New/activity unrest was reported for 3 volcanoes between August 23 - 29, 2017. During the same period, ongoing activity was reported for 17 volcanoes.
New activity/unrest: Ibu, Halmahera (Indonesia) | Pacaya, Guatemala | Sangay, Ecuador.
Ongoing activity: Aira, Kyushu (Japan) | Bagana, Bougainville (Papua New Guinea) | Bezymianny, Central Kamchatka (Russia) | Bogoslof, Fox Islands (USA) | Cleveland, Chuginadak Island (USA) | Dukono, Halmahera (Indonesia) | Ebeko, Paramushir Island (Russia) | Fuego, Guatemala | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Piton de la Fournaise, Reunion Island (France) | Poas, Costa Rica | Sabancaya, Peru | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Suwanosejima, Ryukyu Islands (Japan) | Turrialba, Costa Rica.
Ibu, Halmahera (Indonesia)
1.488°N, 127.63°E, Elevation 1325 m
Based on satellite images and model data, the Darwin VAAC reported that on 24 and 28 August ash plumes from Ibu rose 1.5-1.8 km (5,000-6,000 ft) a.s.l. and drifted W.
Geological summary: The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.
14.382°N, 90.601°W, Elevation 2569 m
INSIVUMEH reported that during 21-28 August Strombolian explosions at Pacaya’s Mackenney cone ejected material as high as 75 m above the crater rim, and during 27-28 August as far as 100 m onto the W flank. Cloud cover sometimes prevented visual observations; explosions could be heard within a 5-km radius.
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.
2.005°S, 78.341°W, Elevation 5286 m
Based on satellite data, the Washington VAAC reported that a plume from Sangay with possible ash content rose 7 km (23,000 ft) a.s.l. and drifted over 30 km SW. A thermal anomaly was identified on 23 August.
Geological summary: The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes, and its most active. The dominantly andesitic volcano has been in frequent eruption for the past several centuries. The steep-sided, 5230-m-high glacier-covered volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.
Aira, Kyushu (Japan)
31.593°N, 130.657°E, Elevation 1117 m
JMA reported that 17 explosive events at Showa Crater (at Aira Caldera’s Sakurajima volcano) during 21-28 August ejected material as far as 800 m. Ash plumes rose as high as 1.4 km above the crater rim. The Alert Level remained at 3 (on a 5-level scale).
Geological 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.
Bagana, Bougainville (Papua New Guinea)
6.137°S, 155.196°E, Elevation 1855 m
Based on analyses of satellite imagery and model data, the Darwin VAAC reported that during 24-28 August ash plumes from Bagana rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted WNW, W, and SW.
Geological summary: Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical 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 flanks on all sides.
Bezymianny, Central Kamchatka (Russia)
55.972°N, 160.595°E, Elevation 2882 m
KVERT reported that during 18-25 August a daily thermal anomaly over Bezymianny was identified in satellite images. A lava flow continued to flow down the W flank of the dome; incandescence from the dome was visible at night. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Geological summary: Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.
Bogoslof, Fox Islands (USA)
53.93°N, 168.03°W, Elevation 150 m
AVO reported that a satellite image of Bogoslof acquired at 0628 on 24 August showed elevated surface temperatures and a small plume that was most likely steam drifting 17 km S. During 24-25 August a robust steam plume drifting 70 km SE and elevated surface temperatures were identified in satellite data. A four-minute-long explosion that began at 1629 on 26 August generated an eruption cloud that rose 8.2 km (27,000 ft) a.s.l. and drifted SE. The event was also observed in seismic and infrasound data, and one lightning stroke was detected.
Three short-duration eruptive events occurred during 27-28 August. The first, a two-minute-long explosion at 1508 on 27 August, produced a volcanic cloud that rose 7.9 km (26,000 ft) a.s.l. and drifted SE. The second event started at 0323 on 28 August and lasted 25 minutes. The resulting small cloud drifted ESE and quickly dissipated. The third event was detected at 1117 on 28 August and generated a small volcanic cloud that rose 7.6-9.1 (25,000-30,000 ft) a.s.l. Slightly elevated surface temperatures were observed in a few satellite images during 28-29 August. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
Geological summary: Bogoslof is the emergent summit of a submarine volcano that lies 40 km north of the main Aleutian arc. It rises 1500 m above the Bering Sea floor. Repeated construction and destruction of lava domes at different locations during historical time has greatly modified the appearance of this "Jack-in-the-Box" volcano and has introduced a confusing nomenclature applied during frequent visits of exploring expeditions. The present triangular-shaped, 0.75 x 2 km island consists of remnants of lava domes emplaced from 1796 to 1992. Castle Rock (Old Bogoslof) is a steep-sided pinnacle that is a remnant of a spine from the 1796 eruption. Fire Island (New Bogoslof), a small island located about 600 m NW of Bogoslof Island, is a remnant of a lava dome that was formed in 1883.
Cleveland, Chuginadak Island (USA)
52.825°N, 169.944°W, Elevation 1730 m
AVO reported that elevated surface temperatures at Cleveland were identified in satellite data during 25-28 August. Small vapor plumes from the summit were observed in webcam images during 28-29 August. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
Geological summary: Beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited, dumbbell-shaped Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Cleveland is joined to the rest of Chuginadak Island by a low isthmus. The 1730-m-high Mount Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name for Mount Cleveland, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.
Dukono, Halmahera (Indonesia)
1.693°N, 127.894°E, Elevation 1229 m
Based on analyses of satellite imagery, wind model data, and notices from PVMBG, the Darwin VAAC reported that during 23-28 August ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted N, NW, and W.
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.
Ebeko, Paramushir Island (Russia)
50.686°N, 156.014°E, Elevation 1103 m
Based on observations by volcanologists in Severo-Kurilsk (Paramushir Island), about 7 km E of Ebeko, explosions on 22 August generated ash plumes that rose as high as 2 km (6,600 ft) a.s.l. and drifted SW. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Geological summary: The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.
14.473°N, 90.88°W, Elevation 3763 m
INSIVUMEH reported that on 25 August lahars descended the Pantaleón, Cenizas, El Jute, and Las Lajas drainages on Fuego’s W, SSW, and SE flanks. The lahar in the Pantaleón river (fed by the Santa Teresa and El Mineral rivers) was 35 m wide, 2.5-3 m deep, and carried trees and blocks more than 2-3 m in diameter. The Cenizas river lahar was about 25 m wide, 3 m deep, and carried blocks up to 2 m in diameter. The lahars in El Jute and Las Lajas drainages were 20 m wide, 1.5 m deep, and carried tree debris and blocks up to 2 m in diameter. Explosions during 26-29 August generated ash plumes that rose as high as 950 m above the crater and drifted 7-12 km SW, W, and NW. Incandescent material was ejected 100-200 m above the crater rim, and caused avalanches of material around the crater area. Explosions were audible within a 20-km radius, and shock waves vibrated local structures. Ash fell in areas downwind including Panimache I and II, Morelia, Finca Palo verde, Sangre de Cristo, and El Porvenir. On 29 August lahars 10 m wide and 1.5 m deep descended the Santa Teresa and El Mineral drainages, carrying tree debris and blocks up to 2 m in diameter.
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.
Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Elevation 1222 m
During 23-29 August HVO reported that the lava lake continued to rise, fall, and spatter in Kilauea’s Overlook crater. Webcams recorded incandescence from long-active sources within Pu'u 'O'o Crater. The 61G lava flow, originating from a vent on Pu'u 'O'o Crater's E flank, continued to enter the ocean at Kamokuna. Surface lava flows were active above the pali and on the coastal plain. Slumping of seaward portions of the delta continued, and cracks running parallel to the coastline continued to widen. HVO warned of the potential for larger-scale delta collapses.
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 on 19 August explosions at Klyuchevskoy generated ash plumes that rose 6-7 km (19,700-23,000 ft) a.s.l.; the plumes drifted 140 km NW initially, and then 270 km SW and 90 km NE. Ash plumes during 20-25 August drifted as far as 560 km NW, W, and SW. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
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.
Piton de la Fournaise, Reunion Island (France)
21.244°S, 55.708°E, Elevation 2632 m
OVPF reported that the eruption at Piton de la Fournaise that began on 14 July ended at 0300 on 28 August, as indicated by the disappearance of tremor. OVPF noted that seismic events beneath the SE part of the Enclos Fouqué region continued to be recorded, and carbon dioxide levels in the soil remained high.
Geological summary: The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.
Poas, Costa Rica
10.2°N, 84.233°W, Elevation 2708 m
OVSICORI-UNA reported that events at Poás at 0920 and 0930 on 24 August and at 0945 on 29 August generated plumes that rose 500-600 m above the crater rim.
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.
15.787°S, 71.857°W, Elevation 5960 m
Observatorio Vulcanológico del Sur del IGP (OVS-IGP) and Observatorio Vulcanológico del INGEMMET (OVI) reported that explosive activity at Sabancaya was similar to the previous week; there was an average of 46 explosions recorded per day during 21-27 August. The earthquakes were dominated by long-period signals and signals indicating emissions, with fewer numbers of hybrid events recorded. Gas-and-ash plumes rose 3.4 km above the crater rim and drifted no more than 50 km SE and NW. The MIROVA system detected eight thermal anomalies. The report warned the public not to approach the crater within a 12-km radius.
Geological summary: Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Elevation 3283 m
KVERT reported that a thermal anomaly over Sheveluch was identified daily in satellite images during 18-25 August. 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.
3.17°N, 98.392°E, Elevation 2460 m
Based on PVMBG observations, webcam and satellite images, and wind data, the Darwin VAAC reported that during 23-27 August ash plumes from Sinabung rose 4-4.9 km (13,000-16,000 ft) a.s.l. and drifted E and ESE.
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 andesitic-to-dacitic edifice 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.
Suwanosejima, Ryukyu Islands (Japan)
29.638°N, 129.714°E, Elevation 796 m
Based on JMA notices and satellite-image analyses, the Tokyo VAAC reported that during 24-25 August ash plumes from Suwanosejima rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted E and NE.
Geological 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 people live on the island.
Turrialba, Costa Rica
10.025°N, 83.767°W, Elevation 3340 m
OVSICORI-UNA reported that an event at Turrialba at 0715 on 24 August generated a plume that rose 400 m above the crater rim and drifted NW. Another event at 1025 on 28 August produced a plume that rose 300 m and drifted NW.
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.