GVP/USGS Weekly Volcanic Activity Report 18-24 October 2006

Kimberly.Genareau@xxxxxxx · Wed, 25 Oct 2006 17:29:29 -0700

**************************************
GVP/USGS Weekly Volcanic Activity Report
18-24 October 2006
http://www.volcano.si.edu/reports/usgs/
**************************************

Ongoing Activity 

ARENAL Costa Rica 10.46°N, 84.70°W; summit elev. 1,657 m

In September, activity originating from Arenal's Crater C consisted of gas
emissions, sporadic Strombolian eruptions, lava flows traveling N, and
occasional avalanches from lava-flow fronts. Blocks from the lava-flow fronts
traveled N, NE, and NW, periodically reaching vegetation where they produced
small fires. Volcanic activity was at relatively low levels, however, with few
eruptions occurring and a small amount of pyroclastic material ejected.
Eruptions produced ash plumes that rose about 2.2 km (7,100 ft) a.s.l. Ash and
acid rain fell on the NE and SE flanks. Small avalanches of volcanic material
traveled down several ravines. Crater D showed only fumarolic activity.

Geologic Summary. Conical Volcán Arenal is the youngest stratovolcano in Costa
Rica and one of its most active. The 1,657-m-high andesitic volcano towers above
the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric
project. The earliest known eruptions of Arenal took place about 7,000 years
ago. Growth of Arenal has been characterized by periodic major explosive
eruptions at several-hundred-year intervals and periods of lava effusion that
armor the cone. Arenal's most recent eruptive period began with a major
explosive eruption in 1968. Continuous explosive activity accompanied by slow
lava effusion and the occasional emission of pyroclastic flows has occurred
since then from vents at the summit and on the upper western flank.

Source: Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad
Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/

Arenal Information from the Global Volcanism Program

http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1405-033

BARREN ISLAND Andaman Islands, Indian Ocean, India 12.29°N, 93.88°E; summit
elev. 354 m

Based on pilot observations, the Darwin VAAC reported that ash-and-steam plumes
from Barren Island on 19 and 20 October reached altitudes of 1.5 km (5,000 ft)
a.s.l. and drifted WNW.

Geologic Summary. Barren Island, a possession of India in the Andaman Sea about
135 km NE of Port Blair in the Andaman Islands, is the only historically active
volcano along the N-S-trending volcanic arc extending between Sumatra and Burma
(Myanmar). The 354-m-high island is the emergent summit of a volcano that rises
from a depth of about 2,250 m. The small, uninhabited 3-km-wide island contains
a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is
open to the sea on the W, was created during a major explosive eruption in the
late Pleistocene that produced pyroclastic-flow and -surge deposits. The
morphology of a fresh pyroclastic cone that was constructed in the center of the
caldera has varied during the course of historical eruptions. Lava flows fill
much of the caldera floor and have reached the sea along the western coast
during eruptions in the 19th century and more recently in 1991 and 1995.

Source: Darwin Volcanic Ash Advisory Center 
http://www.bom.gov.au/products/IDD41295.shtml 

Barren Island Information from the Global Volcanism Program 

http://www.volcano.si.edu/world/volcano.cfm?vnum=0600-01=

BULUSAN Luzon, Philippines 12.770°N, 124.05°E; summit elev. 1,565 m

PHIVOLCS reported an explosion from Bulusan on 19 October. The following day,
steam plumes drifted W and WSW. On 23 October, an explosion produced a brownish
ash plume that rose to about 2.6 km (8,400 ft) a.s.l. and drifted SE and SW.
Light ashfall (trace to 0.5 mm thick) from both explosions was reported from
neighborhoods in the municipality of Irosin.

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 
http://www.phivolcs.dost.gov.ph/

Bulusan Information from the Global Volcanism Program 

http://www.volcano.si.edu/world/volcano.cfm?vnum=0703-01=

FOURPEAKED Alaska Peninsula, USA 58.770°N, 153.672°W; summit elev. 2,105 m

The AVO reported that earthquake activity and gas emissions continued at
Fourpeaked during 14-20 October. Steam-and-gas plumes rising from a location
near the summit were visible on a recently installed web camera.

Geologic Summary. Poorly known Fourpeaked volcano in NE Katmai National Park
consists of isolated outcrops surrounded by the Fourpeaked Glacier, which
descends eastward almost to the Shelikof Strait. The orientation of lava flows
and extensive hydrothermal alteration of rocks near the present summit suggest
that it probably marks the vent of Fourpeaked volcano.

Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/

Fourpeaked Information from the Global Volcanism Program

http://www.volcano.si.edu/world/volcano.cfm?vnum=1102-26-

KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m

Seismic data and satellite observations reported by KVERT indicated that
moderate ash eruptions from Karymsky continued during 14-20 October. Weak local
shallow earthquakes occurred at a rate of 100-290 per day. Ash explosions that
were thought to have risen to about 3.6 km (11,800 ft) a.s.l. drifted E on 17-19
October.  A thermal anomaly from the volcanic crater was noted on 13, 15, and
17-19 October. Based on a pilot observation, the Tokyo VAAC reported that on 23
October an ash plume rose to 5.2 km (17,000 ft) a.s.l. and drifted E. The Level
of Concern 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.

Sources: Kamchatkan Volcanic Eruption Response Team 
http://www.kscnet.ru/ivs/kvert/updates.shtml, 

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

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 18-24 October, lava from Kilauea continued to flow off of a lava delta
into the ocean at the East Lae'apuki and East Ka'ili'ili entries. Incandescence
was intermittently visible from the East Pond and January vents, South Wall
complex, and Drainhole and Beehive vents in Pu'u 'O'o's crater. Summit inflation
S of Halema'uma'u caldera continued. Weak incandescence was visible on the
Pulama pali during 18-19 October. Tremor at Pu'u 'O'o remained at a typical
moderate level.

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://volcanoes.usgs.gov/update.html

Kilauea information from the Global Volcanism Program 

http://www.volcano.si.edu/world/volcano.cfm?vnum=1302-01-

METIS SHOAL Tonga Islands, Tonga 19.18°S, 174.87°W; summit elev. 43 m

Further information obtained regarding the floating pumice rafts between Tonga
and Fiji indicated that the source was Metis Shoal. Mariners in the region were
being informed of this activity in early September via "Rag of the
Air" radio broadcasts from Fiji. The earliest report found to this point
comes from a boat with callsign KB1LSY, noting that "thick pumice"
slowed them for 30 minutes during the early morning hours of 28 August as they
were approaching the northern islands of the Lau Group in Fiji, about 500 km NW
of Metis Shoal. By 15 October yachts sailing between Tonga and Fiji reported no
remaining pumice.

Geologic Summary. Metis Shoal, a submarine volcano midway between the islands of
Kao and Late, has produced a series of ephemeral islands since the first
reported activity in the mid-19th century. During periods of inactivity, waves
have been observed to break on rocky reefs or sandy banks with depths of 10 m or
less. Dacitic tuff cones formed during the first 20th-century eruptions in 1967
and 1979 were soon eroded beneath the sea surface. An eruption in 1995 produced
an island with a diameter of 280 m and a height of 43 m following growth of a
lava dome above the surface.

Sources: Encore II Crew http://www.encorevoyages.com/, 

KB1LSY Crew http://www.pangolin.co.nz/yotreps/tracker.php?ident=KB1LSY,

Bob McDavitt's Weathergram, McDavitt's Pacific Weathergrams 
http://www.pangolin.co.nz/yotreps/list_manager.php#Bob

Metis Shoal information from the Global Volcanism Program 

http://www.volcano.si.edu/world/volcano.cfm?vnum=0403-07=

POÁS  Costa Rica 10.20°N, 84.233°W; summit elev. 2,708 m

OVSICORI-UNA reported that during September, Laguna Caliente, a summit lake of
Poás, was mostly gray in color and produced gas columns that reached the crater
rim. The level of the lake had dropped 5 cm with respect to August measurements
and had a temperature of 46 degrees Celsius. On 25 October, a phreatic eruption
produced a plume that drifted 12 km SW of the crater. Fumarolic activity from a
pyroclastic cone on the floor of the crater produced gas plumes that drifted W
and SW. New points of gas discharge were noted from the crater floor, the SE and
NE crater walls, the N terrace, and the NE edge of the crater.

Geologic Summary. The broad, well-vegetated edifice of Poás, one of the most
active volcanoes of Costa Rica, contains three craters along a N-S line. The
frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic
volcano, which is one of Costa Rica's most prominent natural landmarks, are
easily accessible by vehicle from the nearby capital city of San José. A
N-S-trending fissure cutting the 2,708-m-high complex stratovolcano extends to
the lower northern flank, where it has produced the Congo stratovolcano and
several lake-filled maars. The southernmost of the two summit crater lakes,
Botos, is cold and clear and last erupted about 7,500 years ago. The more
prominent geothermally heated northern lake, Laguna Caliente, is one of the
world's most acidic natural lakes, with a pH of near zero. It has been the site
of frequent phreatic and phreatomagmatic eruptions since the first historical
eruption was reported in 1828. Poás eruptions often include geyser-like ejection
of crater-lake water.

Source: Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad
Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/

Poás Information from the Global Volcanism Program 

http://www.volcano.si.edu/world/volcano.cfm?vnum=1405-04= 

RABAUL New Britain Island, Papua New Guinea 4.271°S, 152.203°E; summit elev. 688
m

The RVO reported that a few Vulcanian eruptions from Rabaul occurred on 18
October and produced ash plumes to 1 km (3,300 ft) a.s.l. Ashfall was reported
from E Rabaul town. Seismicity was at background levels and the rate of ground
deformation was low. 

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=

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 explosions from
Sakura-jima on 21 October produced plumes that rose straight up to 3.4 km
(11,000 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 
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 a pilot report, the Washington VAAC reported that on 21 October,
emission plumes from Sangay reached altitudes of 6.7 km (22,000 ft) a.s.l.

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

According to the Washington VAAC, a series of minor emissions from Santa María's
Santiaguito lava-dome complex on 18 October was visible on satellite imagery.
The small plumes of gas and light ash drifted 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.

Source: Washington Volcanic Ash Advisory Center 
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= 

SEMERU Java, Indonesia 8.11°S, 112.92°E; summit elev. 3,676 m

Based on a pilot report, the Darwin VAAC reported that on 18 October, an
eruption plume from Semeru reached 4.6 km (15,000 ft) a.s.l.

Geologic Summary. Semeru is the highest volcano on Java and one of its most
active. The symmetrical stratovolcano rises abruptly to 3,676 m above coastal
plains to the S and lies at the southern end of a volcanic massif extending N to
the Tengger caldera. Semeru has been in almost continuous eruption since 1967.
Frequent small-to-moderate Vulcanian eruptions have accompanied intermittent
lava dome extrusion, and periodic pyroclastic flows and lahars have damaged
villages below the volcano. A major secondary lahar on 14 May 1981 caused more
than 250 deaths and damaged 16 villages.

Source: Darwin Volcanic Ash Advisory Centre 
http://www.bom.gov.au/info/vaac/advisories.shtml

Semeru Information from the Global Volcanism Program

http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-30= 

SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev. 1,052 m

During 13-20 October, lava-dome growth at Soufrière Hills continued and was
concentrated on the NE part of the edifice.  A new E-facing shear lobe with a
smooth, curved back enlarged during the reporting period. Rockfalls and small
pyroclastic flows originating from the active lobe affected the NE flank. On a
few occasions, pyroclastic flows from the N flank spilled over Farrel's wall
(the crater rim). The vent above Gage's wall was less active compared to the
previous reporting period. A vent S of the active lobe periodically produced
both ash and gas. Ash fell in northern areas of the island. Heavy rainfall
resulted in mudflow activity in all drainage systems.

Based on information from the MVO, pilot reports, and the Piarco MWO, the
Washington VAAC reported that continuous ash and gas emissions on 18, 20, and
22-23 October produced plumes that drifted W, NW, and NE. Plumes reached
altitudes of 2.7 km (9,000 ft) a.s.l. A hotspot was detected on satellite
imagery.

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 
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

Observations and data from deformation-monitoring instruments showed that during
11-17 October the lava dome at Mount St. Helens continued to grow in the S
crater and produce small rockfalls. On 22 October, a M 3.5 earthquake triggered
the collapse of material from the largest of the lava-dome spines. The resulting
ash plume rose to about 3.2 km (10,500 ft) a.s.l. and quickly dissipated to the
W. 

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 18 October.

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 
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= 

TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m

IG reported that during 18-19 October, emissions from Tungurahua increased in
intensity and ash content and seismic tremor was continuous. During the night,
lava fountains reached heights of 6 km (19,800 ft) a.s.l. and blocks rolled 800
m down the flanks. According to the Washington VAAC, a pilot reported an ash
plume to an altitude of 8.5 km (28,000 ft) a.s.l. Ash plumes drifted NE and E
and generated ashfall about 50 km E, in Puyo. According to news articles, about
300 villagers evacuated from the flanks. During 20-24 October, emissions
continued and produced plumes to 7-8 km (23,000-26,000 ft) a.s.l. Ashfall was
reported from towns on the N, NW, W, SW, and E flanks.

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.

Sources: Instituto Geofísico-Escuela Poltécnica Nacional 
http://www.igepn.edu.ec/vulcanologia/tungurahua/actividad/informet.htm,

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

Tungurahua Information from the Global Volcanism Program

http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08=

TURRIALBA Costa Rica 10.025°N, 83.767°W; summit elev. 3,340 m

Fumarolic activity and gas discharge in and to the W of Turrialba's central
crater continued throughout September. New points of gas discharge, small
landslides, and accelerated vegetation die-off were noted from various locations
within the crater.

Geologic Summary. Turrialba, the easternmost of Costa Rica's Holocene volcanoes,
is a large vegetated basaltic-to-dacitic stratovolcano located across a broad
saddle NE of Irazú volcano overlooking the city of Cartago. The massive
3340-m-high Turrialba is exceeded in height only by Irazú, covers an area of 500
sq km, and is one of Costa Rica's most voluminous volcanoes. Three well-defined
craters occur at the upper SW end of a broad 800 x 2200 m wide summit depression
that is breached to the NE. Most activity at Turrialba originated from the
summit vent complex, but two pyroclastic cones are located on the SW flank. Five
major explosive eruptions have occurred at Turrialba during the past 3500 years.
Turrialba has been quiescent since a series of explosive eruptions during the
19th century that were sometimes accompanied by pyroclastic flows. Fumarolic
activity continues at the central and SW summit craters.

Source: Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad
Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/

Turrialba Information from the Global Volcanism Program 
http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1405-07=

UBINAS  Perú 16.355°S, 70.903°W; summit elev. 5,672 m

Based on pilot reports, the Buenos Aires VAAC reported continuous emissions from
Ubinas on 17, 19, 21, and 23-24 October. The plumes rose to 5.5-6.4 km
(18,000-21,000 ft) a.s.l. and drifted SE, SW, E, and N.

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 
http://www.bom.gov.au/products/Volc_ash_recent.shtml

Ubinas Information from the Global Volcanism Program 
http://www.volcano.si.edu/world/volcano.cfm?vnum=1504-02

+++++++++++++++++++++++++++++++++++++

Sally Kuhn Sennert

Global Volcanism Program

Smithsonian Institution

National Museum of Natural History MRC-119

Department of Mineral Sciences

Washington, D.C., 20560

http://www.volcano.si.edu/reports/usgs/index.cfm 
<http://www.volcano.si.edu/reports/usgs/index.cfm> 

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.
==============================================================