*************************************************************
GVP/USGS Weekly Volcanic Activity Report
11-17 April 2007
http://www.volcano.si.edu/reports/usgs/
*************************************************************
New Activity/Unrest: | Concepción, Nicaragua | Etna, Italy | Nevado del
Huila, Columbia | Piton de la Fournaise, Reunion Island | Reventador,
Ecuador
Ongoing Activity: | Batu Tara, Indonesia | Colima, México | Karymsky,
Russia | Kilauea, USA | Kliuchevskoi, Russia | Rabaul, Papua New Guinea
| Santa María, Guatemala | Shiveluch, Russia | Soufrière Hills,
Montserrat | St. Helens, USA | Tungurahua, Ecuador | Ubinas, Perú
New Activity/Unrest
CONCEPCIÓN Nicaragua 11.538°N, 85.622°W; summit elev. 1,700 m
INETER reported that explosions in the crater of Concepción on 8 April
produced an ash-and-gas plume that rose to an altitude of 2.7 km (8,900
ft) a.s.l. and drifted W.
Geologic Summary. Volcán Concepción is one of Nicaragua's highest
volcanoes and is also one of its most active. The symmetrical volcano
forms the NW half of the dumbbell-shaped island of Ometepe in Lake
Nicaragua. Concepción is connected to neighboring Madera volcano by a
narrow isthmus. N-S-trending fractures cutting across the volcano are
associated with spatter cones, cinder cones, and maars located on the
middle N flank and on the lower S flank down to Lake Nicaragua.
Concepción has had frequent moderate explosive eruptions in the past
century, most of which have originated from a small summit crater.
Source: Instituto Nicaragüense de Estudios Territoriales (INETER)
http://www.ineter.gob.ni/
Concepción Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1404-12=
ETNA Sicily, Italy 37.73°N, 15.00°E; summit elev. 3,315 m
A summit eruption that occurred at Etna on 11 April began with an
increase in volcanic tremor and was followed by lava fountaining. A
resultant ash plume drifted E; ashfall was reported as far as Zafferana,
about 10 km to the E. Two lava flows were observed at the summit of
Etna, one towards the E within the Valle del Bove, and the second to the
S. The E lava flow stopped 3 km away at the base of the Serra Giannicola
Grande, within the W Valle del Bove. The second flow stopped near Mt.
Frumento Supino (less than 1 km S of the summit). The INGV-CT monitoring
web cameras showed that the eruption lasted about 5 hours.
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: Istituto Nazionale di Geofisica e Vulcanologia Sezione di
Catania http://www.ct.ingv.it/
Etna Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0101-06=
NEVADO DEL HUILA Columbia 2.93°N, 76.03°W; summit elev. 5,365 m ; All
times are local (= UTC -4 hours)
According to the Washington VAAC, a pilot reported an ash plume from
Nevado del Huila on 17 April. An ash plume that was evident on satellite
imagery at 0415 rose to an approximate altitude of 11.3 km (37,000 ft)
a.s.l. and drifted E. An additional plume drifted SW. Later that day,
INGEOMINAS reported increased seismicity. At 0257 on 18 April,
INGEOMINAS reported an eruptive event. Based on a news article, an
eruption triggered landslides and swelled rivers. About 5,000 people
evacuated from areas to the S.
Geologic Summary. Nevado del Huila, the highest active volcano in
Colombia, is an elongated N-S-trending volcanic chain mantled by a
glacier icecap. The andesitic-dacitic volcano was constructed within a
10-km-wide caldera. Volcanism at Nevado del Huila has produced six
volcanic cones whose ages in general migrated from south to north. Two
glacier-free lava domes lie at the southern end of the Huila volcanic
complex. The first historical eruption from this little known volcano
took place in the 16th century. Two persistent steam columns rise from
the central peak, and hot springs are also present.
Sources: Instituto Colombiano de Geología y Minería (INGEOMINAS)
http://www.ingeominas.gov.co/,
Washington Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/messages.html,
Mail and Guardian Online
http://www.mg.co.za/articlepage.aspx?area=/breaking_news/breaking_news__international_news/&articleid=305130
Nevado del Huila Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1501-05=
PITON DE LA FOURNAISE Réunion Island, Indian Ocean 21.23°S, 55.71°E;
summit elev. 2,631 m
OVPDLF reported that the eruption of Piton de la Fournaise from the
S-part of Grand Brûlé continued during 11-17 April. On 12 and 13 April,
strong seismicity was followed by emissions; a gray plume from the
summit of Dolomieu crater drifted NW. Also on 13 April, lava fountaining
increased and resulted in several broad lava flows moving towards the
sea. On 14 April, projected material reached 100-200 m above the point
of emission.
Geologic Summary. The massive Piton de la Fournaise shield volcano on
the island of Réunion is one of the world's most active volcanoes. Most
historical eruptions have originated from the summit and flanks of
Dolomieu, a 400-m-high lava shield that has grown within the youngest of
three large calderas. This latter caldera is 8 km wide and is breached
to below sea level on the eastern side. More than 150 eruptions, most of
which have produced fluid basaltic lava flows within the caldera, have
been documented since the 17th century.
Sources: Observatoire Volcanologique du Piton de la Fournaise (OVPDLF)
http://ovpf.univ-reunion.fr/,
Thomas Staudacher, Observatoire Volcanologique du Piton de la Fournaise
(OVPDLF) via the Volcano Listserv
http://www.volcano.si.edu/reports/volclist/
Piton de la Fournaise Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0303-02=
REVENTADOR Ecuador 0.078°S, 77.656°W, summit elev. 3,562 m
On 11 April, a steam plume from Reventador rose to an altitude of 3.8 km
(12,500 ft) a.s.l. Visual observations were hindered during 12-17 April
due to inclement weather. On 13 April, the lava flow on the S flank,
first observed on 28 March, was 15 m thick and possibly active.
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.
Source: Instituto Geofísico-Escuela Politécnica Nacional
http://www.igepn.edu.ec/
Reventador Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-01=
Ongoing Activity
BATU TARA Lesser Sunda Islands, Indonesia 7.792°S, 123.579°E; summit
elev. 748 m
Based on satellite imagery and direct observations by CVGHM, the Darwin
VAAC reported that on 11 April a diffuse plume from Batu Tara rose to an
altitude of 1.5 km (5,000 ft) a.s.l. and drifted W. On 17 April, CVGHM
lowered the Alert Level from 3 to 2 (on a scale of 1-4).
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=
COLIMA Western México 19.514°N, 103.62°W; summit elev. 3,850 m
Multiple steam and gas-and-ash plumes were observed from Colima during
11-12 and 15-16 April. Based on satellite imagery and the Mexico City
MWO, the Washington VAAC reported that on 12 April continuous
ash-and-steam emissions from Colima produced an ash plume that rose to
an altitude of 6.1 km (20,000 ft) a.s.l. and drifted W.
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=
KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m
Seismic activity at Karymsky was above background levels during 10-13
April. Ash plumes from explosions may have reached altitudes of 4 km
(13,000 ft) a.s.l. during the reporting period. The Level of Concern
Color Code remained at Orange <http://www.avo.alaska.edu/color_codes.php>.
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/updates.shtml,
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
On 11 April, lava from the E arm of Kilauea’s Campout flow at the base
of the long-abandoned Royal Gardens ignited fires within the
subdivision. During 11-17 April, lava continued to flow across a lava
delta into the ocean at the Kamokuna entry, but lava was not seen
entering the ocean at East Lae'apuki. Incandescence was intermittently
visible from several breakouts on the Pulama pali and from several vents
in the Pu'u 'O'o crater. Earthquake activity was scattered at the summit
and S-flank areas.
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
Seismic activity at Kliuchevskoi continued above background levels
during 10-13 April. Based on observations and video data, lava flowed
down the NW flank and Strombolian activity occurred at the crater.
Everyday during 10-13 April a gas-and-steam plume possibly containing a
small amount of ash rose to an altitude of 6.3 km (20,700 ft) a.s.l. and
drifted E. A thermal anomaly in the crater was detected on satellite
imagery during 10-12 April. The Level of Concern Color Code remained at
Orange <http://www.avo.alaska.edu/color_codes.php>.
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)
http://www.kscnet.ru/ivs/kvert/updates.shtml
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 10-17 April, Rabaul caldera's Tavurvur cone
emitted steam and steam-and-ash plumes that rose to 1.1-2.7 km
(3,600-8,900 ft) a.s.l. and drifted S and SE. Weak roaring noises
occasionally accompanied the emissions. Small amounts of incandescent
material were ejected from the crater during 13-15 April.
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 and Herman Patia, Rabaul Volcano Observatory
Rabaul Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-14=
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 occasionally produced ash plumes that rose to altitudes of
5.3 km (17,400 ft) a.s.l. and drifted E on 11 and 16 April. Lava-flow
fronts on the SW flanks of Caliente Dome emitted gases on 11 April and
produced avalanches of block and ash on 16 April. On 13 April, the
Washington VAAC reported that an ash plume was visible on satellite
imagery drifting W.
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
Seismic activity at Shiveluch continued above background levels during
4-10 April. Based on seismic interpretation, observation, and video
data, possible ash-and-steam plumes rose to altitudes of 4.5-7 km
(14,800-23,000 ft) a.s.l. throughout the reporting period. Based on
satellite imagery during 10-12 April, plumes drifted N, NW, SE, and SW
and a thermal anomaly was present. The Level of Concern Color Code
remained at Orange <http://www.avo.alaska.edu/color_codes.php>.
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: Kamchatkan Volcanic Eruption Response Team (KVERT)
http://www.kscnet.ru/ivs/kvert/updates.shtml
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
Based on visual observations, lava-dome growth at Soufrière Hills
continued at a reduced rate during 6-13 April. Material originating from
the E-facing shear lobe was shed down the Tar River Valley. Minor
rockfalls and pyroclastic flows were noted. On 17 April, a small
pyroclastic flow was observed to the NW in the upper part of Tyres
Ghaut. The lava-dome volume was an estimated 208 million cubic meters.
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 11-17 April 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-
TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m
IG reported that based on visual observations and reports from pilots,
ash plumes from Tungurahua rose to altitudes of 6.7-8 km (22,000-26,200
ft) a.s.l. and drifted NNW on 11 April. Fumarolic activity originated
from the NE and E edges of the crater. During 12-17 April, ash plumes,
occasionally accompanied by roaring, rose to altitudes of 5.8-8 km
(19,000-26,200 ft) a.s.l. and drifted mainly W. Ashfall was reported
from areas downwind on 12 April. During 13-14 April, Strombolian
activity was observed; incandescent material was ejected about 200-300 m
above the summit and blocks descended 500-800 m down the flanks. During
15-17 April, lahars descended several NW, W, and SW valleys. In the
Pampas sector, lahars with blocks 50 cm in diameter disrupted 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=
UBINAS Perú 16.355°S, 70.903°W; summit elev. 5,672 m
Based on a significant meteorological notice (SIGMET), the Buenos Aires
VAAC reported that an ash plume from Ubinas rose to altitudes of 5.5-7
km (26,000-27,000 ft) a.s.l. on 10 April and drifted W. INGEMMET
reported that on 11 April, emissions of gas and ash produced plumes to
altitudes of 6.2-6.4 km (20,000-21,000 ft) a.s.l. and drifted E. Based
on an additional SIGMET, the Buenos Aires VAAC reported that an ash
plume rose to altitudes of 6.1-6.4 km (20,000-21,000 ft) a.s.l. and
drifted SE.
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.
Sources: Instituto Geológical Minero y Metalúrgico (INGEMMET)
http://www.ingemmet.gob.pe/,
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/>++++++++++++++++++++++++++++++++++++++++++
==============================================================
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.
==============================================================
