo (8 km WSW), and San Pedro Yepocapa (8 km NW). Block avalanches descended the Ceniza (SSW), Seca (W), Trinidad (S), Taniluyá (SW), Las Lajas (SE), and Honda drainages, often reaching vegetated areas. Explosions ejected incandescent material 100-400 m above the summit during 13-19 July.

Geological summary: Volcán Fuego, one of Central America's most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

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 data drifting 80 km NW, NE, and ESE during 8-11 and 15 July. A thermal anomaly was visible during 8 and 10-13 July. 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.

Krysuvik-Trolladyngja, Iceland

63.917°N, 22.067°W, Summit elev. 360 m

The fissure eruption in the W part of the Krýsuvík-Trölladyngja volcanic system, close to Fagradalsfjall on the Reykjanes Peninsula, continued during 14-20 July. Lava fountaining and overflows from the fifth vent were sometimes visible, and lava from the crater flowed in tubes as well as on the surface. Visible activity at the vent occasionally paused for various lengths of time. The Aviation Color Code remained at Orange due to the lack of ash and tephra emissions, though IMO warned of the potential for lapilli and scoria fallout within a 650 m radius of the active vent. Authorities warned of increased gas emissions hazards.

Geological summary: The Krýsuvík-Trölladyngja volcanic system is described by the Catalogue of Icelandic Volcanoes as an approximately 50-km-long composite fissure swarm trending about N38°E, including a 30-km-long swarm of fissures, with no central volcano. It is one of the volcanic systems arranged en-echelon along the Reykjanes Peninsula west of Kleifarvatn lake. The Fagradalsfjall and Krýsuvík fissure swarms are considered splits or secondary swarms of the Krýsuvík–Trölladyngja volcanic system. Small shield volcanoes have produced a large portion of the erupted volume within the system. Several eruptions have taken place since the settlement of Iceland, including the eruption of a large basaltic lava flow from the Ogmundargigar crater row around the 12th century. The latest eruption, identified through tephrochronology, took place during the 14th century.

Lewotolok, Lembata Island (Indonesia)

8.274°S, 123.508°E, Summit elev. 1431 m

PVMBG reported that daily white-and-gray plumes from Lewotolok rose as high as 1 km and drifted W, NW, NE, and E during 13-20 July. Rumbling was heard daily. Incandescent material was ejected as far as 1 km from the summit vent in various directions during 16-18 July. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 3 km away from the summit crater.

Geological summary: The Lewotolok (or Lewotolo) stratovolcano occupies the eastern end of an elongated peninsula extending north into the Flores Sea, connected to Lembata (formerly Lomblen) Island by a narrow isthmus. It is symmetrical when viewed from the north and east. A small cone with a 130-m-wide crater constructed at the SE side of a larger crater forms the volcano's high point. Many lava flows have reached the coastline. Eruptions recorded since 1660 have consisted of explosive activity from the summit crater.

Merapi, Central Java (Indonesia)

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

BPPTKG reported that the lava dome just below Merapi’s SW rim and the lava dome in the summit crater both remained active during 9-15 July. The SW rim lava-dome volume was an estimated 1.83 million cubic meters and continued to shed material down the flank. One pyroclastic flow traveled 1.1 km down the SW flank and as far as 1.5 km SE. Avalanches traveled a maximum of 1.5 km SE (58 times), 2 km SW (98 times), 1 km W (one time), and 700 m NW (three times). The volume of the summit lava dome was 2.796 million cubic meters. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 5 km away from the summit.

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 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent 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.

Nevado del Ruiz, Colombia

4.892°N, 75.324°W, Summit elev. 5279 m

On 21 July Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity at Nevado del Ruiz was generally characterized by higher number of earthquakes that had larger magnitudes than the previous week. Gas-and-steam emissions were sometimes visible in webcam images rising as high as 1.1 km above the summit and drifting WNW and WSW; these emissions sometimes contained ash. Episodes of drumbeat seismicity were recorded during 13-14 and 17 July, indicating ascent or growth of a lava dome in Arenas Crater. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Geological summary: Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

Sangay, Ecuador

2.005°S, 78.341°W, Summit elev. 5286 m

IG reported a high level of activity at Sangay during 13-20 July. Weather clouds and rain sometimes prevented visual and webcam observations of the volcano. Daily ash plumes were identified in satellite images by the Washington VAAC, rising between 900 m to as high as 5.4 km above the volcano and drifting W, SW, SE, and NE. Ashfall was reported in Barca and Guamote (40 km WNW) on 14 July and in Guamote on 19 July. Signals indicating lahars were recorded by the seismic network during 15-16 and 18-20 July.

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.

Santa Maria, Guatemala

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

INSIVUMEH reported that during 13-20 July daily explosions at Santa María’s Santiaguito lava-dome complex generated ash plumes that rose as high as 1 km above the summit and drifted as far as 12 km SW and W. Collapses of blocky lava from Caliente dome sent avalanches down the SW and W flanks, often reaching the base, and caused minor ashfall mostly on the volcano’s flank. Ashfall was also reported in San Marcos (8 km SW) and Loma Linda Palajunoj (6 km WSW) during 14-15 and 19-20 July. On 15 July blocks of extruded lava formed a lava flow on the W flank that was 700 m long. Block-and-ash flows descended the W and NE flanks.

Geological summary: Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile 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 vents, with activity progressing W towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Semisopochnoi, Aleutian Islands (USA)

51.93°N, 179.58°E, Summit elev. 1221 m

AVO reported that unrest continued at Semisopochnoi during 13-20 July. Periods of low-level tremor and steam plumes from Mount Cerberus were occasionally recorded. Elevated surface temperatures at the N cone of Mount Cerberus were identified in satellite images during 13-14 July and robust steam-and-gas emissions were seen in webcam images. A plume with low amounts of sulfur dioxide drifting about 200 km N was identified in satellite data on 17 July. Sulfur dioxide emissions were also detected the next day. 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 Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part. The three-peaked Mount Cerberus was constructed within the caldera during the Holocene. Each of the peaks contains a summit crater; lava flows on the N flank of Cerberus appear younger than those on the south side. Other post-caldera volcanoes include the symmetrical 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 eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone could have been recently active.

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 9-16 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.

Sinabung, Indonesia

3.17°N, 98.392°E, Summit elev. 2460 m

Video taken on 13 July and posted on social media showed new vents on the upper W flank of Sinabung that were producing steam-and-ash emissions. PVMBG reported that white-and-gray plumes rose 100-300 m from the summit and drifted E and SE. During 14-18 June white plumes rose as high as 300 m. An eruptive event that began around 1850 on 19 July and lasted about 11 minutes produced an ash plume that rose 1 km and drifted ESE. 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: 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.

Whakaari/White Island, North Island (New Zealand)

37.52°S, 177.18°E, Summit elev. 294 m

GeoNet reported continuing unrest at Whakaari/White Island. During overflights of the island on 15 and 20 July scientists observed minor steam-and-gas activity around the 2019 Primary Crater lava domes and noted that the Main Crater area continues to fill with water. Other fumarolic vents remained active and unchanged. Overall, seismicity was at low levels during the previous few months, punctuated by a few notable events; a short-lived tremor episode was recorded on 2 June, discrete acoustic signals recorded during 18-20 June were associated with geysering in a new vent N of 2019 Crater, and a 15-minute low-frequency volcanic earthquake occurred on 30 June. Nighttime incandescence has persisted in webcam views since the 30 June earthquake. Thermal infrared measurements taken on 15 July confirmed that temperatures at dome vents had notably increased, from around 110 degrees Celsius measured in late May-early June to 498-654 degrees. Gas emissions had not notably changed over the previous few months as confirmed during the 20 July overflight. The Volcanic Alert Level remained at 1 and the Aviation Color Code remained at Green.

Geological summary: The uninhabited Whakaari/White Island is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

Source: GVP


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