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GVP/USGS Weekly Volcanic Activity Report
14-20 March 2007
http://www.volcano.si.edu/reports/usgs/
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New Activity/Unrest: | Anatahan, Mariana Islands | Batu Tara, Indonesia
| Fuego, Guatemala | Merapi, Indonesia | Ruapehu, New Zealand |
Stromboli, Italy | Talang, Indonesia | Tungurahua, Ecuador
Ongoing Activity: | Bulusan, Philippines | Chikurachki, Russia |
Kilauea, USA | Manam, Papua New Guinea | Rabaul, Papua New Guinea |
Sakura-jima, Japan | Sangay, Ecuador | Soufrière Hills, Montserrat | St.
Helens, USA | Suwanose-jima, Japan | Ubinas, Perú
New Activity/Unrest
ANATAHAN Mariana Islands, central Pacific Ocean 16.35°N, 145.67°E;
summit elev. 788 m
USGS reported that seismicity from Anatahan increased on 24 February and
remained elevated through 17 March, occasionally punctuated by higher
levels of tremor and increased gas emissions. On 13 March, seismic
activity increased significantly; a gas plume that was visible on MODIS
satellite imagery suggested increased emissions. The next day the
Volcanic Alert Level was increased from Normal to Advisory. On 20 March,
low levels of tremor were recorded.
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=
BATU TARA Lesser Sunda Islands, Indonesia 7.792°S, 123.579°E; summit
elev. 748 m
Based on satellite imagery and CVGHM, the Darwin VAAC reported that
during 14-16 and 19-20 March emissions from Batu Tara produced diffuse
plumes that drifted NE, SE, and E. Plumes rose to 1.2 km (3,900 ft)
a.s.l. on 19 and 20 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.
Source: 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
INSIVUMEH reported that incandescent material from Fuego was ejected 200
m above the summit on 15 March. The activity was accompanied by rumbling
noises and shockwaves that vibrated windows several kilometers away. Two
lava flows were observed; one traveled about 1,500 m W toward the
Taniluyá River valley. An ash plume drifted S and SW. On 16 March,
Strombolian activity propelled material 300 m above the summit and
shockwaves were felt as far as 15 km away. The lava flows from 15 March
advanced and three more flows were observed in different ravines on 16
March. Ash plumes rose to an altitude of 5.4 km (17,799 ft) a.s.l. and
drifted S, SW, and E. Two pyroclastic flows traveled about 800 m; one NW
and another W and SW.
Based on pilot reports, INSIVUMEH reports, and satellite imagery, the
Washington VAAC reported that ash plumes reached altitudes of 4.1-6.1 km
(13,500-20,000 ft) a.s.l. during 15-16 March. A hotspot was visible on
satellite imagery both days.
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=
MERAPI central Java, Indonesia 7.542°S, 110.442°E; summit elev. 2,947 m
Based on pilot reports, the Darwin VAAC reported that an eruption plume
from Merapi reached an altitude of 6.1 km (20,000 ft) a.s.l. and drifted
NE on 19 March.
Geologic Summary. Merapi, one of Indonesia's most active volcanoes, lies
in one of the world's most densely populated areas and dominates the
landscape immediately N of the major city of Yogyakarta. The steep-sided
modern Merapi edifice, its upper part unvegetated due to frequent
eruptive activity, was constructed to the SW of an arcuate scarp cutting
the eroded older Batulawang volcano. Pyroclastic flows and lahars
accompanying growth and collapse of the steep-sided active summit lava
dome have devastated cultivated and inhabited lands on the volcano's
western-to-southern flanks and caused many fatalities during historical
time. The volcano is the object of extensive monitoring efforts by the
Merapi Volcano Observatory.
Source: Darwin Volcanic Ash Advisory Center
http://www.bom.gov.au/products/IDD41300.shtml
Merapi Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-25=
RUAPEHU North Island, New Zealand 39.28°S, 175.57°E; summit elev. 2,779 m
According to news articles, a “moderate” lahar from Ruapehu's crater
lake traveled E down the Whangaehu River valley on 18 March and reached
the sea 140 km away after a soft rock-and-ash dam was breached. The
section of dam that failed was about 40 m long and 7 m high. There were
no reports of injuries or major damage to infrastructure and only some
flooding to farmlands at the base of the volcano. The volume of water
and debris was estimated at 1.3 million cubic meters. On 19 March, IGNS
confirmed a 6-m drop in the crater lake level and reported an increase
in seismicity following the lahar.
Geologic Summary. Ruapehu, one of New Zealand's most active volcanoes,
is a complex stratovolcano constructed during at least four
cone-building episodes. The 110 cu km volcanic massif is elongated in a
NNE-SSW direction and is surrounded by another 100 cu km ring plain of
volcaniclastic debris. A single historically active vent, Crater Lake,
is located in the broad summit region, but at least five other vents on
the summit and flanks have been active during the Holocene. Frequent
mild-to-moderate explosive eruptions have occurred in historical time
from the Crater Lake vent. Lahars produced by phreatic eruptions from
the summit crater lake are a hazard to a ski area on the upper flanks
and to river valleys below the volcano.
Sources: New Zealand GeoNet Project http://data.geonet.org.nz/geonews/sab/,
Associated Press
http://abcnews.go.com/International/wireStory?id=2961085&CMP=OTC-RSSFeeds0312,
Stuff http://www.stuff.co.nz/stuff/3998184a10.html,
New Zealand Herald
http://www.nzherald.co.nz/event/story.cfm?c_id=1501171&objectid=10429739
Ruapehu Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0401-10=
STROMBOLI Aeolian Islands, Italy 38.79°N, 15.21°E; summit elev. 926 m
INGV-CT reported that the eruption at Stromboli that started on 27
February continued during 15 March. On 9 March, the vent at 400 m
elevation that fed the lava flows closed and another vent opened on the
N flank of the NE Crater at 550 m elevation. It remained active for less
than 24 hours. After it closed, the 400-m vent re-opened and lava again
flowed to the sea. On 15 March, a major explosion occurred during an
effusive flank eruption.
Geologic Summary. Spectacular incandescent nighttime explosions at
Stromboli volcano have long attracted visitors to the "Lighthouse of the
Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent
its name to the frequent mild explosive activity that has characterized
its eruptions throughout historical time. The small, 926-m-high island
of Stromboli is the emergent summit of a volcano that grew in two main
eruptive cycles, the last of which formed the western portion of the
island. The active summit vents are located at the head of the Sciara
del Fuoco, a horseshoe-shaped scarp formed as a result of slope failure
that extends to below sea level and funnels pyroclastic ejecta and lava
flows to the NW. Essentially continuous mild Strombolian explosions,
sometimes accompanied by lava flows, have been recorded at Stromboli
since Roman times.
Source: Istituto Nazionale di Geofisica e Vulcanologia Sezione di
Catania http://www.ct.ingv.it/
Stromboli Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0101-04=
TALANG Sumatra, Indonesia 00.98°S, 100.68°E; summit elev. 2,896 m
Based on information from CVGHM, the Darwin VAAC reported that on 19 and
20 March ash plumes from Talang rose 3.4-3.9 km (11,000-12,800 ft)
a.s.l. CVGHM raised the Alert Level to 3 (on a scale of 1-4).
Geologic Summary. Talang, which forms a twin volcano with the extinct
Pasar Arbaa volcano, has two crater lakes on its flanks. The largest of
these is 1 x 2 km wide Danau Talang. No historical eruptions have
occurred from the summit of the volcano, which lacks a crater. All
historical eruptions from Gunung Talang volcano have involved
small-to-moderate 19th-century explosive activity originating from a
series of small craters in a valley on the upper NE flank.
Source: Darwin Volcanic Ash Advisory Center
http://www.bom.gov.au/products/IDD41300.shtml
Talang Information from the Global Volcano Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0601-16=
TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m
IG reported that during 14-20 March, explosions from Tungurahua were
accompanied by noises that resembled "cannon shots." On 16, 18, and 20
March, explosions rattled windows at the observatory in Guadalupe, about
11 km N. Incandescent material was ejected 100-200 m above the summit on
14, 16, and 20 March and rolled 500-800 m down the flanks on 16,18, and
20 March. Ash plumes rose to altitudes of 6.5-12 km (21,300-39,400 ft)
a.s.l. during the reporting period and drifted mainly NW and W. Ashfall
was reported as far as Cotaló (13 km NW) on 16 March and from other
areas S, W, and NW during 14-20 March. Rainfall contributed to lahars in
valleys W and NW on 15 and 16 March.
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
BULUSAN Luzon, Philippines 12.770°N, 124.05°E; summit elev. 1,565 m
Based on news articles, ash fell on the SW slopes and villages near
Bulusan on 15 March. According to the interpretation of a resident
volcanologist, the ashfall was not caused by explosions, instead
voluminous steaming during 12-15 March “agitated the ash deposits on the
crater wall.”
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: The Philippine Star
http://www.abs-cbnnews.com/storypage.aspx?StoryId=70268
Bulusan Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0703-01=
CHIKURACHKI Kuril Islands, Russia 50.325°N, 155.458°E; summit elev. 1,816 m
AVO reported that a sulfur dioxide cloud from Chikurachki was seen on
satellite imagery on 16 March extending 580 km NW. The altitude of the
cloud was unknown.
Geologic Summary. Chikurachki, the highest volcano on Paramushir Island
in the northern Kuriles, is actually a relatively small cone constructed
on a high Pleistocene volcanic edifice. Oxidized scoria deposits
covering the upper part of the young cone give it a distinctive red
color. Lava flows from 1,816-m-high Chikurachki reached the sea and form
capes on the NW coast; several young lava flows also emerge from beneath
the scoria blanket on the eastern flank. The more erosionally modified
Tatarinov group of six volcanic centers is located immediately to the S
of Chikurachki. Tephrochronology gives evidence of only one eruption in
historical time from Tatarinov, although its southern cone contains a
sulfur-encrusted crater with fumaroles that were active along the margin
of a crater lake until 1959.
Source: Alaska Volcano Observatory http://www.avo.alaska.edu/
Chikurachki Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0900-36=
KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m
During 14-19 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. On 14 March, ‘a’a
flows from the Campout flow were seen on the pali. Tremor at Kilauea's
summit continued at low 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-
MANAM offshore New Guinea, Papua New Guinea 4.10°S, 145.06°E; summit
elev. 1,807 m
RVO reported that Manam's Main Crater emitted gray ash plumes during
11-19 March. The plumes rose to altitudes of 2.3 km (7,500 ft) a.s.l.
and drifted SE. Incandescence was visible the evenings of 11, 12, 16,
and 18 March. Vapor clouds and occasional diffuse ash clouds were
emitted from South Crater during 11-20 March.
According to a news article, four people were killed and one injured
from an “ash-and-mud” avalanche in a valley on the northern part of the
island. RVO received the report on 15 March, but had not yet confirmed
whether it was a mudflow.
Geologic Summary. The 10-km-wide island of Manam is one of Papua New
Guinea's most active volcanoes. Four large radial valleys extend from
the unvegetated summit of the conical 1,807-m-high stratovolcano to its
lower flanks. These "avalanche valleys," regularly spaced 90 degrees
apart, channel lava flows and pyroclastic avalanches that have sometimes
reached the coast. Five satellitic centers are located near the island's
shoreline. Two summit craters are present; both are active, although
most historical eruptions have originated from the southern crater,
concentrating eruptive products during the past century into the SE
avalanche valley. Frequent historical eruptions have been recorded since
1616.
Sources: Herman Patia, Rabaul Volcano Observatory,
Reuters http://www.planetark.org/dailynewsstory.cfm/newsid/40945/story.htm
Manam Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0501-02=
RABAUL New Britain Island, Papua New Guinea 4.271°S, 152.203°E; summit
elev. 688 m
RVO reported that during 13-21 March, Rabaul caldera's Tavurvur cone
emitted ash plumes that rose to 1.1-3.7 km (3,600-12,000 ft) a.s.l. and
drifted E, SE, S, and W. Loud roaring noises occasionally accompanied
emissions. During 16-21 March, multiple explosions occurred, some of
which produced shockwaves. Summit incandescence was observed at night
and lava fragments were projected onto the flanks. Ashfall was reported
from areas downwind during the reporting period.
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: Herman Patia, Rabaul Volcano Observatory
Rabaul Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-14=
SAKURA-JIMA Kyushu, Japan 31.58°N, 130.67°E; summit elev. 1,117 m
Based on information from JMA, the Tokyo VAAC reported that an ash plume
from Sakura-jima reached an altitude greater than 3.7 km (12,000 ft)
a.s.l. on 20 March.
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
Sakura-jima Information from the Global Volcanism Program
http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=0802-08=
SANGAY Ecuador 2.03°S, 78.34°W; summit elev. 5,188 m
Based on pilot reports and satellite imagery, the Washington VAAC
reported that an ash plume from Sangay on 17 March rose to an altitude
of 5.2 km (17,000 ft) a.s.l. A hotspot was visible on satellite imagery.
A pilot reported an ash plume on 20 March to an unreported altitude.
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=
SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev.
1,052 m
During 9-16 March, lava-dome growth at Soufrière Hills continued and was
concentrated on the NE side. Intermittent pyroclastic flows, possibly
originating from the large blocky spine on the edge of the E lobe,
traveled E down the Tar River Valley and produced large ash plumes. One
of the plumes on 12 March rose to an altitude of 3 km (10,000 ft) a.s.l.
and drifted NW. On 13 March, a steam-rich plume rose to 2.4 km (8,000
ft) a.s.l. and drifted W. By 14 March, the spine was completely shed. On
15 March, heavy rains caused mudflow activity in several drainages.
Pyroclastic flows were observed NW in Tyre’s Ghaut and ashfall was
reported from the Salem /Old Towne areas. On 16 March, pyroclastic flows
were observed in Tyre’s Ghaut and in the Tar River Valley. A resultant
ash plume drifted WNW. Based on satellite imagery, the Washington VAAC
reported that diffuse ash plumes drifted NW during 17-18 March.
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.
Sources: Montserrat Volcano Observatory http://www.mvo.ms/,
Washington Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/messages.html
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 showed that during 14-20
March, lava-dome growth and lava-spine extrusion at Mount St. Helens
continued. Seismicity persisted at low levels, punctuated by M 1.5-2.5
and occasionally larger earthquakes. Inclement weather 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-
SUWANOSE-JIMA Ryukyu Islands, Japan 29.53°N, 129.72°E; summit elev. 799 m
Based on information from JMA, the Tokyo VAAC reported an explosion from
Suwanose-jima on 17 March. Ash was not seen on satellite imagery.
Geologic Summary. The 8-km-long, spindle-shaped island of Suwanose-jima
in the northern Ryukyu Islands consists of an andesitic stratovolcano
with two historically active summit craters. Only about 50 persons live
on the sparsely populated island. The summit of the volcano is truncated
by a large breached crater extending to the sea on the E flank that was
formed by edifice collapse. Suwanose-jima, one of Japan’s most
frequently active volcanoes, was in a state of intermittent strombolian
activity from On-take, the NE summit crater, that began in 1949 and
lasted nearly a half century. The largest historical eruption took place
in 1813-14, when thick scoria deposits blanketed residential areas,
after which the island was uninhabited for around 70 years. The SW
crater produced lava flows that reached the western coast in 1813, and
lava flows reached the eastern coast of the island in 1884.
Source: Tokyo Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
Suwanose-jima Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0802-03=
UBINAS Perú 16.355°S, 70.903°W; summit elev. 5,672 m
Based on pilot reports, the Buenos Aires VAAC reported that an ash cloud
from Ubinas rose to 5.5-6.4 km (18,000-21,000 ft) a.s.l. on 14 March and
drifted SW.
Geologic Summary. A small, 1.2-km-wide caldera that cuts the top of
Ubinas, Peru's most active volcano, gives it a truncated appearance.
Ubinas is the northernmost of three young volcanoes located along a
regional structural lineament about 50 km behind the main volcanic front
of Peru. The upper slopes of the stratovolcano, composed primarily of
Pleistocene andesitic lava flows, steepen to nearly 45 degrees. The
steep-walled, 150-m-deep summit caldera contains an ash cone with a
500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche
deposits from the collapse of the SE flank of Ubinas extend 10 km from
the volcano. Widespread plinian pumice-fall deposits from Ubinas include
some of Holocene age. Holocene lava flows are visible on the volcano's
flanks, but historical activity, documented since the 16th century, has
consisted of intermittent minor explosive eruptions.
Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html
Ubinas Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1504-02
**+++++++++++++++++++++++++++++++++++++**
**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/>++++++++++++++++++++++++++++++++++++++++++
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