The Weekly Volcanic Activity Report: April 8 - 14, 2020

The Weekly Volcanic Activity Report: April 8 - 14, 2020

New activity/unrest was reported for 4 volcanoes from April 8 and 14, 2020. During the same period, ongoing activity was reported for 12 volcanoes.

New activity/unrest: Kerinci, Indonesia | Krakatau, Indonesia | Semeru, Eastern Java (Indonesia) | Shishaldin, Fox Islands (USA).

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Fuego, Guatemala | Ibu, Halmahera (Indonesia) | Klyuchevskoy, Central Kamchatka (Russia) | Mayon, Luzon (Philippines) | Merapi, Central Java (Indonesia) | Rincon de la Vieja, Costa Rica | Sheveluch, Central Kamchatka (Russia) | Suwanosejima, Ryukyu Islands (Japan) | Taal, Luzon (Philippines).

New activity/unrest

Kerinci, Indonesia

1.697°S, 101.264°E, Summit elev. 3800 m

According to the Darwin VAAC, PVMBG reported that on 10 April an ash plume from Kerinci rose 600 m above the summit and drifted NW. On 13 April an observer noted that an ash plume rose to 900 m above the summit; the emission was not visible in satellite data. An ash plume rose 400 m above the summit on 14 April; meteorological clouds obscured views. The Alert Level remained at 2 (on a scale of 1-4), and the public was warned to remain outside of the 3-km exclusion zone.

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.

Krakatau, Indonesia

6.102°S, 105.423°E, Summit elev. 155 m

PVMBG reported that at 2158 and 2235 on 10 April an eruptive event at Anak Krakatau generated dense white, gray, and black ash plumes that rose as high as 2 km above the summit and drifted S and E. The events were followed by Strombolian activity that ejected incandescent material onto the crater floor and summit areas; video revealed lightning visible in the ash cloud. The Darwin VAAC issued a notice at 0145 on 11 April stating that an eruption plume had risen to 14.3 km (47,000 ft) a.s.l., but noted low confidence in the altitude due to the possible mixing of the eruption plume with meteorological storm clouds. An intense thermal anomaly was visible. An hour later the VAAC reported an on-going sulfur-rich plume rising to 11.3 km (37,000 ft) a.s.l. and drifting W; the previous plume remained visible and continued to drift NW. Later that day ash plumes rose to 3 km (10,000 ft) a.s.l. and drifted N. During 12-13 April plumes comprised mostly of sulfur dioxide and steam rose to 3 km (10,000 ft) a.s.l.; the plumes did not have a strong ash signal. 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.

Semeru, Eastern Java (Indonesia)

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

PVMBG reported that during 6-12 April dense white-gray plumes rose 200-500 m above Semeru’s summit. Incandescent material was ejected 20 m above the Jonggring-Seloko Crater. Incandescent material from the ends of lava flows descended 200-1,000 m, reaching a maximum distance of 750-1,500 m from the crater. 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.

Shishaldin, Fox Islands (USA)

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

AVO reported elevated seismicity at Shishaldin during 8-13 April characterized by occasional low-frequency earthquakes. Minor steaming from the summit crater was sometimes seen in satellite and webcam data. A small thermal anomaly was visible in satellite data during 8-9 April. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.

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.

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that during 6-13 April incandescence from Minamidake Crater (at Aira Caldera’s Sakurajima volcano) was visible nightly. The seismic network recorded 16 eruptive events and 6 explosions. Ash plumes rose as high as 2 km above the crater rim and material was ejected 300-500 m away from the crater. 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, the Darwin VAAC reported that during 8-14 April ash plumes from Dukono rose to 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted in multiple directions. 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 4-5 and 9 April that sent ash plumes up to 1.5 km (4,900 ft) a.s.l. Ash plumes drifted NE. A thermal anomaly was visible in satellite images on 5 April. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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

Fuego, Guatemala

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

In a special report from 6 April INSIVUMEH reported a change in the eruptive pattern at Fuego indicated by seismic and acoustic data. Lava effused from a summit vent and traveled 400 m down the Ceniza (SSW) drainage. Avalanches of material descended the flank as far as 1 km, reaching vegetated areas. Explosions caused rumbling, shock waves, and ash plumes that rose 1.1 km above the summit. The report noted that this activity was similar to the eight-day phase during 16-24 March.

There were 5-14 explosions per hour recorded during 7-14 April, generating ash plumes that rose as high as 1.1 km above the crater rim and generally drifted 10-20 km in multiple directions. Minor ashfall was reported in several areas downwind including Santa Sofía (12 km SW), Morelia (9 km SW), Panimaché I and II (8 km SW), Quisache, and Sangre de Cristo (8 km WSW). Explosions sometimes produced shock waves that rattled houses in communities within a 25-km radius. Incandescent material was ejected 100-600 m high. Lava flows in the Ceniza drainage had variable lengths during the week, from 200 to 600 m long. Avalanches of blocks from the lava flows traveled sometimes long distances, and in some cases set fire to vegetated areas.

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

Ibu, Halmahera (Indonesia)

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

The Darwin VAAC reported that during 8-10 and 13 April ash plumes from Ibu rose 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted N, SE, and S 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.

Klyuchevskoy, Central Kamchatka (Russia)

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

KVERT reported that Strombolian activity at Klyuchevskoy was visible during 3-10 April along with a bright thermal anomaly identified in satellite images. Vulcanian activity was visible during 6-9 April; ash plumes drifted 200 km S, SE, and E at altitudes of 5.5-6 km (18,000-19,700 ft) a.s.l. on those same days. The 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.

Mayon, Luzon (Philippines)

13.257°N, 123.685°E, Summit elev. 2462 m

PHIVOLCS reported that during 7-14 April white steam plumes periodically emitted from Mayon rose as high as 400 m above the summit and drifted mainly NW, W, and SW. Crater incandescence was visible nightly. The Alert Level remained at 2 (on a 0-5 scale) and PHIVOLCS reminded residents to stay away from the 6-km-radius Permanent Danger Zone and the 7-km Extended Danger Zone on the SSW and ENE flanks.

Geological summary: Beautifully symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the Philippines' most active volcano. The structurally simple edifice has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. Historical eruptions date back to 1616 and range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often devastated populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Merapi, Central Java (Indonesia)

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

PVMBG reported that an eruption at Merapi began at 0910 on 10 April and lasted for one minute and 43 seconds. A gray ash plume rose as high as 3 km above the summit and drifted NW. 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.

Rincon de la Vieja, Costa Rica

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

OVSICORI-UNA reported periodic hydrothermal explosions at Rincón de la Vieja during 8-14 April. A possible small eruption occurred at 0658 on 8 April and was followed by a decrease in the amplitude of tremor signals. Beginning at 0033 on 11 April a small-scale hydrothermal explosion was recorded by the infrasoiund and seismic networks for 20 seconds. Water and sediment was ejected onto the upper flanks of the volcano. The event was recorded by the webcam located in Sensoria, 4 km N of the crater. In the morning local residents noted that the water in the Pénjamo River was milky white. A small hydrothermal explosion at 0251 on 13 April produced a plume of steam and gas that rose 500 m.

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.

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 3-10 April. Explosions on 8 April generated ash plumes that rose to 10 km (32,800 ft) a.s.l. and drifted 526 km SE during 8-9 April. 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 during 3-10 April incandescence from Suwanosejima’s Ontake Crater was visible nightly. Small eruptions occasionally occurred, producing gray-white plumes that rose as high as 900 m above the crater rim; rumbling sounds were noted in a village 4 km SSW. 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.

Taal, Luzon (Philippines)

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

PHIVOLCS reported that during 8-9 April steam plumes rose 100-300 m above the Taal’s main vent and drifted SW. Weak steaming (plumes up to 20 m high) from ground cracks was visible during 8-14 April along the Daang Kastila trail which connects the N part of Volcano Island to the N part of the main crater. PHIVOLCS had lowered the Alert Level to 1 (on a scale of 0-5) on 19 March and recommended no entry onto Volcano Island, the area defined as the Permanent Danger Zone.

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

Source: GVP

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