Active volcanoes in the world: May 27 - June 2, 2015

Active volcanoes in the world: May 27 - June 2, 2015

New activity/unrest was observed at 11 volcanoes from May 27 - June 2, 2015. During the same period, ongoing activity was observed at 14 volcanoes. 

New activity/unrest: Calbuco, Chile  | Concepcion, Nicaragua  | Guallatiri, Chile  | Karangetang [Api Siau], Siau Island (Indonesia)  | Kuchinoerabujima, Ryukyu Islands (Japan)  | Lokon-Empung, Sulawesi (Indonesia)  | Piton de la Fournaise, Reunion Island (France)  | Semisopochnoi, United States  | Sinabung, Indonesia  | Telica, Nicaragua  | Wolf, Isla Isabela (Ecuador).

Ongoing activity: Aira, Kyushu (Japan)  | Bagana, Bougainville (Papua New Guinea)  | Chirpoi, Kuril Islands (Russia)  | Colima, Mexico  | Dukono, Halmahera (Indonesia)  | Karymsky, Eastern Kamchatka (Russia)  | Kilauea, Hawaiian Islands (USA)  | Nevado del Ruiz, Colombia  | Popocatepetl, Mexico  | Reventador, Ecuador  | Sheveluch, Central Kamchatka (Russia)  | Shishaldin, Fox Islands (USA)  | Soputan, Sulawesi (Indonesia)  | Villarrica, Chile.

New activity/unrest

Calbuco, Chile
41.326°S, 72.614°W, Summit elev. 2003 m

On 27 May OVDAS-SERNAGEOMIN reported that seismicity at Calbuco fluctuated at low levels and continued to decline. According to ONEMI, the 10-km evacuation zone remained in effect, with controlled access to some communities allowed for part of the day; about 500 people remained displaced. On 28 May OVDAS-SERNAGEOMIN lowered the Alert Level remained to Yellow (the second lowest level on a four-color scale).

Geologic summary: Along with its neighbor Osorno, Calbuco is one of the most active volcanoes of the southern Chilean Andes. The isolated late-Pleistocene to Holocene andesitic volcano rises to 2003 m south of Lake Llanquihué in the Chilean lake district. Guanahuca, Guenauca, Huanauca, and Huanaque, all listed as synonyms of Calbuco (Catalog of Active Volcanoes of the World), are actually synonyms of nearby Osorno volcano (Moreno 1985, pers. comm.). The 2003-m-high Calbuco is elongated in a SW-NE direction and is capped by a 400-500 m wide summit crater. The complex evolution of Calbuco included edifice collapse of an intermediate edifice during the late Pleistocene that produced a 3 cu km debris avalanche that reached the lake. Calbuco has erupted frequently during the Holocene, and one of the largest historical eruptions in southern Chile took place from Calbuco in 1893-1894 and concluded with lava dome emplacement. Subsequent eruptions have enlarged the lava-dome complex in the summit crater.

Concepcion, Nicaragua
11.538°N, 85.622°W, Summit elev. 1700 m

INETER noted that 159-177 gas explosions had been detected during 27 May-1 June, bringing the total number to 1,493 detected by the network since an unspecified date of increased activity.

Geologic summary: Volcán Concepción is one of Nicaragua's highest and most active volcanoes. The symmetrical basaltic-to-dacitic stratovolcano forms the NW half of the dumbbell-shaped island of Ometepe in Lake Nicaragua and is connected to neighboring Madera volcano by a narrow isthmus. A steep-walled summit crater is 250 m deep and has a higher western rim. N-S-trending fractures on the flanks of the volcano have produced chains of spatter cones, cinder cones, lava domes, and maars located on the NW, NE, SE, and southern sides extending in some cases down to Lake Nicaragua. Concepción was constructed above a basement of lake sediments, and the modern cone grew above a largely buried caldera, a small remnant of which forms a break in slope about halfway up the north flank. Frequent explosive eruptions during the past half century have increased the height of the summit significantly above that shown on current topographic maps and have kept the upper part of the volcano unvegetated.

Guallatiri, Chile
18.42°S, 69.092°W, Summit elev. 6071 m

OVDAS-SERNAGEOMIN reported that at 0004 and 0517 on 31 May volcano-tectonic events at Guallatiri with local magnitudes of 3.5 and 3.7, respectively, were detected by the seismic network. Very minor deformation was also detected. No other changes were observed in recent momnths; white plumes continued to rise 200 m. The Alert Level was raised to Yellow (the second lowest level on a four-color scale).

Geologic summary: One of northern Chile's most active volcanoes, Volcán Guallatiri is a symmetrical ice-clad stratovolcano at the SW end of the Nevados de Quimsachata volcano group. The 6071-m-high Guallatiri lies just west of the border with Bolivia and is capped by a central dacitic dome or lava complex, with the active vent situated at its southern side. Thick lava flows are prominent on the lower northern and western flanks of the andesitic-to-rhyolitic volcano. Minor explosive eruptions have been reported from Guallatiri since the beginning of the 19th century. Intense fumarolic activity with "jet-like" noises continues, and numerous solfataras extend more than 300 m down the west flank.

Karangetang [Api Siau], Siau Island (Indonesia)
2.78°N, 125.4°E, Summit elev. 1784 m

Based on observations conducted at the Karangetang Volcano Observation Post in the village of Salili, PVMBG reported that white plumes rose as high as 400 m above Karangetang's main crater and 25 m above Crater II during 20-27 May. Incandescence from the lava dome was observed at night. Lava flows began to appear on 22 April; incandescent avalanches from the fronts of 300-m-long lava flows traveled as far as 2 km towards Batuawang and Kahetang drainages (E). Seismicity was dominated by signals characteristic of avalanches. Harmonic tremor was continuously detected. The Alert Level remained at 3 (on a scale of 1-4); visitors and residents were warned not to approach Karangetang within a 4-km radius.

Geologic summary: Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, north of Sulawesi. The 1784-m-high stratovolcano contains five summit craters along a N-S line. Karangetang 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.

Kuchinoerabujima, Ryukyu Islands (Japan)
30.443°N, 130.217°E, Summit elev. 657 m

JMA reported that at 0959 on 29 May an explosive and phreatomagmatic eruption at Kuchinoerabujima generated an ash plume that rose 9 km above Shindake Crater's rim and drifted ESE. Pyroclastic flows descended the SW flank and reached the coast on the NW flank. Volcanic earthquakes increased after that event, but then decreased around 1300. The Alert Level was raised to 5 (the highest level on a 1-5 scale). According to a news article all residents and visitors (137-141) were safely evacuated by a ferry to neighboring Yakushima Island. Later that day ash plumes rose 200 m and drifted SW. Scientists conducted an overflight and confirmed pyroclastic flow deposits on the NW and NE flanks.

Ash plumes continued to be emitted the next day, rising as high as 1.2 km. A field team observed discolored trees on the SE and SW flanks, and fallen trees near the coast on the NW flank. Cloud cover prevented views of the eruption area, but the team was able to confirm continued fumarolic activity from a crack in the W part of the crater as well as incandescence.

Geologic summary: A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyus, 15 km west of Yakushima. Furutake, Shintake, and Noike were erupted from south to north, respectively, to form a composite cone that is parallel to the trend of the Ryukyu Islands. The highest peak, Furutake, reaches only 657 m above sea level. The youngest cone, 640-m-high Shintake, was formed after the NW side of Furutake was breached by an explosion. All historical eruptions have occurred from Shintake, although a lava flow from the S flank of Furutake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shintake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.

Lokon-Empung, Sulawesi (Indonesia)
1.358°N, 124.792°E, Summit elev. 1580 m

PVMBG reported that an eruption at 1520 on 20 May from Lokon-Empung's Tompaluan Crater generated an ash plume that rose 1.5 km and drifted NNW. The eruption was accompanied by loud "thumping" noises heard at the local observation post. During 21-27 May white plumes rose as high as 150 m. Seismicity fluctuated but slightly decreased overall. The Alert Level remained at 3 (on a scale of 1-4). Residents and tourists were reminded not to approach Tompaluan Crater within a radius of 2.5 km.

Geologic summary: The twin volcanoes Lokon and Empung, rising about 800 m above the plain of Tondano, are among the most active volcanoes of Sulawesi. Lokon, the higher of the two peaks (whose summits are only 2.2 km apart), has a flat, craterless top. The morphologically younger Empung volcano has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century, but all subsequent eruptions have originated from Tompaluan, a 150 x 250 m wide double crater situated in the saddle between the two peaks. Historical eruptions have primarily produced small-to-moderate ash plumes that have occasionally damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred.

Piton de la Fournaise, Reunion Island (France)
21.244°S, 55.708°E, Summit elev. 2632 m

OVPDLF reported that the eruption at Piton de la Fournaise that began on 17 May ended on 30 May at 2050 when tremor was no longer detected.

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

Semisopochnoi, United States
51.93°N, 179.58°E, Summit elev. 1221 m

A decline in seismicity at Semisopochnoi over the previous few months, and no activity observed in satellite images, prompted AVO to lower the Aviation Color Code and the Volcano Alert Level to Unassigned on 28 May. Increased seismicity had been detected in January.

Geologic summary: Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is 1221-m-high Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part. The three-peaked 774-m-high Mount Cerberus volcano was constructed during the Holocene within the caldera. Each of the peaks contains a summit crater; lava flows on the northern flank of Cerberus appear younger than those on the southern side. Other post-caldera volcanoes include the symmetrical 855-m-high Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented historical eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone within the caldera could have been active during historical time.

Sinabung, Indonesia
3.17°N98.392°E, Summit elev. 2460 m

PVMBG reported that foggy weather often prevented visual observations of Sinabung during 25 May-2 June, except for a few clearer periods on some days. White plumes rose 200-700 m above the crater, and lava flows on the flanks were incandescent as far as 2 km S and SE. Pyroclastic flows traveled 2-3 km down the S and SE flanks during 26-28 May. An ash plume from a pyroclastic flow on 28 May rose into the fog. Two pyroclastic flows occurred on 2 June but fog prevented visual observations. Seismicity consisted of avalanche signals, low-frequency and hybrid events, tremor, tectonic events, and volcanic earthquakes; RSAM values increased due to an increase of avalanche signals. Deformation data showed a trend of inflation. The Alert Level was raised to 4 (on a scale of 1-4), indicating that people within 7 km of the volcano on the S to E flanks should evacuate. On 3 June BNPB reported that the lava dome volume had increased to more than 3 million cubic meters and was unstable.

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, 2460-m-high andesitic-to-dacitic volcano 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.

Telica, Nicaragua
12.602°N, 86.845°W, Summit elev. 1061 m

Based on webcam views and satellite images, the Washington VAAC reported that on 26 May an ash plume from Telica drifted W at an altitude of 4.3 km (14,000 ft) a.s.l. Later that day a gas-and-ash plume rose to an altitude below 3 km (10,000 ft) a.s.l. and drifted 75 km W. INETER reported continuing small gas explosions during 28 May-1 June; a total of 798 explosions since an unspecified time of increased activity. Ashfall was reported in Posoltega (16 km SW), Corinto (40 km WSW), Chinandega (30 km W), Chichigalpa (20 km WSW), and El Realejo (35 km WSW).

Geologic 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 1061-m-high 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 SE of Telica, 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.

Wolf, Isla Isabela (Ecuador)
0.02°N, 91.35°W, Summit elev. 1710 m

IG reported that the eruption at Wolf that began on 25 May continued through 2 June. Lava flows first reached the sea on 28 May. During an overflight on 29 May scientists observed a gas plume rising 2-3 km above the volcano and drifting NW, and smelled a strong sulfur odor. Active lava flows descended the E and NE flanks; cloud cover prevented views of the other areas but thermal images showed anomalies from lava flows on the SE and S flanks. The sulfur dioxide emission rate was 40,600 tons per day based on data collected during the flight. Satellite data collected since the beginning of the eruption indicated very minimal ash present in the plume. In addition, no ashfall was reported in the Galapagos Islands. The report also noted that activity had decreased during the recent few days.

Geologic summary: Wolf, the highest volcano of the Galápagos Islands, straddles the equator at the north end of the archipelago's largest island, Isabela. The 1710-m-high edifice has steeper slopes than most other Isabela volcanoes, reaching angles up to 35 degrees. A 6 x 7 km caldera, at 700 m one of the deepest of the Galápagos Islands, is located at the summit. A prominent bench on the west side of the caldera rises 450 above the caldera floor, much of which is covered by a lava flow erupted in 1982. Radial fissures concentrated along diffuse rift zones extend down the north, NW, and SE flanks, and submarine vents lie beyond the north and NW fissures. Similar unvegetated flows originating from a circumferential chain of spatter and scoria cones on the eastern caldera rim drape the forested flanks to the sea. The proportion of aa lava flows at Volcán Wolf exceeds that of other Galápagos volcanoes. An eruption in in 1797 was the first documented historical eruption in the Galápagos Islands.

Ongoing activity

Aira, Kyushu (Japan)
31.593°N, 130.657°E, Summit elev. 1117 m

JMA reported 18 explosions during 25-29 May and 24 during 29 May-1 June from Showa Crater at Aira Caldera’s Sakurajima volcano, some that ejected tephra as far as 1,300 m, and incandescence from the crater was occasionally visible at night. On 29 May and 1 June explosions generated large ash plumes that rose 3.3 km above the crater. 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 wind data, the Darwin VAAC reported that on 28 May an ash plume from Bagana rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted almost 160 km NW.

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, roughly 1850-m-high 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 volcano's flanks on all sides. Satellite thermal measurements indicate a continuous eruption from before February 2000 through at least late August 2014.

Chirpoi, Kuril Islands (Russia)
46.525°N, 150.875°E, Summit elev. 742 m

SVERT reported that satellite images over Snow, a volcano of Chirpoi, detected weak steam-and-gas emissions on 25 May. A thermal anomaly was detected on 25, 28, and 30 May. Cloud cover obscured views on other days during 26 May-1 June. The Aviation Color Code remained at Yellow.

Geologic summary: Chirpoi, a small island lying between the larger islands of Simushir and Urup, contains a half dozen volcanic edifices constructed within an 8-9 km wide, partially submerged caldera. The southern rim of the caldera is exposed on nearby Brat Chirpoev Island. The symmetrical Cherny volcano, which forms the 691 m high point of the island, erupted twice during the 18th and 19th centuries. The youngest volcano, Snow, originated between 1770 and 1810. It is composed almost entirely of lava flows, many of which have reached the sea on the southern coast. No historical eruptions are known from 742-m-high Brat Chirpoev, but its youthful morphology suggests recent strombolian activity.

Colima, Mexico
19.514°N, 103.62°W, Summit elev. 3850 m

Based on satellite images and webcam views, the Washington VAAC reported that on 27 May two ash plumes from Colima rose to an altitude of 5.8 km (19,000 ft) a.s.l. Later that day an ash plume drifted 40 km W.

Geologic 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)
1.68°N, 127.88°E, Summit elev. 1335 m

Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 29 May an ash plume from Dukono rose to an altitude of 2.4 km (10,000 ft) a.s.l. and drifted 75 km SE. On 2 June an ash plume rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 130 km NW.

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.

Karymsky, Eastern Kamchatka (Russia)
54.049°N, 159.443°E, Summit elev. 1513 m

KVERT reported that moderate activity at Karymsky likely continued during 22-29 May. Satellite images detected an ash plume drifting 45 km SE on 23 May. The Aviation Color Code remained at Orange.

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

HVO reported that seismicity beneath Kilauea's summit, upper East Rift Zone, and Southwest Rift Zone was at background levels during 27 May-2 June. The lava lake continued to be active in the deep pit within Halema'uma'u Crater; the lake level was about 44 m below the crater floor on 29 May and 73 m below the floor on 31 May. The June 27th NE-trending lava flow continued to be active with surface flows within 7.9 km NE of Pu'u 'O'o.

Geologic 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 of Kilauea 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.

Nevado del Ruiz, Colombia
4.892°N, 75.324°W, Summit elev. 5279 m

The Washington VAAC reported that on 26 May an ash emission from Nevado del Ruiz was visible in the webcam and reported by the Air Force Weather Agency (AFWA). Weather clouds prevented satellite views.

Geologic 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.

Popocatepetl, Mexico
19.023°N, 98.622°W, Summit elev. 5426 m

CENAPRED reported that during 27 May-2 June the seismic network at Popocatépetl recorded 60-145 daily emissions consisting of water vapor, gas, and ash; cloud cover sometimes prevented visual observations. Explosions occurred daily, and nighttime crater incandescence was observed. Gas-and-steam plumes drifted in multiple directions. On 29 May at 1600 a series of explosions generated steam-and-ash plumes, and ashfall in multiple municipalities. Another series of explosions was detected from 1600-1918 on 30 May. Slight ashfall was recorded in Amozoc, Puebla (60 km E) on 31 May. The Alert Level remained at Yellow, Phase Two.

Geologic summary: Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5426 m 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major plinian eruptions, the most recent of which took place about 800 CE, have occurred from Popocatépetl since the mid Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since precolumbian time.

Reventador, Ecuador
0.077°S, 77.656°W, Summit elev. 3562 m

During 27 May-2 June IG reported moderate seismic activity including explosions, long-period earthquakes, harmonic tremor, and signals indicating emissions at Reventador; cloud cover sometimes prevented visual observations. On 27 May a steam-and-ash plume rose 1 km and drifted SW. The next day frequent vapor emissions with a slight amounts of ash rose 800 m above the crater and mainly drifted NW. During 29-30 May steam plumes with minor amounts of ash rose 1 km and drifted SW and NW. On 2 June an ash plume rose 300 m and drifted NW.

Geologic 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.

Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m

KVERT reported that during 22-29 May lava-dome extrusion onto Sheveluch’s N flank was accompanied by fumarolic activity. A thermal anomaly was detected in satellite images on 23 May. 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 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.

Shishaldin, Fox Islands (USA)
54.756°N, 163.97°W, Summit elev. 2857 m

AVO reported that seismicity at Shishaldin continued to be elevated over background levels 27 May-2 June, indicating that low-level eruptive activity confined to the summit crater likely continued. Elevated surface temperatures were periodically detected in satellite images, and minor steaming was recorded by the webcam during 27-28 May. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geologic summary: The beautifully symmetrical volcano of Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 2857-m-high, glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steady steam plume rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is Holocene in age and largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the west and NE sides at 1500-1800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.

Soputan, Sulawesi (Indonesia)
1.108°N, 124.73°E, Summit elev. 1784 m

PVMBG reported that during 20-27 May white plumes were observed rising as high as 100 m above Soputan even though inclement weather sometimes obscured crater views. Variable seismicity was dominated by volcanic earthquakes and signals indicating emissions and avalanches. Low-frequency harmonic tremor was occasionally detected. The Alert Level remained at 3 (on a scale of 1-4). Residents and tourists were advised not to approach the craters within a radius of 4 km, or 6.5 km on the WSW flank.

Geologic summary: The small Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano rises to 1784 m and is located SW of Sempu volcano. It was constructed at the southern end of a SSW-NNE trending line of vents. During historical time the locus of eruptions has included both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.

Villarrica, Chile
39.42°S, 71.93°W, Summit elev. 2847 m

OVDAS-SERNAGEOMIN reported no significant changes at Villarrica during 27 May-2 June. Seismicity fluctuated at low-to-moderate levels, and continued to indicate small explosions and degassing from the lava lake. Deformation data suggested minor inflation. The Alert Level remained at Orange (the second highest level on a four-color scale) and the public was warned to stay outside of a 5-km radius around the crater and 200 m away from drainages in the SW and NE quadrants.

Geologic summary: Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot Villarrica's flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano have been produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 sq km of the volcano, and lahars have damaged towns on its flanks.

Source: GVP

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