Thursday, April 26, 2018

[ Volcano ] Smithsonian / USGS Weekly Volcanic Activity Report 20-26 July 2016

Smithsonian / USGS Weekly Volcanic Activity Report 20-26 July 2016

New Activity/Unrest: Chikurachki, Paramushir Island (Russia)  | Chirpoi, Kuril Islands (Russia)  | Kilauea, Hawaiian Islands (USA)  | Pacaya, Guatemala
Ongoing Activity: Alaid, Kuril Islands (Russia)  | Bagana, Bougainville (Papua New Guinea)  | Bulusan, Luzon (Philippines)  | Colima, Mexico  | Dukono, Halmahera (Indonesia)  | Kanlaon, Philippines  | Klyuchevskoy, Central Kamchatka (Russia)  | Nevado del Ruiz, Colombia  | Nevados de Chillán, Chile  | Poas, Costa Rica  | Popocatepetl, Mexico  | Sheveluch, Central Kamchatka (Russia)  | Sinabung, Indonesia  | Tengger Caldera, Eastern Java (Indonesia)  | Turrialba, Costa Rica
The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Wednesday, notices of volcanic activity posted on these pages are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week, but rather a summary of activity at volcanoes that meet criteria discussed in detail in the "Criteria and Disclaimers" section. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network.
Note: Many news agencies do not archive the articles they post on the Internet, and therefore the links to some sources may not be active. To obtain information about the cited articles that are no longer available on the Internet contact the source.
New Activity/Unrest
Chikurachki  | Paramushir Island (Russia)  | 50.324°N, 155.461°E  | Summit elev. 1781 m
Based on satellite data, KVERT reported that an eruption at Chikurachki began on 27 July. An ash plume, first identified at 1748, rose to altitudes of 4-5 km (13,100-16,400 ft) a.s.l. and drifted about 100 km NE. The Aviation Color Code was raised to Orange.
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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
Chirpoi  | Kuril Islands (Russia)  | 46.525°N, 150.875°E  | Summit elev. 742 m
SVERT reported that a thermal anomaly over Snow, a volcano of Chirpoi, was detected in satellite images during 18 and 20-24 July. Steam-and-gas emissions were visible drifting SW on 16 July and may have contained minor amounts of ash. Steam-and-gas emissions during 22-24 July drifted as far as 90 km N. 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.
Source: Sakhalin Volcanic Eruption Response Team (SVERT)
Kilauea  | Hawaiian Islands (USA)  | 19.421°N, 155.287°W  | Summit elev. 1222 m
HVO reported that during 20-26 July 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. The 61G lava flow, originating from a vent on Pu'u 'O'o Crater's E flank, continued to advance across the coastal plain. The most distal part of the flow had stalled on 18 July but was again active by 22 July. Based on National Park personnel observations, the flow front was about 370 m from the ocean by 24 July. At 0112 on 26 July lava reached the ocean. Nighttime webcam views of the flow field showed incandescent areas from skylights, and advancing lava on the pali and coastal plain.
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 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.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO)
Pacaya  | Guatemala  | 14.381°N, 90.601°W  | Summit elev. 2552 m
INSIVUMEH reported that during 23-24 July Strombolian explosions at Pacaya's Mackenney cone ejected material 75 m above the crater. During 24-26 July blue and white fumarolic plumes drifted S and N, and faint crater incandescence was visible at night and in the early morning.
Geologic 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.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)
Ongoing Activity
Alaid  | Kuril Islands (Russia)  | 50.861°N, 155.565°E  | Summit elev. 2285 m
KVERT reported that Strombolian activity at a new cinder cone in Alaid's summit crater was detected during 15-22 July, with lava flowing down the SW flank. Satellite images showed a thermal anomaly at the volcano during 19-21 July. 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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
Bagana  | Bougainville (Papua New Guinea)  | 6.137°S, 155.196°E  | Summit elev. 1855 m
Based on analyses of satellite imagery and model data, the Darwin VAAC reported that during 21-23 July ash plumes from Bagana rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted 22-55 km SW, W, and NW.
Geologic Summary. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical, roughly 1850-m-high cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50-m-thick with prominent levees that descend the volcano's flanks on all sides. Satellite thermal measurements indicate a continuous eruption from before February 2000 through at least late August 2014.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
Bulusan  | Luzon (Philippines)  | 12.77°N, 124.05°E  | Summit elev. 1565 m
PHIVOLCS reported that on 20 July white-to-light-gray plumes rose to low levels above Bulusan and drifted WNW. During 21-25 July diffuse white plumes rose as high as 250 m above the crater and drifted NW and SW. The Alert Level remained at 1, indicating abnormal conditions and a 4-km-radius Permanent Danger Zone (PDZ).
Geologic Summary. Luzon's southernmost volcano, Bulusan, was constructed along the rim of the 11-km-diameter dacitic-to-rhyolitic Irosin caldera, which was formed about 36,000 years ago. Bulusan lies at the SE end of the Bicol volcanic arc occupying the peninsula of the same name that forms the elongated SE tip of Luzon. A broad, flat moat is located below the topographically prominent SW rim of Irosin caldera; the NE rim is buried by the andesitic Bulusan complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit of 1565-m-high Bulusan volcano is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded at Bulusan since the mid-19th century.
Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)
Colima  | Mexico  | 19.514°N, 103.62°W  | Summit elev. 3850 m
Based on information from the Mexico City MWO, and webcam and satellite views, the Washington VAAC reported that during 21 and 23-25 July ash plumes from Colima rose to altitudes of 4.3-7 km (14,000-23,000 ft) a.s.l. and drifted W and NW.
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.
Source: Washington Volcanic Ash Advisory Center (VAAC)
Dukono  | Halmahera (Indonesia)  | 1.693°N, 127.894°E  | Summit elev. 1229 m
Based on analyses of satellite imagery, information from PVMBG, and model data, the Darwin VAAC reported that during 20-21, 23, and 25-26 July ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted over 110 km NW, W, and 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.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
Kanlaon  | Philippines  | 10.412°N, 123.132°E  | Summit elev. 2435 m
PHIVOLCS reported that during 20-25 July diffuse white plumes rose above Kanlaon; On 20 July plumes were a dirty-white color, and on 25 July they rose 200 m and drifted NW and 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.
Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)
Klyuchevskoy  | Central Kamchatka (Russia)  | 56.056°N, 160.642°E  | Summit elev. 4754 m
KVERT reported that a Strombolian eruption at Klyuchevskoy continued during 15-22 July. Volcanic bombs were ejected 200-300 m above the summit crater and 50 m above a cinder cone, and landed in the Apakhonchich drainage on the SE flank. A lava flow traveled down the Apakhonchich drainage. Satellite images showed a large and intense daily thermal anomaly at the volcano, and ash plumes drifting over 265 km SW and W during 18-19 July. The Aviation Color Code was raised to Orange.
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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
Nevado del Ruiz  | Colombia  | 4.892°N, 75.324°W  | Summit elev. 5279 m
Based on notices from the Bogota MWO and model data, the Washington VAAC reported that on 24 July a possible ash plume from Nevado del Ruiz rose to an altitude of 7.2 km (23,000 ft) a.s.l. On 26 July an ash plume recorded by the webcam and identified in satellite images rose to an altitude of 6.9 km (22,000 ft) a.s.l. and drifted W. 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.
Source: Washington Volcanic Ash Advisory Center (VAAC)
Nevados de Chillán  | Chile  | 36.863°S, 71.377°W  | Summit elev. 3212 m
The Buenos Aires VAAC reported that on 21 July a webcam recorded an ash puff from Nevados de Chillán that rose to an altitude of 3 km (10,000 ft) a.s.l., and then continuous emissions of gas and minor amounts of ash that rapidly dissipated at crater level.
Geologic Summary. The compound volcano of Nevados de Chillán is one of the most active of the Central Andes of Chile. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, 3212-m-high Cerro Blanco (Volcán Nevado), is located at the NW end of the group, and 3089-m-high Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in altitude. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986, eventually exceeding its height by 20 m.
Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)
Poas  | Costa Rica  | 10.2°N, 84.233°W  | Summit elev. 2708 m
OVSICORI-UNA reported that a small phreatic eruption from the hot lake at Poás recorded at 0819 on 25 July ejected material 50 m above the crater lake's surface.
Geologic 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.
Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)
Popocatepetl  | Mexico  | 19.023°N, 98.622°W  | Summit elev. 5426 m
During 20-26 July CENAPRED reported 26-182 daily emissions from Popocatépetl, some of which contained minor amounts of ash. Cloud cover often prevented observations, though gas-and-steam plumes were visible almost daily. Crater incandescence was visible on some nights. Explosions were detected during 24-26 July: 4 on 24 July, 4 on 25 July, and 1 on 26 July. 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.
Source: Centro Nacional de Prevencion de Desastres (CENAPRED)
Sheveluch  | Central Kamchatka (Russia)  | 56.653°N, 161.36°E  | Summit elev. 3283 m
KVERT reported that during 15-22 July lava-dome extrusion onto Sheveluch's N flank was accompanied by strong fumarolic activity, dome incandescence, ash explosions, and hot avalanches. Satellite images showed a 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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
Sinabung  | Indonesia  | 3.17°N, 98.392°E  | Summit elev. 2460 m
Based on satellite and webcam images, model data, and ground reports from PVMBG, the Darwin VAAC reported that during 21-22 and 24-25 July ash plumes from Sinabung rose to altitudes of 3.7-4.6 km (12,000-15,000 ft) a.s.l. and drifted NW, NE, and SE.
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.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
Tengger Caldera  | Eastern Java (Indonesia)  | 7.942°S, 112.95°E  | Summit elev. 2329 m
Based on analyses of satellite images, the Darwin VAAC reported that during 23-24 July ash plumes from Tengger Caldera's Bromo cone rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted over 45 km NW 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.
Source: Darwin Volcanic Ash Advisory Centre (VAAC)
Turrialba  | Costa Rica  | 10.025°N, 83.767°W  | Summit elev. 3340 m
OVSICORI-UNA reported that an explosion at Turrialba recorded at 1309 on 22 July generated an ash plume that rose 800 m and drifted W. Increased tremor coincided with the event. Ash-and-gas emissions rose from the crater for approximately 15 minutes, starting at 1543. Ash emissions were recorded with the webcam at 0600 on 23 July. Tremor levels fluctuated though the day; periods of increased tremor likely corresponded to ash emissions. Visual observations of the crater were hindered by fog. Tremor amplitude increased at 1800 on 24 July. Two explosions, at 2123 and 2217, ejected hot rock fragments, gas, and ash 500 m above the crater; the gas-and-ash plume drifted SW. Gas-and-ash emissions passively rose from the crater through the next morning. At 0722 on 25 July an explosion generated an ash plumes that rose 3 km above the crater and drifted NW, W, and SW. At 0826 another explosion produced an ash plume that rose 1.5 km.
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.
Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA)


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