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Very strong M7.3 earthquake hits Venezuela at intermediate depth
A very strong earthquake registered by the USGS as M7.3 hit near the coast of Sucre, Venezuela at 21:31 UTC on August 21, 2018. The agency is reporting a depth of 123.2 km (76.5 km). EMSC is reporting M7.3 at a depth of 112 km (69.6 miles). According to the USGS, the epicenter was located  20.9 km (13.0 miles) NNW of Yaguaraparo, 38.4 km (23.9 miles) ENE of Carúpano (population 112 082), 69.4 km (43.1 miles) WNW of Güiria (population 40 000), 107.6 km (66.9 miles) ESE Porlamar (population 87 120) and 109.1 km (67.8 miles) ESE of La Asunción (population  35 084), Venezuela. There are 560 000 people living within 100 km (62 miles). Based on all available data, there is no tsunami threat, PTWC said. Some 52 000 people are estimated to have felt very strong shaking, 2 089 000 strong, 2 587 000 moderate and 3 928 000 light. Buildings were evacuated in the capital Caracas and people fled homes. Shaking was felt as far away as …

The Weekly Volcanic Activity Report: 

April 11 - 17, 2018

The Weekly Volcanic Activity Report: April 11 - 17, 2018

New activity/unrest was reported for 3 volcanoes between April 11 and 17, 2018. During the same period, ongoing activity was reported for 13 volcanoes.
New activity/unrest: Ambae, Vanuatu | Langila, New Britain (Papua New Guinea) | Sinabung, Indonesia.
Ongoing activity: Agung, Bali (Indonesia) | Aira, Kyushu (Japan) | Bagana, Bougainville (Papua New Guinea) | Cleveland, Chuginadak Island (USA) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Fuego, Guatemala | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Mayon, Luzon (Philippines) | Sabancaya, Peru | Sheveluch, Central Kamchatka (Russia) | Turrialba, Costa Rica.

New activity/unrest

Ambae, Vanuatu

15.4°S, 167.83°E, Summit elev. 1496 m
Based on observations from satellites, webcams, pilots, and the Vanuatu Geohazards Observatory (local community reports), the Wellington VAAC reported that during 11-14 April ash plumes from the vent at Ambae’s Lake Voui rose to altitudes of 1.8-4.9 km (6,000-16,000 ft) a.s.l. and drifted N, NW, W, and SE. On 12 April news articles noted that ashfall had affected the N part of Ambae, with photos showing thick ashfall deposits on houses and agricultural land, and reports of contaminated water supplies. On 15 April a VAAC office reported that the eruption has ceased. The Alert Level remained at 3 (on a scale of 0-5).
Geologic summary: Ambae, also known as Aoba, is a massive 2500 km3 basaltic shield that is the most voluminous volcano of the New Hebrides archipelago. A pronounced NE-SW-trending rift zone dotted with scoria cones gives the 16 x 38 km island an elongated form. A broad pyroclastic cone containing three crater lakes is located at the summit within the youngest of at least two nested calderas, the largest of which is 6 km in diameter. Post-caldera explosive eruptions formed the summit craters of Lake Voui (also spelled Vui) and Lake Manaro Ngoru about 360 years ago. A tuff cone was constructed within Lake Voui about 60 years later. The latest known flank eruption, about 300 years ago, destroyed the population of the Nduindui area near the western coast.

Langila, New Britain (Papua New Guinea)

5.525°S, 148.42°E, Summit elev. 1330 m
Based on analyses of satellite imagery and wind model data, the Darwin VAAC reported that on 15 April a discrete, low-level ash plume from Langila rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted S.
Geologic 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.

Sinabung, Indonesia

3.17°N, 98.392°E, Summit elev. 2460 m
PVMBG reported that at 0640 on 12 April an event at Sinabung generated an ash plume that rose 200 m and drifted WNW. At 1655 pyroclastic flows generated ash plumes that drifted WSW. At 0827 on 15 April an event generated an ash plume rose 1 km and drifted WNW. 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.
Geologic 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.

Ongoing activity

Agung, Bali (Indonesia)

8.343°S, 115.508°E, Summit elev. 2997 m
Based on webcam views, satellite data, and ground-based observations, the Darwin VAAC reported that on 11 April an event at Agung generated an ash plume that rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted SW.
Geologic summary: Symmetrical Agung stratovolcano, Bali's highest and most sacred mountain, towers over the eastern end of the island. The volcano, whose name means "Paramount," rises above the SE caldera rim of neighboring Batur volcano, and the northern and southern flanks extend to the coast. The summit area extends 1.5 km E-W, with the high point on the W and a steep-walled 800-m-wide crater on the E. The Pawon cone is located low on the SE flank. Only a few eruptions dating back to the early 19th century have been recorded in historical time. The 1963-64 eruption, one of the largest in the 20th century, produced voluminous ashfall along with devastating pyroclastic flows and lahars that caused extensive damage and many fatalities.

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Summit elev. 1117 m
JMA reported that there were four events and nine explosions at Minamidake crater (at Aira Caldera’s Sakurajima volcano) during 9-16 April. Tephra was ejected as far as 1.3 km from the crater, and plumes rose as high as 2.5 km above the crater rim. Crater incandescence was visible on most nights. The Alert Level remained at 3 (on a 5-level scale).
Geologic 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.

Bagana, Bougainville (Papua New Guinea)

6.137°S, 155.196°E, Summit elev. 1855 m
Based on analyses of satellite imagery and model data, the Darwin VAAC reported that during 14-15 April ash plumes from Bagana rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted about 110 km SW.
Geologic summary: Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides.

Cleveland, Chuginadak Island (USA)

52.825°N, 169.944°W, Summit elev. 1730 m
AVO reported that a small explosion at Cleveland was detected in seismic and infrasound data at 0759 on 13 April; no eruption plume was visible in satellite images. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
Geologic 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.

Dukono, Halmahera (Indonesia)

1.693°N, 127.894°E, Summit elev. 1229 m
Based on analyses of satellite imagery, wind model data, and notices from PVMBG, the Darwin VAAC reported that during 11-16 April ash plumes from Dukono rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted mainly NW, W, SW, and NNE.
Geologic 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 7 and 11-12 April that sent ash plumes as high as 1.8 km (5,900 ft) a.s.l. Ashfall was reported in Severo-Kurilsk on 6 April. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Geologic 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
INSIVUMEH reported that on 9 April a lahar descended the Seca (Santa Teresa) drainage on Fuego’s W flank. The lahar was 10 m wide, 1.5 m deep, and had a consistency similar to cement mix. During 12-13 April explosions generated ash plumes that rose as high as 1 km and drifted 15 km SW and W. Incandescent material was ejected as high as 300 m above the crater rim, and generated avalanches of material in the Seca, Cenizas (SSW), Las Lajas (SE), and Honda (E) ravines. Ash fell in areas downwind including in Santa Sofía (12 km SW), Morelia (9 km SW), Panimaché (8 km SW), (SSW), Las Lajas (SE), and Honda (E) ravines. Ash fell in areas downwind including in Santa Sofía (12 km SW), Morelia (9 km SW), Panimaché (8 km SW), El Porvenir (8 km ENE), and Finca Palo Verde.
Activity increased on 14 April and remained elevated through 17 April. Moderate-to-strong explosions were detected at a rate of 6-9 per hour, and sometimes produced shock waves that vibrated houses in Morelia and Panimaché. Dense ash plumes rose as high as 1.1 km and drifted 20 km W and S, though winds also carried the ash to higher altitudes to the SE. Incandescent material was ejected as high as 300 m above the crater rim, and generated avalanches of material in the crater area. Ashfall was reported in areas downwind including in Santa Sofía, Morelia, Panimaché I and II, El Porvenir, and Finca Palo Verde. The rate of explosions increased to 7-10 per hour on 16 April; explosions sometimes caused structures in Panimache, Morelia, La Reina, and Alotenango (8 km ENE) to vibrate. A lava flow traveled 1.3 km down the Seca drainage.
Geologic 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.

Karymsky, Eastern Kamchatka (Russia)

54.049°N, 159.443°E, Summit elev. 1513 m
KVERT reported that a weak thermal anomaly over Karymsky was identified in satellite data on 11 April. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Geologic 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.

Kilauea, Hawaiian Islands (USA)

19.421°N, 155.287°W, Summit elev. 1222 m
During 11-17 April HVO reported that the lava lake continued to rise, fall, and spatter in Kilauea’s Overlook crater. The lake level was high, with spattering visible from HVO and Jaggar Museum; by 16 April the lake level was 10 m below the rim of the Overlook crater. Surface lava flows were active above Pulama pali. On 11 April a moderate swarm of over 200 earthquakes occurred at depths of 7-9 km below the summit. The largest event was a M 2.4. Seismicity returned to background levels at 0230. Three minor ledge collapses were detected on 12 April, one at 1157 and two just after 1830. Surface lava flows were active above Pulama pali; on 13 April most scattered breakouts were within 2.2 km from Pu'u 'O'o Crater, and one was about 5 km away.
Geologic 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.

Mayon, Luzon (Philippines)

13.257°N, 123.685°E, Summit elev. 2462 m
PHIVOLCS reported that during 11-17 April white steam plumes from Mayon drifted NW, WNW, WSW, and SW. Crater incandescence was visible at night. The sulfur dioxide flux was 2,800, 1,918, 1,621, and 1,617 tonnes/day on 11, 12, 13, and 16 April, respectively. 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.
Geologic 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.

Sabancaya, Peru

15.787°S, 71.857°W, Summit elev. 5960 m
Observatorio Vulcanológico del Sur del IGP (OVS-IGP) and Observatorio Vulcanológico del INGEMMET (OVI) reported that explosive activity at Sabancaya was similar to the previous week; explosions averaged 15 per day during 9-15 April. Seismicity was dominated by long-period events, with signals indicating emissions. Gas-and-ash plumes rose as high as 2.2 km above the crater rim and drifted 30 km NW and SW. Minor ashfall was reported in Huambo and Cabanaconde. The MIROVA system detected three thermal anomalies. The report noted that the public should not to approach the crater within a 12-km radius.
Geologic 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, Summit elev. 3283 m
KVERT reported that a weak thermal anomaly over Sheveluch was identified in satellite images during 6 and 10-12 April. The Aviation Color Code remained at Orange.
Geologic 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.

Turrialba, Costa Rica

10.025°N, 83.767°W, Summit elev. 3340 m
The Washington VAAC reported that on 11 April an ash emission from Turrialba were seen through an OVSICORI-UNA web camera.
Geologic summary: Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive edifice covers an area of 500 km2. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.
Source: GVP

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