The Weekly Volcanic Activity Report: July 10 - 16, 2019

The Weekly Volcanic Activity Report: July 10 - 16, 2019

New activity/unrest was reported for 5 volcanoes from July 10 - 16, 2019. During the same period, ongoing activity was reported for 18 volcanoes.

New activity/unrest: Great Sitkin, Andreanof Islands (USA) | Manam, Papua New Guinea | Shishaldin, Fox Islands (USA) | Stromboli, Aeolian Islands (Italy) | Ubinas, Peru.

Ongoing activity: Aira, Kyushu (Japan) | Asosan, Kyushu (Japan) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Ibu, Halmahera (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Kerinci, Indonesia | Klyuchevskoy, Central Kamchatka (Russia) | Krakatau, Indonesia | Merapi, Central Java (Indonesia) | Nevados de Chillan, Chile | Popocatepetl, Mexico | Reventador, Ecuador | Sangeang Api, Indonesia | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Villarrica, Chile.

New activity/unrest

Great Sitkin, Andreanof Islands (USA)

52.076°N, 176.13°W, Elevation 1740 m

On 15 July AVO reported that seismicity at Great Sitkin had decreased to background levels during the past few weeks with no evidence of eruptive activity in geophysical or satellite data. The Aviation Color Code was lowered to Green and the Volcano Alert Level was lowered to Normal.

Geological summary: The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century. This volcano is located within the Aleutian Islands, a UNESCO Biosphere Reserve property.​

Manam, Papua New Guinea

4.08°S, 145.037°E, Elevation 1807 m

The Darwin VAAC reported that on 12 July an ash plume from Manam rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted N, based on satellite data and weather models.

Geological summary: The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Shishaldin, Fox Islands (USA)

54.756°N, 163.97°W, Elevation 2857 m

AVO increased the Aviation Color Code for Shishaldin to Yellow and the Volcano Alert Level to Advisory on 12 July following several weeks of increasing seismicity and elevated temperatures in the summit crater identified in satellite images. In addition incandescence in the crater was visible during an overflight. Seismic tremor continued to be elevated at least through 16 July.

Geological summary: The beautifully symmetrical volcano of Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 2857-m-high, 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 steady steam plume rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is Holocene in age and largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the west and NE sides at 1500-1800 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. This volcano is located within the Aleutian Islands, a UNESCO Biosphere Reserve property.

Stromboli, Aeolian Islands (Italy)

38.789°N, 15.213°E, Elevation 924 m

INGV reported that the paroxysmal explosive sequence at Stromboli on 3 July changed the morphology of the crater terrace. The rim of the terrace facing the Sciara del Fuoco was removed, and the N1 and N2 vents in Area N (north crater area, NCA) had enlarged and merged into one. After the paroxysmal event explosive activity rapidly decreased, though it remained more intense than normal. The vents of Area C-S (South Central crater area) produced explosions regularly during 8-14 July, and fed lava flows that traveled about halfway down the Sciara del Fuoco. Material from the lava-flow fronts rolled all the way to the coastline. A new lava flow from Area N (north crater area, NCA) began at 1900 on 14 July.

Geological summary: Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium. This volcano is located within the Isole Eolie (Aeolian Islands), a UNESCO World Heritage property.

Ubinas, Peru

16.355°S, 70.903°W, Elevation 5672 m

Instituto Geofísico del Perú (IGP) reported that seismic activity at Ubinas remained elevated during 1-15 July; volcano-tectonic events averaged 279 per day and long-period events (indicating fluid movement) averaged 116 events per day. Minor bluish emissions rose from the crater. The Alert Level remained at Yellow (on a 4-level scale).

Geological summary: A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Perú. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Elevation 1117 m

JMA reported that during 8-16 July very small eruptive events were detected at Minamidake crater (at Aira Caldera’s Sakurajima volcano), though none of them were explosive. 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.

Asosan, Kyushu (Japan)

32.884°N, 131.104°E, Elevation 1592 m

JMA reported that sulfur dioxide emissions at Asosan’s Nakadake Crater reached a high value of 2,300 tons per day on 12 July. Very small events ejected sediment during 13-16 July. The Alert Level remained at 2 (on a scale of 1-5).

Geological summary: The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 km3 of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 CE. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations. This volcano is located within the Aso, a UNESCO Global Geopark property.

Colima, Mexico

19.514°N, 103.62°W, Elevation 3850 m

Centro Universitario de Estudios e Investigaciones de Vulcanologia - Universidad de Colima reported that intermittent steam-and-gas emissions, mainly from the NE side of the crater, and two small explosions were recorded during 5-12 July. Five lahars descended the Montegrande ravine. An overflight on 9 July revealed that the diameter of the vent had slightly increased, likely caused by subsidence, and other areas of minor subsidence within the crater were noted. An area of collapsed material on the outer W wall was also identified. Temperatures inside the crater were 116 degrees Celsius, lower than the temperature of 250 degrees Celsius recorded in May. The temperatures in the fumarolic area decreased from 202 degrees Celsius in May to 169 degrees. A thermal camera located S of the volcano recorded thermal anomalies associated with fumarolic emissions. Weather conditions sometimes prevented observations of the crater.

Geological summary: The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Dukono, Halmahera (Indonesia)

1.693°N, 127.894°E, Elevation 1229 m

Based on satellite and wind model data, and notices from PVMBG, the Darwin VAAC reported that during 11-16 July ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted N and NE. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km exclusion zone.

Geological summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

Ebeko, Paramushir Island (Russia)

50.686°N, 156.014°E, Elevation 1103 m

Volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, observed explosions during 5-12 July that sent ash plumes up to 3.5 km (11,500 ft) a.s.l. The plumes drifted S. A thermal anomaly was visible in satellite images on 11 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.

Ibu, Halmahera (Indonesia)

1.488°N, 127.63°E, Elevation 1325 m

The Darwin VAAC reported that on 15 July an ash plume from Ibu rose to 2.1 km (7,000 ft) a.s.l. and drifted NE 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.

Karymsky, Eastern Kamchatka (Russia)

54.049°N, 159.443°E, Elevation 1513 m

KVERT reported that a thermal anomaly over Karymsky was identified in satellite images during 4-5 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.

Kerinci, Indonesia

1.697°S, 101.264°E, Elevation 3800 m

The Darwin VAAC reported that on 12 July an ash plume from Kerinci rose to an altitude of 4 km (13,000 ft) a.s.l. and drifted SW, based on satellite images and weather models.

Geological summary: Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838. This volcano is located within the Tropical Rainforest Heritage of Sumatra, a UNESCO World Heritage property.

Klyuchevskoy, Central Kamchatka (Russia)

56.056°N, 160.642°E, Elevation 4754 m

KVERT reported that a weak thermal anomaly over Klyuchevskoy was visible in satellite images during 4-5 and 7 July. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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. This volcano is located within the Volcanoes of Kamchatka, a UNESCO World Heritage property.

Krakatau, Indonesia

6.102°S, 105.423°E, Elevation 813 m

PVMBG reported that Anak Krakatau’s seismic network recorded as many as 25 eruptive events during 1-7 July. The events were not followed by visible ash emissions, though observations were hindered by weather conditions. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 2-km radius hazard zone from the crater.

Geological summary: The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927. This volcano is located within the Ujung Kulon National Park, a UNESCO World Heritage property.

Merapi, Central Java (Indonesia)

7.54°S, 110.446°E, Elevation 2910 m

PVMBG reported that during 8-14 July the lava-dome volume at Merapi did not change and was an estimated 475,000 cubic meters, based on analyses of drone images. Extruded lava fell into the upper parts of the SE-flank, generating two block-and-ash flows that traveled 1 km down the Gendol drainage on 13 and 14 July. White plumes rose as high as 300 m above the summit. The Alert Level remained at 2 (on a scale of 1-4), and residents were warned to remain 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, Elevation 3180 m

ONEMI and SERNAGEOMIN reported that an explosive event at Nevados de Chillán’s Nicanor Crater recorded at 0657 on 14 July was associated with a long-period earthquake signal. The explosion ejected incandescent material onto areas near the crater. The Alert Level remained at Orange, the second highest level on a four-color scale, and residents were reminded not to approach the crater within 3 km. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto, Coihueco, and San Fabián.

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.

Popocatepetl, Mexico

19.023°N, 98.622°W, Elevation 5393 m

CENAPRED reported that each day during 9-15 July there were 49-326 steam-and-gas emissions from Popocatépetl, some of which contained minor amounts of ash. As many as three explosions per day were recorded, though weather conditions often prevented visual characterization of ash emissions. An explosion at 1949 on 11 July generated an ash plume that rose 2.8 km above the crater rim. The Alert Level remained at Yellow, Phase Two (middle level on a three-color scale).

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

Reventador, Ecuador

0.077°S, 77.656°W, Elevation 3562 m

IG reported that during 10-16 July seismic data from Reventador’s network indicated a high level of seismic activity, including explosions, long-period earthquakes, harmonic tremor, and signals indicating emissions. Weather often prevented views of the summit area, although during clear conditions ash plumes were visible rising at least 600 m above the crater rim and drifting W and N. Blocks were observed rolling 500-600 m down the flanks on 10 and 16 July.

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.

Sangeang Api, Indonesia

8.2°S, 119.07°E, Elevation 1949 m

The Darwin VAAC reported that during 10-16 July ash plumes from Sangeang Api were visible in satellite images rising to 2.1-3 km (7,000-10,000 ft) a.s.l. and drifting in multiple directions. The Alert Level remained at 2 (on a scale of 1-4).

Geological summary: Sangeang Api volcano, one of the most active in the Lesser Sunda Islands, forms a small 13-km-wide island off the NE coast of Sumbawa Island. Two large trachybasaltic-to-tranchyandesitic volcanic cones, 1949-m-high Doro Api and 1795-m-high Doro Mantoi, were constructed in the center and on the eastern rim, respectively, of an older, largely obscured caldera. Flank vents occur on the south side of Doro Mantoi and near the northern coast. Intermittent historical eruptions have been recorded since 1512, most of them during in the 20th century.

Semeru, Eastern Java (Indonesia)

8.108°S, 112.922°E, Elevation 3657 m

The Darwin VAAC reported that on 10 July an ash plume from Semeru rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted WNW based on satellite images and weather models. Ash plumes rose to 4 km (13,000 ft) a.s.l. on 13 July and drifted NW and W.

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. This volcano is located within the Bromo Tengger Semeru-Arjuno, a UNESCO Biosphere Reserve property.

Sheveluch, Central Kamchatka (Russia)

56.653°N, 161.36°E, Elevation 3283 m

KVERT reported that a thermal anomaly over Sheveluch’s lava dome was identified daily in satellite images during 6-12 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.

Villarrica, Chile

39.42°S, 71.93°W, Elevation 2847 m

POVI reported that webcam images captured deposits of incandescent material on the flank 300 m from Villarrica’s summit crater in the morning of 15 July. Incandescent material from lava fountaining ejected above the crater rim was periodically visible on 16 July.

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

Source: GVP

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