GVP/USGS
Weekly Volcanic Activity Report
28
July-1 August 2006
http://www.volcano.si.edu/reports/usgs/
New
Activity/Unrest: | Bulusan, Philippines | Karangetang,
Indonesia | Mayon,
Philippines | Tungurahua, Ecuador
Ongoing
Activity: | Augustine, USA | Karymsky,
Russia | Kilauea,
USA | Manam,
Papua New Guinea | Merapi, Indonesia
| Popocatépetl, México | Semeru, Indonesia | Soufriere Hills, Montserrat
| St. Helens, USA
| Suwanose-jima, Japan
New
Activity/Unrest
BULUSAN
Luzon, Philippines 12.770°N, 124.05°E; summit elev. 1,565 m
On 29
July, PHIVOLCS reported that the Alert Level at Bulusan was lowered
from 2 to 1
(out of 5 levels) due to a gradual decrease from 28 June of all
monitored
parameters to near-baseline levels.
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=
KARANGETANG
[Api Siau] Siau Island,
Indonesia
2.47°N, 125.29°E; summit
elev. 1,784 m
Fog
limited clear views of summit activity at Karangetang during the
reporting
period. Lava flows were observed during 27-31 July moving E toward the
Kahetang
and Batu Awang rivers at a maximum distance of ~750 m from the vent.
Rockfalls
traveled up to 2 km towards the Keting River.
On 31 July, gas
plumes reached a maximum height of 200 m above the summit (or ~6,500 ft
a.s.l.).
According
to news reports, between 3,000 and 4,000 people from five villages were
evacuated on 27 and 28 July due to advancing lava flows and reports of
lahars.
The news also noted that on 29 July, about 1,300 people remained in
shelters.
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.
Sources:
Center of
Volcanology and
Geological Hazard
Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/index.php?option=com_frontpage&Itemid=1,
AFP http://www.taipeitimes.com/News/world/archives/2006/07/29/2003320916,
Jaknews
http://www.jaknews.com/2006/english/jul/29072006-0800jak01.htm
Karangetang
Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0607-02=
MAYON
southeastern Luzon,
Philippines
13.257°N, 123.685°E;
summit elev. 2,462 m
Lava
flows from Mayon in the SE sector of the Bonga gully advanced ~1.35 km
during
26 July-1 August to reach a maximum distance of 5.8 km SSE from the
summit on 1
August. Smaller lava flows and incandescent blocks descended adjacent
gullies.
On July 29, light ash accumulation was reported about 12 km S and SE,
in Daraga
municipality and Legazpi
City and vicinity,
respectively. Emissions of sulfur-dioxide reached ~12,500 tons per day
on 31
July, a record high for the current period of unrest.
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.
Source:
Philippine Institute of Volcanology and Seismology
http://www.phivolcs.dost.gov.ph/news/mayon71706.html
Mayon
Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0703-03=
TUNGURAHUA
Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m
On 26
July, the United Nations Office for the Coordination of Humanitarian
Affairs
(OCHA) reported that, according to the Ecuadorian Civil Defense,
approximately
13,000 people had been severely affected by the eruption of Tungurahua.
About
815 remained in shelters.
During
26 July-1 August, eruption columns with small-to-moderate ash content
reached
an altitude of ~9 km (~30,000 ft) a.s.l. Ash fall was reported in
Pillate, ~ 7
km to the W on 27-29 and 30 July, as far as Baños ~12 km N and Puela ~8
km S on
29 July and Cotaló ~13 km NW on 30 July. On 27 July, incandescent
material
from explosions descended ~1 km down the flanks. A thermal anomaly was
observed
on satellite imagery during the reporting period.
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,
Relief
Web
http://www.reliefweb.int/rw/RWB.NSF/db900SID/KKEE-6S3MLY?OpenDocument
Tungurahua
Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08=
Ongoing
Activity
AUGUSTINE
SW Alaska, USA
59.363°N, 153.43°W; summit elev. 1,252 m
According
to the Anchorage VAAC, a pilot reported that on 27 July an ash plume
from
Augustine reached an altitude of 1.5 km (5,000 ft) a.s.l. and drifted
SSE. The
AVO did not find seismic evidence for this event, and seismicity levels
remained low. They also stated that rockfalls and avalanches of hot
debris from
the cooling lava dome can produce small, localized ash plumes.
Geologic
Summary. Augustine volcano, rising above Kamishak Bay
in the southern Cook Inlet about 290 km SW of Anchorage, is the most
active
volcano of the eastern Aleutian arc. It consists of a complex of
overlapping
summit lava domes surrounded by an apron of volcaniclastic debris that
descends
to the sea on all sides. Few lava flows are exposed; the flanks consist
mainly
of debris-avalanche and pyroclastic-flow deposits formed by repeated
collapse
and regrowth of the volcano's summit. The latest episode of edifice
collapse
occurred during Augustine's largest historical eruption in 1883;
subsequent
dome growth has restored the volcano to a height comparable to that
prior to
1883. The oldest dated volcanic rocks on Augustine are more than 40,000
years
old. At least 11 large debris avalanches have reached the sea during
the past
1800-2000 years, and five major pumiceous tephras have been erupted
during this
interval. Historical eruptions have typically consisted of explosive
activity
with emplacement of pumiceous pyroclastic-flow deposits followed by
lava dome
extrusion with associated block-and-ash flows.
Sources:
Alaska
Volcano Observatory
http://www.avo.alaska.edu/activity/Augustine.php,
Anchorage Volcanic
Ash Advisory
Center
http://www.ssd.noaa.gov/VAAC/OTH/AK/messages.html
Augustine
Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1103-01-
KARYMSKY
Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit
elev. 1,536 m
Based
on interpretations of seismic and satellite data, KVERT reported that
ash
explosions from the summit crater of Karymsky continued during 26-28
July. On
24 July, volcanologists reported that an ash plume rose to an altitude
of 6 km
(19,700 ft) a.s.l. A large thermal anomaly over the crater was visible
on
satellite imagery. KVERT warned that activity from the volcano could
affect
nearby low-flying aircraft. Karymsky remained at Concern Color Code
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
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
During
26 July-1 August, lava from Kilauea continued to flow off of a lava
delta into
the ocean at the East Lae`apuki
entry.
Incandescence was strongly visible from East Pond and January vents,
moderately
visible from the South Wall complex, and dimly visible from the
Drainhole vent
in Pu`u `O`o's crater during most of the reporting period. Tremor
remained at a
very typical moderate level at Pu`u `O`o.
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-
MANAM
offshore New Guinea, Papua New Guinea 4.10°S, 145.06°E; summit elev.
1,807 m
On 29
July, an ash plume from Manam was visible on satellite imagery at an
altitude
of ~3 km (10,000 ft) a.s.l. 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 Center
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=
MERAPI
central Java, Indonesia 7.542°S,
110.442°E;
summit elev. 2,947 m
Incandescent
rock avalanches from Merapi were observed almost daily during 26 July-1
August,
advancing at a maximum distance of 2 km SE toward the Gendol River.
On 29 July, gas plumes reached maximum heights of 430 m above the
summit
(11,000 ft a.s.l.). Pyroclastic flows were not observed during the
reporting
period. The Alert Level remained at 3 (on a scale of 1-4).
Geologic
Summary. Merapi, one of Indonesia's most active volcanoes, lies in one
of the
world's most densely populated areas and dominates the landscape
immediately N
of the major city of Yogyakarta. The steep-sided modern Merapi edifice,
its
upper part unvegetated due to frequent eruptive activity, was
constructed to
the SW of an arcuate scarp cutting the eroded older Batulawang volcano.
Pyroclastic
flows and lahars accompanying growth and collapse of the steep-sided
active
summit lava dome have devastated cultivated and inhabited lands on the
volcano's western-to-southern flanks and caused many fatalities during
historical time. The volcano is the object of extensive monitoring
efforts by
the Merapi Volcano Observatory.
Source:
Center of
Volcanology and
Geological Hazard
Mitigation (CVGHM) http://www.vsi.esdm.go.id/portal/html/index.php
Merapi
Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-25=
POPOCATÉPETL
México 19.02°N, 98.62°W; summit elev. 5,426 m
According
to the Washington VAAC, ash plumes from Popocatépetl were visible on
satellite
imagery on 25 and 27 July. These were reported by the Mexico City
Meteorological Watch Office to reach altitudes of 9.8 km (32,000 ft.)
a.s.l.
and drift WSW.
Geologic
Summary. Popocatépetl, whose name is the Aztec word for smoking
mountain,
towers to 5,426 m 70 km SE of Mexico City and is North
America's second-highest volcano. Frequent historical
eruptions
have been recorded since the beginning of the Spanish colonial era. A
small
eruption on 21 December 1994 ended five decades of quiescence. Since
1996 small
lava domes have incrementally been constructed within the summit crater
and
destroyed by explosive eruptions. Intermittent small-to-moderate
gas-and-ash
eruptions have continued, occasionally producing ashfall in neighboring
towns
and villages.
Source:
Washington
Volcanic Ash Advisory
Center
http://www.ssd.noaa.gov/VAAC/messages.html
Popocatépetl
Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1401-09=
SEMERU
Java, Indonesia 8.11°S, 112.92°E; summit elev. 3,676 m
According
to the Darwin VAAC, on 24-25 and 31 July small plumes from Semeru were
visible
on satellite imagery and reached unknown altitudes.
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 Center
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
Lava
dome growth continued at Soufrière Hills during 21-28 July. On 27 July,
the
blocky spine first observed on 21 July was seen leaning to the E, and
many new
spines had formed along the S-N-trending crest of the lava dome.
Seismic
activity decreased during the reporting period. On 30 July, a thermal
anomaly
was visible 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
During
26 July-1 August, the lava dome at Mount St.
Helens
continued to grow. Rockfalls accompanied minor earthquakes ranging from
M 3-3.6
on 26, 28, and 31 July. The hazard status remained at Volcano Advisory
(Alert
Level 2); aviation color code Orange.
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 explosions from
Suwanose-jima
during 26-30 July. The resulting plumes reached maximum altitudes of
1.8 km
(6,000 ft) a.s.l. and drifted N. Ash was not identified on satellite
imagery.
Geologic
Summary. The 8-km-long, spindle-shaped island of Suwanose-jima in the
northern Ryukyu Islands consists of
an andesitic stratovolcano
with two historically active summit craters. Only about 50 persons live
on the
sparsely populated island. The summit of the volcano is truncated by a
large
breached crater extending to the sea on the E flank that was formed by
edifice
collapse. Suwanose-jima, one of Japan’s most frequently active
volcanoes,
was in a state of intermittent strombolian activity from On-take, the
NE summit
crater, that began in 1949 and lasted nearly a half century. The
largest
historical eruption took place in 1813-14, when thick scoria deposits
blanketed
residential areas, after which the island was uninhabited for around 70
years.
The SW crater produced lava flows that reached the western coast in
1813, and
lava flows reached the eastern coast of the island in 1884.
Source:
Tokyo Volcanic Ash
Advisory Center
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=
+++++++++++++++++++++++++++++++++++++
National Museum of Natural
History MRC-119
Department of Mineral
Sciences
Phone:
202.633.1805
Fax: 202.357.2476
++++++++++++++++++++++++++++++++++++++++++
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