The Weekly Volcanic Activity Report: June 24 - 30, 2020

The Weekly Volcanic Activity Report: June 24 - 30, 2020

New activity/unrest was reported for 3 volcanoes from June 24 - 30, 2020. During the same period, ongoing activity was reported for 19 volcanoes.

New activity/unrest: Asamayama, Honshu (Japan) | Makushin, Fox Islands (USA) | Turrialba, Costa Rica.

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Kanlaon, Philippines | Karymsky, Eastern Kamchatka (Russia) | Klyuchevskoy, Central Kamchatka (Russia) | Merapi, Central Java (Indonesia) | Nevados de Chillan, Chile | Nishinoshima, Japan | Pacaya, Guatemala | Reventador, Ecuador | Sabancaya, Peru | Sangay, Ecuador | Santa Maria, Guatemala | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Suwanosejima, Ryukyu Islands (Japan) | Yasur, Vanuatu.

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

Asamayama, Honshu (Japan)

36.406°N, 138.523°E, Summit elev. 2568 m

On 25 June JMA raised the Alert Level for Asamayama to 2 (on a scale of 1-5) noting that inflation on the W flank had been recorded since 20 June. The number of shallow (just below the summit, or 1-2 km a.s.l.) volcanic earthquakes had also increased; two volcanic tremors were detected on 20 June. Emissions form the summit crater had not changed and continued to be white in color and rise no more than 200 m above the crater rim.

Geological summary: Asamayama, Honshu's most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has an historical record dating back at least to the 11th century CE. Maekake has had several major plinian eruptions, the last two of which occurred in 1108 (Asamayama's largest Holocene eruption) and 1783 CE.

Makushin, Fox Islands (USA)

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

AVO reported continuing numerous smaller earthquakes in an area about 10 km E of the Makushin’s summit at a depth of about 8 km during 24-30 June; the frequency and magnitude had been declining since 15 June but the rate became variable on 24 June. No surficial activity was visible in satellite or webcam images; only typical minor steaming from summit crater lake. Earthquakes with a M 3 and M 3.8 were recorded at 1653 and 1802 on 28 June, with the larger event strongly felt in Unalaska (14 km E). 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 occasional small ash emissions rose no higher than 100 m above the active crater at Turrialba each day during 23-29 June; no emissions were recorded on 27 June. A series of ash emissions were recorded at 1348, 1739, and 2303 on 28 June and at 0107, 0232, 0306, 0412, and 0818 on 28 June. At least two of those events (0107 and 0412) were accompanied by ballistics that were ejected onto the N wall of the active crater.

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

Aira, Kyushu (Japan)

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

JMA reported that during 22-26 June two eruptive events at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) produced plumes that rose as high as 1,300 m above the crater rim. An explosion at 1807 on 28 June ejected material 1,000-1,300 m away from the crater and produced a plume that rose 600 m above the crater rim. 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.

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 24 and 26-30 June ash plumes from Dukono rose to 2.1 km (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

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 19-26 June that sent ash plumes up to 3.5 km (11,500 ft) a.s.l. Ash plumes drifted in various directions, though during 21-25 June they drifted 50 km WSW. A thermal anomaly over the volcano was identified in satellite images during 21-25 June. 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.

Kanlaon, Philippines

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

PHIVOLCS reported that the seismic network recorded 6-44 volcano-tectonic earthquakes per day at Kanloan during 23-30 June and 1-4 volcanic earthquakes during 27-29 June. Steam plumes rose 100-300 m above the summit and drifted NE, NW, and SW. A M 3.6 earthquake was recorded at 1900 on 23 June and was felt at Intensity III in La Carlota City and at Intensity II in Bago City, Negros Occidental. Sulfur dioxide emissions were 438, 237, and 116 tonnes per day on 13, 24, and 27 June, respectively. 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.

Karymsky, Eastern Kamchatka (Russia)

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

KVERT reported that a bright thermal anomaly over Karymsky was identified in satellite images during 19-26 June. 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.

Klyuchevskoy, Central Kamchatka (Russia)

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

KVERT reported that Strombolian activity at Klyuchevskoy was visible during 19-26 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 during 19-25 June sometimes dense white emissions from Merapi rose as high as 600 m above the summit. The report noted that the lava-dome volume was an estimated 200,000 cubic meters on 13 June based on analyses of drone images. The morphology of the summit crater area had slightly changed after the 21 June eruption. Based on photos taken from the Ngepos Post about 19,000 cubic meters had been removed from the SW part of the summit, likely near or part of the crater rim. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to stay outside of the 3-km exclusion zone.

Geological summary: Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities during historical time.

Nevados de Chillan, Chile

36.868°S, 71.378°W, Summit elev. 3180 m

SERNAGEOMIN reported an increase in the rate of inflation in the vicinity of Nevados de Chillán’s Nicanor Crater beginning on 20 June. The lava dome in the crater that was visible in satellite images on 11 June (but described in previous reports) had increased in volume based on analysis of 23 June images, and lengthened on the E side. The estimated growth rate of 0.1-0.3 cubic meters per second is two orders of magnitude greater than growth of the Gil-Cruz dome measured during December 2018-early 2019 and one order of magnitude greater that dome growth during August-December 2019. Occasional explosions continued to be recorded, with emissions rising to low heights, and nighttime crater incandescence was visible. The Alert Level remained at Yellow, the second lowest level on a four-color scale, and residents were reminded not to approach the crater within 3 km. ONEMI stated that the Alert Level Yellow (the middle level on a three-color scale) remained in place for the communities of Pinto and Coihueco, and that the public should stay at least 2 km away from the crater.

Geological summary: The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, Cerro Blanco (Volcán Nevado), is located at the NW end of the group. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in elevation. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986 and eventually exceeded its height.

Nishinoshima, Japan

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

During an overflight of Nishinoshima on 29 June Japan Coast Guard observers noted black ash plumes vigorously rising from the central crater to more than 3.4 km (11,200 ft) a.s.l. A possible collapse of the SW part of the main crater was evident in photographs taken during the overflight. Strombolian explosions ejected lava above the cone and lava traveled SW, reaching the ocean and producing steam plumes. Discolored yellow-green water was visible as far as 1 km offshore. 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 24-30 June Strombolian explosions at Pacaya’s Mackenney Crater ejected material as high as 200 m above the crater rim and were sometimes audible as far away as 5 km. Lava flows on the SW flank were mostly 100-600 m long but advanced to 2 km by 30 June. Lava advanced to 100 m on the S flank during 25-26 June and to 200 m on the NW flank during 27-29 June.

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.

Reventador, Ecuador

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

IG reported that during 27 May-2 June seismic data from Reventador’s network indicated a high level of seismic activity, including explosions, harmonic tremor, long-period earthquakes, and signals indicating emissions. Gas, steam, and ash emissions observed almost daily with the webcam or reported by the Washington VAAC rose as high as 1 km above the summit crater and drifted N, NW, W, and SW. Cloudy weather sometimes prevented views of the volcano. Incandescent blocks rolled as far as 500 m down mainly the S and E flanks. Nighttime crater incandescence was often visible.

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.

Sabancaya, Peru

15.787°S, 71.857°W, Summit elev. 5960 m

Instituto Geofísico del Perú (IGP) reported that a daily average of 12 explosions occurred at Sabancaya during 22-28 June. Gas-and-ash plumes rose as high as 4 km above the summit and drifted NE, E, and SE; on 27 June ashfall was reported in several areas NE possibly including the districts of Madrigal, Lari, Achoma, Ichupampa, Yanque, Chivay, and Coporaque. There were 10 thermal anomalies identified in satellite data, originating from the lava dome in the summit crater. The Alert Level remained at Orange (the second highest level on a four-color scale) and the public were warned to stay outside of a 12-km radius.

Geological summary: Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Sangay, Ecuador

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

IG reported that during an overflight of Sangay on 24 June scientists observed a small explosion followed by a dense ash plume that rose 500 m above the summit and drifted W. Additionally a pyroclastic flow descended the SE flank. The overflight was conducted in partnership with Servicio Nacional de Gestión de Riesgos y Emergencias (SNGRE) and the Army with the purpose of conducting maintenance on a gas and seismic station, taking visual and infrared photos of the surficial activity, and measuring volcanic gases.

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 24-29 June explosions at Santa María's Santiaguito lava-dome complex generated ash plumes that rose 700-1,000 m above the crater and drifted as far as 1 km S, SW, W, and N. Crater incandescence was visible most nights. Avalanches of blocks descended the SE, S, and SW flanks of Caliente cone and sometimes reached the base of the complex. Local ashfall around the volcano was sometimes reported.

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.

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 24-30 June dense white-gray ash plumes from Semeru rose 200-500 m above the summit and drifted SW and N. 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 19-26 June. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Shishaldin, Fox Islands (USA)

54.756°N, 163.97°W, Summit elev. 2857 m

On 24 June AVO reported that seismicity at Shishaldin had decreased to background levels. Additionally, satellite images showed no new lava in the crater area, typical surface temperatures, and minor steaming. The Volcano Alert Level was lowered to Normal and the Aviation Color Code was lowered to Green.

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

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 19-26 June. Very small eruptive events were occasionally recorded with plumes rising as high as 900 m above the crater rim. The Alert Level remained at 2 (on a 5-level scale).

Geological summary: The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Yasur, Vanuatu

19.532°S, 169.447°E, Summit elev. 361 m

On 25 June the Vanuatu Meteorology and Geo-Hazards Department (VMGD) reported that seismic data and recent visual observations at Yasur confirmed ongoing explosions and gas-and-ash emissions. The Alert Level remained at 2 (on a scale of 0-4). VMGD reminded residents and tourists that hazardous areas were near and around the volcanic crater, within a 600-m-radius exclusion zone, and that volcanic ash and gas could reach areas impacted by trade winds.

Geological summary: Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Source: GVP

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