Active volcanoes in the world: March 30 – April 5, 2016

New activity/unrest was observed at 9 volcanoes between March 30 and April 5, 2016. During the same period, ongoing activity was observed at 19 volcanoes.

New activity/unrest: Chikurachki, Paramushir Island (Russia)  | Kanlaon, Philippines  | Kerinci, Indonesia  | Klyuchevskoy, Central Kamchatka (Russia)  | Langila, New Britian (Papua New Guinea)  | Pavlof, United States  | Popocatepetl, Mexico  | Sangay, Ecuador  | Villarrica, Chile.

Ongoing activity: Aira, Kyushu (Japan)  | Alaid, Kuril Islands (Russia)  | Chirpoi, Kuril Islands (Russia)  | Colima, Mexico  | Dukono, Halmahera (Indonesia)  | Etna, Sicily (Italy)  | Karymsky, Eastern Kamchatka (Russia)  | Kilauea, Hawaiian Islands (USA)  | Masaya, Nicaragua  | Momotombo, Nicaragua  | Nevado del Ruiz, Colombia  | Santa Maria, Guatemala  | Sheveluch, Central Kamchatka (Russia)  | Sinabung, Indonesia  | Telica, Nicaragua  | Tengger Caldera, Eastern Java (Indonesia)  | Turrialba, Costa Rica  | Yasur, Vanuatu  | Zhupanovsky, Eastern Kamchatka (Russia).

New activity/unrest

Chikurachki, Paramushir Island (Russia)
50.324°N, 155.461°E, Summit elev. 1781 m

KVERT reported that a strong explosive eruption at Chikurachki during 29-31 March generated ash plumes that rose to a maximum altitude of 4 km (13,100 ft) a.s.l. and drifted 570 km NE, S, and SW. The volcano was quiet afterwards; the Aviation Color Code was lowered to Yellow on 2 April, and then to Green on 5 April.

Geologic summary: Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidized basaltic-to-andesitic scoria deposits covering the upper part of the young cone give it a distinctive red color. Frequent basaltic plinian eruptions have occurred during the Holocene. Lava flows from 1781-m-high Chikurachki reached the sea and form capes on the NW coast; several young lava flows also emerge from beneath the scoria blanket on the eastern flank. The Tatarinov group of six volcanic centers is located immediately to the south of Chikurachki, and the Lomonosov cinder cone group, the source of an early Holocene lava flow that reached the saddle between it and Fuss Peak to the west, lies at the southern end of the N-S-trending Chikurachki-Tatarinov complex. In contrast to the frequently active Chikurachki, the Tatarinov volcanoes are extensively modified by erosion and have a more complex structure. Tephrochronology gives evidence of only one eruption in historical time from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959.

Kanlaon, Philippines
10.412°N, 123.132°E, Summit elev. 2435 m

PHIVOLCS reported that long-duration tremor began at Kanlaon at 0130 on 30 March. The tremor was accompanied by gas-and-steam plumes that rose 600-700 m and drifted SW and SSW during 30 March-1 April. On 31 March minor ashfall was reported in areas downwind including in parts of La Carlota City (14 km W), La Castellana, and Bago City in Negros Occidental. The tremor continued during 2-4 April, though the energy decreased, and steam plumes rose 400-500 m. On 5 April steam plumes rose 800 m and drifted SW. The Alert Level remained at 1 (on a scale of 0-5).

Geologic summary: Kanlaon volcano (also spelled Canlaon), the most active of the central Philippines, forms the highest point on the island of Negros. The massive 2435-m-high andesitic stratovolcano is dotted with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The largest debris avalanche known in the Philippines traveled 33 km to the SW from Kanlaon. The summit of Kanlaon contains a 2-km-wide, elongated northern caldera with a crater lake and a smaller, but higher, historically active vent, Lugud crater, to the south. Historical eruptions from Kanlaon, recorded since 1866, have typically consisted of phreatic explosions of small-to-moderate size that produce minor ashfalls near the volcano.

Kerinci, Indonesia
1.697°S, 101.264°E, Summit elev. 3800 m

Based on satellite images and ground reports from PVMBG, the Darwin VAAC reported that during 31 March-2 April and 4-5 April ash plumes from Kerinci rose to altitudes of 4.3-4.9 km (14,000-16,000 ft) a.s.l., and drifted NW, N, and E.

Geologic summary: The 3800-m-high Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. Kerinci is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. The volcano contains a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit of Kerinci. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. The frequently active Gunung Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

Klyuchevskoy, Central Kamchatka (Russia)
56.056°N, 160.642°E, Summit elev. 4754 m

KVERT reported strong gas-and-steam activity at Klyuchevskoy during 25 March-1 April. A weak thermal anomaly was detected over the volcano during 25 and 29-30 March. Strong Strombolian activity began at 2325 on 3 April, and satellite images on 5 April began registering a bright thermal anomaly. The Aviation Color Code remained at Yellow.

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.

Langila, New Britian (Papua New Guinea)
5.525°S, 148.42°E, Summit elev. 1330 m

Based on analyses of satellite imagery, the Darwin VAAC reported that during 2-3 April ash plumes from Langila rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 35-65 km N NE, and E.

Geologic summary: Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Pavlof, United States
55.417°N, 161.894°W, Summit elev. 2493 m

AVO reported that the intensity of the eruption at Pavlof greatly decreased during 29-30 March, though a news article noted that ash from the eruption had caused more flights in and out of Yellowknife and Regina, Canada, to be cancelled. Elevated surface temperatures identified in satellite data and visual observations of low-level, intermittent ash plumes were noted during brief breaks in poor weather conditions. Seismicity remained elevated above background levels through 4 April, and was characterized by occasional short-duration tremor bursts. Cloud cover obscured satellite and web-cam views, though weakly elevated surface temperatures were detected in a few satellite images during 1-5 April. Airwave signals, indicative of small explosions at the summit, were recorded by the seismic stations at 1842 on 3 April. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geologic summary: The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows.

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

At 1200 on 30 March CENAPRED reported that during the previous 24 hours the seismic network at Popocatépetl recorded 179 emissions and four explosions. Ash plumes from the explosions rose as high as 3.5 km above the crater; ash from the explosions caused Puebla's airport to close from 2000 on 29 March to 0600 on 30 March.

During 30 March-5 April there were 38-136 emissions and as many as six explosions detected daily; some emissions corresponded with increased crater incandescence. An explosion at 0103 on 31 March produced an ash plume that rose 1.8 km and drifted ENE, and ejected incandescent fragments 1 km away onto the ESE flank. An explosion at 1521 generated an ash plume that rose 2 km and drifted ENE. With the assistance of the Federal Police, on 2 April CENAPRED scientists conducted an overflight of the crater and observed an inner crater that was 325 m in diameter and 50 m deep; the crater had previously been filled with a lava dome, destroyed in January, which had grown to an estimated volume of 2,000,000 cubic meters. Small landslides had occurred on the E wall of the inner crater. An explosion at 2031 on 3 April generated an ash plume that rose 2 km and drifted NE. Incandescent fragments were ejected as far as 3.5 km onto the E and SE flanks, generating fires in that part of the forest. Ash fell in the towns of Juan C. Bonilla (32 km ENE) and Coronango (35 km ENE), both in the state of Puebla. SINAPRED noted that the explosion was the strongest recorded in the previous three years. 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.

Sangay, Ecuador
2.005°S, 78.341°W, Summit elev. 5286 m

Based on satellite images and notices from the Guayaquil MWO, the Washington VAAC reported that on 1 April an ash plume from Sangay rose to an altitude of 6.7 km (22,000 ft) a.s.l. and drifted SW. The next day an ash plume rose to an altitude of 5.5 km (18,000 ft) a.s.l., and a continuing thermal anomaly was detected. On 4 April satellite images detected an ash plume that drifted about 18 km N at an altitude of 5.5 km (18,000 ft) a.s.l.

Geologic summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes, and its most active. The dominantly andesitic volcano has been in frequent eruption for the past several centuries. The steep-sided, 5230-m-high glacier-covered volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

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

OVDAS-SERNAGEOMIN reported that at 0750 on 3 April the seismic stations at Villarrica began recording more energetic volcanic tremor. In addition, the webcam recorded increased surficial activity characterized by Strombolian explosions and intensifying crater incandescence. The Alert Level was raised to Yellow (the second lowest level on a four-color scale) and the public was warned to stay outside of a 1-km radius around the crater and away from drainages.

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.

Ongoing activity

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

JMA reported that on 1 April an explosion at Aira Caldera’s Sakurajima volcano generated an ash plume that rose 2 km above Showa's crater rim. An explosion at Minamidake summit crater also produced an ash plume which rose 800 m above its crater rim. Three of five explosions detected at Showa during 1-4 April generated ash plumes that rose as high as 3.5 km, and ejected tephra as far as 1,300 m. Reports of falling tephra, 2 cm in diameter, came from a town 3 km away. At 0608 on 3 April an ash plume from an explosion rose 700 m above Minamidake. 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.

Alaid, Kuril Islands (Russia)
50.861°N, 155.565°E, Summit elev. 2285 m

KVERT reported that moderate activity at Alaid continued during 25 March-1 April. Satellite images showed an intense daily thermal anomaly over the volcano. A gas-and-steam plume continaing minor amounts of ash drifted about 60 km S and SW during 26 and 30-31 March. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geologic summary: The highest and northernmost volcano of the Kuril Islands, 2285-m-high Alaid is a symmetrical stratovolcano when viewed from the north, but has a 1.5-km-wide summit crater that is breached widely to the south. Alaid is the northernmost of a chain of volcanoes constructed west of the main Kuril archipelago and rises 3000 m from the floor of the Sea of Okhotsk. Numerous pyroclastic cones dot the lower flanks of basaltic to basaltic-andesite Alaid volcano, particularly on the NW and SE sides, including an offshore cone formed during the 1933-34 eruption. Strong explosive eruptions have occurred from the summit crater beginning in the 18th century. Reports of eruptions in 1770, 1789, 1821, 1829, 1843, 1848, and 1858 were considered incorrect by Gorshkov (1970). Explosive eruptions in 1790 and 1981 were among the largest in the Kuril Islands during historical time.

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

SVERT reported that satellite images detected a thermal anomaly over Snow, a volcano of Chirpoi, during 29-30 March and 1 April. 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
9.514°N, 103.62°W, Summit elev. 3850 m

Based on satellite and webcam images, the Washington VAAC reported that during 30 March and 1-2 April ash plumes from Colima rose to altitudes of 4-5.5 km (13,000-18,000 ft) a.s.l. and drifted E and NE.

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)
1.693°N, 127.894°E, Summit elev. 1229 m

Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 30 March-5 April ash plumes from Dukono rose to altitudes of 1.5-2.1 km (5,000-7,000 ft) a.s.l. and drifted as far as 175 km NE, ESE, S, and SW.

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, Summit elev. 3330 m

Based on INGV webcam views, and VONA and SIGMET notices, the Toulouse VAAC reported a small eruption at Etna on 31 March which ended the next day.

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.

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

KVERT reported that moderate activity at Karymsky continued during 25 March-1 April. Fresh ash deposits from the previous week were noted near the volcano. 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 30 March-5 April. The lava lake continued to circulate and spatter in the Overlook vent. Webcams recorded outgassing from multiple spatter cones on the Pu'u 'O'o Crater floor. A very small lava flow briefly erupted onto the crater floor during 31 March-1 April, and on 3 and 4 April. The June 27th NE-trending lava flow continued to be active within 7.6 km NE of Pu'u 'O'o 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.

Masaya, Nicaragua
11.984°N, 86.161°W, Summit elev. 635 m

On 30 March INETER reported that the lava lake rose in Masaya's Santiago crater and several landslide deposits from the precious few days were visible in the NE crater. RSAM values were at moderate-to-high levels. On 4 April SINAPRED noted that tremor continued and the widening of the vent in the SE part of the crater persisted.

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

Momotombo, Nicaragua
12.422°N, 86.54°W, Summit elev. 1297 m

SINAPRED reported that on 2 April explosions at Momotombo produced gas-and-ash plumes and ejected incandescent tephra.

Geologic summary: Momotombo is a young, 1297-m-high stratovolcano that rises prominently above the NW shore of Lake Managua, forming one of Nicaragua's most familiar landmarks. Momotombo began growing about 4500 years ago at the SE end of the Marrabios Range and consists of a somma from an older edifice that is surmounted by a symmetrical younger cone with a 150 x 250 m wide summit crater. Young lava flows from Momotombo have flowed down the NW flank into the 4-km-wide Monte Galán caldera. The youthful cone of Momotombito forms a 391-m-high island offshore in Lake Managua. Momotombo has a long record of strombolian eruptions, punctuated by occasional larger explosive activity. The latest eruption, in 1905, produced a lava flow that traveled from the summit to the lower NE base. A small black plume was seen above the crater after an April 10, 1996 earthquake, but later observations noted no significant changes in the crater. A major geothermal field is located on the southern flank of the volcano.

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

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 0804 on 31 March an episode of short-duration volcanic tremor was associated with an ash emission that rose 3.5 km above Nevado del Ruiz. According to the Washington VAAC the ash plume drifted NW and SW. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

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.

Santa Maria, Guatemala
14.756°N, 91.552°W, Summit elev. 3772 m

INSIVUMEH reported that during 30 March-3 April cloud cover prevented visual observations of Caliente cone, part of Santa María's Santiaguito lava-dome complex, though sounds of small avalanches were noted. At 1000 on 3 April INSIVUMEH issued a special report stating that a strong explosion occurred, and pyroclastic flows descended the E and SE flanks. Parts of the E and W crater rim collapsed, and a mushroom-shaped ash cloud rose 4 km and drifted 30 km S, SW, W, and NW. During 4-5 April white plumes drifted SW and SE, and weak avalanches traveled short distances.

Geologic summary: Symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The 3772-m-high stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank and was formed during a catastrophic eruption in 1902. The renowned plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

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

KVERT reported that during 25 March-1 April lava-dome extrusion onto Sheveluch’s N flank was accompanied by strong fumarolic activity, dome incandescence, ash explosions, and hot avalanches. Satellite images detected an intense daily thermal anomaly over the dome. 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.

Sinabung, Indonesia
3.17°N, 98.392°E, Summit elev. 2460 m

Based on satellite images and information from PVMBG, the Darwin VAAC reported that during 30 March-2 April and 4 April ash plumes from Sinabung rose to altitudes of 3.3-4.2 km (11,000-14,000 ft) a.s.l. and drifted W and NW.

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

On 30 March INETER reported that micro-seismicity at Telica remained high and was characterized by small, high-energy earthquakes. Incandescence emanated from the crater floor. On 4 April SINAPRED noted that seismicity continued at a high level and warned the public to stay away from the crater.

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.

Tengger Caldera, Eastern Java (Indonesia)
7.942°S, 112.95°E, Summit elev. 2329 m

Based on satellite images, wind data, and ground reports from PVMBG, the Darwin VAAC reported that during 2-5 April ash plumes from Tengger Caldera's Bromo cone rose to altitudes of 2.1-3.6 km (7,000-12,000 ft) a.s.l. and drifted 25-45 km SW and W.

Geologic summary: The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most active and most frequently visited volcanoes.

Turrialba, Costa Rica
10.025°N, 83.767°W, Summit elev. 3340 m

OVSICORI-UNA reported that at 0859 on 3 April an explosion at Turrialba lasting less than one minute generated an ash-and-gas plume that rose about 100 m and drifted S and SW. A small amount of ash and a sulfur odor was reported in an area 2 km NW of the volcano.

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.

Yasur, Vanuatu
19.53°S, 169.442°E, Summit elev. 361 m

On 31 March, the Vanuatu Geohazards Observatory stated that the Alert Level for Yasur remained at 2 (on a scale of 0-4) and that explosions were intense. VGO reminded residents and tourists that hazardous areas were near and around the volcanic crater, and that volcanic ash and gas could reach areas impacted by trade winds.

Geologic summary: Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous strombolian and vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. Yasur is largely contained within the small Yenkahe caldera and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E, Summit elev. 2899 m

KVERT reported that moderate activity at Zhupanovsky continued during 25 March-1 April. 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.

Source: GVP