The Weekly Volcanic Activity Report: April 7 – 13, 2021

New activity/unrest was reported for 7 volcanoes from April 7 to 13, 2021. During the same period, ongoing activity was reported for 11 volcanoes.

New activity/unrest: Karymsky, Eastern Kamchatka (Russia) | Krysuvik-Trolladyngja, Iceland | Pacaya, Guatemala | Piton de la Fournaise, Reunion Island (France) | Semisopochnoi, Aleutian Islands (USA) | Soufriere St. Vincent, St. Vincent | Suwanosejima, Ryukyu Islands (Japan).

Ongoing activity: Aira, Kyushu (Japan) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Ibu, Halmahera (Indonesia) | Kilauea, Hawaiian Islands (USA) | Lewotolok, Lembata Island (Indonesia) | Merapi, Central Java (Indonesia) | Raung, Eastern Java (Indonesia) | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia.

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

Karymsky, Eastern Kamchatka (Russia)

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

KVERT reported that the explosive eruption that began at Karymsky on 3 April continued through 11 April. A thermal anomaly was visible in satellite images during 2-6 April; weather conditions obscured views on other days. The 3 April explosion generated an ash plume that rose to 8.5 km (27,900 ft) a.s.l. and drifted 255 km NE. At 1745 on 11 April explosions produced ash plumes that rose to 4 km (13,100 ft) a.s.l. and drifted at least 65 km SE. The Aviation Color Code was raised to Orange (the second highest level on a four-color scale) on 3 April.

Geological summary: Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Krysuvik-Trolladyngja, Iceland

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

IMO reported that the fissure eruption in the W part of the Krýsuvík-Trölladyngja volcanic system, close to Fagradalsfjall on the Reykjanes Peninsula, continued during 7-13 April. Lava from the third fissure flowed S into Geldingadalur and NE towards the Meradalir valley site. Flows from the three fissures connected into one flow field on 7 April. Another new fissure opened at around 0300 on 10 April, halfway between two existing fissures, and all four fissures were simultaneously active. Lava flowed towards Geldingadalur. Gas-rich emission plumes were visible in webcam images rising 1.1-1.3 km (3,600-4,300 ft) a.s.l. At least two new vents opened on 13 April based on webcam views. On 14 April IMO noted that lava was flowing from at least eight vents and unverified reports form the morning suggested two additional vents had opened. Sulfur dioxide gas flux was 29 kilograms per second, comparable to measurements collected during the previous few weeks.

IMO warned visitors that new fissures could open without adequate visible warning, especially in an area just S of Keilir, by Litla-Hrút, where seismicity was concentrated. They also warned of increased gas emissions hazards. The Aviation Color Code remained Orange due to the lack of ash and tephra emissions.

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

Pacaya, Guatemala

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

INSIVUMEH reported that the eruption at Pacaya’s Mackenney Crater continued during 7-13 April. Explosions during 6-7 April produced ash plumes that rose 1 km above the summit and drifted 10 km W and SW. Ballistics were ejected 50-150 m above the summit. Explosions during 8-9 and 11-12 April produced ash plumes that rose as high as 1 km and drifted as far as 10 km NE, W, and SW.

The lava flow on the W and SW flanks was 3.7 km long and continued to be fed. Incandescent lava blocks were spalled from the flow front and vegetation was set on fire. The lava advanced W onto the La Breña farm and SW towards El Patrocinio and El Rodeo, near the Campo Alegre farm. On 12 April the flows burned La Breña coffee and avocado plantations. By 13 April the lava flows were 3.8 km long, and within 370 m of houses in El Patrocinio. Another flow front was 250 m E of El Rodeo, and obstructed the road that connects El Rodeo, El Caracol, and Los Pocitos.

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.

Piton de la Fournaise, Reunion Island (France)

21.244°S, 55.708°E, Summit elev. 2632 m

OVPF reported that a seismic crisis at Piton de la Fournaise began at 1457 on 9 April and was accompanied by rapid deformation beneath the S flank. Seismicity indicated that a fissure opened at 1900 but could not be visually confirmed due to weather conditions. The Alert Level was raised to 2-2. During an overflight at 0840 on 10 April scientists observed a NNW-oriented fissure, 700 m S of Château Fort. Activity was focused at two vents, each producing lava fountains that were no higher than 30 m tall, though fountains also rose from other parts of the fissure. Slow-moving ‘a’a lava flowed SE and then curved E and advanced 1.6 km to 1,800 elevation. The N end of the fissure was no longer active. Two cones had formed over the main vents and were growing larger; by 11 April the more northern vent was the larger of the two. Fountains rose 30-60 m and the lava flow had advanced to 1,750 m elevation. By 1900 on 11 April the lava flow was 3.2 km long and had reached 1,690 m elevation. Lava fountaining continued at the two vents during 12-13 April, rising 20-60 m. The lava flow continued to advance; by 13 April the flow was about 3.6 km long and had reached 1,500-1,550 m elevation.

Geological summary: The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Semisopochnoi, Aleutian Islands (USA)

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

AVO reported that low-level ash emissions from Semisopochnoi were visible in satellite images on 12 April along with a steam plume drifting E beyond the island. Additionally, new ash deposits extending SE at least to the coastline were also visible. The event was recorded by the regional infrasound network. The Aviation Color Code and the Volcano Alert Level remained at Orange and Watch, respectively.

Geological summary: Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part. The three-peaked Mount Cerberus was constructed within the caldera during the Holocene. Each of the peaks contains a summit crater; lava flows on the N flank of Cerberus appear younger than those on the south side. Other post-caldera volcanoes include the symmetrical Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone could have been recently active.

Soufriere St. Vincent, St. Vincent

13.33°N, 61.18°W, Summit elev. 1220 m

University of the West Indies Seismic Research Centre (UWI-SRC) and National Emergency Management Organisation (NEMO) reported that the effusive eruption at Soufrière St. Vincent (often simply referred to as “La Soufriere”) became explosive on 9 April after a period of increased seismicity, gas emission, and rapid dome growth. Earthquake swarms were recorded during 22-25 March and 5 April, signifying a change in the eruption pattern. Small earthquakes associated with dome growth were recorded on 7 April. Episodes of tremor indicating movement of magma and fluids close to the surface began at 0300 on 8 April and were again recorded at 0530, 0800, 1015, and 1300, slowly increasing in magnitude. Five long-period earthquakes and two brief swarms of VT events occurred in between the tremor episodes; ash venting occurred with the last episode. Sulfur dioxide emissions were identified in satellite data, and clouds of steam and gas were visible from the Belmont Observatory. Later that evening, incandescent material over the vent area was visible in webcam images, and views from the observatory indicated that the dome had grown significantly. The Alert Level was raised to Red at around 1830, and the Prime Minister issued an evacuation order for the Red Zone at the N part of the island, affecting 16,000-20,000 people.

An explosive eruption began at 0840 on 9 April when an ash plume rose to 8 km (27,900 ft) a.s.l. and drifted mainly ENE. Ash fell across the island, affecting communities including Chateaubelair and Petite Bordel, the observatory, Belmont and surrounding areas at the S end of the island, and forcing the closure of the Argyle International Airport (20 km S). NEMO stated that evacuations in the Orange and Red zones were impeded by significant ashfall and poor visibility, but by the evening most residents had been evacuated. A second period of vigorous ash venting began at 1445 and initially rose about 4 km (13,100 ft) a.s.l. Lightning was visible in the rising plume. Successive explosions and ash pulses fed the plume for hours and it rose to 16 km (52,000 ft) a.s.l. A third explosive series began at 1835. Ash venting occurred through the night, causing ashfall across St. Vincent and reaching Barbados, about 165 km E, significantly impacting residents on that island.

Periods of banded tremor began at 0330 on 10 April, lasting for periods of 20-30 minutes with 1-3-hour gaps. The tremor episodes were associated with explosive activity and stronger pulses of ash emissions to higher altitudes; ash plumes rose to 10.6-16 km (35,000-52,000 ft) a.s.l. throughout the day. The Washington VAAC stated that ash plumes during 9-10 April had drifted as far as 1,200 km ESE and about 3,000 km ENE. The Grantley Adams International Airport (GAIA) in Barbados also closed.

Ashfall continued to be widespread on 10 April; deposit thickness varied from less than 1 mm in Colonaire (~12.5 km SSE) to 10-15 mm in Rabacca (~7.4 km SSE). Scientists reported darkness at the observatory at 1617; video showed intense and continuous ashfall. Satellite data confirmed that explosions had excavated the 2020-2021 lava dome and parts of the 1979 dome, leaving a large crater.

Overnight during 10-11 April ash again fell island-wide, and also in the Grenadines (to the SSW), Barbados, and Saint Lucia (50 km NNE). Explosions early on 11 April were followed by widespread power and water outages on the island as reported by NEMO, and some houses had collapsed under the significant ashfall. Beginning around midday the periods between episodes of high-amplitude tremor lengthened from 1.5-4 hours to 5-8 hours. The VAAC reported that through the day ash plumes rose 12.2-16 km (40,000-52,000 ft) a.s.l. and continued to drift long distances to the ENE, E, and SE. A large explosion at 0415 on 12 April produced an ash plume that rose to 12.8 km (42,000 ft) a.s.l. Pyroclastic flows descended several valleys on the S and W flanks, reaching the coast at Morne Ronde (4.3 km W), Larikai (3.5 km WNW), and Trois Loupes Bay (3.5 km NW). Damage to vegetation was extensive along the W coast, stretching from Larikai Bay to Turner Bay. The pattern of seismicity again changed; high-amplitude tremor episodes ceased, but two low-amplitude and one high-amplitude episode were recorded during 0600-1700. Explosivity or notable ash venting coincided with the episodes; the spacing between explosive events increased.

A series of Vulcanian explosions began at 0630 on 13 April and lasted about 30 minutes. The VAAC stated that a dense ash plume rose to 11 km (35,000 ft) a.s.l. and drifted E and SE, as well as N and NE. Pyroclastic flows traveled about 6 km WSW, reached the ocean at Wallibou Bay, and extended past the coastline over the sea. Scientists observed the western coastline later in the day and noted that pyroclastic flows had descended all valleys from Larikai (W) to Wallibou, a stretch about 5 km long. Lahar deposits were observed in the Sandy Bay area. The VAAC noted that at 1850 a new ash emission rose to 7.6 km (25,000 ft) a.s.l. and was associated with a thermal anomaly. UWI-SRC stated that a large explosion was recorded around 2300. Pyroclastic flows overnight were channeled to the E into the Rabacca River drainage. The Montserrat Volcano Observatory stated that a sulfur odor and minor ashfall from Soufrière St. Vincent was observed on their island (390 km NNW).

Daily satellite-based measurements of SO2 were notable beginning on 9 April. Though the initial explosion at 0840 showed relatively minor SO2 emissions, stronger, continuous ash and SO2 emissions began later on 9 April (at 1445) and continued into the next day, transitioning into discrete explosive events that continued a least through 14 April. Satellite data showed about 0.4 teragrams (Tg) of SO2 in the plume on 10 April, with some stratospheric injection. Simon Carn noted that this makes the La Soufriere eruption the largest tropical SO2 emission since the 2011 Nabro eruption, and the largest in the Caribbean since satellite measurements began in 1979. The SO2 plume initially fanned out to the NE, E, and SE across the Atlantic Ocean. Measurements during 11-13 April showed similar results of 0.4-0.6 Tg SO2 depending on altitude. The eastern edge of the gas plume reached about 4,700 km to the W coast of Africa by 12 April, and another 2,000 km inland to Mali and Niger on 13 April.

Geological summary: Soufrière St. Vincent is the northernmost and youngest volcano on St. Vincent Island. The NE rim of the 1.6-km wide summit crater is cut by a crater formed in 1812. The crater itself lies on the SW margin of a larger 2.2-km-wide caldera, which is breached widely to the SW as a result of slope failure. Frequent explosive eruptions after about 4,300 years ago produced pyroclastic deposits of the Yellow Tephra Formation, which cover much of the island. The first historical eruption took place in 1718; it and the 1812 eruption produced major explosions. Much of the northern end of the island was devastated by a major eruption in 1902 that coincided with the catastrophic Mont Pelée eruption on Martinique. A lava dome was emplaced in the summit crater in 1971 during a strictly effusive eruption, forming an island within a lake that filled the crater. A series of explosive eruptions in 1979 destroyed the 1971 dome and ejected the lake; a new dome was then built.

Suwanosejima, Ryukyu Islands (Japan)

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

JMA reported that incandescence from Suwanosejima's Ontake Crater was visible at night during 5-9 April. Four explosions generated ash plumes that rose as high as 1.6 km above the crater rim and ejected bombs 600 m away. Ashfall was reported in Toshima village (4 km SSW) during 8-9 April. The Alert Level remained at 2 and the public was warned to stay 1 km away from the crater.

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

Ongoing activity

Aira, Kyushu (Japan)

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

JMA reported that at 0641 on 5 April and explosion at Minamidake Crater (at Aira Caldera’s Sakurajima volcano) produced an ash plume that rose as high as 3 km above the crater rim and ejected material 800-1,000 m away from the crater. Five explosions were recorded during 9-12 April. The highest ash plume rose 2.1 km and bombs were ejected as far as 900 m from the crater. Crater incandescence was visible nightly. 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

PVMBG reported that during 6-10 April ash plumes from Dukono rose 100-700 m above the summit and drifted E, SE, and S. Weather conditions prevented visual observations during 11-12 April. 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 2-9 April that sent ash plumes to 4.5 km (14,800 ft) a.s.l. and drifted in multiple directions. 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

PVMBG reported that during 6-13 April gray-and-white ash plumes from Ibu rose 200-1,000 m above the summit and drifted mainly N, E, and S. 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, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and 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. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions.

Kilauea, Hawaiian Islands (USA)

19.421°N, 155.287°W, Summit elev. 1222 m

HVO reported that the W vent on the inner NW wall of Kilauea's Halema`uma`u Crater continued to supply the lava lake during 31 March-6 April. Lava flowed at a low rate from the main vent into the lake through crusted-over channels and submerged inlets. The total depth of the lake measured about 226 m and lava continued to circulate in the W part; the E half of the lake remained solidified and expanded toward the W. The sulfur dioxide emission rate was 1,200 tons/day on 1 April. HVO field crews observed weak spattering from two areas at the W vent during 1-2 April. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geological summary: Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Lewotolok, Lembata Island (Indonesia)

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

PVMBG reported that the Strombolian eruption at Lewotolok continued during 6-13 April. Gray-and-white ash plumes rose as high as 750 m above the summit and drifted in multiple directions. Incandescent material was ejected 300-500 m above the summit on most days and 500 m SE on 8 April. Incandescent material was ejected to the E during 9 and 11-12 April. Rumbling was occasionally audible. The Alert Level remained at 3 (on a scale of 1-4) and the public was warned to stay 4 km away from the summit crater.

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

Merapi, Central Java (Indonesia)

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

BPPTKG reported that the lava dome just below Merapi’s SW rim and the lava dome in the summit crater both continued to grow during 1-8 April. The SW rim lava-dome volume was an estimated 1,098,000 cubic meters on 7 April, with a growth rate of about 12,800 cubic meters per day, and continued to shed material down the flank. A total of 13 pyroclastic flows traveled a maximum of 1.5 km down the SW flank. Incandescent avalanches, recorded 119 times, traveled as far as 1.1 km down the SW flank. The summit lava dome had grown to 75 m tall. Minor ashfall was reported in Ngipiksari (8 km SSW), Klangon (4 km S), and Deles (3 km SE) on 3 April. The Alert Level remained at 3 (on a scale of 1-4), and the public was warned to stay 5 km away from the summit.

Geological summary: Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities.

Raung, Eastern Java (Indonesia)

8.119°S, 114.056°E, Summit elev. 3260 m

PVMBG reported that daily gray-and-white ash plumes rose 50-600 m above Raung's summit during 6-13 April and drifted mainly N, E, and S. 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: Raung, one of Java's most active volcanoes, is a massive stratovolcano in easternmost Java that was constructed SW of the rim of Ijen caldera. The unvegetated summit is truncated by a dramatic steep-walled, 2-km-wide caldera that has been the site of frequent historical eruptions. A prehistoric collapse of Gunung Gadung on the W flank produced a large debris avalanche that traveled 79 km, reaching nearly to the Indian Ocean. Raung contains several centers constructed along a NE-SW line, with Gunung Suket and Gunung Gadung stratovolcanoes being located to the NE and W, respectively.

Semeru, Eastern Java (Indonesia)

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

PVMBG reported that the eruption at Semeru continued during 7-13 April, though weather conditions often prevented visual confirmation. Gray-and-white ash plumes rose as high as 500 m during 9 and 11-12 April. The Alert Level remained at 2 (on a scale of 1-4), with a general exclusion zone of 1 km and extensions to 5 km in the SSE sector.

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 2-9 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.

Sinabung, Indonesia

3.17°N, 98.392°E, Summit elev. 2460 m

PVMBG reported that the eruption at Sinabung continued during 6-13 April. Weather conditions sometimes prevented visual observations of the volcano, though white fumarolic plumes were visible almost daily rising as high as 700 m above the summit and drifting in multiple directions. An eruptive event on 7 April produced a gray ash plume that rose 1 km. Two eruptive events the next day generated ash plumes that rose as high as 700 m. Avalanches traveled as far as 1.5 km E and SE during 8-11 April. Ash plumes rose 500-1,000 m high on 10 April. The Alert Level remained at 3 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions to 5 km in the SE sector and 4 km in the NE sector.

Geological summary: Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

Source: GVP