New unrest has been noticed around 4 volcanoes, ongoing activity was reported for 12 volcanoes. This report covers active volcanoes in the world recorded from July 18 – July 24, 2012 based on Smithsonian/USGS criteria.
0.95°N, 77.87°W; summit elev. 4764 m
According to INGEOMINAS, the Observatorio de Pasto reported that during 18-24 July seismic activity at Cumbal had decreased. Variable amounts of gas emissions, mostly steam, were observed in the web camera located in Cumbal town (9 km SE) during periods of clear weather, which occurred during 20-21 July. The emissions originated from fumarolic fields located in the main crater on the NE side of Cumbal and Mundo Nuevo crater on the SW side. The Alert Level remained at III (Yellow; “changes in the behavior of volcanic activity”).
Geologic summary: Many youthful lava flows extend from the glacier-capped Cumbal volcano, the southernmost historically active volcano of Colombia. The volcano is elongated in a NE-SW direction and is composed primarily of andesitic-dacitic lava flows. Two fumarolically active craters occupy the summit ridge; the main crater on the NE side and Mundo Nuevo crater on the SW side. A young lava dome occupies the 250-m-wide summit crater, and eruptions from the upper east flank produced a 6-km-long lava field. The oldest crater lies NNE of the summit crater, suggesting SW-ward migration of activity. Explosive eruptions in 1877 and 1926 are the only known historical activity from Cumbal. Fumarole fields are found in the two summit craters, and thermal springs are located on the SE flanks.
1.22°N, 77.37°W; summit elev. 4276 m
INGEOMINAS reported that during 18-24 July earthquakes at Galeras were less than M 1.3 and located at depths not exceeding 3 km. Gas emissions, observed by a network of video cameras, contained ash almost daily. Sulfur dioxide levels fluctuated. On 18 July observatory staff working near the crater reported a strong sulfur odor and fine ash falling on the upper N flank. Ashfall was also reported to the N in the Quebrada Maragato area (municipality of Nariño). The Alert Level remained at III (Yellow; “changes in the behavior of volcanic activity”).
Geologic summary: Galeras, a stratovolcano with a large breached caldera located immediately W of the city of Pasto, is one of Colombia’s most frequently active volcanoes. The dominantly andesitic Galeras volcanic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Longterm extensive hydrothermal alteration has affected the volcano. This has contributed to large-scale edifice collapse that has occurred on at least three occasions, producing debris avalanches that swept to the W and left a large horseshoe-shaped caldera inside which the modern cone has been constructed. Major explosive eruptions since the mid Holocene have produced widespread tephra deposits and pyroclastic flows that swept all but the southern flanks. A central cone slightly lower than the caldera rim has been the site of numerous small-to-moderate historical eruptions since the time of the Spanish conquistadors.
IJEN, Eastern Java (Indonesia)
8.058°S, 114.242°E; summit elev. 2799 m
CVGHM reported that, although weather conditions at Ijen often prevented views of the volcano during 1-24 July, white plumes were occasionally observed rising 50-100 m above the crater. Seismicity indicated unrest, and along with visual observations, prompted CVGHM to raise the Alert Level to 3 (on a scale of 1-4) on 24 July.
Geologic summary: The Ijen volcano complex consists of a group of small stratovolcanoes constructed within the large 20-km-wide Ijen (Kendeng) caldera. The N caldera wall forms a prominent arcuate ridge, but elsewhere the caldera rim is buried by post-caldera volcanoes, including Gunung Merapi stratovolcano, which forms the 2,799 m high point of the Ijen complex. Immediately W of Gunung Merapi is the renowned historically active Kawah Ijen volcano, which contains a nearly 1-km-wide, turquoise-colored, acid crater lake. The picturesque lake is the site of a labor-intensive sulfur mining operation, in which sulfur-laden baskets are hand-carried from the crater floor. A half dozen small-to-moderate phreatic eruptions have taken place from Kawah Ijen during the 20th century.
TONGARIRO, North Island (New Zealand)
39.13°S, 175.642°E; summit elev. 1978 m
A sequence of small volcanic earthquakes beneath Tongariro was detected by a few of the seismometers in the permanent network. Earthquakes with magnitudes less than 2.5 were clustered between Emerald Crater (E of the summit) and the Te Mari craters (2 km E east of Ketetahi hot springs on the N flank) at 2-7 km depth. The sequence started on 13 July, soon declined, and then again increased during 18-20 July. The Alert Level was raised to 1 (on a scale of 0-5) and the Aviation Colour Code was raised to Yellow (on a four-color scale) on 20 July.
In response to the increased seismicity, GeoNet installed four portable seismographs and conducted gas and spring sampling. During 21-22 July seismicity declined; one event was detected on 23 July. Provisional analysis of the gas samples collected during 21-22 July indicated a marked increase in the volcanic gas component of the typical mix of volcanic and hydrothermal gases. Residents reported a gas odor.
Geologic summary: Tongariro is a large andesitic volcanic massif, located immediately NE of Ruapehu volcano, that is composed of more than a dozen composite cones constructed over a period of 275,000 years. Vents along a NE-trending zone extending from Saddle Cone (below Ruapehu volcano) to Te Mari crater (including vents at the present-day location of Ngauruhoe) were active during a several hundred year long period around 10,000 years ago, producing the largest known eruptions at the Tongariro complex during the Holocene. The youngest cone of the complex, Ngauruhoe, has grown to become the highest peak of the massif since its birth about 2500 years ago. The symmetrical, steep-sided Ngauruhoe, along with its neighbor Ruapehu to the south, have been New Zealand’s most active volcanoes during historical time.
BATU TARA, Komba Island (Indonesia)
7.792°S, 123.579°E; summit elev. 748 m
Based on analyses of satellite imagery, the Darwin Volcanic Ash Advisory Centre (VAAC) reported that ash plumes from Batu Tara rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 45 km W during 22-23 July and 110 km N and NW on 24 July.
Geologic summary: The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (formerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy’s Stromboli volcano. Vegetation covers the flanks of Batu Tara to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption from Batu Tara, during 1847-52, produced explosions and a lava flow.
CLEVELAND, Chuginadak Island
52.825°N, 169.944°W; summit elev. 1730 m
AVO reported that elevated surface temperatures from Cleveland were detected in satellite images during 18-20 July. Images revealed nothing unusual during 20-22 July. Cloud cover mostly prevented observations during 22-24 July; a steam plume rose from the crater on 23 July. The Volcano Alert Level remained at Watch and the Aviation Color Code remained at Orange.
Geologic summary: Symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited dumbbell-shaped Chuginadak Island in the east-central Aleutians. The 1,730-m-high stratovolcano is the highest of the Islands of Four Mountains group and is one of the most active in the Aleutians. Numerous large lava flows descend its flanks. It is possible that some 18th to 19th century eruptions attributed to Carlisle (a volcano located across the Carlisle Pass Strait to the NW) should be ascribed to Cleveland. In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions from Mt. Cleveland have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.
14.473°N, 90.880°W; summit elev. 3763 m
INSIVUMEH reported that during 20-24 July explosions from Fuego produced ash plumes that rose 200-400 m above the crater and drifted W and NW. Fumarolic plumes drifted the same direction. Glow radiated 100-150 m above the crater. Lava flows traveled 200-250 m down the Taniluyá (SW) drainage; detached blocks from the lava-flow fronts produced incandescent avalanches.
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 3,763-m-high Fuego and its twin volcano to the N, Acatenango. Construction of Meseta volcano continued until the late Pleistocene or early Holocene, after which growth of the modern Fuego volcano continued the southward migration of volcanism that began at Acatenango. Frequent vigorous historical eruptions have been recorded at Fuego since the onset of the Spanish era in 1524, and have produced major ash falls, along with occasional pyroclastic flows and lava flows. The last major explosive eruption from Fuego took place in 1974, producing spectacular pyroclastic flows visible from Antigua.
KARYMSKY, Eastern Kamchatka (Russia)
54.05°N, 159.45°E; summit elev. 1536 m
KVERT reported mostly weak seismic activity from Karymsky during 13-23 July. Satellite imagery showed a weak thermal anomaly on the volcano during 13-19 July. 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 about 7,600-7,700 radiocarbon years ago. Construction of the Karymsky stratovolcano began about 2,000 years later. The latest eruptive period began about 500 years ago, following a 2,300-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. Most seismicity preceding Karymsky eruptions has originated beneath Akademia Nauk caldera, which is located immediately S of Karymsky volcano and erupted simultaneously with Karymsky in 1996.
KILAUEA, Hawaii (USA)
19.421°N, 155.287°W; summit elev. 1222 m
During 18-24 July HVO reported that the circulating lava lake periodically rose and fell in the deep pit within Kilauea’s Halema’uma’u Crater. Measurements indicated that the gas plume from the vent continued to deposit variable amounts of spatter and Pele’s hair onto nearby areas. The lava pond in a small pit on the E edge of the Pu’u ‘O’o crater floor and two vents along the S edge of the floor were visible with the web cameras. Lava flows were active on the pali and the coastal plain; the active lava-flow front was about 1.9 km from the ocean on 24 July.
Geologic summary: Kilauea, one of five coalescing volcanoes that comprise the island of Hawaii, is one of the world’s most active volcanoes. Eruptions at Kilauea originate primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the caldera to the sea. About 90% of the surface of Kilauea is formed of lava flows less than about 1,100 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.
NEVADO DEL RUIZ, Colombia
4.895°N, 75.322°W; summit elev. 5321 m
According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 22-24 July low levels of tremor were detected at Nevado del Ruiz, possibly associated with continuing gas and ashemissions. Satellite imagery and ground-based observations on 22 July showed high levels of sulfur dioxide emissions. The Alert Level remained at II (Orange; “eruption likely within days or weeks”).
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 summit caldera of an older Ruiz volcano. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. Steep headwalls of massive landslides cut the flanks of Nevado del Ruiz. 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.
19.023°N, 98.622°W; summit elev. 5426 m
CENAPRED reported that during 18-23 July seismicity at Popocatépetl indicated continuing gas-and-ash emissions; cloud cover prevented observations during most of this period. Incandescence from the crater was periodically observed and sometimes increased with accompanying emissions. A steam-and-gas plume rose from the crater on 19 and 24 July, and ash-and-gas plumes were observed on 20 and 22 July. Activity increased for a period during 20-21 July; incandescent tephra was ejected 500 m above the crater and ashfall was reported in Ozumba (18 km W). The Alert Level remained at Yellow, Phase Three.
Geologic summary: Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5,426 m 70 km SE of Mexico City and is North America’s second-highest volcano. Frequent historical eruptions have been recorded since the beginning of the Spanish colonial era. A small eruption on 21 December 1994 ended five decades of quiescence. Since 1996 small lava domes have incrementally been constructed within the summit crater and destroyed by explosive eruptions. Intermittent small-to-moderate gas-and-ash eruptions have continued, occasionally producing ashfall in neighboring towns and villages.
31.585°N, 130.657°E; summit elev. 1117 m
JMA reported that during 20-23 July eight explosions from Sakura-jima’s Showa Crater ejected tephra as far as 1,300 m from the crater. Incandescence from the crater was visible at night during 22-23 July. Based on information from JMA, the Tokyo VAAC reported that explosions during 18-24 July produced plumes that rose to altitudes of 1.8-3.4 km (6,000-11,000 ft) a.s.l. and drifted in multiple directions. Pilots observed ash plumes on 22 and 24 July that rose to altitudes of 2.4-6.1 km (8,000-20,000 ft) a.s.l. JMA reported that an explosion on 24 July from Minami-dake Crater ejected tephra as far as 1,700 m from the crater.
Geologic summary: Sakura-jima, one of Japan’s most active volcanoes, is a post-caldera cone of the Aira calderaat the northern half of Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow was associated with the formation of the 17 x 23-km-wide Aira caldera about 22,000 years ago. The construction of Sakura-jima began about 13,000 years ago and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kita-dake summit cone ended about 4,850 years ago, after which eruptions took place at Minami-dake. 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.
2.002°S, 78.341°W; summit elev. 5230 m
According to the Washington VAAC, a pilot reported that a possible eruption from Sangay occurred prior to 1438 on 20 July. Ash was not observed in satellite imagery and a SIGMET issued for the event was later cancelled.
Geologic summary: The isolated Sangay volcano, located E of the Andean crest, is the southernmost of Ecuador’s volcanoes, and its most active. It has been in frequent eruption for the past several centuries. The steep-sided, 5,230-m-high glacier-covered volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the E, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. Sangay towers above the tropical jungle on the E side; on the other sides flat plains of ash from the volcano have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The more or less constant eruptive activity has caused frequent changes to the morphology of the summit crater complex.
SHIVELUCH, Central Kamchatka (Russia)
56.653°N, 161.360°E; summit elev. 3283 m
KVERT reported that during 13-21 July explosive activity at Shiveluch continued. Observers noted gas-and-steam activity during 12-13, 15-18, 21, and 23 July; weather conditions prevented observations of the volcano on the other days. Satellite imagery showed a thermal anomaly on the lava dome during 13-20 July. The Aviation Color Code remained at Orange.
Geologic summary: The high, isolated massif of Shiveluch volcano (also spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group and forms one of Kamchatka’s largest and most active volcanoes. The currently active Molodoy Shiveluch lava-dome complex was constructed during the Holocene within a large breached caldera formed by collapse of the massive late-Pleistocene Strary Shiveluch volcano. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Frequent collapses of lava-dome complexes, most recently in 1964, have produced large debris avalanches whose deposits cover much of the floor of the breached caldera. Intermittent explosive eruptions began in the 1990s from a new lava dome that began growing in 1980. The largest historical eruptions from Shiveluch occurred in 1854 and 1964.
SOUFRIERE HILLS, Montserrat
16.72°N, 62.18°W; summit elev. 915 m
MVO reported that during 13-20 July activity at the Soufrière Hills lava dome was at a low level. Heavy rain on the morning of 19 July generated lahars in several valleys on the W flank of the volcano. Lahars in the Belham valley (NW) were small and restricted to the upper reaches of the valley. The Hazard Level remained at 2 (on a scale of 1-5).
Geologic summary: The complex dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. English’s Crater, a 1-km-wide crater breached widely to the E, was formed during an eruption about 4,000 years ago in which the summit collapsed, producing a large submarine debris avalanche. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits at Soufrière Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.
1.467°S, 78.442°W; summit elev. 5023 m
IG reported that during 18-24 July visual observations of Tungurahua were limited due to cloud cover. On 20 July a steam plume drifted W, and on 21 July a steam plume rose 200 m above the crater and drifted the same direction. Many of the drainages contained muddy waters through the reporting period; a lahar descended the Mapayacu drainage (SW) on 23 July.
Geologic summary: The steep-sided Tungurahua stratovolcano towers more than 3 km above its northern base. It sits ~140 km S of Quito, Ecuador’s capital city, and is one of Ecuador’s most active volcanoes. Historical eruptions have all originated from the summit crater. They have been accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano’s base. The last major eruption took place from 1916 to 1918, although minor activity continued until 1925. The latest eruption began in October 1999 and prompted temporary evacuation of the town of Baños on the N side of the volcano.
Source: Global Volcanism Program
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