Active volcanoes in the world: July 15 – 21, 2015

New activity/unrest was observed at 7 volcanoes from July 15 – 21, 2015. During the same period, ongoing activity was observed at 14 volcanoes. 

New activity/unrest: Chirinkotan, Kuril Islands (Russia)  | Cleveland, Chuginadak Island (USA)  | Colima, Mexico  | Gamalama, Halmahera (Indonesia)  | Nevado del Ruiz, Colombia  | Raung, Eastern Java (Indonesia)  | Sabancaya, Peru.

Ongoing activity: Aira, Kyushu (Japan)  | Bulusan, Luzon (Philippines)  | Dukono, Halmahera (Indonesia)  | Guallatiri, Chile  | Karymsky, Eastern Kamchatka (Russia)  | Kilauea, Hawaiian Islands (USA)  | Klyuchevskoy, Central Kamchatka (Russia)  | Popocatepetl, Mexico  | Reventador, Ecuador  | Sheveluch, Central Kamchatka (Russia)  | Shishaldin, Fox Islands (USA)  | Sinabung, Indonesia  | Tungurahua, Ecuador  | Zhupanovsky, Eastern Kamchatka (Russia).

New activity/unrest

Chirinkotan, Kuril Islands (Russia)
48.98°N, 153.48°E, Summit elev. 724 m

Based on satellite image observations, the Tokyo VAAC reported that a possible eruption at Chirinkotan on 21 July may have produced an ash plume that rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted SE. A subsequent notice stated that ash was observed in images and then dissipated. SVERT reported that on 22 July a thermal anomaly over Chirinkotan was detected in satellite images as well as steam-and-gas emissions. The Aviation Color Code was raised to Yellow.

Geologic summary: The small, mostly unvegetated 3-km-wide island of Chirinkotan occupies the far end of an E-W-trending volcanic chain that extends nearly 50 km west of the central part of the main Kuril Islands arc. Chirinkotan is the emergent summit of a volcano that rises 3000 m from the floor of the Kuril Basin. A small 1-km-wide caldera about 300-400 m deep is open to the SE. Lava flows from a cone within the breached crater reached the north shore of the island. Historical eruptions have been recorded at Chirinkotan since the 18th century. Fresh lava flows also descended the SE flank of Chirinkotan during an eruption in the 1880s that was observed by the English fur trader Captain Snow.

Cleveland, Chuginadak Island (USA)
52.825°N, 169.944°W, Summit elev. 1730 m

AVO reported that at 0817 on 21 July an explosion at Cleveland was detected in both infrasound and seismic data. Cloud cover up to 9.1 km (30,000 ft) a.s.l. obscured views; no ash above the cloud deck was observed. Observers on a boat at the NE side of Cleveland reported seeing a dusting of ash on the snow near the summit as well as moderate steaming from the summit area. The Aviation Color Code was raised to Orange and the Volcano Alert Level was raised to Watch.

Geologic 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.

Colima, Mexico
19.514°N, 103.62°W, Summit elev. 3850 m

The Washington VAAC reported that on 15 July the webcam at Colima recorded no ash emissions; however, incandescent avalanches continued to descend the flanks. According to a news article the lava dome had been excavated during increased activity from 10 to 12 July; on 16 July explosions were less continuous and extrusion of a lava flow on the S flank has decreased. A total of 670 evacuees remained in temporary shelters.

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.

Gamalama, Halmahera (Indonesia)
0.8°N, 127.33°E, Summit elev. 1715 m

BNPB reported that a phreatic explosion at Gamalama on 16 July generated a gray-and-white plume that rose as high as 1.5 km above the crater and drifted N. The Alert Level remained at 2 (on a scale of 1-4); visitors and residents were warned not to approach the crater within a radius of 1.5 km. The Sultan Babullah International airport in Ternate was closed on 18 July. Several explosions during 18-19 July produced white-and-gray plumes that rose 300-800 m and drifted NW. A preliminary count of refugees showed there were 1,505 people (450 families) displaced by the eruption. Ash deposits were 1.5-6 mm thick in northwestern villages.

Based on pilot reports, ground-based observations, wind data, PVMBG reports, and satellite images, the Darwin VAAC reported that during 16-20 July ash plumes rose to altitudes of 2.1-5.5 km (7,000-18,000 ft) a.s.l. and drifted 20-130 km NE, NW, W, and SW.

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

Nevado del Ruiz, Colombia
4.892°N, 75.324°W, Summit elev. 5279 m

According to the Washington VAAC, the Manizales Observatory reported that activity at Nevado del Ruiz increased at 0530 on 18 July, and an ash plume rose to an altitude of 6.1 km (20,000 ft) a.s.l. Weather clouds prevented satellite and webcam views. Later that day the Bogata MWO reported that an ash plume drifted SW at an altitude of 6.1 km (20,000 ft) a.s.l., and a NOTAM detailed an ash plume drifting S at the same altitude.

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.

Raung, Eastern Java (Indonesia)
8.125°S, 114.042°E, Summit elev. 3332 m

Based on PVMBG information, and satellite-image and pilot observations, the Darwin VAAC reported that during 15-21 July ash multiple ash plumes from Raung rose to varying altitudes of 3.7-6.1 km (12,000-20,000 ft) a.s.l. and drifted as far as 340 km in multiple directions. On 16 July BNPB reported that a dense gray-to-black ash plume rose as high as 2 km above Raung's crater rim and drifted WNW. Incandescent lava at the summit was visible and tremor was continuous. Roaring and thumping sounds were reported by residents. Ashfall was reported in areas downwind, including Cumedak (19 km W) and Sumberjambe (13 km NW). According to a news article, the Juanda International Airport in Surabaya reopened on 17 July after on-and-off closures the previous week. BNPB noted that the eruption continued on 18 July with ash plumes rising as high as 1.5 km and drifting N. Tremor continued, although the amplitude had declined during the previous week. The Alert Level remained at 3 (on a scale of 1-4), and the public was reminded not to approach the crater within a 3-km radius.

Geologic summary: Raung, one of Java's most active volcanoes, is a massive stratovolcano in easternmost Java that was constructed SW of the rim of Ijen caldera. The 3332-m-high, unvegetated summit of Gunung Raung is truncated by a dramatic steep-walled, 2-km-wide caldera that has been the site of frequent historical eruptions. A prehistoric collapse of Gunung Gadung on the W flank produced a large debris avalanche that traveled 79 km, reaching nearly to the Indian Ocean. Raung contains several centers constructed along a NE-SW line, with Gunung Suket and Gunung Gadung stratovolcanoes being located to the NE and W, respectively.

Sabancaya, Peru
15.78°S, 71.85°W, Summit elev. 5967 m

INGEMMET volcanologists who climbed to the summit of Sabancaya during 9-10 July observed ash deposits from emissions during the previous weeks.

Geologic summary: Sabancaya, located on the saddle between 6288-m-high Ampato and 6025-m-high 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 volcanoes, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. Both Nevado Ampato and Nevado Sabancaya are only slightly affected by glacial erosion and consist of a series of lava domes aligned along a NW-SW trend. The name of 5967-m-high Sabancaya (meaning "tongue of fire" in the Quechua Indian 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.

Ongoing activity

Aira, Kyushu (Japan)
31.593°N, 130.657°E, Summit elev. 1117 m

JMA reported five explosions during 13-21 July from Showa Crater at Aira Caldera’s Sakurajima volcano, some that ejected tephra as far as 500 m, and incandescence from the crater that was occasionally visible. A small-scale eruption occurred from Minami-Dake Crater on 16 July. The Alert Level remained at 3 (on a 5-level scale).

Geologic summary: The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Bulusan, Luzon (Philippines)
12.77°N, 124.05°E, Summit elev. 1565 m

PHIVOLCS reported that at 1310 on 17 July an explosion at Bulusan, detected by the seismic network for 11 minutes, generated an ash plume that rose 200 m above the crater and drifted WNW. Ashfall was reported in areas to the N and NE in the Sorsogon Province, including Inlagadian (municipality of Casiguran), Tigkiw, Tugawe, Nazareno, Bugtong, and Rizal (municipality of Gubat), and Fabrica, San Isidro, Sta. Cruz, and San Ramon (municipality of Barcelona). 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.

Dukono, Halmahera (Indonesia)
1.68°N, 127.88°E, Summit elev. 1335 m

Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 16-19 July ash plumes from Dukono rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted 20-120 km N, NW, W, and SW.

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.

Guallatiri, Chile
18.42°S, 69.092°W, Summit elev. 6071 m

On 7 July OVDAS-SERNAGEOMIN reported that the Alert Level for Guallatiri was lowered to Green (the lowest level on a four-color scale) because activity had returned to the baseline levels observed prior to the Alert-Level increase in May. Baseline levels were characterized by low levels of seismicity, no deformation, and white emissions.

Geologic summary: One of northern Chile's most active volcanoes, Volcán Guallatiri is a symmetrical ice-clad stratovolcano at the SW end of the Nevados de Quimsachata volcano group. The 6071-m-high Guallatiri lies just west of the border with Bolivia and is capped by a central dacitic dome or lava complex, with the active vent situated at its southern side. Thick lava flows are prominent on the lower northern and western flanks of the andesitic-to-rhyolitic volcano. Minor explosive eruptions have been reported from Guallatiri since the beginning of the 19th century. Intense fumarolic activity with "jet-like" noises continues, and numerous solfataras extend more than 300 m down the west flank.

Karymsky, Eastern Kamchatka (Russia)
54.049°N, 159.443°E, Summit elev. 1513 m

KVERT reported that explosive activity at Karymsky likely continued during 3-10 July; a thermal anomaly over the volcano was visible in satellite images on 6 July. Weather clouds obscured views of the volcano on the other days. The Aviation Color Code remained at Orange.

Geologic summary: Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Summit elev. 1222 m

HVO reported that seismicity beneath Kilauea's summit, upper East Rift Zone, and Southwest Rift Zone was at background levels during 15-22 July. The lava lake continued to circulate and spatter in the Overlook vent. Webcams recorded multiple incandescent outgassing vents within Pu'u 'O'o. The June 27th NE-trending lava flow continued to be active with surface flows within 8 km NE of Pu'u 'O'o Crater; smoke plumes rose from burning forest at the most distant part of the flow.

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

Klyuchevskoy, Central Kamchatka (Russia)
56.056°N, 160.642°E, Summit elev. 4754 m

On 21 July KVERT reported that an eruption at Klyuchevskoy ended on 24 March, although activity during 1-10 May was characterized by gas-and steam plumes with minor amounts of ash and a thermal anomaly. Seismicity continued at a high level, and gas-and-steam emissions continued. The Aviation Color Code was lowered to Green.

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.

Popocatepetl, Mexico
19.023°N, 98.622°W, Summit elev. 5426 m

CENAPRED reported that during 15-21 July the seismic network at Popocatépetl recorded 18-64 daily emissions consisting of water vapor, gas, and sometimes ash; cloud cover often prevented visual observations. Variable nighttime crater incandescence was observed, and explosions were detected during 17-19 July. Two explosions on 20 July produced ash plumes that rose less than 500 m. 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.

Reventador, Ecuador
0.077°S, 77.656°W, Summit elev. 3562 m

During 15-21 July IG reported a high level of seismic activity including explosions, tremor, long-period earthquakes, harmonic tremor, and signals indicating emissions at Reventador; cloud cover often prevented visual observations. On 14 July a steam-and-ash plume rose 1 km and drifted W, and on 16 July an ash plume rose 1.3 km and drifted NW. On 17 July an ash plume rose 700 m, and light gray deposits possibly from a pyroclastic flow were observed. On 20 July explosions produced ash plumes that rose 1 km and drifted NW. The next day a steam-and-ash plume rose 1.5 km and drifted E. Explosions ejected incandescent material onto the flanks.

Geologic 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, Summit elev. 3283 m

KVERT reported that during 10-17 July lava-dome extrusion onto Sheveluch’s N flank was accompanied by fumarolic activity, dome incandescence, and hot avalanches. Satellite images showed a thermal anomaly over the dome during 10-11, 14, and 16 July. The Aviation Color Code remained at Orange.

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

Shishaldin, Fox Islands (USA)
54.756°N, 163.97°W, Summit elev. 2857 m

AVO reported that seismicity at Shishaldin continued to be elevated over background levels 15-21 July indicating that low-level eruptive activity confined to the summit crater likely continued. Cloud cover prevented satellite and webcam observations. Elevated surface temperatures were detected in satellite images during 19-20 July. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.

Geologic summary: The beautifully symmetrical volcano of Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 2857-m-high, glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steady steam plume rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is Holocene in age and largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the west and NE sides at 1500-1800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.

Sinabung, Indonesia
3.17°N, 98.392°E, Summit elev. 2460 m

During 18-19 July BNPB reported that Sinabung remained active; pyroclastic flows traveled 2.5-3 km E and SE, ash plumes rose as high as 1 km, and lava was active as far as 1.5 km SE. Seismicity was high and the lava dome continued to extrude. A total of 11,111 people (3,150 families) remained displaced. The Alert Level remained at 4 (on a scale of 1-4). Based on satellite images, weather models, and information from PVMBG, the Darwin VAAC reported that during 18-20 July explosions generated ash plumes that rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted E. White plumes rose 200 m on 21 July.

Geologic summary: Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical, 2460-m-high andesitic-to-dacitic volcano is at the southern end of the four overlapping summit craters. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

Tungurahua, Ecuador
1.467°S, 78.442°W, Summit elev. 5023 m

IG reported moderate seismic activity at Tungurahua during 14-21 July, characterized by long-period events, tremor, and a few explosions. Cloud cover often prevented visual observations. Explosions during 14-15 July generated ash plumes that rose 2 km above the crater and drifted W. Crater incandescence was visible at night. Ashfall overnight during 15-16 July was reported in Choglontus (13 km WSW), Bilbao, and El Manzano (8 km SW). On 17 July vapor-and-ash plumes were observed and ash fell in Choglontus. A lahar descended the Juive (NW) drainage on 18 July.

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

Zhupanovsky, Eastern Kamchatka (Russia)
53.589°N, 159.15°E, Summit elev. 2899 m

KVERT reported that moderate explosive activity at Zhupanovsky continued during 10-17 July. A strong explosion on 12 July produced an ash plume that rose to an altitude of 10 km (32,800 ft) a.s.l. and drifted 1,200 km E. Ashfall was reported in Petropavlovsk-Kamchatsky. Another explosion on 14 July generated ash plumes that rose to an altitude of 2 km (6,600 ft) a.s.l. and drifted SW and 60 km S. During an overflight on 16 July, volcanologists observed fresh deposits at the foot of the volcano from collapses of the S section of Priemysh Crater (the active crater) that likely occurred on 12 July. Moderate activity at the crater continued through 19 July; the Aviation Color Code was lowered to Yellow.

Geologic summary: The Zhupanovsky volcanic massif consists of four overlapping stratovolcanoes along a WNW-trending ridge. The elongated volcanic complex was constructed within a Pliocene-early Pleistocene caldera whose rim is exposed only on the eastern side. Three of the stratovolcanoes were built during the Pleistocene, the fourth is Holocene in age and was the source of all of Zhupanovsky's historical eruptions. An early Holocene stage of frequent moderate and weak eruptions from 7000 to 5000 years before present (BP) was succeeded by a period of infrequent larger eruptions that produced pyroclastic flows. The last major eruption took place about 800-900 years BP. Historical eruptions have consisted of relatively minor explosions from the third cone.

Source: GVP.