VOLCANO: Smithsonian/USGS Weekly Volcanic Activity Report 11-17 May 2011

[Kirsten Chojnicki <kchojnic@xxxxxxx>]

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Smithsonian/USGS Weekly Volcanic Activity Report 11-17 May 2011
From: Sally Kuhn Sennert <kuhns@xxxxxx>

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Smithsonian/USGS Weekly Volcanic Activity Report
11-17 May 2011

Sally Kuhn Sennert - Weekly Report Editor
kuhns@xxxxxx
URL: http://www.volcano.si.edu/reports/usgs/


New Activity/Unrest: | Aso, Kyushu | Bulusan, Luzon | Etna, Sicily 
(Italy) | Kizimen, Eastern Kamchatka (Russia) | Telica, Nicaragua | 
Tungurahua, Ecuador | Ulawun, New Britain | Yasur, Vanuatu (SW Pacific)

Ongoing Activity: | Bagana, Bougainville | Batu Tara, Komba Island 
(Indonesia) | Dukono, Halmahera | Karymsky, Eastern Kamchatka (Russia) |
 Katmai, Alaska Peninsula | Kilauea, Hawaii (USA) | Popocatépetl, México
 | Sakura-jima, Kyushu | Santa María, Guatemala | Shiveluch, Central 
Kamchatka (Russia) | Soufrière Hills, Montserrat


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


ASO Kyushu 32.881°N, 131.106°E; summit elev. 1592 m

Based on pilot observations, the Tokyo VAAC reported that on 15 May an 
ash plume from Aso rose to an altitude of 2.1 km (7,000 ft) a.s.l. and 
drifted NE. JMA reported that the next day plumes rose to altitudes of 
1.8-2.1 km (6,000-7,000 ft) a.s.l. A pilot noted that an ash plume rose 
to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted N that same day. 
During 17-18 May the JMA reported that ash plumes rose to an altitude of
 1.8 km (6,000 ft) a.s.l. and drifted E and SE.

Geologic Summary. The 24-km-wide Aso caldera was formed during four 
major explosive eruptions from 300,000 to 80,000 years ago. These 
produced voluminous pyroclastic flows that covered much of Kyushu. A 
group of 17 central cones was constructed in the middle of the caldera, 
one of which, Naka-dake, is one of Japan's most active volcanoes. It was
 the location of Japan's first documented historical eruption in 553 AD.
 The Naka-dake complex has remained active throughout the Holocene. 
Several other cones have been active during the Holocene, including the 
Kometsuka scoria cone as recently as about 210 AD. Historical eruptions 
have largely consisted of basaltic to basaltic-andesite ash emission 
with periodic Strombolian and phreatomagmatic activity. The summit 
crater of Naka-dake is accessible by toll road and cable car, and is one
 of Kyushu's most popular tourist destinations.

Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html


BULUSAN Luzon 12.770°N, 124.05°E; summit elev. 1565 m

On 13 May, PHIVOLCS reported that an explosion from Bulusan's summit 
crater was accompanied by a rumbling sound audible up to 5 km away. The 
event was recorded by the seismic network as an explosion-type 
earthquake lasting for about 10 minutes. Cloud cover prevented 
observations of the summit area. Field investigation conducted 
immediately after the explosion confirmed the presence of thin ash 
deposits (0.5- 2.5 mm) approximately 9 km away from the crater in the NW
 and SW sectors. Several barangays in the municipalities of Juban and 
Irosin reported light ashfall. The Alert Level remained at 1 (on a scale
 of 0-5). Entry into the permanent danger zone, defined by a 4-km radius
 around the volcano, was prohibited.

During 15-16 May the seismic network detected four earthquakes. Then, on
 16 May, the number of earthquakes rapidly increased to 80 in a 
seven-hour period. On 17 May PHIVOLCS reported that 144 earthquakes were
 recorded in the previous 24 hours. Steam rose from the active vents.

Geologic Summary. Luzon's southernmost volcano, Bulusan, was constructed
 within the 11-km-diameter dacitic Irosin caldera, which was formed more
 than 36,000 years ago. A broad, flat moat is located below the 
prominent SW caldera rim; 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 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/


ETNA Sicily (Italy) 37.734°N, 15.004°E; summit elev. 3330 m

Sezione di Catania - Osservatorio Etneo reported that on 8 May mild and 
discontinuous Strombolian activity resumed at the pit crater located on 
the E flank of Etna's SE Crater cone. On 11 May volcanic tremor 
amplitude progressively increased, and at about 2030 lava started to 
overflow the E crater rim. The activity intensified during the following
 hours and, shortly before 0400 on 12 May, culminated with lava 
fountaining which generated an ash cloud that drifted SSE. The lava 
fountaining lasted around 2 hours, showing a gradual diminution around 
0545; an abrupt drop in the volcanic tremor amplitude at 0610 marked the
 end of the eruptive activity.

Geologic Summary. Mount Etna, towering above Catania, Sicily's second 
largest city, has one of the world's longest documented records of 
historical volcanism, dating back to 1500 BC. Historical lava flows 
cover much of the surface of this massive basaltic stratovolcano, the 
highest and most voluminous in Italy. Two styles of eruptive activity 
typically occur at Etna. Persistent explosive eruptions, sometimes with 
minor lava emissions, take place from one or more of the three prominent
 summit craters, the Central Crater, NE Crater, and SE Crater. Flank 
eruptions, typically with higher effusion rates, occur less frequently 
and originate from fissures that open progressively downward from near 
the summit. A period of more intense intermittent explosive eruptions 
from Etna's summit craters began in 1995. The active volcano is 
monitored by the Instituto Nazionale di Geofisica e Volcanologia (INGV) 
in Catania.

Source: Sezione di Catania - Osservatorio Etneo http://www.ct.ingv.it/


KIZIMEN Eastern Kamchatka (Russia) 55.130°N, 160.32°E; summit elev. 2376 m

KVERT reported that on 5 and 11 May seismicity from Kizimen was high; 
seismic data was not collected the other days during 6-13 May because of
 technical problems. Satellite images showed a large bright thermal 
anomaly daily on the volcano. During 6-7 May, ash plumes drifted 45 km 
SE and gas-and-steam plumes drifted 59 km N. Ashfall formed a layer as 
thick as 1 mm in Milkovo village, 120 km SW, on 10 May. A The Aviation 
Color Code remained at Orange.

Geologic Summary. Kizimen is an isolated, conical stratovolcano that is 
morphologically similar to Mount St. Helens prior to its 1980 eruption. 
The summit of Kizimen consists of overlapping lava domes, and blocky 
lava flows descend the flanks of the volcano, which is the westernmost 
of a volcanic chain north of Kronotsky volcano. The 2,376-m-high Kizimen
 was formed during four eruptive cycles beginning about 12,000 years ago
 and lasting 2,000-3,500 years. The largest eruptions took place about 
10,000 and 8300-8400 years ago, and three periods of longterm lava-dome 
growth have occurred. The latest eruptive cycle began about 3,000 years 
ago with a large explosion and was followed by lava-dome growth lasting 
intermittently about 1,000 years. An explosive eruption about 1,100 
years ago produced a lateral blast and created a 1.0 x 0.7 km wide 
crater breached to the NE, inside which a small lava dome (the fourth at
 Kizimen) has grown. A single explosive eruption, during 1927-28, has 
been recorded in historical time.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php


TELICA Nicaragua 12.602°N, 86.845°W; summit elev. 1061 m

Based on reports from INETER, the Washington VAAC stated that emissions 
of gas-and-ash from Telica were detected and ash fell in areas 4 km N. 
Seismicity was elevated for a period of time.

Geologic Summary. Telica, one of Nicaragua's most active volcanoes, has 
erupted frequently since the beginning of the Spanish era. The Telica 
volcano group consists of several interlocking cones and vents with a 
general NW alignment. Sixteenth-century eruptions were reported at 
symmetrical Santa Clara volcano at the SW end of the Telica group. 
However, its eroded and breached crater has been covered by forests 
throughout historical time, and these eruptions may have originated from
 Telica, whose upper slopes in contrast are unvegetated. The steep-sided
 cone of 1061-m-high Telica is truncated by a 700-m-wide double crater; 
the southern crater, the source of recent eruptions, is 120 m deep. El 
Liston, immediately SE of Telica, has several nested craters. The 
fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of 
Telica, form a prominent geothermal area frequented by tourists, and 
geothermal exploration has occurred nearby.

Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html


TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m

IG reported that, although visual observations of Tungurahua during 
11-15 May were often limited due to cloud cover, gas-and-steam plumes 
were noted during 12-14 May that rose 200-300 m above the crater and 
drifted E, SE, W, and NW. A small explosion on 15 May produced an ash 
plume that rose 500 m above the crater and drifted E. An ash plume the 
next day rose 200 m and drifted E. On 16 May an ash plume rose to an 
altitude of 8 km (26,200 ft) a.s.l. and drifted E, NE, and N. 
Incandescent blocks were ejected from the crater and rolled up to 500 m 
down the flanks. Ashfall was reported in the region of the Negro river.

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: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/


ULAWUN New Britain 5.05°S, 151.33°E; summit elev. 2334 m

RVO reported that during 13-14 and 17 May gray-to-brown ash plumes rose 
above Ulawun. On 17 May the emissions were forceful for a short time and
 booming noises were reported. Light ashfall was reported in areas 
between Ubili in the NW and Voluvolu in the NE.

Geologic Summary. The symmetrical basaltic to andesitic Ulawun 
stratovolcano is the highest volcano of the Bismarck arc, and one of 
Papua New Guinea's most frequently active. Ulawun rises above the N 
coast of New Britain opposite Bamus volcano. The upper 1,000 m of the 
2,334-m-high volcano is unvegetated. A steep-walled valley cuts the NW 
side of the volcano, and a flank lava-flow complex lies to the S of this
 valley. Historical eruptions date back to the beginning of the 18th 
century. Twentieth-century eruptions were mildly explosive until 1967, 
but after 1970 several larger eruptions produced lava flows and basaltic
 pyroclastic flows, greatly modifying the summit crater.

Source: Rabaul Volcano Observatory (RVO)


YASUR Vanuatu (SW Pacific) 19.53°S, 169.442°E; summit elev. 361 m

On 12 May, the Vanuatu Geohazards Observatory reported that, based on 
information collected by the Vanuatu Meteorology and Geohazards 
Department, satellite imagery showed strong degassing from Yasur during 
the previous week. Residents living close to the volcano reported 
persistent strong explosions that were heard and felt on 12 May. The 
Vanuatu Volcano Alert Level (VVAL) remained at 2 (on a scale of 0-4).

Geologic Summary. Yasur, the best-known and most frequently visited of 
the Vanuatu volcanoes, has been in more-or-less continuous Strombolian 
and vulcanian activity since Captain Cook observed ash eruptions in 
1774. This style of activity may have continued for the past 800 years. 
Yasur is a mostly unvegetated pyroclastic cone with a nearly circular, 
400-m-wide summit crater. Yasur is largely contained within the small 
Yenkahe caldera in SE Tanna Island. It is the youngest of a group of 
Holocene volcanic centers constructed over the down-dropped NE flank of 
the Pleistocene Tukosmeru volcano. Active tectonism along the Yenkahe 
horst accompanying eruptions of Yasur has raised Port Resolution harbor 
more than 20 m during the past century.

Source: Vanuatu Geohazards Observatory http://www.geohazards.gov.vu/


Ongoing Activity


BAGANA Bougainville 6.140°S, 155.195°E; summit elev. 1750 m

Based on analyses of satellite imagery, the Darwin VAAC reported that on
 16 May an ash plume from Bagana rose to an altitude of 2.1 km (7,000 
ft) a.s.l. and drifted 55 km NE.

Geologic Summary. Bagana volcano, occupying a remote portion of central 
Bougainville Island, is one of Melanesia's youngest and most active 
volcanoes. Bagana is a massive symmetrical lava cone largely constructed
 by an accumulation of viscous andesitic lava flows. The entire lava 
cone could have been constructed in about 300 years at its present rate 
of lava production. Eruptive activity at Bagana is 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.

Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html


BATU TARA Komba Island (Indonesia) 7.792°S, 123.579°E; summit elev. 748 m

Based on analyses of satellite imagery, the Darwin VAAC reported that on
 15 and 17 May ash plumes from Batu Tara rose to an altitude of 1.8 km 
(6,000 ft) a.s.l. and drifted 75-130 km W and NW.

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.

Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html


DUKONO Halmahera 1.68°N, 127.88°E; summit elev. 1335 m

Based on analyses of satellite imagery, the Darwin VAAC reported that 
during 11-12 May ash plumes from Dukono rose to an altitude of 4.3 km 
(14,000 ft) a.s.l. and drifted 75-110 km NE and E. On 16 May an ash 
plume rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted over 90
 km E.

Geologic Summary. Reports from this remote volcano in northernmost 
Halmahera are rare, but Dukono has been one of Indonesia's most active 
volcanoes. More-or-less continuous explosive eruptions, sometimes 
accompanied by lava flows, occurred from 1933 until at least the 
mid-1990s, when routine observations were curtailed. During a major 
eruption in 1550, a lava flow filled in the strait between Halmahera and
 the N-flank cone of Gunung Mamuya. Dukono is a complex volcano 
presenting a broad, low profile with multiple summit peaks and 
overlapping craters. Malupang Wariang, 1 km SW of Dukono's 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) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html


KARYMSKY Eastern Kamchatka (Russia) 54.05°N, 159.45°E; summit elev. 1536 m

KVERT reported moderate seismic activity at Karymsky during 6-13 May. 
Possible ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. on 10
 May and to an altitude of 4.2 km (13,800 ft) a.s.l. on the other days. 
Pilots reported that on 6 May ash plumes rose to an altitude of 3 km 
(9,800 ft) a.s.l. Satellite imagery showed a thermal anomaly and ash 
plumes that drifted 340 km E during 6-7 May. 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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php


KATMAI Alaska Peninsula 58.280°N, 154.963°W; summit elev. 2047 m

Based on analysis of satellite imagery, pilot observations, KVERT 
reports, and information from AVO, the Anchorage VAAC reported that on 
11 May strong winds in the Katmai area re-suspended loose ash deposited 
during the 1912 eruption. The Volcano Alert Level remained at Normal and
 the Aviation Color Code remained at Green.

Geologic Summary. Prior to 1912, Mount Katmai was a compound 
stratovolcano with four NE-SW-trending summits, most of which were 
truncated by caldera collapse in that year. Most of the two overlapping 
pre-1912 Katmai volcanoes are Pleistocene in age, but Holocene lava 
flows from a flank vent descend the SE flank of the SW stratovolcano 
into the Katmai River canyon. Katmai was initially considered to be the 
source of the Valley of Ten Thousand Smokes ash flow in 1912. However, 
the 3 x 4 km wide caldera of 1912 is now known to have formed as a 
result of the voluminous eruption at nearby Novarupta volcano. The steep
 walled young caldera has a jagged rim that rises 500-1,000 m above the 
caldera floor and contains a 250-m-deep, still-rising lake. Lake waters 
have covered a small post-collapse lava dome (Horseshoe Island) that was
 seen on the caldera floor at the time of the initial ascent to the 
caldera rim in 1916. Post-1912 glaciers have formed on a bench within 
Katmai caldera.

Source: Anchorage Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AK/messages.html


KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m

HVO reported that two lava lakes at Kilauea were active during 11-17 
May. The level of the summit lava lake fluctuated but remained mostly 
stable deep in the vent inset within the E wall of Halema'uma'u Crater. 
Lava from a vent above the south side cascaded down into the lake. A gas
 plume from the vent generally drifted SW or W and deposited very small 
amounts of ash nearby. At Pu'u 'O'o crater, lava mostly from vents near 
the W edge of the lake continued to fill in a perched lava lake in the 
center of the crater floor. The lake level fluctuated and occasionally 
overflowed the edges, sending lava onto the Pu'u 'O'o crater floor.

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.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO) http://hvo.wr.usgs.gov/


POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m

CENAPRED reported steam-and-gas emissions from Popocatépetl during 11-17
 May. The emissions occasionally contained small amounts of ash during 
14-17 May.

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.

Source: Centro Nacional de Prevencion de Desastres (CENAPRED) http://www.cenapred.unam.mx/es/


SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m

Based on information from JMA, the Tokyo VAAC reported that during 11-18
 May explosions from Sakura-jima sometimes produced plumes that rose to 
altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. Plumes occasionally 
drifted SE and S. During 11, 13-14, and 17 May, pilots observed ash 
plumes that rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l.

Geologic Summary. Sakura-jima, one of Japan's most active volcanoes, is a
 post-caldera cone of the Aira caldera at 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.

Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html


SANTA MARIA Guatemala 14.756°N, 91.552°W; summit elev. 3772 m

INSIVUMEH reported that during 12-13 May explosions from Santa María's 
Santiaguito lava dome complex produced ash plumes that rose 900 m above 
Caliente dome and drifted SE, depositing fine ash in areas downwind. 
During 14-15 May explosions produced ash plumes that rose 2 km above 
Caliente dome. Pyroclastic flows descended the SW and E flanks. Rumbling
 noises and block avalanches were also noted. Ash was deposited on the 
E, S, SW, and W flanks including the communities of Loma Linda, San 
Marcos, and Palajunoj. During 16-17 May explosions produced ash plumes 
that rose 0.7-1 km above Caliente dome and drifted SW. A pyroclastic 
flow traveled E.

Geologic Summary. Symmetrical, forest-covered Santa María volcano is one
 of a chain of large stratovolcanoes that rises dramatically above the 
Pacific coastal plain of Guatemala. The stratovolcano has a 
sharp-topped, conical profile that is cut on the SW flank by a large, 
1-km-wide crater, which formed during a catastrophic eruption in 1902 
and extends from just below the summit to the lower flank. The renowned 
Plinian eruption of 1902 followed a long repose period and devastated 
much of SW Guatemala. The large 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, accompanied by almost continuous minor 
explosions and periodic lava extrusion, larger explosions, pyroclastic 
flows, and lahars.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/


SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m

KVERT reported that during 5-7 May seismic data at Shiveluch indicated 
that possible ash plumes rose to an altitude of 3.9 km (12,800 ft) 
a.s.l. According to ground-based observations ash plumes rose to an 
altitude of 7.5 km (24,600 ft) a.s.l. on 7 May and to altitudes of 3-4 
km (9,800-13,100 ft) a.s.l. during 5-6 and 8 May. Satellite imagery 
showed ash plumes drifting 196 km N during 5-6 May. On 7 May small ash 
clouds drifted S and SE, and gas-and-steam plumes drifted 230 km E. A 
thermal anomaly was detected during 7-8 May. KVERT noted that the 
Aviation Color Code remained at Orange. Based on information from KEMSD,
 the Tokyo VAAC reported that on 15 May an eruption produced a plume 
that rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted E.

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.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php,
Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html


SOUFRIERE HILLS Montserrat 16.72°N, 62.18°W; summit elev. 915 m

MVO reported that during 6-13 May activity at the Soufrière Hills lava 
dome was at a low level. On 11 May a pyroclastic flow that occurred in 
the February 2010 collapse scar traveled about 1 km. An ash cloud rose 
1.8 km and drifted NNE, causing light ashfall in Lookout village. The 
Hazard Level remained at 3.

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.

Source: Montserrat Volcano Observatory (MVO) http://www.mvo.ms/

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