*********************************************************
GVP/USGS Weekly Volcanic Activity Report
21-27 March 2007
http://www.volcano.si.edu/reports/usgs/
*********************************************************
New Activity/Unrest: | Batu Tara, Indonesia | Fuego, Guatemala |
Reventador, Ecuador | Tungurahua, Ecuador
Ongoing Activity: | Anatahan, Mariana Islands | Colima, México | Ebeko,
Russia | Galeras, Colombia | Karymsky, Russia | Kilauea, USA |
Kliuchevskoi, Russia | Rabaul, Papua New Guinea | Sangay, Ecuador |
Santa María, Guatemala | Shiveluch, Russia | Soufrière Hills, Montserrat
| St. Helens, USA
New Activity/Unrest
BATU TARA Lesser Sunda Islands, Indonesia 7.792°S, 123.579°E; summit
elev. 748 m
Based on reports from fishermen and people in coastal communities about
50 km away, CVGHM reported that eruption plumes from Batu Tara rose to
altitudes of 1.2-2.2 km (3,900-7,200 ft) a.s.l. and drifted E during
18-19 March. In response, the Alert Level was raised from 1 to 2 (on a
scale of 1-4). Based on information from CVGHM and satellite imagery,
the Darwin VAAC reported that continuous diffuse plumes rose to 1.5 km
(5,000 ft) a.s.l. and drifted mainly SE during 21-27 March.
Geologic Summary. The small isolated island of Batu Tara in the Flores
Sea about 50 km north of 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 only known historical eruption from Batu Tara, during 1847-52,
produced explosions and a lava flow.
Sources: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://portal.vsi.esdm.go.id/joomla/,
Darwin Volcanic Ash Advisory Center
http://www.bom.gov.au/info/vaac/advisories.shtml
Batu Tara Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0604-26=
FUEGO Guatemala 14.47°N, 90.88°W; summit elev. 3,763 m
Based on satellite imagery, the Washington VAAC reported that a small
plume from Fuego drifted E on 21 March. During 21-22, 24, and 26-27
March, INSIVUMEH reported that explosions produced gas-and-ash plumes
that rose to altitudes of 4.7-5.1 km (15,400-16,700 ft) a.s.l. Ashfall
was reported from areas 5-8 km SSE and 9 km W. On 24 March, explosions
were followed by lava blocks rolling down the W flank toward the
Taniluyá River valley and gas emissions. Resultant plumes drifted 15 km
SW. Similar activity on 26 March caused ashfall in areas 10-25 km away
to the W and SE. On 27 March, the Washington VAAC reported that another
small plume was visible on satellite imagery drifting W.
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 ashfalls,
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.
Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e
Hidrologia (INSIVUMEH)
http://www.insivumeh.gob.gt/geofisica/boletin%20formato.htm,
Washington Volcanic Ash Advisory Center
http://www.ssd.noaa.gov/VAAC/messages.html
Fuego Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-09=
REVENTADOR Ecuador 0.078°S, 77.656°W, summit elev. 3,562 m
IG reported that during early March, the number of tectonic earthquakes
from Reventador increased. Steam-and-ash plumes were sporadically
visible and rose to altitudes of 4 km (13,000 ft) a.s.l. occasionally
during 8-22 March. On 21 March, noises were reported. The next day,
seismic signals changed and indicated possible emissions. On 24 March,
local people saw ash plumes and incandescent material near the crater
and heard roaring noises. An explosion produced a plume that rose to an
altitude of 6.6 km (21,700 ft) a.s.l. and drifted W. Based on reports
from IG, the Washington VAAC reported an ash plume to altitudes of 3.7-7
km (12,000-23,000 ft) a.s.l. that drifted NE and WNW during 26-27 March.
A thermal anomaly was present on satellite imagery during 24-27 March.
Geologic Summary. Reventador is the most frequently active of a chain of
Ecuadorian volcanoes in the Cordillera Real, well E of the principal
volcanic axis. It is a forested stratovolcano that rises above the
remote jungles of the western Amazon basin. A 3-km-wide caldera breached
to the E was formed by edifice collapse and is partially filled by a
young, unvegetated stratovolcano that rises about 1,300 m above the
caldera floor. Reventador 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.
Sources: Instituto Geofisico-Escuela Poltecnica Nacional
http://www.igepn.edu.ec/,
Washington Volcanic Ash Advisory Center
http://www.ssd.noaa.gov/VAAC/messages.html
Reventador Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-01=
TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m
IG reported that during 21-27 March, constant emissions of ash and steam
from Tungurahua produced plumes that rose to altitudes of 7-10 km
(23,000-32,800 ft) a.s.l. and drifted mainly W, NW, and N. Ashfall was
reported from areas downwind and from areas SW within 8 km, on all days
except 25 and 27 March. Noises resembling "cannon shots" and blocks
rolling down the flanks were heard on 21, 22, and 25 March; windows
rattled as far away as 11 km N in Guadalupe. On 23 March, lahars
traveled mainly down NW gorges and affected the roads between Ambato and
Baños, and between Baños and Penipe.
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 been restricted to 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 Poltécnica Nacional
http://www.igepn.edu.ec/
Tungurahua Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08=
Ongoing Activity
ANATAHAN Mariana Islands, central Pacific Ocean 16.35°N, 145.67°E;
summit elev. 788 m
On 25 March, USGS reported that the Volcanic Alert Level at Anatahan was
decreased from Advisory to Normal. Seismicity returned to low levels on
17 March. A gas-and-steam plume that was visible on MODIS imagery on 13
March remained present but diffuse during 17-25 March.
Geologic Summary. The elongate, 9-km-long island of Anatahan in the
central Mariana Islands consists of large stratovolcano with a 2.3 x 5
km, E-W-trending compound summit caldera. The larger western caldera is
2.3 x 3 km wide, and its western rim forms the island's 790-m high
point. Ponded lava flows overlain by pyroclastic deposits fill the floor
of the western caldera, whose SW side is cut by a fresh-looking smaller
crater. The 2-km-wide eastern caldera contained a steep-walled inner
crater prior to the 2003 eruption whose floor was only 68 m above sea
level. Sparseness of vegetation on the most recent lava flows on
Anatahan had indicated that they were of Holocene age, but the first
historical eruption of Anatahan did not occur until May 2003, when a
large explosive eruption took place forming a new crater inside the
eastern caldera.
Source: Emergency Management Office of the Commonwealth of the Mariana
Islands and the US Geological Survey Hawaiian Volcano Observatory
http://hvo.wr.usgs.gov/cnmi/index.html
Anatahan Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0804-20=
COLIMA Western México 19.514°N, 103.62°W; summit elev. 3,850 m
During 21-27 March, incandescent material from Colima was expelled as
high as 50-150 m above the summit. Steam and steam-and-ash plumes rose
to altitudes of 4.3-4.9 km (14,100-16,100 ft) a.s.l. and drifted SW, NW,
and N. Based on information from Mexico City MWO and satellite imagery,
the Washington VAAC reported ash plumes to altitudes of 5.2 km (17,000
ft) a.s.l. that drifted NE during 23-24 March.
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 4,320 m high point
of the complex) on the N and the historically active Volcán de Colima on
the S. Volcán de Colima (also known as Volcán Fuego) is a youthful
stratovolcano constructed within a 5-km-wide caldera, breached to the S,
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.
Sources: Gobierno del Estado de Colima
http://www.colima-estado.gob.mx/2006/seguridad/indvolcan.php,
Washington Volcanic Ash Advisory Center
http://www.ssd.noaa.gov/VAAC/messages.html
Colima Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1401-04=
EBEKO Kuril Islands, Russia 50.68°N, 156.02°E; summit elev. 1,156 m
According to a news article, gas-and-steam clouds from Ebeko rose to
1.3-1.5 km (4,100-4,800 ft) a.s.l. on 22 March. Nearby residents
reported smelling sulfur and chlorine.
Geologic 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. The eastern part of the southern crater of Ebeko
contains strong solfataras and a large boiling spring. The central
crater of Ebeko 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 of Ebeko, on the outer flanks of the cone, and in lateral
explosion craters.
Source: RIA Novosti http://en.rian.ru/russia/20070322/62412666.html
Ebeko Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0900-38=
GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4,276 m
On 20 March, INGEOMINAS reported that the Alert Level for Galeras was
decreased from 2 (probable eruption in days to weeks) to 3 (changes in
the behavior of volcanic activity have been noted) on a scale of 4-1 due
to decreased seismicity, low gas emissions, and no indication of changes
below the surface of the lava dome.
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.
Long-term 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.
Source: Instituto Colombiano de Geología y Minería
http://www.ingeominas.gov.co/
Galeras Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1501-08=
KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m
Seismic activity at Karymsky increased on 23 March. Ash plumes may have
reached altitudes of 4.6 km (15,000 ft) a.s.l., although no visual
observations were reported. Diffuse emissions were seen on satellite
imagery.
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: Alaska Volcano Observatory http://www.avo.alaska.edu/
Karymsky Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-13=
KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m
During 21-27 March, lava from Kilauea continued to flow across lava
deltas into the ocean at the East Lae'apuki and Kamokuna entries.
Incandescence was intermittently visible from several breakouts on the
pali and from several vents in Pu’u 'O'o's crater. A few small
earthquakes were located in the summit and Poliokeawe (South Flank)
areas. On 27 March, a’a’ flows were active on the pali. Tremor at Pu'u
'O'o' continued at moderate levels.
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 by
lava flows less than about 1,100 years old; 70% of the volcano's surface
is younger than 600 years. The latest Kilauea eruption began in January
1983 along the E rift zone. This long-term ongoing eruption from Pu`u
`O`o-Kupaianaha has produced lava flows that have traveled 11-12 km from
the vents to the sea, paving broad areas on the S flank of Kilauea and
adding new land beyond the former coastline.
Source: US Geological Survey Hawaiian Volcano Observatory
http://volcano.wr.usgs.gov/hvostatus.php
Kilauea information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1302-01-
KLIUCHEVSKOI Kamchatka Peninsula, Russia 56.06°N, 160.64°E; summit elev.
4,835 m
Strombolian activity from Kliuchevskoi was observed during 16-18
February and 21-22 March. Lava bombs were ejected about 50-100 m above
the crater. Clouds inhibited visual observations during most of February
and March, but a thermal anomaly was detected on satellite imagery each
day.
Geologic Summary. Kliuchevskoi is Kamchatka's highest and most active
volcano. Since its origin about 7,000 years ago, the beautifully
symmetrical, 4,835-m-high basaltic stratovolcano has produced frequent
moderate-volume explosive and effusive eruptions without major periods
of inactivity. More than 100 flank eruptions have occurred during the
past 3,000 years, mostly on the NE and SE flanks of the conical volcano
between 500 m and 3,600 m elevation. The morphology of its 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 major explosive and effusive eruptions from flank craters.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) via the
Volcano Listserv http://www.volcano.si.edu/reports/volclist/index.htm
Kliuchevskoi Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-26=
RABAUL New Britain Island, Papua New Guinea 4.271°S, 152.203°E; summit
elev. 688 m
RVO reported that during 21-26 March, Rabaul caldera's Tavurvur cone
emitted steam and steam-and-ash plumes that rose to 1-2.7 km
(3,300-8,900 ft) a.s.l. and drifted E and SE. Roaring noises
occasionally accompanied emissions. Incandescent material that was
expelled during explosions landed on and rolled down the flanks. On 25
March, explosions shook buildings in Rabaul town.
Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle
Peninsula at the NE end of New Britain forms a broad sheltered harbor.
The outer flanks of the 688-m-high asymmetrical pyroclastic shield
volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km
caldera is widely breached on the E, where its floor is flooded by
Blanche Bay. Two major Holocene caldera-forming eruptions at Rabaul took
place as recently as 3,500 and 1,400 years ago. Three small
stratovolcanoes lie outside the northern and NE caldera rims.
Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on
the caldera floor near the NE and western caldera walls. Several of
these, including Vulcan cone, which was formed during a large eruption
in 1878, have produced major explosive activity during historical time.
A powerful explosive eruption in 1994 occurred simultaneously from
Vulcan and Tavurvur volcanoes and forced the temporary abandonment of
Rabaul city.
Source: Steve Saunders, Rabaul Volcano Observatory
Rabaul Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-14=
SANGAY Ecuador 2.03°S, 78.34°W; summit elev. 5,188 m
Based on information from IG, the Washington VAAC reported that an ash
plume from Sangay was present on 22 March. The altitude and drift
direction of the plume were not reported.
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.
Source: Washington Volcanic Ash Advisory Center
http://www.ssd.noaa.gov/VAAC/messages.html
Sangay Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-09=
SANTA MARÍA Guatemala 14.756°N, 91.552°W; summit elev. 3,772 m
INSIVUMEH reported that explosions from Santa María's Santiaguito lava
dome complex produced ash-and-steam plumes that rose to altitudes of
3.8-4.8 km (12,500-15,700 ft) a.s.l. during 21-22 and 25 March and
drifted W. Ashfall was reported from nearby areas. On 25 and 26 March,
avalanches occurred from lava-flow fronts on the SW flanks of Caliente
Dome. On 27 March, an explosion produced a pyroclastic flow that
traveled down the SW flank.
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.
Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e
Hidrologia (INSIVUMEH)
http://www.insivumeh.gob.gt/geofisica/boletin%20formato.htm,
Washington Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/messages.html
Santa María Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-03=
SHIVELUCH Kamchatka Peninsula, Russia 56.653°N, 161.360°E; summit elev.
3,283 m
Based on satellite imagery, the Tokyo VAAC reported that emissions of
gas and steam from Shiveluch continued on 22 March. Ash was not
identified on satellite imagery.
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 horseshoe-shaped 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. During the 1990s,
intermittent explosive eruptions took place from a new lava dome that
began growing in 1980. The largest historical eruptions from Shiveluch
occurred in 1854 and 1964.
Source: Tokyo Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
Shiveluch Information from the Global Volcanism Program
http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1000-27=
SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev.
1,052 m
During 16-26 March, lava-dome growth at Soufrière Hills continued and
was concentrated on the NE side. Pyroclastic flows mainly affected the
sector from the ENE to the NW of the dome and traveled intermittently E
down the Tar River Valley. Small flows (<500 m in length) occurred NW in
Tyres Ghaut, and one flow was observed at the top of Farrell's Plain. On
18 March, steam venting following heavy rains was observed NW on Cork Hill.
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 east, was formed during an eruption about 4000 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 http://www.mvo.ms/
Soufrière Hills Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1600-05=
ST. HELENS Washington, USA 46.20°N, 122.18°W; summit elev. 2,549 m
Data from deformation-monitoring instruments and observations from a
remote camera showed that during 21-27 March lava-dome growth at Mount
St. Helens continued. Seismicity persisted at low levels, punctuated by
M 1.5-2.5 and occasionally larger earthquakes. Clouds occasionally
inhibited visual observations.
Geologic Summary. Prior to 1980, Mount St. Helens formed a conical,
youthful volcano sometimes known as the Fuji-san of America. During the
1980 eruption the upper 400 m of the summit was removed by slope
failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially
filled by a lava dome. Mount St. Helens was formed during nine eruptive
periods beginning about 40-50,000 years ago, and has been the most
active volcano in the Cascade Range during the Holocene. The modern
edifice was constructed during the last 2,200 years, when the volcano
produced basaltic as well as andesitic and dacitic products from summit
and flank vents. Historical eruptions in the 19th century originated
from the Goat Rocks area on the N flank, and were witnessed by early
settlers.
Source: US Geological Survey Cascades Volcano Observatory
http://vulcan.wr.usgs.gov/Volcanoes/MSH/CurrentActivity/framework.html
St. Helens Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1201-05-
**+++++++++++++++++++++++++++++++++++++**
**Sally Kuhn Sennert**
**SI/USGS Weekly Volcanic Activity Report Editor**
**Global Volcanism Program**
http://www.volcano.si.edu/reports/usgs/
Smithsonian Institution, National Museum of Natural History
Department of Mineral Sciences, MRC-119
Washington, D.C., 20560
Phone: 202.633.1805
Fax: 202.357.2476
<http://www.volcano.si.edu/reports/usgs/>++++++++++++++++++++++++++++++++++++++++++
==============================================================
To unsubscribe from the volcano list, send the message:
signoff volcano
to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx
To contribute to the volcano list, send your message to:
volcano@xxxxxxxx Please do not send attachments.
==============================================================
