GVP/USGS Weekly Volcanic Activity Report
20-26 June 2007
http://www.volcano.si.edu/reports/usgs/
New Activity/Unrest: | Kilauea, USA | Kliuchevskoi, Russia
Ongoing Activity: | Arenal, Costa Rica | Batu Tara, Indonesia | Dukono,
Indonesia | Karangetang, Indonesia | Karymsky, Russia | Lokon-Empung,
Indonesia | Manam, Papua New Guinea | Rabaul, Papua New Guinea |
Reventador, Ecuador | Sakura-jima, Japan | Semeru, Indonesia |
Shiveluch, Russia | Soputan, Indonesia | Soufrière Hills, Montserrat |
St. Helens, USA | Talang, Indonesia | Tengger Caldera, Indonesia |
Tungurahua, Ecuador
New Activity/Unrest
KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m
During 20-26 June, incandescence was not visible from the vents in
Kilauea’s Pu'u 'O'o crater. A tiltmeter at Pu'u 'O'o continued to show
steady tilting inward toward the crater, and the crater floor was
estimated to have subsided 100 m between 17 and 21 June.
On 19 June, new ground cracks were discovered in an area west of Mauna
Ulu. On 20 June, HVO scientists measured sulfur dioxide concentrations
greater than 10 parts per million (ppm) in a broad area adjacent to
Halema‘uma‘u crater. Typical concentrations are generally negligible
except for areas downwind of Halema‘uma‘u crater, where they can get up
to 2.5 ppm in narrow zones. On 21 June, scientists confirmed that lava
was not entering the ocean at the Poupou entry.
During 21-26 June lava was not visible anywhere on the flow field or at
the site of the 18/19 June eruption. The crack W of Kane Nui o Hamo
continued to emit steam and fume. The summit area continued to inflate
very slowly and seismic tremor values at Pu'u 'O'o were below pre-June
17 levels. On 25 June, sulfur dioxide and carbon dioxide emissions were
at approximately pre-June 17 levels after a gradual decline. HVO lowered
the Volcanic Alert Level from Watch to Advisory and Aviation Color Code
from Orange to Yellow. Aerial observation revealed that steaming from
the site of the 18/19 June fissure eruption decreased, though the
steaming cracks at the base of Kane Nui o Hamo were vigorously fuming.
Ground-based mapping of the new lava flow was also completed; the
eruption occurred from two places along the fissure, separated by about
40 m.
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
KVERT reported that during 15-22 June, seismic activity at Kliuchevskoi
continued above background levels and a thermal anomaly in the crater
was detected on satellite imagery. Based on video and visual
observations, ash plumes rose to an altitude of 5 km (16,400 ft) a.s.l.
and drifted NE on 15 June. Clouds inhibited observations on other days.
Plumes were seen drifting N, W, and S on satellite imagery during 15-22
June.
A large ash cloud, about 300 km in diameter, was observed near Yelizovo
airport during 20-21 June. Based on atmospheric profiles, the plumes
rose to estimated altitudes of 6.5-9.5 km (21,300-31,200 ft) a.s.l. and
drifted SE.
On 25 June, KVERT reported that seismic activity decreased during 22-24
June. Ash plumes were visible on satellite imagery drifting multiple
directions. The plumes rose to estimated altitudes of 5.5-6.5 km
(18,000-21,300 ft) a.s.l. based on atmospheric profiles. A thermal
anomaly continued to be detected in the crater. The Level of Concern
Color Code was lowered to Orange.
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=
Ongoing Activity
ARENAL Costa Rica 10.46°N, 84.70°W; summit elev. 1,657 m
In May, activity originating from Arenal's Crater C consisted of gas
emissions, sporadic Strombolian eruptions, lava flows traveling SW, and
occasional avalanches from lava-flow fronts. Blocks from the lava-flow
fronts periodically reached vegetation and started small fires. Volcanic
activity was at relatively low levels and few eruptions occurred. Small
amounts of pyroclastic material were ejected and affected the NE and SE
flanks. 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
BATU TARA Lesser Sunda Islands, Indonesia 7.792°S, 123.579°E; summit
elev. 748 m
Based on visual observations, CVGHM reported that on 19 June an ash
plume from Batu Tara rose to an altitude of 1.7 km (5,600 ft) a.s.l.
Clouds inhibited visual observations on the other days during 18-25
June. The Alert Level remained at 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.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://portal.vsi.esdm.go.id/joomla/
Batu Tara Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0604-26=
DUKONO Halmahera, Indonesia 1.70°N, 127.87°E; summit elev. 1,185 m
Based on visual observations, CVGHM reported that during 18-25 June ash
plumes from Dukono rose to an altitude of 1.4 km (4,600 ft) a.s.l. The
Alert Level remained at 2 (on a scale of 1-4).
Geologic Summary. Reports from this remote volcano in northernmost
Halmahera are rare, but Dukono has been one of Indonesia's most active
volcanoes. More-or-less continuous explosive eruptions, sometimes
accompanied by lava flows, occurred since 1933 until at least the
mid-1990s, when routine observations were curtailed. During a major
eruption in 1550, a lava flow filled in the strait between Halmahera and
the N-flank cone of Gunung Mamuya. Dukono is a complex volcano
presenting a broad, low profile with multiple summit peaks and
overlapping craters. Malupang Wariang, 1 km SW of Dukono's summit crater
complex, contains a 700 x 570 m crater that has also been active during
historical time.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://portal.vsi.esdm.go.id/joomla/
Dukono Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0608-01=
KARANGETANG [Api Siau] Siau Island, Indonesia 2.47°N, 125.29°E; summit
elev. 1,784 m
Based on visual observations, CVGHM reported that during 18-25 June ash
plumes from Karangetang’s main crater produced plumes that rose to an
altitude of 2 km (6,600 ft) a.s.l. Activity at Crater II consisted of
diffuse ash plumes that rose to an altitude of 1.8 km (5,900 ft) a.s.l.
and incandescent ash that rose about 10 m. The Alert Level remained at 2
(on a scale of 1-4).
Geologic Summary. Karangetang (also known as Api Siau) lies at the
northern end of the island of Siau, N of Sulawesi. The 1,784-m-high
stratovolcano contains five summit craters along a N-S line. One of
Indonesia's most active volcanoes, Karangetang has had more than 40
recorded eruptions since 1675. Twentieth-century eruptions have included
frequent explosions, sometimes accompanied by pyroclastic flows and lahars.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://portal.vsi.esdm.go.id/joomla/
Karangetang Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0607-02=
KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m
During 15-22 June, seismic activity at Karymsky was above background
levels and possibly indicated that ash explosions produced plumes to an
altitude of 5.8 km (19,000 ft) a.s.l. all days.
Based on information from KEMSD, the Tokyo VAAC reported that eruption
plumes rose to 3-4.6 km (10,000-15,000 ft) a.s.l. during 24-25 June. Ash
was not identified on satellite imagery.
Geologic Summary. Karymsky, the most active volcano of Kamchatka's
eastern volcanic zone, is a symmetrical stratovolcano constructed within
a 5-km-wide caldera that formed about 7,600-7,700 radiocarbon years ago.
Construction of the Karymsky stratovolcano began about 2,000 years
later. The latest eruptive period began about 500 years ago, following a
2,300-year quiescence. Much of the cone is mantled by lava flows less
than 200 years old. Historical eruptions have been Vulcanian or
Vulcanian-Strombolian with moderate explosive activity and occasional
lava flows from the summit crater. Most seismicity preceding Karymsky
eruptions has originated beneath Akademia Nauk caldera, which is located
immediately S of Karymsky volcano and erupted simultaneously with
Karymsky in 1996.
Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)
http://www.kscnet.ru/ivs/kvert/updates.shtml,
Tokyo Volcanic Ash Advisory Center (VAAC)
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=
LOKON-EMPUNG northern Sulawesi, Indonesia 1.36°N, 124.79°E; summit elev.
1,580 m
Based on visual observations, CVGHM reported that during 18-25 June
diffuse ash plumes from Lokon-Empung rose to an altitude of 1.6 km
(5,200 ft) a.s.l. The Alert Level remained at 2 (on a scale of 1-4).
Geologic Summary. The twin volcanoes Lokon and Empung, rising about 800
m above the plain of Tondano, are among the most active volcanoes of
Sulawesi. Lokon, the higher of the two peaks (whose summits are only 2.2
km apart) has a flat, craterless top. The morphologically younger Empung
volcano has a 400-m-wide, 150-m-deep crater that erupted last in the
18th century, but all subsequent eruptions have originated from
Tompaluan, a 150 x 250 m wide double crater situated in the saddle
between the two peaks. Historical eruptions have primarily produced
small-to-moderate ash plumes that have occasionally damaged croplands
and houses, but lava-dome growth and pyroclastic flows have also occurred.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://portal.vsi.esdm.go.id/joomla/
Lokon-Empung Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0606-10=
MANAM offshore New Guinea, Papua New Guinea 4.10°S, 145.06°E; summit
elev. 1,807 m
Based on satellite image observations, the Darwin VAAC reported that an
eruption plume from Manam rose to an altitude of 3.4 km (11,000 ft)
a.s.l. on 23 June and drifted WNW.
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.
Source: Darwin Volcanic Ash Advisory Centre
http://www.bom.gov.au/products/IDD41300.shtml
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 20-26 June, emissions from Rabaul caldera's
Tavurvur cone consisted of white vapor plumes containing little ash
occasionally accompanied by blue vapor. The plumes rose to an altitude
less than 1.7 km (5,600 ft) a.s.l. and drifted W, NW, N, and SSE. Fine
ash fell in areas downwind, including Rabaul Town. A mild smell of
hydrogen sulfide gas was reported from Rabaul Town. Weak roaring noises
were heard and incandescence was visible at night.
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=
REVENTADOR Ecuador 0.078°S, 77.656°W, summit elev. 3,562 m
Based on seismic interpretation, IG reported that lahars occurred on the
flanks of Reventador on 20, 21, and 23 June. Clouds inhibited visual
observations during 20-24 June.
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 Poltécnica Nacional
http://www.igepn.edu.ec/,
Reventador Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-01=
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 eruption
plumes from Sakura-jima rose to an altitude of 2.4 km (8,000 ft) a.s.l.
and drifted N during 20-21 June. Ash was not detected on satellite imagery.
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=
SEMERU Java, Indonesia 8.11°S, 112.92°E; summit elev. 3,676 m
Based on visual observations, CVGHM reported that during 18-25 June
multiple ash explosions from Semeru produced plumes that rose to an
altitude of 4.2 km (13,800 ft) a.s.l. The Alert Level remained at 2 (on
a scale of 1-4).
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: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://portal.vsi.esdm.go.id/joomla/
Semeru Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-30=
SHIVELUCH Kamchatka Peninsula, Russia 56.653°N, 161.360°E; summit elev.
3,283 m
KVERT reported that seismic activity at Shiveluch continued above
background levels during 15-22 June. Based on seismic interpretation,
ash plumes rose to an altitude of 5.3 km (17,400 ft) a.s.l. during the
reporting period. On 15 June, gas-and-steam plumes drifted S. A large
thermal anomaly was detected in the crater on satellite imagery during
14-17 and 20 June. The Level of Concern Color Code remained at Orange.
Based on information from KEMSD, the Tokyo VAAC reported that an
eruption plume rose to 5.8 km (19,000 ft) a.s.l. during 25-26 June. Ash
was not identified on satellite imagery.
Geologic Summary. The high, isolated massif of Shiveluch volcano (also
spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya
volcano group and forms one of Kamchatka's largest and most active
volcanoes. The currently active Molodoy Shiveluch lava-dome complex was
constructed during the Holocene within a large horseshoe-shaped caldera
formed by collapse of the massive late-Pleistocene Strary Shiveluch
volcano. At least 60 large eruptions of Shiveluch have occurred during
the Holocene, making it the most vigorous andesitic volcano of the
Kuril-Kamchatka arc. Frequent collapses of lava-dome complexes, most
recently in 1964, have produced large debris avalanches whose deposits
cover much of the floor of the breached caldera. During the 1990s,
intermittent explosive eruptions took place from a new lava dome that
began growing in 1980. The largest historical eruptions from Shiveluch
occurred in 1854 and 1964.
Sources: Kamchatkan Volcanic Eruption Response Team (KVERT)
http://www.kscnet.ru/ivs/kvert/updates.shtml,
Tokyo Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
Shiveluch Information from the Global Volcanism Program
http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1000-27=
SOPUTAN Sulawesi, Indonesia 1.11°N, 124.73°E; summit elev. 1,784 m
Based on visual observations, CVGHM reported that during 18-25 June
diffuse ash plumes from Soputan rose to an altitude of 1.8 km (5,900 ft)
a.s.l. The Alert Level remained at 3 (on a scale of 1-4).
Geologic Summary. The small conical volcano of Soputan on the southern
rim of the Quaternary Tondano caldera is one of Sulawesi's most active
volcanoes. During historical time the locus of eruptions has included
both the summit crater and Aeseput, a prominent NE-flank vent that
formed in 1906 and was the source of intermittent major lava flows until
1924.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://portal.vsi.esdm.go.id/joomla/
Soputan Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0606-03=
SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev.
1,052 m
MVO reported that during 20-25 June the lava dome at Soufrière Hills
changed very little based on visual observations, and seismic activity
was very low. Low-level rockfall and pyroclastic flow activity
continued, however, and predominantly affected the Tar River Valley to
the E. The Alert Level remained at 4 (on a scale of 0-5).
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 indicated that during 20-26
June lava-dome growth at Mount St. Helens continued. Seismicity
persisted at low levels, punctuated by M 1.5-2.5, and occasionally
larger, earthquakes. In some instances, clouds 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-
TALANG Sumatra, Indonesia 00.98°S, 100.68°E; summit elev. 2,896 m
Based on visual observations, CVGHM reported that during 18-25 June
thick brown ash plumes from Talang’s Main Crater rose to an altitude of
3.1 km (10,200 ft) a.s.l. Diffuse white ash plumes rose to an altitude
of about 3 km (10,000 ft) a.s.l. from the South Crater. The Alert Level
remained at 2 (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: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://portal.vsi.esdm.go.id/joomla/
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 during 18-25 June diffuse ash plumes from Tengger
Caldera rose to an altitude of 2.4 km (7,900 ft) a.s.l. The Alert Level
remained at 2 (on a scale of 1-4).
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://portal.vsi.esdm.go.id/joomla/
Tengger Caldera Information from the Global Volcanism Program
http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=0603-31=
TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m
The IG reported that during 20-25 June mudflows and lahars traveled on
the S, W, NW, and N flanks of Tungurahua and interrupted traffic. A
steam plume with little ash content was observed on 21 June. On 22 June,
ashfall was reported SW in Choglontus and roaring noises were heard. A
small landslide occurred on the edge of the Chambo river; another
landslide affected a highway. On 23 June, a steam plume with little ash
content rose to an altitude of 5.8 km (19,000 ft) a.s.l. and drifted W.
The next day, ashfall was reported. During 23-24 June, roaring noises
were heard.
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=
**+++++++++++++++++++++++++++++++++++++**
**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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