Active volcanoes in the world: April 22 - 28, 2015

Active volcanoes in the world: April 22 - 28, 2015

New activity/unrest was observed at 5 volcanoes from April 22 - 28, 2015. During the same period, ongoing activity was observed at 26 volcanoes.

New activity/unrest: Barren Island, Andaman Islands (India) | Calbuco, Chile | Kilauea, Hawaiian Islands (USA) | Sinabung, Indonesia | Tungurahua, Ecuador.

Ongoing activity: Aira, Kyushu (Japan) | Asosan, Kyushu (Japan) | Bardarbunga, Iceland | Chikurachki, Paramushir Island (Russia) | Chirpoi, Kuril Islands (Russia) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Gamalama, Halmahera (Indonesia) | Karangetang [Api Siau], Siau Island (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Klyuchevskoy, Central Kamchatka (Russia) | Krakatau, Indonesia | Manam, Papua New Guinea | Nevado del Ruiz, Colombia | Papandayan, Western Java (Indonesia) | Popocatepetl, Mexico | Santa Maria, Guatemala | Semeru, Eastern Java (Indonesia) | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Suwanosejima, Ryukyu Islands (Japan) | Tengger Caldera, Eastern Java (Indonesia) | Turrialba, Costa Rica | Villarrica, Chile | Yasur, Vanuatu | Zhupanovsky, Eastern Kamchatka (Russia).

New activity/unrest

Barren Island, Andaman Islands (India)
12.278°N, 93.858°E, Elevation 354 m

According to the Darwin VAAC, a pilot observed an ash plume from Barren Island that rose to an altitude of 3 km (10,000 ft) a.s.l. Ash was not identified in satellite images.

Geologic summary: Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S-trending volcanic arc extending between Sumatra and Burma (Myanmar). The 354-m-high island is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Calbuco, Chile
41.326°S, 72.614°W, Elevation 2003 m

OVDAS-SERNAGEOMIN reported that an eruption from Calbuco began at 1804 on 22 April, prompting the Alert Level to be raised to Red (the highest level on a four-color scale) and causing a 20-km exclusion zone to be declared. The eruption was preceded by an hour-long period of volcano-tectonic events followed by long-period events; no increases in seismicity had been noted since 2009 when real-time seismic monitoring started. After a large seismic event detected at 1735, a 90 minute eruption generated a sub-Plinian, gray ash plume that rose 15 km above the main crater and drifted mainly ENE, although fine ash drifted N and NW. Column collapses occurred locally and radially, affecting the headwaters of major rivers. Residents within the exclusion zone, in Chamiza, Lago Chapo, and Correntoso sectors, and in the town of Puerto Montt, were ordered to evacuate. Several roads and bridges were impassable due to ashfall. 

A larger second event on 23 April began at 0100, lasted six hours, and also generated a sub-Plinian ash plume that rose higher than 15 km and drifted N, NE, and E. Incandescent tephra was ejected as far as 5 km; deposits were concentrated to the N and NE, with thicknesses varying from tens of centimeters in the Región de Los Lagos to a few millimeters in the Los Ríos and La Araucanía areas. Pyroclastic flows traveled a maximum distance of 7 km and lahars traveled 15 km. Pumice fell in Región de Los Lagos, and ash fell in Los Ríos and La Araucanía. Tephra also fell in Argentine territory, NE of the volcano. Scientists aboard an overflight observed ash emissions from at least six vents on the W, SW, and S sides of the old lava dome. About 5,000 people had been evacuated andONEMI warned people not to go within 200 m of drainages due to lahar hazards. At around 2330 a third phase of surficial activity was noted; ash plumes rose 2 km and drifted NE and E. On 24 April the ash plume continued to rise 2 km and explosions were detected. News articles noted that international flights in and out of several major cities were delayed or canceled. According to a news article, ash from the eruption reached southern Brazil on 25 April prompting some airlines to cancel flights using airports in Santiago, Buenos Aires, and Montevideo. Some houses in areas near the volcano collapsed from the weight of the ash. The ash plume persisted on 25 April, but rose to a lower height of 400 m, and sporadic explosions were detected. Seismicity declined during 26-27 April; the ash plume rose 1.5 km, and drifted NE and SE. ONEMI noted on 27 April that 246 of 4,514 evacuees were in shelters; the number of displaced people had peaked at 6,514 during 24-26 April. 

A satellite-based estimate of sulfur dioxide emissions was 0.3-0.4Tg by 28 April, detected as high as 21 km altitude. Although most ash had fallen out of the plume over Chile and Argentina, some may have remained in the stratospheric plume drifting around the globe; the leading edge of the gas plume had reached the Indian Ocean, S of Madagascar.

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.

Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Elevation 1222 m

During 22-28 April HVO reported that Kilauea’s 27 June NE-trending lava flow continued to be active with three areas of breakouts within and along the flow-field margins, within 8 km of Pu'u 'O'o. The three main areas of breakouts were the 21 February breakout on the flank of Pu'u 'O'o, the 9 March breakout near the forested cone of Kahauale'a, and a relatively small forked breakout 5-6 km farther NE of Pu'u 'O'o. Forest burned about 8 km NE of the crater. The thermal webcam recorded multiple incandescent outgassing vents in the crater. Lava that sporadically erupted from vents on the SE and S parts of Pu'u 'O'o's crater floor covered the floor. 

The circulating lava lake occasionally rose and fell in the deep pit within Halema'uma'u Crater. Gas emissions remained elevated. Abrupt inflation began at 1640 on 21 April; concurrently the lava lake rose and was 20 m below the crater floor on 23 April, the highest level since the eruption began in 2008. A small collapse from the overhanging W wall at about 0520 triggering a small explosive event that ejected spatter out onto the Halema'uma'u crater floor. The lake continued to rise and was 12 m below the floor on 25 April. Two collapses of the W crater wall each triggered explosions that ejected clumps of spatter (some 30 cm in diameter) up onto the rim of Halema'uma'u and dusted the Jaggar Museum area with ash. During 25-26 April the lava lake rose to within about 4 m of the crater floor. During 27-28 April the lava lake fluctuated but was mostly 3-4 m below the rim, and briefly reached the rim on 28 April at a time without spattering.

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.

Sinabung, Indonesia
3.17°N, 98.392°E, Elevation 2460 m

PVMBG reported that during 6-12 April white plumes rose as high as 500 m above Sinabung; misty conditions prevented observations on 13 April. Lava was incandescent as far from the lava dome as 1.5 km S and SE. The main lava flow remained 2.9 km long. After pyroclastic flows descended the flanks on 2 April, a new lava flow from the growing lava dome formed near the crater and traveled 170 m SSE. Recorded seismicity consisted of avalanche signals, low-frequency and hybrid events, tectonic events, and volcanic earthquakes. Overall seismicity decreased compared to 30 March-6 April. Tilt and EDM (Electronic Distance Measurement) data fluctuated but showed overall deflation. The Alert Level remained at 3 (on a scale of 1-4). Visitors and tourists were prohibited from approaching the crater within a radius of 6 km on the S, 5 km on the SE flanks, and 3 km in the other directions. 

According to social media sources, the Darwin VAAC reported that on 28 April an ash plume from Sinabung rose to an altitude of 4.3 km (14,000 ft) a.s.l. and apyroclastic flow descended the flank. Meteorological cloud cover prevented satellite observations.

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.

Tungurahua, Ecuador
1.467°S, 78.442°W, Elevation 5023 m

IG reported moderate-to-high seismic activity at Tungurahua during 22-28 April, characterized by long-period events, tremor, and explosions. Cloud cover often prevented visual observations, and rainfall was recorded almost daily. During 22-23 April gray and red ash fell in Choglontus (13 km WSW), and a landslide in the area of Manto de la Novia was reported in the morning. During 23-24 April gray tephra fell in Bilbao (W), Chontapamba (W), Pillate (8 km W), Baños (8 km N), and Quero (20 km NW). Emissions with minor ash content were visible on 24 April; one emission rose 200 m and drifted NW. Ashfall on 25 April was reported in Chontapamba, Pillate, Romero, and Guambaló. During 25-26 April lahars descended the Quero, Bilbao, Chontapamba, Juive (NW), Mapayacu (SW), Pingullo (NW), Pondoa (N), Vazcún (N), Achupashal (NW), La Pirámide (NW), and Romero drainages. On 27 April ash fell in Pillate, and a vapor emission rose 2 km and drifted W. On 28 April an emission with a minor ash content rose 3 km and drifted W. Roaring was noted and lahars descended the La Pampa (NW) and Rea drainages.

Geologic summary: Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. Historical eruptions have all originated from the summit crater, accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.

Ongoing activity

Aira, Kyushu (Japan)
31.593°N, 130.657°E, Elevation 1117 m

JMA reported that 29 explosions from Showa Crater at Aira Caldera’s Sakurajima volcano ejected tephra as far as 1,300 m during 20-24 April. Nine of the explosions generated ash plumes that rose 3 km above the crater rim; one explosion, on 24 April, produced an ash plume that rose 4 km. Incandescence from the crater was visible on one night. The Alert Level remained at 3 (on a scale of 1-5). Based on JMA notices, the Tokyo VAAC reported that explosions during 22-28 April generated plumes which rose to altitudes of 1.5-4.9 km (5,000-16,000 ft) a.s.l. and drifted S, SE, E, NE, and N.

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.

Asosan, Kyushu (Japan)
32.884°N, 131.104°E, Elevation 1592 m

JMA reported that, based on seismic data, the eruption from Asosan’s Nakadake Crater that began on 25 November 2014 continued during 20-24 April. A plume rose 1.5 km above the crater rim and incandescence from the vent was observed at night. Field surveys confirmed that ash emissions from the active vent rose as high as 200 m above the crater rim. High-amplitude tremor continued. The Alert Level remained at 2 (on a scale of 1-5).

Geologic summary: The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 cu km of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 AD. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.

Bardarbunga, Iceland
64.63°N, 17.53°W, Elevation 2009 m

On 26 April the Icelandic Met Office (IMO) lowered the Aviation Color Code for Bárdarbunga to Green (the lowest on a four-color scale). No further signs of unrest had been noted since the end of the eruption on 27 February; seismicity within the caldera and the associated dyke intrusion continued to decline.

Geologic summary: The large central volcano of Bárdarbunga lies beneath the NW part of the Vatnajökull icecap, NW of Grímsvötn volcano, and contains a subglacial 700-m-deep caldera. Related fissure systems include the Veidivötn and Trollagigar fissures, which extend about 100 km SW to near Torfajökull volcano and 50 km NE to near Askja volcano, respectively. Voluminous fissure eruptions, including one at Thjorsarhraun, which produced the largest known Holocene lava flow on Earth with a volume of more than 21 cu km, have occurred throughout the Holocene into historical time from the Veidivötn fissure system. The last major eruption of Veidivötn, in 1477, also produced a large tephra deposit. The subglacial Loki-Fögrufjöll volcanic system located SW of Bárdarbunga volcano is also part of the Bárdarbunga volcanic system and contains two subglacial ridges extending from the largely subglacial Hamarinn central volcano; the Loki ridge trends to the NE and the Fögrufjöll ridge to the SW. Jökulhlaups (glacier-outburst floods) from eruptions at Bárdarbunga potentially affect drainages in all directions.

Chikurachki, Paramushir Island (Russia)
50.324°N, 155.461°E, Elevation 1781 m

KVERT reported that, based on analysis of satellite images of Chikurachki from 18 April, a thermal anomaly and ash plumes were not detected; an observer from Severo-Kurilsk (60 km NW, Paramushir Island) had reported a minor ash plume. The Aviation Color Code was lowered back to Green on 24 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.

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 steam-and-gas emissions on 20 April. Cloud cover obscured views during 21-27 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
19.514°N, 103.62°W, Elevation 3850 m

Based on satellite images, and webcam views, Mexico City MWO notices, and wind data, the Washington VAAC reported multiple ash emissions from Colima during 21-26 and 28 April. Ash plumes rose to altitudes of 5.5-7.3 km (15,000-24,000 ft) a.s.l. and drifted NW to NE. On 25 April ashfall was reported in areas 85 km N.

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

PVMBG reported that during March-22 April dense white-gray plumes rose as high as 2 km above Dukono's Malupang Warirang Crater and were accompanied by rumbling and roaring. Seismicity remained high and consisted of explosion signals, volcanic earthquakes, and tremor. The Alert Level remained at 2 (on a scale of 1-4). Residents and tourists were advised not to approach the crater within a radius of 2 km. Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 26-28 April ash plumes from Dukono rose to altitudes of 2.7-3 km (9,000-10,000 ft) a.s.l. and drifted 35-150 km E.

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.

Gamalama, Halmahera (Indonesia)
0.8°N, 127.33°E, Elevation 1715 m

PVMBG reported that during March-22 April diffuse white plumes rose as high as 50 m above Gamalama; on 7 April the plumes became dense and rose 100 m. Seismicity fluctuated but remained generally low. The Alert Level remained at 2 (on a scale of 1-4); visitors and residents were warned not to approach the crater within a radius of 1.5 km.

Geologic summary: Gamalama (Peak of Ternate) is a near-conical stratovolcano that comprises the entire island of Ternate off the western coast of Halmahera and is one of Indonesia's most active volcanoes. The island of Ternate was a major regional center in the Portuguese and Dutch spice trade for several centuries, which contributed to the thorough documentation of Gamalama's historical activity. Three cones, progressively younger to the north, form the summit of Gamalama, which reaches 1715 m. Several maars and vents define a rift zone, parallel to the Halmahera island arc, that cuts the volcano. Eruptions, recorded frequently since the 16th century, typically originated from the summit craters, although flank eruptions have occurred in 1763, 1770, 1775, and 1962-63.

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

PVMBG reported that during 15-22 April diffuse white and bluish-white plumes rose as high as 300 m above Karangetang's main crater and 25 m above Crater II. Incandescence from the lava dome was observed at night. Seismicity indicated lava-dome growth and an overall decline in activity compared to February data. The Alert Level remained at 3 (on a scale of 1-4); visitors and residents were warned not to climb Karangetang any higher than 500 a.s.l.

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.

Karymsky, Eastern Kamchatka (Russia)
54.049°N, 159.443°E, Elevation 1513 m

KVERT reported moderate activity at Karymsky during 17-24 April. Satellite images detected a thermal anomaly over the volcano during 16-17 and 23 April, andash plumes drifting 35 km SE on 23 April. 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 gas-and-steam activity at Klyuchevskoy was recorded by the webcam during 16-17, 19, 21, and 23 April. Satellite images detected a weak thermal anomaly over the volcano during 16-17 and 23 April. A gas plume containing a small amount of ash drifted 147 km E on 21 April. On 26 April the Aviation Color Code was lowered to Yellow; KVERT noted that gas-and-steam activity and tremor continued.

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.

Krakatau, Indonesia
6.102°S, 105.423°E, Elevation 813 m

PVMBG reported that during 1 March-21 April diffuse white plumes rose 25-50 m above Anak Krakatau, although foggy weather often prevented observations. Seismicity continued to be dominated by shallow and deep volcanic earthquakes, as well as signals indicating emissions. The Alert Level remained at 2 (on a scale of 1-4). Residents and visitors were warned not to approach the volcano within 1 km of the crater.

Geologic summary: The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan volcanoes, and left only a remnant of Rakata volcano. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

Manam, Papua New Guinea
4.08°S, 145.037°E, Elevation 1807 m

Based on observations of satellite imagery and wind data analyses, the Darwin VAAC reported that during 27-28 April ash plumes from Manam rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 75-130 km W.

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.

Nevado del Ruiz, Colombia
4.892°N, 75.324°W, Elevation 5279 m

Based on satellite image analyses, the Washington VAAC reported that on 22 April a small puff of gas with minor amounts of ash from Nevado del Ruiz drifted over 40 km W and dissipated.

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.

Papandayan, Western Java (Indonesia)
7.32°S, 107.73°E, Elevation 2665 m

PVMBG reported that during 1 March-21 April seismicity at Papandayan was dominated by shallow volcanic earthquakes but also consisted of volcanic earthquakes, low-frequency earthquakes, and local and remote tectonic earthquakes. Visual monitoring occurred from the Pakuwon Village post; observers noted white plumes rising at most 100 m above the crater. The Alert Level remained at 2 (on a scale of 1-4); residents and tourists were reminded not to approach the craters within a 1-km radius.

Geologic summary: Papandayan is a complex stratovolcano with four large summit craters, the youngest of which was breached to the NE by collapse during a brief eruption in 1772 and contains active fumarole fields. The broad 1.1-km-wide, flat-floored Alun-Alun crater truncates the summit of Papandayan, and Gunung Puntang to the north gives the volcano a twin-peaked appearance. Several episodes of collapse have given the volcano an irregular profile and produced debris avalanches that have impacted lowland areas beyond the volcano. A sulfur-encrusted fumarole field occupies historically active Kawah Mas ("Golden Crater"). After its first historical eruption in 1772, in which collapse of the NE flank produced a catastrophic debris avalanche that destroyed 40 villages and killed nearly 3000 persons, only small phreatic eruptions had occurred prior to an explosive eruption that began in November 2002.

Popocatepetl, Mexico
19.023°N, 98.622°W, Elevation 5426 m

CENAPRED reported that during 22-28 April the seismic network at Popocatépetl recorded 25-91 daily emissions mostly consisting of water vapor and gas. Cloud cover sometimes prevented observations of the crater, although gas plumes and nighttime crater incandescence were noted daily. On 22 April an explosion at 0121 produced diffuse gas and water vapor emissions. Explosions at 1643 and 1758 generated ash plumes. 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.

Santa Maria, Guatemala
14.756°N, 91.552°W, Elevation 3772 m

INSIVUMEH reported that during 23-24 and 27-28 April grayish-white ash plumes rose 400-500 m from Santa María's Santiaguito lava-dome complex and drifted SW. An explosion at 0450 on 24 April generated a small plume that drifted SW, and explosions at 0517 and 0602 on 28 April generated plumes that rose 500 m and drifted SW.

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.

Semeru, Eastern Java (Indonesia)
8.108°S, 112.92°E, Elevation 3676 m

PVMBG reported that white plumes and grayish white plumes from Semeru rose as high as 600 m above the crater during January-20 April, although inclement weather often prevented observations. Seismicity fluctuated, and was dominated by explosions and emission signals. During January incandescent avalanches from lava-flow fronts traveled 100-300 m. Eruptions were heard five times during 16-28 February. Nine explosions were heard during 1-15 March; minor ashfall from one of the explosions fell on the observation post. The Alert Level remained at 2 (on a scale from 1-4); visitors and residents were warned to avoid the SE flank within 4 km of the crater.

Geologic summary: Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises abruptly to 3676 m above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano. Semeru has been in almost continuous eruption since 1967.

Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Elevation 3283 m

KVERT reported that during 17-24 April lava-dome extrusion onto Sheveluch’s N flank was accompanied by incandescence, hot block avalanches, and fumarolicactivity. A thermal anomaly was detected during 16-18 and 23 April; cloud cover obscured views on the other days. 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 22-28 April, indicating that low-level eruptive activity confined to the summit crater likely continued. Cloud cover frequently prevented satellite and webcam observations. Slight steaming was recorded by the webcam on 26 April and elevated temperatures were detected in satellite images during 27-28 April. The Aviation Color Code remained at Orange and the Volcano Alert Levelremained 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.

Suwanosejima, Ryukyu Islands (Japan)
29.638°N, 129.714°E, Elevation 796 m

Based on JMA notices, the Tokyo VAAC reported that explosions at Suwanose-jima during 24-25 April generated plumes that rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted N and SE.

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

Tengger Caldera, Eastern Java (Indonesia)
7.942°S, 112.95°E, Elevation 2329 m

PVMBG reported that during January-10 April white plumes from Tengger Caldera's Bromo cone rose 50-100 m above the crater. A sulfur dioxide odor was noted at the Bromo observation post. Seismicity was dominated by tremor, but also included volcanic earthquakes. The Alert Level remained at 2 (on a scale of 1-4). Residents and visitors were warned not to approach the crater within a radius of 1 km.

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, Elevation 3340 m

Based on webcam views, and observers at the Tobías Bolaños and Juan Santamaría international airports, the Washington VAAC reported that gas emissions with minor ash content rose from Turrialba and drifted W during 23-24 April.

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.

Villarrica, Chile
39.42°S, 71.93°W, Elevation 2847 m

OVDAS-SERNAGEOMIN reported that during 15-28 April seismicity at Villarrica fluctuated but remained at moderate levels. Intermittent crater incandescence was observed and diffuse gas plumes mostly consisting of water vapor rose from the crater. Data from monitoring stations and pictures taken during an overflight on 21 April confirmed the presence of a lava lake and Strombolian explosions. During 23-27 April Strombolian explosions ejected material that remained mostly within the crater or no more than 100 m away. The Alert Level remained at Orange (the second highest level on a four-color scale) and the public was warned to stay outside of a 5-km radius around the crater and 200 m away from drainages.

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.

Yasur, Vanuatu
19.53°S, 169.442°E, Elevation 361 m

On 27 April, the Vanuatu Geohazards Observatory stated that Yasur continued in a state of unrest; the Alert Level remained at 1 (on a scale of 0-4). VGO reminded residents and tourists that hazardous areas were in proximity to and around the volcanic crater, and in volcanic ash and gas prone areas exposed to 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. Yasur, located at the SE tip of Tanna Island, is a mostly unvegetated 361-m-high pyroclastic cone with 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 of Yasur has raised Port Resolution harbor more than 20 m during the past century.

Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E, Elevation 2899 m

KVERT reported that strong gas-and-steam activity was observed at Zhupanovsky during 10-17 April. A thermal anomaly over the volcano was observed in satellite images during 16-17 and 23 April; cloud cover obscured views during 18-22 and 24 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


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