New activity/unrest was observed at 6 volcanoes from May 6 - 12, 2015. During the same period, ongoing activity was observed at 16 volcanoes.
New activity/unrest: Bulusan, Luzon (Philippines) | Calbuco, Chile | Hakoneyama, Honshu (Japan) | Karangetang [Api Siau], Siau Island (Indonesia) | Kilauea, Hawaiian Islands (USA) | Telica, Nicaragua.
Ongoing activity: Aira, Kyushu (Japan) | Batu Tara, Komba Island (Indonesia) | Chirinkotan, Kuril Islands (Russia) | Chirpoi, Kuril Islands (Russia) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Etna, Sicily (Italy) | Grimsvotn, Iceland | Karymsky, Eastern Kamchatka (Russia) | Klyuchevskoy, Central Kamchatka (Russia) | Manam, Papua New Guinea | Popocatepetl, Mexico | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Turrialba, Costa Rica | Zhupanovsky, Eastern Kamchatka (Russia).
Bulusan, Luzon (Philippines)
12.77°N, 124.05°E, Elevation 1565 m
PHIVOLCS reported that at 2146 on 6 May a phreatic explosion from a vent on the upper NW flank of Bulusan generated an ash plume that rose 250 m before drifting W. Seismic data indicated that the event lasted 3.5 minutes. Traces of ash were reported in Sitio Tulay of Bagsangan Barangay, and in the Cogon, Monbon, and Tinampo Barangays. The Alert Level was raised to 1, indicating abnormal conditions and a 4-km radius Permanent Danger Zone (PDZ). During 8-9 and 11-12 May diffuse white emissions rose from vents on the SW and upper NW flanks.
Geologic 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.
41.326°S, 72.614°W, Elevation 2003 m
OVDAS-SERNAGEOMIN reported that on 6 May activity at Calbuco fluctuated; a sudden increase of tremor that began at 1304 and lasted two hours was accompanied by increased gas-and-ash emissions. During 7-11 May the gas-and-ash emissions were steady and low (less than 1 km), and drifted E, SE, and S; inclement weather prevented observations during 8-10 and 12 May. Moderate levels of tremor were detected through 9 May, and then decreased to low levels through 12 May. According to ONEMI, the number of evacuees within the 20-km evacuation zone remained at 6,685 on 12 May. In addition 3,221 animals, including sheep, goats, cows, and horses, had been evacuated. The Alert Level remained at Red (the highest level on a four-color scale).
Satellite images showed that the aerosol plume from the initial few days of the eruption had traveled around the world once; faint layers of the plume were 14-16 km above parts of South America during 8-9 May.
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.
Hakoneyama, Honshu (Japan)
35.233°N, 139.021°E, Elevation 1438 m
On 6 May JMA raised the Alert Level for Hakoneyama from 1 to 2 (on a 5-level scale). Seismicity had increased on 26 April, and on 5 May three events occurred that were Intensity I. Inclinometer data showed variations related to seismicity, and vigorous steaming from the hot springs was observed. Seismicity remained elevated at least through 10 May.
Geologic summary: Hakoneyama volcano is truncated by two overlapping calderas, the largest of which is 10 x 11 km wide. The calderas were formed as a result of two major explosive eruptions about 180,000 and 49,000-60,000 years ago. Scenic Lake Ashi lies between the SW caldera wall and a half dozen post-caldera lava domes that were constructed along a SW-NE trend cutting through the center of the calderas. Dome growth occurred progressively to the south, and the largest and youngest of these, Kamiyama, forms the high point of Hakoneyama. The calderas are breached to the east by the Hayakawa canyon. A phreatic explosion about 3000 years ago was followed by collapse of the NW side of Kamiyama, damming the Hayakawa valley and creating Lake Ashi. The latest magmatic eruptive activity about 2900 years ago produced a pyroclastic flow and a lava dome in the explosion crater, although phreatic eruptions took place as recently as the 12-13th centuries CE. Seismic swarms have occurred during the 20th century. Lake Ashi, along with major thermal areas in the caldera, forms a popular resort area SW of Tokyo.
Karangetang [Api Siau], Siau Island (Indonesia)
2.78°N, 125.4°E, Elevation 1784 m
BNPB reported that activity at Karangetang had increased. On 7 May at 1400 an eruption that ejected incandescent material and produced a dense ash plume also generated a pyroclastic flow that traveled as far as 4 km E, leveling four houses in Kora-Kora. There were no reported fatalities, and 465 people quickly evacuated. The next day pyroclastic flows descended the S flank 2.5 km, in the Kahetang (E) and Awang drainages. Incandescent material continued to be ejected. 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.
Based on satellite images, the Darwin VAAC reported that on 8 May an ash plume that rose to an altitude of 3 km (10,000 ft) a.s.l. drifted almost 85 km E, and dissipated two days later. On 12 May an ash plume rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted 55 km SW. Pyroclastic flow activity was also reported.
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.
Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Elevation 1222 m
During 6-12 May HVO reported that the circulating lava lake occasionally rose and fell in the pit within Kilauea's Halema'uma'u Crater. Lava overflowed the rim multiple times almost daily, and since the first overflow on 28 April, had built up a rim that by 8 May was 10 m higher than the Halema'uma'u crater floor. Contemporaneously with deflation detected during 10-12 May, the lake receded, and by 12 May was barely visible from the Jaggar Museum.
At Pu'u 'O'o Crater, lava erupted from several vents multiple times onto the crater floor. An overflight on 8 May revealed an active lava pond in an isolated vent W of the main crater. The June 27th NE-trending lava flow continued to be active with three areas of breakouts within and along the flow-field margins, within 8 km NE of Pu'u 'O'o. Most of the surface flows were fed from the 21 February breakout and located less than 3 km from the NE rim of Pu'u 'O'o. Forest burned about 8 km NE of the crater.
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.
12.602°N, 86.845°W, Elevation 1061 m
Based on satellite images, the Washington VAAC reported that on 11 May multiple emissions of gas and ash from Telica rose to an altitude below 1.8 km (6,000 ft) a.s.l. and drifted W. The emissions dissipated within six hours.
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.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Elevation 1117 m
JMA reported 105 explosions during 1-11 May from Showa Crater at Aira Caldera’s Sakurajima volcano tephra was ejected as far as 1,800 m. Incandescence from the crater was visible at night. Explosions occurred at 2309 on 4 May, and at 1049 and 1126 on 8 May. Sulfur dioxide gas emissions measured during fieldwork conducted on 8 May were 2,300 tons per day (400 tons per day was measured on 16 April). An explosion at 2021 on 10 May generated a large ash plume that rose 3.2 km.
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.
Batu Tara, Komba Island (Indonesia)
7.792°S, 123.579°E, Elevation 748 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 6-9 May ash plumes from Batu Tara rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 55-85 km W and WNW.
Geologic summary: The small isolated island of Batu Tara in the Flores Sea about 50 km N of Lembata (fomerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption, during 1847-52, produced explosions and a lava flow.
Chirinkotan, Kuril Islands (Russia)
48.98°N, 153.48°E, Elevation 724 m
SVERT reported that on 10 May a thermal anomaly over Chirinkotan was detected in satellite images. Cloud cover prevented views of the volcano on the other days during 4-11 May. The Aviation Color Code remained at Yellow.
Geologic summary: The small, mostly unvegetated 3-km-wide island of Chirinkotan occupies the far end of an E-W-trending volcanic chain that extends nearly 50 km west of the central part of the main Kuril Islands arc. Chirinkotan is the emergent summit of a volcano that rises 3000 m from the floor of the Kuril Basin. A small 1-km-wide caldera about 300-400 m deep is open to the SE. Lava flows from a cone within the breached crater reached the north shore of the island. Historical eruptions have been recorded at Chirinkotan since the 18th century. Fresh lava flows also descended the SE flank of Chirinkotan during an eruption in the 1880s that was observed by the English fur trader Captain Snow.
Chirpoi, Kuril Islands (Russia)
46.525°N, 150.875°E, Elevation 742 m
SVERT reported that satellite images over Snow, a volcano of Chirpoi, detected a thermal anomaly during 6-8 and 11 May. Cloud cover obscured views on other days during 4-11 May. 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.
19.514°N, 103.62°W, Elevation 3850 m
Based on satellite images, wind data, webcam views, and the Mexico City MWO, the Washington VAAC reported that on 7 May ash plumes from Colima rose to an altitude of 6.7 km (22,000 ft) a.s.l. and drifted 80-200 km E. On 10 May ash plumes rose to altitudes of 5.2-6.7 km (17,000-22,000 ft) a.s.l. and drifted NE and ESE. Ash emissions were recorded by the webcam on 11 May.
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, Elevation 1335 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 8-10 May ash plumes from Dukono rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 45-110 km E and NE.
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.
Etna, Sicily (Italy)
37.734°N, 15.004°E, Elevation 3330 m
INGV reported weak Strombolian activity inside Etna’s New Southeast Crater (NSEC) during 11-12 May, mainly from a depression on the E part of the crater and sometimes from a second vent in the middle of the crater. This activity was preceded by a sudden increase in tremor amplitude and intense degassing during 2-3 May; visible activity did not accompany the episode, and after a few days tremor returned to normal levels.
Geologic summary: Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur at Etna. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more of the three prominent summit craters, the Central Crater, NE Crater, and SE Crater (the latter formed in 1978). Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.
64.42°N, 17.33°W, Elevation 1725 m
According to the Icelandic Meteorological Office, a small glacial outburst flood (jökulhlaup) from Grímsvötn's subglacial lake was occurring on 6 May, increasing the water level in the Gígjukvísl River. Electrical conductivity measurements indicated a considerable increase of a geothermal contribution to the river water. Based on information from the Institute of Earth Sciences, the water available for drainage was 0.2-0.3 cubic kilometers, therefore the maximum discharge of the flood was expected to be less than 700 cubic meters per second, occurring towards the middle of the week. Seismic tremor had increased due to the flood and not volcanic activity. The report warned that hydrogen sulfide released from the floodwater as it drains is particularly potent at the river outlet at the ice margin, where concentrations may reach poisonous levels.
Geologic summary: Grímsvötn, Iceland's most frequently active volcano in historical time, lies largely beneath the vast Vatnajökull icecap. The caldera lake is covered by a 200-m-thick ice shelf, and only the southern rim of the 6 x 8 km caldera is exposed. The geothermal area in the caldera causes frequent jökulhlaups (glacier outburst floods) when melting raises the water level high enough to lift its ice dam. Long NE-SW-trending fissure systems extend from the central volcano. The most prominent of these is the noted Laki (Skaftar) fissure, which extends to the SW and produced the world's largest known historical lava flow during an eruption in 1783. The 15-cu-km basaltic Laki lavas were erupted over a 7-month period from a 27-km-long fissure system. Extensive crop damage and livestock losses caused a severe famine that resulted in the loss of one-fifth of the population of Iceland.
Karymsky, Eastern Kamchatka (Russia)
54.049°N, 159.443°E, Elevation 1513 m
KVERT reported moderate activity at Karymsky during 1-8 May. Satellite images showed a weak thermal anomaly over the volcano during 4-6 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.
Klyuchevskoy, Central Kamchatka (Russia)
56.056°N, 160.642°E, Elevation 4754 m
KVERT reported that moderate activity continued at Klyuchevskoy during 1-9 May. Satellite images detected a daily weak thermal anomaly over the volcano, and gas-and-steam plumes containing ash drifting over 450 km SE during 2-5 May. The Aviation Color Code was lowered to Yellow on 13 May.
Geologic 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.
Manam, Papua New Guinea
4.08°S, 145.037°E, Elevation 1807 m
RVO reported that activity at both Manam's Southern Crater and Main Crater was low during 1-30 April; variable amounts of white emissions rose from both craters. Incandescence from Southern Crater was visible at night during 2, 6, 8-10, 15, 21, and 29-30 April, and from main Crater during 8-10, 15, 21, and 29-30 April. The seismicity was characterized by sub-continuous and continuous volcanic tremor, and discrete low-frequency earthquakes. Sulfur dioxide flux was slightly higher at the end of April; distinct sulfur dioxide levels were detected on 2 May.
Geologic 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.
19.023°N, 98.622°W, Elevation 5426 m
CENAPRED reported that during 6-12 May the seismic network at Popocatépetl recorded 17-56 daily emissions mostly consisting of water vapor and gas. Nighttime crater incandescence was noted almost every night; sometimes the incandescence would become more intense with accompanying emissions. Explosions were detected at 0949 and 1113 on 7 May. The next day steam-and-gas emissions with low ash content drifted SSW. An explosion was detected at 0411. Ash was visible in water vapor-and-gas emissions during 10-11 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.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Elevation 3283 m
KVERT reported that during 1-8 May lava-dome extrusion onto Sheveluch’s N flank was accompanied by incandescence, hot block avalanches, and fumarolic activity. A daily thermal anomaly was also detected in satellite images. 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, Elevation 2857 m
AVO reported that seismicity at Shishaldin continued to be elevated over background levels 6-12 May indicating that low-level eruptive activity confined to the summit crater likely continued. Periodically, elevated temperatures in the crater were detected and steaming was recorded by the webcam, although cloud cover sometimes prevented views of the volcano. 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.
Turrialba, Costa Rica
10.025°N, 83.767°W, Elevation 3340 m
OVSICORI-UNA reported that a 4-minute-long ash emission from Turrialba occurred at 1004 on 6 May. The ash plume rose vertically about 600 m above the crater. Another ash emission occurred at 1245 on 11 May, and tremor was detected. No direct observations of ash were possible due to inclement weather.
Geologic summary: Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive 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.
Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E, Elevation 2899 m
KVERT reported that moderate activity continued at Zhupanovsky during 1-8 May. Satellite images detected a thermal anomaly over the volcano on 3 and 5 May. The Aviation Color Code remained at Orange.
Geologic summary: The Zhupanovsky volcanic massif consists of four overlapping stratovolcanoes along a WNW-trending ridge. The elongated volcanic complex was constructed within a Pliocene-early Pleistocene caldera whose rim is exposed only on the eastern side. Three of the stratovolcanoes were built during the Pleistocene, the fourth is Holocene in age and was the source of all of Zhupanovsky's historical eruptions. An early Holocene stage of frequent moderate and weak eruptions from 7000 to 5000 years before present (BP) was succeeded by a period of infrequent larger eruptions that produced pyroclastic flows. The last major eruption took place about 800-900 years BP. Historical eruptions have consisted of relatively minor explosions from the third cone.