Active volcanoes in the world: May 10 - 16, 2017

Active volcanoes in the world: May 10 - 16, 2017

New activity/unrest was reported for 6 volcanoes between May 10 and 16, 2017. During the same period, ongoing activity was reported for 18 volcanoes.

New activity/unrest: Aira, Kyushu (Japan) | Fuego, Guatemala | Manam, Papua New Guinea | Masaya, Nicaragua | Poas, Costa Rica | Sheveluch, Central Kamchatka (Russia).

Ongoing activity: Bagana, Bougainville (Papua New Guinea) | Bezymianny, Central Kamchatka (Russia) | Bogoslof, Fox Islands (USA) | Cleveland, Chuginadak Island (USA) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Ibu, Halmahera (Indonesia) | Karangetang, Siau Island (Indonesia) | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Langila, New Britain (Papua New Guinea) | Nevado del Ruiz, Colombia | Reventador, Ecuador | Sabancaya, Peru | Sinabung, Indonesia | Suwanosejima, Ryukyu Islands (Japan) | Turrialba, Costa Rica.

New activity/unrest

Aira, Kyushu (Japan)

31.593°N, 130.657°E, Elevation 1117 m

According to JMA, fieldwork at Aira Caldera’s Sakurajima volcano revealed that the sulfur dioxide flux rose from 300 tons on 28 April to 1,700 tons on 8 May; the last time sulfur dioxide flux was above 1,000 tons was 23 June 2015. At 1312 on 12 May an explosion at Showa Crater generated a plume that rose 700 m above the crater rim, into a weather cloud. Four events were detected during 13-15 May; one of the events, an explosion at Showa Crater on 14 May, produced a plume that rose 2.3 km above the crater rim. 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.

Fuego, Guatemala

14.473°N, 90.88°W, Elevation 3763 m

INSIVUMEH reported that during 9-16 May explosions at Fuego generated ash plumes that rose as high as 950 m above the crater rim and drifted 7-12 km W, SW, S, and E. Ashfall was reported in San Pedro Yepocapa (8 km N), Morelia (9 km SW), Santa Sofía (12 km SW), and Panimache I and II (8 km SW) during 9-12 May. On 14 May a hot lahar descended the Río Ceniza (SSW) and Santa Teresa (W) drainages, carrying blocks 2 m in diameter, branches, and tree trunks. Sounds from colliding blocks were audible more than 1 km away, and steam plumes rose from the lahar. During 14-16 May avalanches descended the Ceniza and Las Lajas (SE) drainages, and gas emissions rose from pyroclastic-flow deposits in the ravines.

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.

Manam, Papua New Guinea

4.08°S, 145.037°E, Elevation 1807 m

RVO reported that during 11-14 May Manam’s Main Crater was quiet, emitting only dense white vapor. On 12 May Southern Crater emitted dark gray ash plumes, and on 13 May only whitish-blue vapor emissions were observed. During 0100-0400 on 14 May roaring and explosions were heard in Bogia Station; incandescent lava fragments were ejected from the crater. Seismicity was low (RSAM averaged 50 units) and dominated by low-frequency events during 11-12 May. RSAM increased on 13 May, peaking at 450 units at 2330, and then dropped to 110 units at 0500 on 14 May. RSAM increased to 250 by 0800 and remained at that level through 14 May. The Alert Level remained at Stage 2.

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

Masaya, Nicaragua

11.984°N, 86.161°W, Elevation 635 m

The Washington VAAC reported that on 13 May a west-drifting ash emission from Masaya was identified in satellite images and observed by a pilot.

Geological summary: Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.

Poas, Costa Rica

10.2°N, 84.233°W, Elevation 2708 m

OVSICORI-UNA noted ash emissions at Poás on 10 May. Gas emissions were measured by an instrument mounted on a drone, revealing a gas plume rich in sulfur dioxide and low in carbon dioxide. During 10-11 May tremor amplitude was variable but low, and several volcano-tectonic events were detected. During 11-13 May tremor was constant, and volcano-tectonic and long-period events were detected; the seismicity possibly indicated small eruptions. Deformation was high, with vertical inflation of 3 cm since February.

Geological summary: The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Sheveluch, Central Kamchatka (Russia)

56.653°N, 161.36°E, Elevation 3283 m

KVERT reported continuing lava-dome extrusion at Sheveluch’s N flank during 5-11 May. A daily thermal anomaly over the dome was identified in satellite images, and ash plumes drifted 90 km NNE and NW on 8 and 10 May. Strong explosions on 12 May generated ash plumes identified in satellite images that rose 9-10 km (29,500-32,800 ft) a.s.l., spread 70 km wide, and drifted 115 km NW. The Aviation Color Code was raised to Red. A few hours later satellite images showed a thermal anomaly and no ash emissions; the Aviation Color Code was lowered to Orange. Explosions on 16 May generated ash plumes that rose 8-9 km (26,200-29,500 ft) a.s.l., prompting KVERT to again raise the Aviation Color Code to Red. Pyroclastic flows descended the flanks and produced ash plumes that rose 3.5-4 km (11,500-13,100 ft) a.s.l. and drifted NE. Within a few hours satellite images showed a thermal anomaly and no ash emissions; the Aviation Color Code was lowered to Orange. An ash cloud with the dimensions of 51 x 43 km was still visible in satellite images, moving E.

Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 cu km 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.

Ongoing activity

Bagana, Bougainville (Papua New Guinea)

6.137°S, 155.196°E, Elevation 1855 m

Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 10-14 May ash plumes from Bagana rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted SW, W, NW, and E.

Geological 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.

Bezymianny, Central Kamchatka (Russia)

55.972°N, 160.595°E, Elevation 2882 m

KVERT reported gas-and-steam activity at Bezymianny during 5-12 May, and a thermal anomaly identified in satellite images during 5 and 8-9 May. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological summary: Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Bogoslof, Fox Islands (USA)

53.93°N, 168.03°W, Elevation 150 m

AVO reported that an increase in seismic and infrasound activity from Bogoslof was detected from stations on nearby islands starting at 2232 on 16 May, suggesting the beginning of an explosive eruption. The Aviation Color Code (ACC) was raised to Orange and the Volcano Alert Level (VAL) was raised to Watch. A pilot reported an ash plume rising as high as 10.4 km (34,000 ft) a.s.l., and the Worldwide Lightning Location Network detected lightning associated with the cloud. The ACC was raised to Red and the VAL was raised to Warning. The eruption lasted about 73 minutes.

Geological summary: Bogoslof is the emergent summit of a submarine volcano that lies 40 km north of the main Aleutian arc. It rises 1500 m above the Bering Sea floor. Repeated construction and destruction of lava domes at different locations during historical time has greatly modified the appearance of this "Jack-in-the-Box" volcano and has introduced a confusing nomenclature applied during frequent visits of exploring expeditions. The present triangular-shaped, 0.75 x 2 km island consists of remnants of lava domes emplaced from 1796 to 1992. Castle Rock (Old Bogoslof) is a steep-sided pinnacle that is a remnant of a spine from the 1796 eruption. Fire Island (New Bogoslof), a small island located about 600 m NW of Bogoslof Island, is a remnant of a lava dome that was formed in 1883.

Cleveland, Chuginadak Island (USA)

52.825°N, 169.944°W, Elevation 1730 m

AVO reported that no significant volcanic activity at Cleveland was detected in seismic, infrasound, or satellite data during 10-16 May. The webcam recorded some gas plumes during 13-14 May. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geological summary: 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. Cleveland is joined to the rest of Chuginadak Island by a low isthmus. The 1730-m-high Mount 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 for Mount Cleveland, 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.

Colima, Mexico

19.514°N, 103.62°W, Elevation 3850 m

On 12 May the Centro Universitario de Estudios e Investigaciones de Vulcanologia - Universidad de Colima reported that during the previous week seismic data revealed 26 high-frequency events, 21 long-period events, 2.5 hours of tremor, 12 landslides, and three low-intensity explosions.

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

Dukono, Halmahera (Indonesia)

1.693°N, 127.894°E, Elevation 1229 m

Based on analyses of satellite imagery, wind model data, and notices from PVMBG, the Darwin VAAC reported that during 10-16 May ash plumes from Dukono rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted in multiple directions as far as 150 km.

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 an ash plume from Ebeko was identified in satellite images drifting about 50 km NE on 7 May. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

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

Ibu, Halmahera (Indonesia)

1.488°N, 127.63°E, Elevation 1325 m

Based on analyses of satellite imagery and information from PVMBG, the Darwin VAAC reported that during 10-11 May ash plumes from Ibu rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted E and SW. An ash plume on 16 May rose to 1.5 km (5,000 ft) a.s.l.

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.

Karangetang, Siau Island (Indonesia)

2.781°N, 125.407°E, Elevation 1797 m

Based on analyses of satellite imagery, wind data, and ground-based visual observations, the Darwin VAAC reported that on 10 May a gas-and-steam plume, possibly containing ash, rose from Karangetang to an altitude of 3.6 km (12,000 ft) a.s.l. and drifted over 35 km SE.

Geological summary: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, north of Sulawesi. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented in the historical record (Catalog of Active Volcanoes of the World: Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts has also produced pyroclastic flows.

Kilauea, Hawaiian Islands (USA)

19.421°N, 155.287°W, Elevation 1222 m

HVO reported that the lava delta at Kamokuna (the ocean entry area at Kilauea), which had been growing since late March, collapsed on 3 May. Two large cracks parallel to the coast were visible on 27 April, suggesting instability. Between 0935 and 0940 on 3 May a large steam plume appeared in the middle of the lava delta in the area of large cracks. Weak fountaining or spattering likely occurred initially, because new tephra deposits were visible in the steaming area; that activity ended by 0940. Images acquired over the next 25 minutes showed a progressively weaker steam plume, and a subsiding delta. Photos of the ocean entry taken on 7 May showed multiple streams of lava flowing into the ocean.

During 10-16 May HVO reported that the lava lake continued to rise, fall, and spatter in Kilauea’s Overlook crater. Webcams recorded incandescence from long-active sources within Pu'u 'O'o Crater, from a vent high on the NE flank of the cone, and from a small lava pond in a pit on the W side of the crater. The 61G lava flow, originating from a vent on Pu'u 'O'o Crater's E flank, continued to enter the ocean at Kamokuna. Surface lava flows were active above and near the pali.

Geological summary: Kilauea volcano, which overlaps the east 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 sq km, destroying nearly 200 houses and adding new coastline to the island.

Klyuchevskoy, Central Kamchatka (Russia)

56.056°N, 160.642°E, Elevation 4754 m

KVERT reported that ash plumes from Klyuchevskoy were identified in satellite images drifting 270 km SE and NW during 5-6 and 10-11 May, respectively. A weak thermal anomaly was noted on 5 and 10 May. 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 wind model data, the Darwin VAAC reported that during 10-14 May ash plumes from Langila drifted N, NW, and S at altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l.

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.

Nevado del Ruiz, Colombia

4.892°N, 75.324°W, Elevation 5279 m

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 9-15 May seismicity at Nevado del Ruiz continued to indicate unrest; the number and magnitude of events were higher compared to the previous week. Significant amounts of water vapor and gas continued to be emitted. Gas, steam, and ash plumes rose 1.7 km above the crater rim on 12 May and drifted NW and SW. According to the Washington VAAC the Bogota MWO reported an ash emission on 13 May. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Geological summary: Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers >200 sq km. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

Reventador, Ecuador

0.077°S, 77.656°W, Elevation 3562 m

During 10-16 May IG reported a high level of seismic activity at Reventador including explosions, long-period earthquakes, harmonic tremor, and signals indicating emissions. Steam, gas, and ash plumes rose as high as 700 m above the crater rim during 10-12 May. Crater glow was noted during 11-12 May.

Geological summary: Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

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 during 8-14 May explosive activity at Sabancaya slightly decreased from the previous week, with an average of 38 explosions detected per day. The number of long-period events continued to increase, while hybrid events were sporadic. Gas-and-ash plumes rose as high as 4.2 km above the crater rim and drifted more than 40 km NE, E, and SE.

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.

Sinabung, Indonesia

3.17°N, 98.392°E, Elevation 2460 m

Based on PVMBG observations, webcam and satellite images, and wind data, the Darwin VAAC reported that during 10-16 May ash plumes from Sinabung rose to altitudes of 3-4.9 km (10,000-16,000 ft) a.s.l. and drifted E and NE.

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.

Suwanosejima, Ryukyu Islands (Japan)

29.638°N, 129.714°E, Elevation 796 m

Based on JMA notices and satellite-image analyses, the Tokyo VAAC reported that on 10 May plumes from Suwanosejima rose to an altitude of 2.7 km (9,000 ft) a.s.l. and drifted E.

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

Turrialba, Costa Rica

10.025°N, 83.767°W, Elevation 3340 m

OVSICORI-UNA reported an explosion at Turrialba on 10 May, followed by weak and passive ash emissions during 10-11 May. Several long-period earthquakes were recorded, and inflation continued. Gas measurements indicated a sulfur dioxide flux of 1,000 tons/day, and a high carbon dioxide/sulfur dioxide ratio. An event at 0900 on 12 May generated a plume, though poor visibility prevented a height estimate. An event at 0730 on 14 May generated a plume that rose 500 m above the crater rim and drifted N. Low-amplitude tremor was detected during 15-16 May, and a discontinuous ash plume rose no more than 500 m and drifted N and NW.

Geological 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 3340-m-high Turrialba is exceeded in height only by Irazú, covers an area of 500 sq km, and is one of Costa Rica's most voluminous volcanoes. 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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