The Weekly Volcanic Activity Report: June 20 - 26, 2018

The Weekly Volcanic Activity Report: June 20 - 26, 2018

New activity was observed at 7 volcanoes between June 20 and 26, 2018. During the same period, ongoing activity was reported for 16 volcanoes.

New activity/unrest: Fernandina, Ecuador | Great Sitkin, Andreanof Islands (USA) | Ibu, Halmahera (Indonesia) | Kadovar, Papua New Guinea | Krakatau, Indonesia | Sierra Negra, Isla Isabela (Ecuador) |  Telica, Nicaragua.

Ongoing activity: Aira, Kyushu (Japan) | Cleveland, Chuginadak Island (USA) | Copahue, Central Chile-Argentina border |  Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Fuego, Guatemala | Kilauea, Hawaiian Islands (USA) | Kirishimayama, Kyushu (Japan) | Klyuchevskoy, Central Kamchatka (Russia) | Langila, New Britain (Papua New Guinea) | Mauna Loa, Hawaiian Islands (USA) | Nishinoshima, Japan | Sabancaya, Peru | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Yasur, Vanuatu.

The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 23:00 UTC every Wednesday, notices of volcanic activity posted 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. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network.

New activity/unrest

Fernandina, Ecuador

0.37°S, 91.55°W, Elevation 1476 m

On 21 June Parque Nacional Galápagos reported that lava flows at Fernandina were no longer reaching the ocean, though white plumes continued to rise from flows at the coastline.

Geological summary: Fernandina, the most active of Galápagos volcanoes and the one closest to the Galápagos mantle plume, is a basaltic shield volcano with a deep 5 x 6.5 km summit caldera. The volcano displays the classic "overturned soup bowl" profile of Galápagos shield volcanoes. Its caldera is elongated in a NW-SE direction and formed during several episodes of collapse. Circumferential fissures surround the caldera and were instrumental in growth of the volcano. Reporting has been poor in this uninhabited western end of the archipelago, and even a 1981 eruption was not witnessed at the time. In 1968 the caldera floor dropped 350 m following a major explosive eruption. Subsequent eruptions, mostly from vents located on or near the caldera boundary faults, have produced lava flows inside the caldera as well as those in 1995 that reached the coast from a SW-flank vent. Collapse of a nearly 1 km3 section of the east caldera wall during an eruption in 1988 produced a debris-avalanche deposit that covered much of the caldera floor and absorbed the caldera lake.

Great Sitkin, Andreanof Islands (USA)

52.076°N, 176.13°W, Elevation 1740 m

AVO reported continuing low-level unrest at Great Sitkin during 20-26 June; seismic activity remained at or near background levels. A recently analyzed satellite image acquired on 11 June, one day after short-duration explosive event was recorded, showed a minor ash deposit on the snow extending 2 km from a vent in the summit crater. The Aviation Color Code remained at Yellow and the Volcano Alert Level remained at Advisory.

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.

Ibu, Halmahera (Indonesia)

1.488°N, 127.63°E, Elevation 1325 m

PVMBG reported that at 0857 on 21 June an event at Ibu generated an ash plume that rose at least 600 m above the crater rim and drifted N. Signals indicating an explosion and rock avalanches were detected in seismic data. During 22-26 June ash plumes rose as high as 850 m and drifted WNW and W. 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.

Kadovar, Papua New Guinea

3.608°S, 144.588°E, Elevation 365 m

According to the Darwin VAAC an ash plume from Kadovar identified by a pilot and in satellite images rose to an altitude of 1.8 km (6,000 ft) a.s.l. on 20 June and drifted W.

Geological summary: The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. Kadovar is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. The village of Gewai is perched on the crater rim. A 365-m-high lava dome forming the high point of the andesitic volcano fills an arcuate landslide scarp that is open to the south, and submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. No certain historical eruptions are known; the latest activity was a period of heightened thermal phenomena in 1976.

Krakatau, Indonesia

6.102°S, 105.423°E, Elevation 813 m

PVMBG and BNPB reported that an eruption at Anak Krakatau began on 18 June, along with increased seismicity, and reminded residents that the Alert Level remained at 2 (on a scale of 1-4); visitors were warned not to approach the volcano within 1 km of the crater. Foggy conditions hampered visual observations during 19-20 June, but on 21 June gray plumes were observed rising 100-200 m above the summit. An event at 0714 on 25 June produced a dense ash plume that rose about 1 km and drifted N.

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 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 volcanoes, and left only a remnant of Rakata volcano. 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.

Sierra Negra, Isla Isabela (Ecuador)

0.83°S, 91.17°W, Elevation 1124 m

On 22 June IG reported increased seismic activity at Sierra Negra on the S end of Isabela Island; the largest event, a M 4.2, was recorded at 0624 and felt in El Cura and San Joaquín, NE of the volcano. A M 5.3 earthquake was detected at 0315 on 26 June, occurring at a depth of 5.3 km below Sierra Negra. The event was strongly felt on the upper flanks and in Puerto Villamil (23 km SE). Several aftershocks and subsequent tremor were recorded. An earthquake swarm began at 1117, characterized by events located 3-5 km depth. A M 4.2 earthquake was recorded at 1338, and followed by increasing amplitudes of seismic and infrasound signals. Parque Nacional Galápagos staff heard noises described as bellows coming from Volcán Chico fissure vent, and coupled with the seismicity and infrasound data, suggested the start of an eruption. An IG report posted 20 minutes later described a thermal anomaly identified in satellite images in the N area of the caldera, near Volcán Chico. Park staff observed lava flowing towards the crater’s interior as well as towards the N flank.

Geological summary: The broad shield volcano of Sierra Negra at the southern end of Isabela Island contains a shallow 7 x 10.5 km caldera that is the largest in the Galápagos Islands. Flank vents abound, including cinder cones and spatter cones concentrated along an ENE-trending rift system and tuff cones along the coast and forming offshore islands. The 1124-m-high volcano is elongated in a NE direction. Although it is the largest of the five major Isabela volcanoes, it has the flattest slopes, averaging less than 5 degrees and diminishing to 2 degrees near the coast. A sinuous 14-km-long, N-S-trending ridge occupies the west part of the caldera floor, which lies only about 100 m below its rim. Volcán de Azufre, the largest fumarolic area in the Galápagos Islands, lies within a graben between this ridge and the west caldera wall. Lava flows from a major eruption in 1979 extend all the way to the north coast from circumferential fissure vents on the upper northern flank. Sierra Negra, along with Cerro Azul and Volcán Wolf, is one of the most active of Isabela Island volcanoes.

Telica, Nicaragua

12.606°N, 86.84°W, Elevation 1036 m

INETER and SINAPRED reported that an eruption at Telica began at 0708 on 21 June. Explosions produced an ash plume that rose 500 m above the crater and drifted E, S, and SW, and ejected tephra that was deposited within a 1-km-radius of the volcano. Ashfall was reported in areas including La Joya, Las Marías (7 km NNW), Pozo Viejo (10 km NNW), Ojo de Agua, San Lucas (11 km NNW), Las Higueras, Las Grietas (12 km NNW), and Posoltega (16 km WSW).

Geological summary: Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately E, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.


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Ongoing activity

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Elevation 1117 m

JMA reported that there were four events and one explosion at Minamidake crater (at Aira Caldera’s Sakurajima volcano) during 18-25 June, with ash plumes rising as high as 1.9 km above the crater rim. Crater incandescence was visible at night on 18 June. The Alert Level remained at 3 (on a 5-level scale).

Geological summary: The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Cleveland, Chuginadak Island (USA)

52.825°N, 169.944°W, Elevation 1730 m

AVO reported that a satellite image of Cleveland acquired on 25 June showed a small, circular lava flow about 80 m in diameter in the summit crater. The presence of a flow over the active vent increases the chances of an explosion, so AVO raised the Aviation Color Code to Orange and the Volcano Alert Level to Watch.

Geological summary: The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited, dumbbell-shaped Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

Copahue, Central Chile-Argentina border

37.856°S, 71.183°W, Elevation 2953 m

The Buenos Aires VAAC reported that on 24 June diffuse steam emissions with possible ash were visible in webcam views rising to an altitude of 3.6 km (12,000 ft) a.s.l.

Geological summary: Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded at Copahue since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.

Dukono, Halmahera (Indonesia)

1.693°N, 127.894°E, Elevation 1229 m

Based on PVMBG observations and satellite data, the Darwin VAAC reported that during 20-26 June ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted NW, W, and SW.

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

KVERT reported that on 15 June an ash plume from Ebeko was visible in satellite images drifting 14 km SE. Video data from SVERT and KBGS RAS (Kamchatka Branch, Geophysical Service, Russian Academy of Sciences) showed ash explosions during 17-18 June that sent ash plumes to 2.5-3 km (8,200-10,000 ft) a.s.l. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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

Fuego, Guatemala

14.473°N, 90.88°W, Elevation 3763 m

INSIVUMEH and CONRED reported that during 20-26 June multiple lahars at Fuego were often hot, steaming, and had a sulfur odor, and were generated from heavy rains and the recent accumulation of pyroclastic-flow deposits from the 3 June events. Lahars remained a significant hazard, and descended the Cenizas (SSW), Las Lajas (SE), Santa Teresa (W), and Taniluyá (SW) drainages. They were 25-45 m wide, as deep as 3 m, and often carried blocks up to 3 m in diameter, tree trunks, and branches. The agencies warned that because the Las Lajas drainage is full of deposits, lahars can continue to descend that drainage or create new channels in San Miguel Los Lotes (one of the hardest-hit areas). 

Explosions continued, producing ash plumes that rose as high as 1.3 km above the crater and drifted as far as 15 km in multiple directions. Ashfall was reported in Panimache, Morelia, Sangre de Cristo, and finca Palo Verde on 22 June. Avalanches of material descended the SE, S, and W flanks (Santa Teresa, Las Lajas, and Cenizas drainages). According to CONRED, as of 26 June, the number of people confirmed to have died due to the 3 June pyroclastic flows was 112, and 197 more were missing. In addition, 12,823 remained evacuated.

Geological summary: Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3763-m-high Fuego and its twin volcano to the north, Acatenango. 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 Acatenango. In contrast to 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.

Kilauea, Hawaiian Islands (USA)

19.421°N, 155.287°W, Elevation 1222 m

HVO reported that the eruption at Kilauea’s Lower East Rift Zone (LERZ) and at Halema`uma`u Crater continued during 20-26 June. Lava fountaining and spatterwas concentrated at Fissure 8, feeding lava flows that spread through Leilani Estates and Lanipuna Gardens subdivisions, and built out the coastline where the fast-moving flow entered the ocean in the area of the former Kapoho Bay. Fissure 16/18 was often incandescent, and lava effusion was visible at Fissure 6 on 21 June. Fissure 22 produced weak lava fountains on 22 June, and weak spattering and small lava flows on 26 June. 

Inward slumping of the crater rim and walls of Halema`uma`u continued, adjusting from the withdrawal of magma and subsidence of the summit area. Steam plumes rose from areas in the crater as well as from circumferential cracks adjacent to the crater. Explosions from collapse events occurred daily, producing gas-and-ash-poor plumes that rose less than 1.8 km (6,000 ft) a.s.l. and drifted SW. On 24 June HVO noted that since late May these plumes rarely rose higher than 3 km (10,000 ft) a.s.l. where they can cause an aviation hazard; the Aviation Color Code was reduced to Orange. 

Fountaining at Fissure 8 continued; lava fountains rose occasionally higher than the 55-m-high spatter cone. Pele's hair and other volcanic glass from the fountaining fell within Leilani Estates. The fountains continued to feed the fast-moving lava flow that traveled NE, and then SE around Kapoho Crater, and into the ocean. Occasional overflows sent small flows down the sides of the channel. The lava-flow front at the ocean was almost 3.2 km wide by 25 June, with lava entering the ocean on the S side of the flow front mainly through an open channel, but also along a 1-km-long area marked with billowing laze plumes.

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.

Kirishimayama, Kyushu (Japan)

31.934°N, 130.862°E, Elevation 1700 m

JMA reported that at Shinmoedake (Shinmoe peak), a stratovolcano of the Kirishimayama volcano group, an explosive eruption at 0909 on 22 June generated an ash plume that rose 2.6 km above the crater rim and drifted E. Tephra was ejected 1.1 km away, and shock waves were felt in the Miyazaki region. Minor amounts of ash fell in Kirishima prefecture and Kagoshima prefecture to the S, Miyakonojo city (Miyazaki prefecture) to the E, and Takahara Town. The Alert Level remained at 3 (on a scale of 1-5).

Geological summary: Kirishimayama is a large group of more than 20 Quaternary volcanoes located north of Kagoshima Bay. The late-Pleistocene to Holocene dominantly andesitic group consists of stratovolcanoes, pyroclastic cones, maars, and underlying shield volcanoes located over an area of 20 x 30 km. The larger stratovolcanoes are scattered throughout the field, with the centrally located, 1700-m-high Karakunidake being the highest. Onamiike and Miike, the two largest maars, are located SW of Karakunidake and at its far eastern end, respectively. Holocene eruptions have been concentrated along an E-W line of vents from Miike to Ohachi, and at Shinmoedake to the NE. Frequent small-to-moderate explosive eruptions have been recorded since the 8th century.

Klyuchevskoy, Central Kamchatka (Russia)

56.056°N, 160.642°E, Elevation 4754 m

KVERT reported that a weak thermal anomaly over Klyuchevskoy was identified in satellite images during 16-17 and 19 June. 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.

Langila, New Britain (Papua New Guinea)

5.525°S, 148.42°E, Elevation 1330 m

Based on analyses of satellite imagery and model data, the Darwin VAAC reported that during 20-21 June ash plumes from Langila rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted W and NW.

Geological summary: Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Mauna Loa, Hawaiian Islands (USA)

19.475°N, 155.608°W, Elevation 4170 m

On 21 June HVO reported that seismicity and deformation at Mauna Loa had been at near-background levels for at least the previous six months. The Aviation Color Code was lowered to Green and the Volcano Alert Level was lowered to Normal. During 2014 through most of 2017 seismicity was variable but elevated, and ground deformation was consistent with an influx of magma in the shallow reservoir.

Geological summary: Massive Mauna Loa shield volcano rises almost 9 km above the sea floor to form the world's largest active volcano. Flank eruptions are predominately from the lengthy NE and SW rift zones, and the summit is cut by the Mokuaweoweo caldera, which sits within an older and larger 6 x 8 km caldera. Two of the youngest large debris avalanches documented in Hawaii traveled nearly 100 km from Mauna Loa; the second of the Alika avalanches was emplaced about 105,000 years ago (Moore et al. 1989). Almost 90% of the surface of the basaltic shield volcano is covered by lavas less than 4000 years old (Lockwood and Lipman, 1987). During a 750-year eruptive period beginning about 1500 years ago, a series of voluminous overflows from a summit lava lake covered about one fourth of the volcano's surface. The ensuing 750-year period, from shortly after the formation of Mokuaweoweo caldera until the present, saw an additional quarter of the volcano covered with lava flows predominately from summit and NW rift zone vents.

Nishinoshima, Japan

27.247°N, 140.874°E, Elevation 25 m

JMA reported that seismic, thermal, RADAR, and sulfur dioxide data all showed no eruptive activity at Nishinoshima since mid-August 2017. During an overflight on 14 June the Japan Coast Guard noted white fumarolic plumes rising about 20 m from the E side of main cone’s inner wall and from the center of the crater. Ocean water all around the island was discolored, especially in the N-to-NW quadrant where the yellowish brown water extended 200-300 m from the shore. On 20 June the JMA reduced the warning level for the island, specifying hazards were less severe “around the crater” (encompassing areas within 500 m).

Geological summary: The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Another eruption that began offshore in 2013 completely covered the previous exposed surface and enlarged the island again. Water discoloration has been observed on several occasions since. The island is the summit of a massive submarine volcano that has prominent satellitic peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the sea surface 9 km SSE.

Sabancaya, Peru

15.787°S, 71.857°W, Elevation 5960 m

Observatorio Vulcanológico del Sur del IGP (OVS-IGP) and Observatorio Vulcanológico del INGEMMET (OVI) reported that explosions at Sabancaya averaged 29 per day during 18-24 June. Hybrid earthquakes were infrequent and low magnitude. Gas-and-ash plumes rose as high as 1.8 km above the crater rim and drifted 30 km S, SE, and E. The MIROVA system detected 11 thermal anomalies, and on 21 June the sulfur dioxide gas flux was high at 4,900 tons/day. The report noted that the public should not approach the crater within a 12-km radius.

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

Sheveluch, Central Kamchatka (Russia)

56.653°N, 161.36°E, Elevation 3283 m

KVERT reported that a weak thermal anomaly over Sheveluch was identified in satellite images during 16-17 and 19 June. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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

Sinabung, Indonesia

3.17°N, 98.392°E, Elevation 2460 m

Based on observations by PVMBG, satellite and webcam images, and model data, the Darwin VAAC reported that during 20-22 June ash plumes from Sinabung rose 3-3.7 km (10,000-12,000 ft) a.s.l. and drifted SE and E. The Alert Level remained at 4 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions of 7 km on the SSE sector, 6 km in the ESE sector, and 4 km in the NNE 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. 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.

Yasur, Vanuatu

19.532°S, 169.447°E, Elevation 361 m

Based on webcam images and local visual observations the Wellington VAAC reported that during 20-21 June intermittent, low-level ash plumes from Yasur rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted SE.

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

Source: GVP

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