The Weekly Volcanic Activity Report: June 17 – 23, 2020

New activity/unrest was reported for 6 volcanoes from June 17 to 23, 2020. During the same period, ongoing activity was reported for 18 volcanoes.

New activity/unrest: Erta Ale, Ethiopia | Karymsky, Eastern Kamchatka (Russia) | Laguna del Maule, Central Chile-Argentina border | Makushin, Fox Islands (USA) | Turrialba, Costa Rica | Veniaminof, United States.

Ongoing activity: Aira, Kyushu (Japan) | Cleveland, Chuginadak Island (USA) | Copahue, Central Chile-Argentina border | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Ibu, Halmahera (Indonesia) | Kanlaon, Philippines | Kick 'em Jenny, North of Grenada | Klyuchevskoy, Central Kamchatka (Russia) | Merapi, Central Java (Indonesia) | Nishinoshima, Japan | Pacaya, Guatemala | Rincon de la Vieja, Costa Rica | Sangay, Ecuador | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Whakaari/White Island, North Island (New Zealand).

New activity/unrest

Erta Ale, Ethiopia

13.6°N, 40.67°E, Summit elev. 613 m

Satellite data showed a minor thermal anomaly in Erta Ale’s S pit crater on 12 June and a larger anomaly on 17 June at the site of the previous lava lake.

Geological summary: Erta Ale is an isolated basaltic shield that is the most active volcano in Ethiopia. The broad, 50-km-wide edifice rises more than 600 m from below sea level in the barren Danakil depression. Erta Ale is the namesake and most prominent feature of the Erta Ale Range. The volcano contains a 0.7 x 1.6 km, elliptical summit crater housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera is renowned for one, or sometimes two long-term lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the N flank.

Karymsky, Eastern Kamchatka (Russia)

54.049°N, 159.443°E, Summit elev. 1513 m

KVERT reported that a thermal anomaly over Karymsky was identified in satellite images during 11-19 June, possibly due to ongoing Strombolian activity. 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.

Laguna del Maule, Central Chile-Argentina border

36.058°S, 70.492°W, Summit elev. 2162 m

SERNAGEOMIN’s Volcanological Observatory of the Southern Andes (OVDAS) of Chile and SEGEMAR’s Argentine Observatory of Volcanic Surveillance (OAVV) reported anomalous activity at Laguna del Maule Volcanic Complex. Elevated levels of carbon dioxide were detected in an area SW of the caldera lake, along the lower part of the Cabecera de Troncoso River, about 5 km from the lake’s shore. Carbon dioxide emissions were measured in February 2020 and notably elevated relative to March 2019 measurements. An impacted area possibly stretched as far as 500 m from the point representing the highest carbon dioxide emission rate; observers noted areas of discolored brown and orange soil aonlg with dead or emaciated animals.

Three swarms of volcano-tectonic (VT) earthquakes recorded in mid-June were mainly located in the Las Nieblas area, SW of the lake, at depths of 2-8 km. The first began at 0340 on 11 June and totaled at least 400 events. The second swarm began at 2338 on 12 June was characterized by 121 events, located 8.8 km W of the crater. The third swarm began at 2334 on 15 June and was characterized by 190 events located 10.4 km SW of the crater. All of the earthquakes were small magnitudes; the largest event was a local M 2.5. On 18 June the Alert Level was raised to Yellow, the second lowest color on a four-color scale; ONEMI recommended restricting access within a radius of 2 km from the emission center. Seismic activity continued to be recorded, though at lesser magnitudes.

Geological summary: The 15 x 25 km wide Laguna del Maule caldera contains a cluster of small stratovolcanoes, lava domes, and pyroclastic cones of Pleistocene-to-Holocene age. The caldera lies mostly on the Chilean side of the border, but partially extends into Argentina. Fourteen Pleistocene basaltic lava flows were erupted down the upper part of the Maule river valley. A cluster of Pleistocene cinder cones was constructed on the NW side of the Maule lake, which occupies part of the northern portion of the caldera. The latest activity produced an explosion crater on the E side of the lake and a series of Holocene rhyolitic lava domes and blocky lava flows that surround it.

Makushin, Fox Islands (USA)

53.891°N, 166.923°W, Summit elev. 1800 m

AVO reported that numerous smaller earthquakes in an area about 12 km SE of Makushin’s summit were recorded after two events greater than M 4 occurred on 15 June. The earthquake activity continued during 16-23 June, though at a declining rate and magnitudes. No surficial activity was visible in satellite or webcam images; only typical minor steaming from summit fumaroles was visible. The Aviation Color Code and Volcano Alert Level remained at Yellow and Advisory, respectively.

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.

Turrialba, Costa Rica

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

OVSICORI-UNA reported that ash emissions at Turrialba rose no higher than100 m above the crater rim from events recorded at 1714, 1723, and 1818 on 18 June and at 1023 and 1039 on 19 June. A small ash emission was visible at 1715 on 22 June.

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.

Veniaminof, United States

56.17°N, 159.38°W, Summit elev. 2507 m

On 18 June AVO stated that periods of seismic tremor and occasional earthquakes had been recorded at Veniaminof over the past few days. The increase above background levels prompted AVO to raise the Volcano Alert Level to Advisory and the Aviation Color Code to Yellow. Periods of low-amplitude seismic tremor decreased in frequency during 19-20 June, and were not detected at all by 21 June.

Geological summary: Veniaminof, on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.

Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Summit elev. 1117 m

JMA reported that very small eruptive events were recorded at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) during 19-22 June. 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, Summit elev. 1730 m

AVO reported that no additional volcanic activity was detected at Cleveland after the short-lived explosion recorded on 1 June. The Volcano Alert Level was lowered to Advisory and the Aviation Color Code was lowered to Yellow.

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.

Copahue, Central Chile-Argentina border

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

On 17 June OVDAS-SERNAGEOMIN reported increased activity at Copahue during the previous days, characterized by low-altitude gas emissions containing particulate matter. A period of increased seismicity was recorded in the afternoon on 16 June accompanied by crater incandescence and emissions visible in webcam images.

The report noted that very-long-period earthquakes had been recorded in previous months, and a series of volcano-related seismic events were detected in an area SSW of the volcano on 20 March. Additionally, satellite images showed a reduction in the size of the crater lake. These recent changes coupled with increased seismicity prompted SERNAGEOMIN to raise the Alert Level to Yellow (second lowest level on a four-color scale) and restrict access to an area within 1 km of El Agrio Crater. ONEMI raised a Yellow Alert (the middle level on a three-color scale) for residents of the Alto Biobío municipality.

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, Summit elev. 1229 m

Based on satellite and wind model data, and information from PVMBG, the Darwin VAAC reported that during 16-23 June ash plumes from Dukono rose to 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted NW and W. 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

KVERT reported that a thermal anomaly over Ebeko was identified in satellite images on 14, 16, and 18 June. Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions on 17 June that sent ash plumes up to 2 km (6,600 ft) a.s.l. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

Ibu, Halmahera (Indonesia)

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

The Darwin VAAC reported that during 20-21 June ash plumes from Ibu rose to 1.8 km (6,000 ft) a.s.l. and drifted NW and W 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.

Kanlaon, Philippines

10.412°N, 123.132°E, Summit elev. 2435 m

PHIVOLCS reported that ground deformation data from continuous GPS measurements at Kanlaon indicated slight deflation of the lower and middle flanks since January. Tilt data from instruments on the SE flank recorded continuing deflation on the lower flanks and inflation of the mid-flank since April 2020. White steam plumes rose 100-200 m above the summit and drifted NW and SW.

The seismic network recorded as many as 10 volcanic earthquakes per day during 17-21 June. A series of earthquakes beneath the lower W flank began at 1603 on 21 June, and by 0800 the next morning there were a total of 136 events recorded. Five of the earthquakes (recorded at 0101, 0104, 0134, 0206, and 0507 on 22 June) were M 3-4.7, and were felt at Intensities II to IV in La Carlota City and Bago City, Negros Occidental, and Canlaon City, Negros Oriental. During 22-23 June there were a total of 104 volcano-tectonic earthquakes beneath the W flank. The Alert Level remained at 1 (on a scale of 0-5) and PHIVOLCS reminded the public to remain outside of the 4-km-radius Permanent Danger Zone.

Geological summary: Kanlaon volcano (also spelled Canlaon), the most active of the central Philippines, forms the highest point on the island of Negros. The massive andesitic stratovolcano is dotted with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The largest debris avalanche known in the Philippines traveled 33 km SW from Kanlaon. The summit contains a 2-km-wide, elongated northern caldera with a crater lake and a smaller, but higher, historically active vent, Lugud crater, to the south. Historical eruptions, recorded since 1866, have typically consisted of phreatic explosions of small-to-moderate size that produce minor ashfalls near the volcano.

Kick 'em Jenny, North of Grenada

12.3°N, 61.64°W, Summit elev. -185 m

The University of the West Indies (UWI) Seismic Research Centre (SRC) and the National Disaster Management Agency (NaDMA) reported that a period of elevated seismicity at Kick 'em Jenny was recorded over a seven-day period in June. According to a news article, only 29 earthquakes were recorded during April-May all with magnitudes of 1.6-2. During 5-12 June there were 1,384 recorded earthquakes with magnitudes as high as 1.8. The Alert Level remained at Yellow (the second lowest level on a four-color scale) and the maritime exclusion zone did not change from the radius of 1.5 km.

Geological summary: Kick 'em Jenny, a historically active submarine volcano 8 km off the N shore of Grenada, rises 1300 m from the sea floor. Recent bathymetric surveys have shown evidence for a major arcuate collapse structure, which was the source of a submarine debris avalanche that traveled more than 15 km W. Bathymetry also revealed another submarine cone to the SE, Kick 'em Jack, and submarine lava domes to its S. These and subaerial tuff rings and lava flows at Ile de Caille and other nearby islands may represent a single large volcanic complex. Numerous historical eruptions, mostly documented by acoustic signals, have occurred since 1939, when an eruption cloud rose 275 m above the sea. Prior to the 1939 eruption, which was witnessed by a large number of people in northern Grenada, there had been no written mention of the volcano. Eruptions have involved both explosive activity and the quiet extrusion of lava flows and lava domes in the summit crater; deep rumbling noises have sometimes been heard onshore. Historical eruptions have modified the morphology of the summit crater.

Klyuchevskoy, Central Kamchatka (Russia)

56.056°N, 160.642°E, Summit elev. 4754 m

KVERT reported that Strombolian activity at Klyuchevskoy was visible during 12-19 June along with a bright thermal anomaly identified in satellite images. A lava flow continued to advance down the Apakhonchich drainage on the SE flank. Avalanches of material on the S side of the lava flow were sometimes visible. 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.

Merapi, Central Java (Indonesia)

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

BPPTKG reported that two explosions at Merapi were recorded at 0913 and 0927 on 21 June; the first lasted under six minutes and the second lasted under two minutes. A dense ash plume rose around 6 km above the summit and drifted W, causing ashfall in areas downwind including in the districts of Magelang and Kulonprogo, and as far as the Girimulyo District (45 km). 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.

Nishinoshima, Japan

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

The Tokyo VAAC reported that ash plumes from Nishinoshima rose to 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted NE and E. The marine exclusion zone was defined as a radius of about 2.6 km from the island.

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.

Pacaya, Guatemala

14.382°N, 90.601°W, Summit elev. 2569 m

INSIVUMEH reported that during 17-19 June Strombolian explosions at Pacaya’s Mackenney Crater ejected material as high as 100 m above the crater rim and continued to build a cone in the crater. Active lava flows were 250 m long on the N flank and 200 m long on the S flank by 19 June. In a special report INSIVUMEH noted that increased on 20 June accompanying active lava flows that traveled 650 m SW and 200 m NW by the next day. During 20-23 June Strombolian explosions ejected incandescent material as high as 200 m above the summit and produced ash plumes that rose 100 m. The explosions were heard in areas up to 5 km away.

Geological summary: Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

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 continued to be recorded by the seismic network and webcams during 16-23 June. Several small eruptive events were recorded during 16-17 June; the largest event occurred at 1635 on 17 June and produced a plume that rose 1 km above the crater rim. Eruptive events were detected at 1442 on 19 June and 1046 on 23 June, though inclement weather conditions prevented visual confirmation.

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, Summit elev. 5286 m

On 16 June the Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) declared a Yellow Alert for the province of Chimborazo due to a recent increase in ashfall from Sangay. IG reported a continuing high level of activity during 16-22 June, though weather clouds often prevented visual observations. According to the IG and Washington VAAC notices ash plumes rose 570-870 m above the summit and drifted W and SW. Incandescent blocks descending the SE flank were seen through breaks in cloud cover overnight during 17-18 June.

SNGRE reported that lahars in the Upano River in the morning of 21 June followed heavy rains two days earlier. In Macas (40 km SE) the lahars caused the closure of the E45 Macas-Puyo road, destroying a 27-m section and damaging a 30-m section, and the evacuation of 21 people.

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, Summit elev. 3657 m

PVMBG and the Darwin VAAC reported that on most days during 18-23 June ash plumes from Semeru rose 300-500 m above the summit and drifted SE, S, SW, and W. 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 12-19 June. A webcam captured an explosion on 13 June that sent ash up to 5 km (16,400 ft) a.s.l. The ash cloud drifted 120 km NE. 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 12-19 June. An explosion was recorded on 18 June, though inclement weather conditions prevented visual confirmation. 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.

Whakaari/White Island, North Island (New Zealand)

37.52°S, 177.18°E, Summit elev. 294 m

GeoNet reported that during the previous few months activity levels at Whakaari/White Island had gradually declined based on the volcano monitoring team’s collective interpretation of all the monitoring data. The Volcanic Alert Level was lowered to 1 on 16 June; the Aviation Color Code was lowered to Green on 22 June.

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