New activity/unrest was reported for 5 volcanoes between May 31 and June 6, 2017. During the same period, ongoing activity was reported for 19 volcanoes.
New activity/unrest: Bulusan, Luzon (Philippines) | Copahue, Central Chile-Argentina border | Karymsky, Eastern Kamchatka (Russia) | Marapi, Indonesia | Sheveluch, Central Kamchatka (Russia).
Ongoing activity: Aira, Kyushu (Japan) | Bagana, Bougainville (Papua New Guinea) | Bogoslof, Fox Islands (USA) | Cleveland, Chuginadak Island (USA) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Fuego, Guatemala | Ibu, Halmahera (Indonesia) | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Langila, New Britain (Papua New Guinea) | Manam, Papua New Guinea | Planchon-Peteroa, Central Chile-Argentina border | Poas, Costa Rica | Popocatepetl, Mexico | Sabancaya, Peru | Sinabung, Indonesia | Turrialba, Costa Rica.
Bulusan, Luzon (Philippines)
12.77°N, 124.05°E, Elevation 1565 m
PHIVOLCS reported that a minor phreatic eruption at Bulusan occurred at 1029 on 5 June and was recorded by the seismic network for 12 minutes. The eruption could not be visually observed due to dense weather clouds covering the summit. Minor ashfall, a sulfuric odor, and rumbling sound were reported in barangays Monbon and Cogon in Irosin, while sulfuric odor was noted in barangay Bolos, Irosin. The Alert Level remained at 1, indicating abnormal conditions and a 4-km-radius Permanent Danger Zone (PDZ).
Geological summary: Luzon's southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. Bulusan lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic Bulusan complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit of 1565-m-high Bulusan volcano is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded at Bulusan since the mid-19th century.
Copahue, Central Chile-Argentina border
37.856°S, 71.183°W, Elevation 2953 m
OVDAS-SERNAGEOMIN reported that webcams recorded an increase in ash emissions at Copahue on 4 June. There were no significant changes in the magnitude or number of earthquakes recorded by the seismic network. The report noted that due to inclement weather making visual observations difficult, the observatory did not know if the ash emission began in the early hours of 4 June, or the day before. The Alert Level was raised to Yellow (the second lowest on a four-color scale); SERNAGEOMIN recommended no entry into a restricted area within 1 km of the crater.
Geological summary: Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded at Copahue since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.
Karymsky, Eastern Kamchatka (Russia)
54.049°N, 159.443°E, Elevation 1513 m
Based on Tokyo VAAC data, KVERT reported that an explosive eruption at Karymsky began at 0040 on 4 June. An ash plume rose 3 km (9,800 ft) a.s.l. and drifted over 40 km NE. The Aviation Color Code was raised to Orange (the second highest level on a four-color scale). Less than four hours later ash plumes rose 2 km (6,600 ft) a.s.l. and drifted 85 km ENE. The VAAC reported that a possible ash plumes rose 4 km 13,000 ft) a.s.l. during 5-6 June and drifted E.
Geological summary: Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.
0.381°S, 100.473°E, Elevation 2891 m
PVMBG reported four explosions at Marapi on 4 June, each lasting less than one minute. The explosions occurred at 1001, 1011, 1256, and 1550, and produced dense ash-and-steam plumes that rose 300 m, at least 700 m, 200 m, and 250 m above the crater, respectively. The plumes drifted E. Ejected bombs were deposited around the crater. Seismicity increased after the explosions. Minor ashfall was reported in the Pariangan District (8 km SSE), Tanah Datar Regency. The Alert Level remained at 2 (on a scale of 1-4). Residents and visitors were advised not to enter an area within 3 km of the summit.
Geological summary: Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2000 m above the Bukittinggi plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Elevation 3283 m
KVERT reported that during 26-27 and 31 May powerful explosions at Sheveluch generated ash plumes that rose 8 km (26,200 ft) a.s.l. and drifted 550 km ESE and about 650 km WSW. A thermal anomaly was identified in satellite images during 26 May-2 June. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 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.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Elevation 1117 m
JMA reported 15 events at Showa Crater (at Aira Caldera’s Sakurajima volcano) during 22-29 May, two of which were explosive. Material was ejected as high as 800 m above the crater rim. Ash plumes rose as high as 3.4 km on 31 May and 3 km on 2 June. Very small events occurred at Minamidake summit crater during 4-5 June. The Alert Level remained at 3 (on a 5-level scale).
Geological summary: The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.
Bagana, Bougainville (Papua New Guinea)
6.137°S, 155.196°E, Elevation 1855 m
Based on analyses of satellite imagery and model data, the Darwin VAAC reported that on 3 and 5 May ash plumes from Bagana rose to altitudes of 1.5-2.1 km (5,000-7,000 ft) a.s.l. and drifted W and SE.
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.
Bogoslof, Fox Islands (USA)
53.93°N, 168.03°W, Elevation 150 m
AVO reported that a short-duration (less than 10 minute) explosion at Bogoslof began at 1842 on 31 May based on seismic and infrasound data. A volcanic cloud identified in satellite images rose 7.3 km (24,000 ft) a.s.l., drifted WNW, and dissipated over the Bering Sea. The explosion was preceded by a several hour-long swarm of very small earthquakes. Seismicity decreased in the hours prior to the explosion and remained below the detection threshold. A sulfur dioxide plume from an explosion on 28 May was visible in satellite data drifting over the Hudson Bay region of Canada on 2 June. A short-duration explosive event at 0750 on 5 June produced a small volcanic cloud observed by a pilot. Low-amplitude tremor was detected in seismic data beginning at about 1229 on 5 June but then decreased to background levels. A vessel in the area reported vigorous steaming and a white plume rising several thousand feet above sea level. A brief explosive event was detected at 0600 on 6 June. The event likely produced a low-level (less than 3 km or 10,000 ft a.s.l.) emission; a possible plume at 1.8 km (6,000 ft) a.s.l. was identified in a satellite image following the detection of the activity in seismic and infrasound data, but quickly dissipated. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
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 cloudy satellite images during 31 May-5 June. The webcam recorded steam emissions during periods of clear weather. Small low-frequency events were recorded by the seismic station located on the flank of the volcano beginning at 0939 on 6 June. The events were consistent with lava-dome growth, but growth could not be visually confirmed. 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.
19.514°N, 103.62°W, Elevation 3850 m
On 2 June the Centro Universitario de Estudios e Investigaciones de Vulcanologia – Universidad de Colima reported that during the previous week seismic data revealed 21 high-frequency events, 14 long-period events, 1.7 hours of tremor, 12 landslides, and zero explosions. During 25-26 May sulfur dioxide emissions were low at 35-51 tons per day, close to the detectable limits.
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 31 May-6 June ash plumes from Dukono rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted NW, W, SW, and E.
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
Based on observations by residents of Severo-Kurilsk (Paramushir Island) about 7 km E of Ebeko, KVERT reported that explosive activity continued at the volcano during 25 May-2 June. 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.
14.473°N, 90.88°W, Elevation 3763 m
INSIVUMEH reported increased activity at Fuego on 1 June, characterized by an increase in the number of explosions (6-7 per hour) and ash plumes rising as high as 950 m above the crater and drifting W. Explosions generated shock waves that rattled structures in multiple areas including Panimaché I and II (8 km SW), Morelia (9 km SW), Santa Sofía (12 km SW), El Porvenir, and Sangre de Cristo (8 km WSW). Incandescent material was ejected as high as 500 m above the crater rim, and caused avalanches of material on the flanks. On 2 June explosions produced ash plumes that rose 550-950 m and drifted 10-12 km W and SW. Shock waves were detected within a radius of 25 km. Incandescent material was ejected 300-500 m high, causing avalanches in the Ceniza (SSW), Taniluyá (SW), and Santa Teresa (W) drainages. During 3-4 June there were 2-4 explosions recorded per hour. Ash plumes rose 650-1,050 m high and drifted 8-10 km W and SW. Weak shock waves rattled nearby buildings. Avalanches from ejected incandescent material continued to descend the three drainages. On 4 June a hot lahar descended the Pantaleón (W) drainage, carrying blocks more than 2 m in diameter, branches, and tree trunks. The lahar was 30 m wide and had a strong sulfur odor. During 4-5 June incandescent material rose 150 m and a lava flow traveled 300 m down the Santa Teresa drainage. On 6 June INSIVUMEH noted that eruptive episode number five had ended, with remnant lava flows in the Santa Teresa (2 km long) and Ceniza (3 km long) drainage. Explosions generated ash plumes that rose 950 m and drifted 15 km W and NW.
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.
Ibu, Halmahera (Indonesia)
1.488°N, 127.63°E, Elevation 1325 m
PVMBG reported that eruptions at Ibu on 1 and 5 June generated ash plumes that rose 150-250 m above the crater and drifted N and SE, respectively.
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.
Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Elevation 1222 m
During 31 May-6 June 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 (which had many small spattering sites along the margin) 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. Field observations on 31 May revealed that the lava delta had grown to an area of approximately 0.01 square kilometers. A solidified lava ramp extended from the tube exit high on the sea cliff down to the delta, whose leading edge was about 100 m from the tube exit on the sea cliff.
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 a weak thermal anomaly over Klyuchevskoy was identified in satellite images during 27 and 30-31 May and 2 June. Explosions during 1-2 June generated ash plumes that rose to 6 km (19,700 ft) a.s.l. and drifted about 400 km SSE. Ash plumes drifted over Petropavlovsk-Kamchatsky and Elizovo. 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 on 1 June ash plumes from Langila rose 1.8 km (6,000 ft) a.s.l. and drifted N and NW.
Geological summary: Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.
Manam, Papua New Guinea
4.08°S, 145.037°E, Elevation 1807 m
RVO reported that although weather clouds often obscured views of Manam during 1-7 June white emissions were periodically seen rising from Southern Crater and Main Crater. Seismicity was very low. The Alert Level remained at Stage 1.
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.
Planchon-Peteroa, Central Chile-Argentina border
35.223°S, 70.568°W, Elevation 3977 m
Based on Observatorio Volcanológico de los Andes del Sur (OVDAS) – SERNAGEOMIN observations, ONEMI reported on 17 May that the number and magnitude of earthquakes at Planchón-Peteroa had gradually declined during the past months, reaching baseline levels. Minor to no surface activity was noted. OVDAS-SERNAGEOMIN lowered the Alert Level to Green (the lowest level on a three-color scale), and ONEMI canceled the Yellow Alert for the communities of Molina (66 WNW), Curicó (68 km NW), Romeral (75 km NW), and Teno (68 km NW) that had been in place since 1 July 2016.
Geological summary: Planchón-Peteroa is an elongated complex volcano along the Chile-Argentina border with several overlapping calderas. Activity began in the Pleistocene with construction of the basaltic-andesite to dacitic Volcán Azufre, followed by formation of basaltic and basaltic-andesite Volcán Planchón, 6 km to the north. About 11,500 years ago, much of Azufre and part of Planchón collapsed, forming the massive Río Teno debris avalanche, which traveled 95 km to reach Chile's Central Valley. Subsequently, Volcán Planchón II was formed. The youngest volcano, andesitic and basaltic-andesite Volcán Peteroa, consists of scattered vents between Azufre and Planchón. Peteroa has been active into historical time and contains a small steaming crater lake. Historical eruptions from the complex have been dominantly explosive, although lava flows were erupted in 1837 and 1937.
Poas, Costa Rica
10.2°N, 84.233°W, Elevation 2708 m
OVSICORI-UNA reported that tremor amplitude at Poás fluctuated from low to medium levels during 30-31 May, often associated with the vigor of emissions of water vapor, magmatic gases, and material from vents. An event at 1200 on 2 June generated a plume consisting of water vapor, gases, and minor amounts of ash that rose 600 m above the crater. Another event recorded at 1353 could not be confirmed visually due to weather conditions. An event at 0858 on 6 June generated a plume that rose 1 km.
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.
19.023°N, 98.622°W, Elevation 5426 m
Each day during 31 May-2 June CENAPRED reported 51-78 and steam and gas emissions from Popocatépetl; the daily count increased to 144-276 during 2-5 June. Explosions were detected during 31 May-1 June (1-2 per day) and during 2-5 June (13-22 per day) though cloudy conditions prevented visual confirmation of ash, gas, and steam plumes. Observers noted material being ejected 200 m from the crater on 3 June. Crater incandescence was visible on some nights. The Alert Level remained at Yellow, Phase Two.
Geological 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.
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 for the second week in a row explosive activity at Sabancaya slightly increased from the previous week; there was an average of 47 explosions recorded per day during 29 May-4 June. Seismicity was dominated by long-period events, and the number and magnitude of hybrid events were low. Gas-and-ash plumes rose as high as 3 km above the crater rim and drifted more than 40 km E and SE. The MIROVA system detected five thermal anomalies, spread over the SE, N, and NW flanks. Sulfur dioxide flux was as high as 1,703 tons per day on 3 June.
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.
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 31 May-5 June ash plumes from Sinabung rose 3.4-5.5 km (11,000-18,000 ft) a.s.l. and drifted in multiple directions.
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.
Turrialba, Costa Rica
10.025°N, 83.767°W, Elevation 3340 m
OVSICORI-UNA reported that volcano-tectonic amplitude at Turrialba fluctuated from low to moderate levels during 30-31 May. Plumes of water vapor, magmatic gases, and material rose no higher than 300 m above the crater rim, sporadically contained ash, and drifted NW. On 3 June at 1930 an event produced an ash plume that rose 300 m and drifted SW. The report noted that during the previous week ash emissions had been sporadic and not generated by explosions.
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.
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