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GVP/USGS Weekly Volcanic Activity Report 6-12 September 2006
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From: Sally Kuhn <kuhns@xxxxxx>
GVP/USGS Weekly Volcanic Activity Report
6-12 September 2006
http://www.volcano.si.edu/reports/usgs/
New Activity/Unrest: | Cleveland, Alaska | Etna, Italy | Karymsky,
Russia | Mayon, Philippines | Soufriere Hills, Montserrat | Talang,
Indonesia | Tengger Caldera, Indonesia| Turrialba, Costa Rica
Ongoing Activity: | Arenal, Costa Rica | Kilauea, USA | Poas, Costa Rica
| Sakura-jima, Japan | St. Helens, USA | Tungurahua, Ecuador | Ubinas, Perú
New Activity/Unrest
CLEVELAND Aleutian Islands, USA 52.82°N, 169.95°W; summit elev. 1,730 m
On 7 September, AVO raised the level of Concern Color Code
<http://www.avo.alaska.edu/color_codes.php> for Cleveland from
unassigned to Yellow after a short-lived explosion on 24 August was
verified by video footage. The resultant ash plume reached an altitude
of about 3 km (~10,000 ft) a.s.l. and produced ash fall. An hour later,
only minor steaming from the summit was noted. A weak thermal anomaly in
the summit crater was present in subsequent satellite images.
Geologic Summary. The symmetrical Mount Cleveland stratovolcano is
situated at the western end of the uninhabited dumbbell-shaped
Chuginadak Island in the east-central Aleutians. The 1,730-m-high
stratovolcano is the highest of the Islands of Four Mountains group and
is one of the most active in the Aleutians. Numerous large lava flows
descend its flanks. It is possible that some 18th to 19th century
eruptions attributed to Carlisle (a volcano located across the Carlisle
Pass Strait to the NW) should be ascribed to Cleveland. In 1944
Cleveland produced the only known fatality from an Aleutian eruption.
Recent eruptions from Mt. Cleveland have been characterized by
short-lived explosive ash emissions, at times accompanied by lava
fountaining and lava flows down the flanks.
Source: Alaska Volcano Observatory
http://www.avo.alaska.edu/activity/avoreport.php?view=update
Cleveland Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1101-24-
ETNA Sicily, Italy 37.73°N, 15.00°E; summit elev. 3,315 m
On 14 July, a fissure opened on the E flank of the SE Crater of Etna and
produced a lava flow that traveled E to the Valle del Bove. Moderate
strombolian activity from the E flank of the SE Crater produced a small
amount of ashfall on Catania (~25 km SSE of the volcano). The lava flow
reached a maximum distance of 3 km within the Valle del Bove and ceased
on 24 July. On 26 July, strong explosions were heard from the rim of the
NE crater.
On 31 August, strombolian activity from the summit of the SE Crater
produced lapilli and bombs that fell mainly in the crater. The ejecta
filled the crater and overflowed on the E side on 5 September, forming
lava falls that accumulated in a steep-sided circular depression on the
middle part of the E flank. On 7 September, the sluggish a’a’ flow
breached the E rim and spread out on the E flank of the SE Crater and
towards the Valle del Bove rim. Explosive activity at the SE Crater
summit produced lava blocks that fell to the base of the cone.
On 10 September, a rockfall from a wall that divided the SE Crater and
the depression on the middle part of the E flank produced an ash plume
that drifted W. Lava flows and strombolian activity from the summit of
the SE Crater continued on 11 September.
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=
KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m
KVERT reported on 8 September that the Concern Color Code level at
Karymsky was lowered from Orange to Yellow. Approximately 30-90 shallow
earthquakes occurred daily. During 1-4 September, a thermal anomaly was
detected in the crater.
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
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=
MAYON southeastern Luzon, Philippines 13.257°N, 123.685°E; summit elev.
2,462 m
Seismic activity and lava extrusion from Mayon decreased during 6-12
September. Steam plumes from the summit crater drifted mainly W, N, and
E. Ground-deformation measurements showed an overall deflation. On 11
September, the Alert Level was lowered from 4 to 3 (scale is 0-5, 0
referring to No Alert status).
Geologic Summary. The beautifully symmetrical Mayon volcano, which rises
to 2,462 m above the Albay Gulf, is the Philippines' most active
volcano. The structurally simple volcano has steep upper slopes that
average 35-40° and is capped by a small summit crater. The historical
eruptions of this basaltic-andesitic volcano date back to 1616 and range
from Strombolian to basaltic Plinian. Eruptions occur predominately from
the central conduit and have also produced lava flows that travel far
down the flanks. Pyroclastic flows and mudflows have commonly swept down
many of the approximately 40 ravines that radiate from the summit and
have often devastated populated lowland areas. Mayon’s most violent
eruption, in 1814, killed more than 1,200 people and devastated several
towns. Eruptions that began in February 2000 led PHIVOLCS to recommend
on 23 February the evacuation of people within a radius of 7 km from the
summit in the SE and within a 6 km radius for the rest of the volcano.
Sources: Philippine Institute of Volcanology and Seismology
http://www.phivolcs.dost.gov.ph/news/mayon71706.html,
News Balita http://news.balita.ph/html/article.php/20060909085851691,
Reuters http://www.alertnet.org/thenews/newsdesk/MAN168080.htm
Mayon Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0703-03=
SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev.
1,052 m
During 6-12 September, lava-dome growth at Soufrière Hills was
substantial and concentrated on the W part of the edifice. A vent that
had opened above Gage’s Wall on 31 August vigorously emitted plumes of
hot gases. A second vent near the summit of the dome emitted
ash-and-steam plumes.
Based on information from the MVO, pilot reports, and the Piarco MWO,
the Washington VAAC reported that ash, gas, and steam emissions on 6 and
7 September produced diffuse plumes that drifted WNW. On 10, 11, and 12
September, ash-and-gas plumes reached altitudes of 3 km (10,000 ft)
a.s.l. and drifted E and SW. A hotspot was detected on satellite imagery
on 6, 7, and 10-12 September.
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=
TALANG Sumatra, Indonesia 00.98°S, 100.68°E; summit elev. 2,896 m
CVGHM raised the Alert Level at Talang to 3 (on a scale of 1-4) on 9
September due to an increase in tremor. On 10 September, a brownish
plume rose 250 m above the summit (~10,000 ft a.s.l.).
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.
Sources: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://www.vsi.esdm.go.id/portal/html/index.php, Washington Post
http://www.washingtonpost.com/wp-dyn/content/article/2006/09/10/AR2006091000683.html
Talang Information from the Global Volcano Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0601-16=
TENGGER CALDERA Java, Indonesia 7.942°S, 112.950°E; summit elev. 2,329 m
CVGHM reported that the Alert Level for Tengger Caldera was raised one
level to 3 (on a scale of 1-4) on 9 September due to an increase in tremor.
Geologic Summary. The 16-km-wide Tengger caldera in eastern Java
occupies the northern end of a volcanic massif extending from Semeru
volcano. The massive Tengger volcanic complex consists of five
overlapping stratovolcanoes, each truncated by a caldera. The most
recent is the 9 x 10 km wide Sandsea caldera, which formed incrementally
during the late Pleistocene and early Holocene. An overlapping cluster
of post-caldera cones was constructed on the floor of the Sandsea
caldera within the past several thousand years. The youngest of these is
Bromo, one of Java's most frequently visited and most active volcanoes.
More than 50 mild-to-moderate explosive eruptions have occurred there
since 1804.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://www.vsi.esdm.go.id/portal/html/index.php
Tengger Caldera Information from the Global Volcanism Program
http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=0603-31=
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 August. On 30 August, scientists
visiting the area noted that localized vegetation in and around the
summit area had been heavily impacted by gases. Areas not affected by
increased fumarolic activity in June 2005 had been singed by noxious
gases, including a tree belt on the NW outer flank. Below the tree belt,
farmers reported an intensification of gas odors. The shapes of the
gas-scarred areas reflected prevailing wind directions.
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.una.ac.cr/ovsi/
Turrialba Information from the Global Volcanism Program
http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1405-07=
Ongoing Activity
ARENAL Costa Rica 10.46°N, 84.70°W; summit elev. 1,657 m
In August, 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. 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 ~500 m above the crater (~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.una.ac.cr/ovsi/
Arenal Information from the Global Volcanism Program
http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1405-033
KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m
During 6-12 September, 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 vent in Pu'u 'O'o's crater.
Summit inflation S of Halema'uma'u caldera continued. 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-
POÁS Costa Rica 10.20°N, 84.233°W; summit elev. 2,708 m
OVSICORI-UNA reported that during August, Laguna Caliente, a summit lake
of Poás, was gray in color and produced gas columns that reached the
crater rim. The level of the lake had dropped 47 cm with respect to July
measurements and had a temperature of 41 degrees Celsius. 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.una.ac.cr/ovsi/informes.html
Poás Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1405-04=
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 explosion
at Sakura-jima produced an eruption cloud on 6 September.
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=
ST. HELENS Washington, USA 46.20°N, 122.18°W; summit elev. 2,549 m
During 6-12 September, the lava dome at Mount St. Helens continued to
grow and produce small rockfalls. On 9 and 10 September, five shallow
earthquakes greater than M 2 occurred in association with the growing dome.
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
During 6-12 September, seismicity at Tungurahua remained low and visual
observations were limited due to inclement weather. On 7 September,
lahars descended the NW gorges of Chontapamba and Mandur. On 8 and 9
September, steam-and-gas plumes with little to no ash content rose to
~100-500 m above the summit (~16,800-18,100 ft a.s.l.) and drifted NW.
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/vulcanologia/tungurahua/actividad/informet.htm
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 pilot reports, the Buenos Aires VAAC reported continuous
emission of ash plumes from Ubinas during 5, 9, and 11 September. The
plumes rose to altitudes of ~4.9-5.5 km (~16,000-18,000 ft) a.s.l. and
drifted NE and E.
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 S. Kuhn**
**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/
Phone: 202.633.1805
Fax: 202.357.2476
<http://www.volcano.si.edu/reports/usgs/>++++++++++++++++++++++++++++++++++++++++++
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