Smithsonian / USGS Weekly Volcanic Activity Report 6-12 July 2016
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Smithsonian / USGS Weekly Volcanic Activity Report
6-12 July 2016
Sally Kuhn Sennert - Weekly Report Editor (kuhns@xxxxxx)
URL: http://www.volcano.si.edu/reports_weekly.cfm
New Activity/Unrest: Bulusan, Luzon (Philippines) | Copahue, Central Chile-Argentina border | Kilauea, Hawaiian Islands (USA) | Pacaya, Guatemala
Ongoing Activity: Alaid, Kuril Islands (Russia) | Bagana, Bougainville (Papua New Guinea) | Chirpoi, Kuril Islands (Russia) | Dukono, Halmahera (Indonesia) | Fuego, Guatemala | Klyuchevskoy, Central Kamchatka (Russia) | Nevado del Ruiz, Colombia | Pavlof, United States | Santa Maria, Guatemala | 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
Bulusan | Luzon (Philippines) | 12.77°N, 124.05°E | Summit elev. 1565 m
PHIVOLCS reported that on 5 July voluminous emissions of white-to-grayish-white steam plumes rose 250 m above Bulusan's summit crater, and drifted SSE and SSW. Copious amounts of white steam rose 700 m above the crater the next day. During 7-9 July cloud cover obscured views of the crater. Diffuse white steam plumes drifted down the flanks on 10 July and rose as high as 70 m during 11-12 July. 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) http://www.phivolcs.dost.gov.ph/
Copahue | Central Chile-Argentina border | 37.856°S, 71.183°W | Summit elev. 2953 m
OVDAS- SERNAGEOMIN reported that during 16-30 June the eruption at Copahue was characterized by phreato-magmatic explosions and Strombolian activity. On 4 July, SERNAGEOMIN posted on their social media page photos from an overflight showing Strombolian activity from a crater atop of a pyroclastic cone which was forming on the floor of El Agrio crater. Based on webcam and satellite views, the Buenos Aires VAAC reported that during 7-8 July diffuse gas-and-steam plumes with minor amounts of ash rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted E and SE. The Alert Level remained at Yellow; SERNAGEOMIN recommended no entry into a restricted area within 1.5 km of the crater.
Geologic Summary. Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded at Copahue since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.
Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/;
Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.smn.gov.ar/vaac/buenosaires/productos.php
Kilauea | Hawaiian Islands (USA) | 19.421°N, 155.287°W | Summit elev. 1222 m
HVO reported that during 6-12 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. Episode 61g, a lava flow originating from a vent on Pu'u 'O'o Crater's E flank, continued to advance across the coastal plain, burning vegetation in the adjacent kipuka at the base of the pali. By 10 July the lava flow was about 1 km from the ocean.
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) http://hvo.wr.usgs.gov/
Pacaya | Guatemala | 14.381°N, 90.601°W | Summit elev. 2552 m
INSIVUMEH reported that Strombolian explosions from Pacaya's Mackenney cone were observed during 7-10 July. During 11-12 July weather conditions prevented visual observations of the crater, although weak crater incandescence was visible at night.
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) http://www.insivumeh.gob.gt/
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 1-8 July, and lava flowed down the SW flank. Satellite images showed a daily thermal anomaly at the volcano, and ash plumes drifting 150 km SW during 3-4 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) http://www.kscnet.ru/ivs/kvert/index_eng.php
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 6-10 July ash plumes from Bagana rose to altitude of 2.1-2.7 km (7,000-9,000 ft) a.s.l. and drifted as far as 120 km SE, 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) ftp://ftp.bom.gov.au/anon/gen/vaac/
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 5-7 July. 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) http://www.imgg.ru/?id_d=659
Dukono | Halmahera (Indonesia) | 1.693°N, 127.894°E | Summit elev. 1229 m
Based on analyses of satellite imagery and model data, the Darwin VAAC reported that during 6-10 and 12 July ash plumes from Dukono rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted in multiple directions.
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) ftp://ftp.bom.gov.au/anon/gen/vaac/
Fuego | Guatemala | 14.473°N, 90.88°W | Summit elev. 3763 m
INSIVUMEH reported that during 7-10 July there were 6-8 explosions per hour at Fuego, generating ash plumes that rose as high as 950 m above the crater and drifted W and NW. Ash fell in Yepocapa (8 km N), Sangre de Cristo (8 km WSW), Panimache (8 km SW), and other nearby areas. Some explosions generated shock waves, and incandescent material was ejected 150 m high. There were 18 explosions detected during 11-12 July; ash plumes rose as high as 850 m and drifted more than 10 km W and SW.
Geologic 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.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/
Klyuchevskoy | Central Kamchatka (Russia) | 56.056°N, 160.642°E | Summit elev. 4754 m
KVERT reported that a Strombolian eruption at Klyuchevskoy continued during 1-8 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 350 km SW, S, and SE during 2-5 July. Video data showed that activity intensified on 6 July; strong explosions generated ash plumes that rose as high as 7.5 km (24,600 ft) a.s.l. Satellite images showed dense ash plumes drifting 400 km SE and E during 6-7 July. The Aviation Color Code remained at 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) http://www.kscnet.ru/ivs/kvert/index_eng.php
Nevado del Ruiz | Colombia | 4.892°N, 75.324°W | Summit elev. 5279 m
Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that a webcam recorded minor ash emissions rising from Nevado del Ruiz during 6-7 July. Based on notices from the Bogota MWO, satellite images, and model data, the Washington VAAC reported that on 8 July ash plumes rose to altitudes of 6.1-6.4 km (20,000-21,000 ft) a.s.l. and drifted W. A thermal anomaly was visible on 9 July. 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.
Sources: Servicio Geológico Colombiano (SGC) http://www.ingeominas.gov.co/;
Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html
Pavlof | United States | 55.417°N, 161.894°W | Summit elev. 2493 m
On 11 July, AVO noted that during the previous 24 hours a steam cloud from Pavlof was seen drifting SW by observers in Sand Point (90 km E) and by pilots flying near the volcano. Satellite images showed the cloud drifting 72 km SW. No unusual seismicity was detected. At 1300 the webcam recorded a minor ash emission rising tens of meters and drifting a few kilometers SW. The Aviation Color Code remained at Yellow and Volcano Alert Level remained at Advisory.
Geologic Summary. The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows.
Source: US Geological Survey Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/
Santa Maria | Guatemala | 14.756°N, 91.552°W | Summit elev. 3772 m
INSIVUMEH reported that during 7-8 July explosions at Santa María's Santiaguito lava-dome complex generated ash plumes that rose as high as 1 km and drifted 10 km S and W. On 10 July a strong, loud explosion was followed by pyroclastic flows that traveled 2 km down the S and SW flanks, and an ash plume that rose 3 km and drifted 40 km W. INSIVUMEH reminded the public to stay at least 5 km away from the volcano. Gas plumes rose from the crater during 11-12 July.
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.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/
Sheveluch | Central Kamchatka (Russia) | 56.653°N, 161.36°E | Summit elev. 3283 m
KVERT reported that during 1-8 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 thermal anomaly over the dome. On 4 July re-suspended ash from the vicinity of Sheveluch drifted 65 km SE. 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) http://www.kscnet.ru/ivs/kvert/index_eng.php
Sinabung | Indonesia | 3.17°N, 98.392°E | Summit elev. 2460 m
Based on satellite images, model data, notices from the Jarkarta MWO, and information from PVMBG, the Darwin VAAC reported that during 6, 8-9, and 11 July ash plumes from Sinabung rose to altitudes of 3.7-5.5 km (12,000-18,000 ft) a.s.l. and drifted SE, E, NE, and W.
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) ftp://ftp.bom.gov.au/anon/gen/vaac/
Tengger Caldera | Eastern Java (Indonesia) | 7.942°S, 112.95°E | Summit elev. 2329 m
Based on satellite images, wind data, and information from PVMBG, the Darwin VAAC reported that during 6-12 July ash plumes from Tengger Caldera's Bromo cone rose to altitudes of 2.7-3 km (9,000-10,000 ft) a.s.l. and drifted as far as 120 km S, SSW, SW, and W. BNPB reported that the Abdul Rachman Saleh Airport in Malang (26 km W) closed from 2300 on 11 July to 0900 on 12 July due to thin ash deposits around the airport. The Alert Level remained at 2 (on a scale of 1-4); residents and visitors were reminded 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.
Sources: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/;
Badan Nacional Penanggulangan Bencana (BNPB) http://www.bnpb.go.id/
Turrialba | Costa Rica | 10.025°N, 83.767°W | Summit elev. 3340 m
OVSICORI-UNA reported that strong tremor at Turrialba started at 0658 on 7 July. An accompanying explosion produced an ash plume that rose 1 km above the crater and likely drifted WNW and WSW. Weather conditions mostly prevented views of the crater, although at 1551 a large amount of water-vapor-and-gas emissions with minor amounts of ash were observed. Ashfall was recorded in areas downwind including in neighborhoods of San José (Coronado, La Uruca, Tibás, Rancho Redondo, Guadalupe, Sabanilla, Moravia, Ipís, Sabanilla, La Guácima of Alajuela, and San Rafael de Alajuela), Heredia (38 km W), and Turrubares. Almost continuous tremor was detected through the next day; a period of increased tremor amplitude was detected during 1030-1230. Emissions of gas, water vapor, and large amounts of ash were visible with the webcam. Ash fell in many of the same areas as the day before. Tremor levels dropped at 2030, though increased again at 0030 on 9 July. Ash emissions rose no higher than 500 m above the crater around 0900 on 9 July. Ash emissions to 300 m above the crater and elevated tremor levels continued throughout the day. Ashfall was reported in Ipís de Guadalupe and San Rafael de Heredia. Tremor significantly declined at 0115 on 10 July. Views of the crater at 0600 showed emissions of water vapor and gas with minor amounts of ash. Tremor again increased on 11 July, at 0930, and a possible ash emission occurred between 1000 and 1030, although weather conditions prevented confirmation.
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) http://www.ovsicori.una.ac.cr/
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