Active volcanoes in the world: June 22 - 28, 2016

Active volcanoes in the world: June 22 - 28, 2016

New activity/unrest was observed at 5 volcanoes between June 22 and 28, 2016. During the same period, ongoing activity was observed at 15 volcanoes.

New activity/unrest: Bulusan, Luzon (Philippines) | Kanlaon, Philippines | Pacaya, Guatemala | Santa Maria, Guatemala | Turrialba, Costa Rica.

Ongoing activity: Alaid, Kuril Islands (Russia) | Chirpoi, Kuril Islands (Russia) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Fuego, Guatemala | Grimsvotn, Iceland | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Nevado del Ruiz, Colombia | Poas, Costa Rica | Reventador, Ecuador | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Tenger Caldera, Eastern Java (Indonesia) | Yasur, Vanuatu.

New activity/unrest

Bulusan, Luzon (Philippines)
12.77°N, 124.05°E, Elevation 1565 m

PHIVOLCS reported that during 0900-0918 on 23 June Bulusan's NW summit vent vigorously emitted dirty-white steam plumes that drifted down the WNW flank. The color of the plume suggested low-energy ash emissions; no seismic signals surrounding the event were detected, indicating a shallow source. Minor amounts of ash fell in the neighborhoods of Poblacion (11 km NW), Añog (12 km NW), and Bacolod (13 km NW) in the Municipality of Juban, and Mabini (12 km NNW) in the Municipality of Casiguran. A sulfur odor was detected in the neighborhoods of Mabini, Bacolod, Añog, and Puting Sapa (Juban). Steam plumes rose as high as 200 m during 25-26 June and drifted NW; steam plumes drifted down the flank on 28 June. The Alert Level remained at 1, indicating abnormal conditions and a 4-km-radius Permanent Danger Zone (PDZ).

Geological summary: Luzon's southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. Bulusan lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic Bulusan complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit of 1565-m-high Bulusan volcano is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded at Bulusan since the mid-19th century.

Kanlaon, Philippines
10.412°N, 123.132°E, Elevation 2435 m

PHIVOLCS reported that during 22-23 and 25-26 June white steam plumes from Kanlaon rose as high as 800 m and drifted NW and SW; wispy steam plumes were observed on 27 June. Starting at 1640 on 23 June the seismic network recorded a 4-minute-long, explosion-type signal; weather clouds prevented visual observations of the summit area. The Alert Level remained at 1 (on a scale of 0-5).

Geological 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.

Pacaya, Guatemala
14.381°N, 90.601°W, Elevation 2552 m

INSIVUMEH reported that the seismic network at Pacaya recorded weak explosions during 23-28 June. During 23-25 June blue and white fumarolic plumes rose 100 m and drifted S and SW. Faint incandescence from the crater was visible on some nights; abundant incandescence was noted during 27-28 June.

Geological summary: Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

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

In a special report posted on 23 June, INSIVUMEH reported that a strong explosion at Caliente cone, part of Santa María's Santiaguito lava-dome complex, occurred at 1337 and generated avalanches on the SE and SW flanks, and a very dense ash plume that rose 2 km and drifted SW and S. Gas plumes rose 50 m above the crater during 26-28 June.

Geological 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.

Turrialba, Costa Rica
10.025°N, 83.767°W, Elevation 3340 m

OVSICORI-UNA reported that at 2030 on 23 June tremor increased at Turrialba and continued to fluctuate through the next day. At 0544 on 24 June a short-lived (less than three minutes) emission of ash and gas rose no higher than 200 m above the crater. A small gas-and-ash plume rose from the crater at 0650. Wind directions shifted from NW to SW. Tremor disappeared at 0740 but then reappeared at 0850 and continued. Neighborhoods in San José reported ashfall and a sulfur odor. From 2005 on 24 June through 1500 on 25 June there were 14 episodes of increased tremor amplitude, accompanied by gas-and-ash emissions that rose no more than 200 m. Rocks were occasionally ejected from the crater. A few more periods of increased tremor and ash-and-gas emissions were recorded later that evening and the morning of 26 June. Several neighborhoods in San José and Heredia reported ashfall and a sulfur odor. Between 0604 and 1930 on 26 June the seismic network recorded almost continuous, variable-amplitude volcanic tremor, with frequent spikes in amplitude associated with passive gas-and-ash emissions. At around 1930 tremor amplitude decreased and ash emissions ceased. Local areas continued to report ashfall. Tremor again increased on 28 June at 2159, though the height of the associated ash emissions was not distinguishable.

Geological summary: Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive 3340-m-high Turrialba is exceeded in height only by Irazú, covers an area of 500 sq km, and is one of Costa Rica's most voluminous volcanoes. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.

Ongoing activity

Alaid, Kuril Islands (Russia)
50.861°N, 155.565°E, Elevation 2285 m

KVERT reported that moderate activity at Alaid continued during 17-24 June. Satellite images showed a thermal anomaly over the volcano during 18, 20, and 22-23 June. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Geological 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, Elevation 742 m

SVERT reported that a thermal anomaly over Snow, a volcano of Chirpoi, was detected in satellite images during 20 and 22-23 June. The Aviation Color Code remained at Yellow.

Geological 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 wind data, the Washington VAAC reported that on 23 June an ash plume from Colima rose to an altitude of 5.8 km (19,000 ft) a.s.l.and drifted SW.

Geological summary: The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Dukono, Halmahera (Indonesia)
1.693°N, 127.894°E, Elevation 1229 m

Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 27-29 June ash plumes from Dukono rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted E.

Geological summary: Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

Fuego, Guatemala
14.473°N, 90.88°W, Elevation 3763 m

INSIVUMEH reported that during 23-24 June explosions at Fuego occurred at a rate of 2-5 per hour, and generated ash plumes that rose 650-950 m above the crater and drifted 10 km SW, W, NW, and N. Lava fountains rose as high as 200 m above the crater, and fed a lava flow that traveled 600 m SE down the Las Lajas (SE) drainage. 

In a special bulletin from 1200 on 26 June, INSIVUMEH stated that the tenth episode of effusive activity at Fuego had ended, having lasted for a period of over 30 hours. The report noted that weak explosions continued, producing ash plumes that rose as high as 850 m and drifted 10 km S, SW, and W. Lava flows had advanced to 600 and 800 m in the El Jute (SE) and Las Lajas drainages, respectively. Explosions during 26-28 June generated ash plumes that rose 550-850 m and drifted SSW. Weak shock waves from explosions were detected during 26-27 June, and abundant crater incandescence was visible during 27-28 June.

Geological summary: Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3763-m-high Fuego and its twin volcano to the north, Acatenango. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at Acatenango. In contrast to the mostly andesitic Acatenango, eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Grimsvotn, Iceland
64.416°N, 17.316°W, Elevation 1719 m

On 23 June the Icelandic Meteorological Office (IMO) stated that the water level of the Skaftá river at Sveinstindur (the closest gauging station at 28 km downstream from the ice margin) and electrical conductivity both rose in recent days, indicating the beginning of a glacial outburst flood (jökulhlaup), originating from Grímsvötn's Western Skaftá ice cauldron. The western ice cauldron last drained in June 2015. The discharge rate of Skaftá at Sveinstindur was 112 m³/s. IMO warned that hydrogen sulfide released from the floodwater as it drains is particularly potent at the river outlet from the ice margin, where concentrations may reach poisonous levels.

Geological 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.

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

HVO reported that during 22-28 June the lava lake continued to rise and fall, circulate, and spatter in Kilauea's Overlook vent. Several incandescent vents on Pu'u 'O'o Crater's floor were evident in webcam images. A lava flow originating from a vent on Pu'u 'O'o Crater's E flank continued to advance and spread SE. Webcams recorded bright incandescence from several skylights along the upper part of the tube system supplying lava to the front part of the flow. The advancement rate of the flow front was 100 m/day the previous week and by 24 June the lava flow had entered the N part of the abandoned Royal Gardens subdivision. The advancement rate had increased to 300 m/day during 25-28 June; satellite images acquired on 27 June revealed that the lava flow was 6.3 km long and was progressing down the pali along the W boundary of the subdivision.

Geological summary: Kilauea volcano, which overlaps the east flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 sq km, destroying nearly 200 houses and adding new coastline to the island.

Klyuchevskoy, Central Kamchatka (Russia)
56.056°N, 160.642°E, Elevation 4754 m

KVERT reported that a Strombolian eruption at Klyuchevskoy continued during 17-24 June. Satellite and video data showed a lava flow continuing to effuse on the SE flank. Satellite images showed an intense thermal anomaly over the volcano, and an ash plume drifting almost 30 km E on 18 June. The Aviation Color Code was raised to Orange.

Geological summary: Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

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

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 0822 on 27 June and at 0748 on 28 June episodes of volcanic tremor were associated with ash emissions that rose 1.8 and 0.9 km above Nevado del Ruiz, respectively. The emissions were confirmed by national park authorities and local residents. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Geological 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.

Poas, Costa Rica
10.2°N, 84.233°W, Elevation 2708 m

According to news articles, phreatic explosions from the hot lake at Poás occurred multiple times in June. Explosions at 0900 on 5 June, 1854 on 13 June, and 1952 on 14 June ejected water and steam many meters above the lake’s surface. Three small explosions, lasting about five seconds each based on the seismic signals, occurred during 0600-0603 on 18 June and ejected water, steam, and debris no more than 50 m above the lake’s surface. Phreatic explosions were also registered on 19 June.

Geological summary: The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Reventador, Ecuador
0.077°S, 77.656°W, Elevation 3562 m

On 24 June IG stated that surficial activity at Reventador had remained high during recent months. While conducting routine maintenance work of the monitoring network on 8 June, IG staff noted continuous gas-and-water-vapor emissions rising 800 m above the crater and drifting NW. Explosions produced sounds similar to gunshots and generated ash plumes that rose 2 km. Deposits from pyroclastic flows and ejected incandescent blocks were evident on all flanks, but particularly the N and S flanks.

Geological summary: Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

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

KVERT reported that during 17-24 June lava-dome extrusion onto Sheveluch’s N flank was accompanied by strong fumarolic activity, dome incandescence, ashexplosions, and hot avalanches. Satellite images showed an intense thermal anomaly over the dome. The Aviation Color Code remained at Orange.

Geological summary: The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 cu km volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

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

Based on PVMBG ground-based observations, the Darwin VAAC reported that during 25-27 June ash plumes from Sinabung rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted E. Tengger Caldera, Eastern Java (Indonesia), 7.942°S, 112.95°E, Elevation 2329 m

Based on satellite images and model data, the Darwin VAAC reported that during 24-28 June ash plumes from Tengger Caldera's Bromo cone rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 55 km SW and W.

Geological summary: Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical, 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.

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

Based on satellite images and model data, the Darwin VAAC reported that during 24-28 June ash plumes from Tengger Caldera's Bromo cone rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 55 km SW and W.

Geological 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.

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

On 28 June the Vanuatu Geohazards Observatory stated that the Alert Level for Yasur remained at 2 (on a scale of 0-4) and that explosions continued to be 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.

Geological 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.

Source: GVP


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