************************************************
GVP/USGS Weekly Volcanic Activity Report
18-24 July 2007
http://www.volcano.si.edu/reports/usgs/
************************************************
New Activity/Unrest: | Cleveland, Alaska | Fuego, Guatemala | Kilauea,
USA | Ol Doinyo Lengai, Tanzania
Ongoing Activity: | Karymsky, Russia | Kliuchevskoi, Russia | Lascar,
Chile | Sangay, Ecuador | Shiveluch, Russia | Soufrière Hills,
Montserrat | 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
AVO raised the Volcanic Alert Level for Cleveland from Advisory to Watch
and the Aviation Color Code from Yellow to Orange
<http://www.avo.alaska.edu/color_codes.php> on 20 July. The change in
Alert Level was based on the presence of an intense thermal anomaly in
the crater and associated steam-and-gas plume observed on satellite
imagery. The thermal anomaly continued to be detected on satellite
imagery during 22-23 July.
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/
Cleveland Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1101-24-
FUEGO Guatemala 14.47°N, 90.88°W; summit elev. 3,763 m
INSIVUMEH reported that during 17-18 July, gas plumes from Fuego rose to
an altitude of 3.9 km (12,800 ft) a.s.l. and drifted SW. On 18 July, a
hot lahar, 20 m wide and 1.5 m high, carried blocks 1-1.5 m in diameter
to the W down the Santa Teresa ravine. On 20 July, the seismic network
recorded 21 explosions. Associated ash plumes rose to altitudes of
4.1-4.7 km (13,500-15,400 ft) a.s.l. and drifted W and SW. Rumbling
noises were reported.
CONRED raised the Alert Level to Yellow in surrounding communities on 22
July, based on a report from INSIVUMEH. INSIVUMEH reported that
Vulcanian explosions produced ash plumes to altitudes of 4.1-5.2 km
(13,500-17,100 ft) a.s.l. and expelled incandescent material 75-250 m
above the crater. The explosions were accompanied by rumbling noises and
shock waves that rattled ceilings and windows within a 25 km radius.
Ashfall was reported from areas approximately 7-8 km to the SW, and
incandescent avalanches of blocks rolled 500-800 m down the S flanks
towards areas of vegetation. A new lava flow that initiated from an area
100 m below the S edge of the central crater traveled about 100 m.
Geologic Summary. Volcán Fuego, one of Central America's most active
volcanoes, is one of three large stratovolcanoes overlooking Guatemala's
former capital, Antigua. The scarp of an older edifice, Meseta, lies
between 3,763-m-high Fuego and its twin volcano to the N, Acatenango.
Construction of Meseta volcano continued until the late Pleistocene or
early Holocene, after which growth of the modern Fuego volcano continued
the southward migration of volcanism that began at Acatenango. Frequent
vigorous historical eruptions have been recorded at Fuego since the
onset of the Spanish era in 1524, and have produced major ashfalls,
along with occasional pyroclastic flows and lava flows. The last major
explosive eruption from Fuego took place in 1974, producing spectacular
pyroclastic flows visible from Antigua.
Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e
Hidrologia (INSIVUMEH)
http://www.insivumeh.gob.gt/geofisica/boletin%20formato.htm,
Coordinadora Nacional para la Reducción de Desastres (CONRED)
http://www.conred.org/boletines/2007/mayo2007/boletin250507a.php
Fuego Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-09=
KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m
During 18-21 July, the E vent and dominant W vent in Kilauea's Pu'u 'O'o
produced lava flows. On 18 July, new vents opened in the Puka Nui pit,
in the SSW area of Pu'u 'O'o crater, and produced lava flows that
ponded. On 20 July, a vent high on the S crater wall, adjacent to the
Puka Nui Gap pit, produced spatter and propelled lava bombs 10 m into
the air. Meanwhile, the lava lake in the West Gap pit continued to fill,
overturn, and occasionally overflow. The spatter cone that built up
around the S wall vent in West Gap pit was submerged beneath the lava
lake surface on 20 July. Uplift of the crater interior continued.
Earthquakes occurred beneath the upper E rift zone, S flank, and
Halema’uma’u crater.
On 20 July, just before midnight, Pu'u 'O'o’s crater floor started to
subside; a tiltmeter recorded a nearly 300 microradian tilt change. Just
after midnight, on 21 July, the West Gap lava lake and Puka Nui pit
drained. A new eruption initiated along a set of fissures that extended
1.7 km E from a point about 150 m E of the E rim of Pu'u 'O'o crater.
Preliminary reports described two 600-800 m long, left-stepping fissures
between Pu'u 'O'o and Kupaianaha. The easternmost fissure fed two lava
flows; the farthest extent of the flow was 1-1.5 miles from the fissure
in the SE direction.
On 22 July, HVO reported that the westernmost fissure was inactive by
mid-morning on 21 July and the uppermost segment of the active lower
fissure was completely sealed by mid-morning on 22 July. The rest of the
fissure erupted lava, constructing several small perched ponds. A
perched pond at the upper segment of the active fissure breached and
produced an a’a’ flow that traveled 300-400 m to the E. At Pu'u 'O'o
crater, several new cracks were observed around its rim, parts of which
had collapsed. During 23-24 July, lava ponds surrounding lower fissure
segments grew in thickness and spilled lava over their edges.
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-
OL DOINYO LENGAI Tanzania, eastern Africa 2.751°S, 35.902°E; summit
elev. 2,890 m
According to news reports, an eruption began at Ol Doinyo Lengai around
19 July, forcing villagers living near the volcano to evacuate. An
article stated that, "…more than 1,500 people, most of them Maasai
families, vacated their homes in Ngaresero, Orbalal and Nayobi villages
following the tremors that triggered the volcanic eruption.” “Villagers
are reported to have heard roaring … before the volcano started
discharging ash and lava.” There were reports of a damaged school and
two injuries, but no reports of deaths.
Geologic Summary. The symmetrical Ol Doinyo Lengai stratovolcano is the
only volcano known to have erupted carbonatite tephras and lavas in
historical time. The prominent volcano, known as "The Mountain of God,"
rises abruptly above the broad plain S of Lake Natron. The cone-building
stage of the volcano ended about 15,000 years ago and was followed by
periodic ejection of natrocarbonatite and nephelinite tephra during the
Holocene. Historical eruptions have consisted of smaller tephra
eruptions and emission of numerous natrocarbonatitic lava flows on the
floor of the summit crater. Petrologists first observed the eruption of
carbonatitic lava flows in the 1960s. Subsequent more frequent visits
have documented long-term lava effusion in the summit crater that would
not have been seen from the foot of the volcano.
Sources: East African Standard
http://allafrica.com/stories/200707201156.html,
Associated Press http://www.sanluisobispo.com/353/story/97561.html
Ol Doinyo Lengai Reports from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0202-12=
Ongoing Activity
KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m
Seismic activity at Karymsky was above background levels during 13-20
July, with 500-900 shallow earthquakes occurring daily. Based on seismic
interpretation, ash plumes may have risen to altitudes as high as 4.5 km
(14,800 ft) a.s.l. Ash plumes drifted SE and SW and a thermal anomaly in
the crater were visible on satellite imagery during 14-18 July. Plumes
rose to estimated altitudes of 4.5 km (14,800 ft) a.s.l. based on
atmospheric profiles. The Level of Concern Color Code remained at Orange
<http://www.avo.alaska.edu/color_codes.php>.
Based on satellite imagery, the Tokyo VAAC reported that an ash plume
rose to an altitude of 5.2 (17,000 ft) a.s.l. on 20 July and drifted SW.
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=
KLIUCHEVSKOI Kamchatka Peninsula, Russia 56.06°N, 160.64°E; summit elev.
4,835 m
KVERT reported that seismic activity at Kliuchevskoi was at background
levels during 13-20 July. Based on observations of satellite imagery,
ash plumes drifted E on 13 July and a thermal anomaly in the crater was
noted during 13-20 July. Ash plumes rose to an altitude of 5.5 km
(18,000 ft) a.s.l. and drifted SE and E during 13-15 July, according to
video and visual observations. Gas-and-steam plumes were observed on 12,
16, and 18 July. The Level of Concern Color Code
<http://www.avo.alaska.edu/color_codes.php> was lowered from Orange to
Yellow due to a decrease in seismicity and an absence of ash plumes
during 17-20 July.
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=
LASCAR northern Chile 23.37°S, 67.73°W; summit elev. 5,592 m
Based on pilot reports and satellite image observations, the Buenos
Aires VAAC reported that an ash plume from Lascar rose to altitudes of
7.6-9.1 km (25,000-30,000 ft) a.s.l. on 18 July and drifted NE.
Geologic Summary. Lascar is the most active volcano of the northern
Chilean Andes. The andesitic-to-dacitic stratovolcano contains six
overlapping summit craters and lies 5 km W of an older, higher
stratovolcano, Volcán Aguas Calientes. Lascar consists of two major
edifices; activity began at the eastern volcano and then shifted to the
western cone. The largest eruption of Lascar took place about 26,500
years ago, and following the eruption of the Tumbres scoria flow about
9,000 years ago, activity shifted back to the eastern edifice, where
three overlapping craters were formed. Frequent small-to-moderate
explosive eruptions have been recorded from Lascar in historical time
since the mid-19th century, along with periodic larger eruptions that
produced ashfall hundreds of kilometers away from the volcano. The
largest historical eruption of Lascar took place in 1993 and produced
pyroclastic flows that extended up to 8.5 km NW of the summit.
Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html
Lascar Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1505-10=
SANGAY Ecuador 2.03°S, 78.34°W; summit elev. 5,188 m
Based on pilot observations, the Washington VAAC reported that an ash
plume from Sangay rose to an altitude of 5.5 km (18,000 ft) a.s.l. and
drifted W on 23 July. Ash was not detected on satellite imagery. On 24
July, a diffuse ash plume at an altitude of 5.2 km (17,000 ft) a.s.l.
was visible on satellite imagery drifting SW.
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 (VAAC)
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=
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 13-20 July. Based on seismic interpretation,
ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. during the
reporting period. Gas-and-steam plumes with some ash rose to altitudes
of 3-4.5 km (9,800-14,800 ft) a.s.l. during 11-15 and 18-19 July. Based
on satellite imagery, plumes drifted S and SW during 15-16 July and a
large thermal anomaly was detected in the crater during 13-20 July. The
Level of Concern Color Code remained at Orange
<http://www.avo.alaska.edu/color_codes.php>.
Based on information reported from KEMSD, the Tokyo VAAC reported that
an eruption plume rose to 5.8 km (19,000 ft) a.s.l. on 24 July. 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=
SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev.
1,052 m
MVO reported that during 13-24 July, the lava dome at Soufrière Hills
changed very little, based on visual observations. Seismic activity was
very low and low-level rockfall activity continued. Heavy rainfall
generated lahars in E drainages on 19 July. The Alert Level remained
elevated 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 18-24
July lava-dome growth at Mount St. Helens continued. Seismicity
persisted at low levels, punctuated by M 1.5-2.5, and occasionally
larger, earthquakes. Clouds inhibited visual observations.
Geologic Summary. Prior to 1980, Mount St. Helens formed a conical,
youthful volcano sometimes known as the Fuji-san of America. During the
1980 eruption the upper 400 m of the summit was removed by slope
failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially
filled by a lava dome. Mount St. Helens was formed during nine eruptive
periods beginning about 40-50,000 years ago, and has been the most
active volcano in the Cascade Range during the Holocene. The modern
edifice was constructed during the last 2,200 years, when the volcano
produced basaltic as well as andesitic and dacitic products from summit
and flank vents. Historical eruptions in the 19th century originated
from the Goat Rocks area on the N flank, and were witnessed by early
settlers.
Source: US Geological Survey Cascades Volcano Observatory
http://vulcan.wr.usgs.gov/Volcanoes/MSH/CurrentActivity/framework.html
St. Helens Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1201-05-
TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m
IG reported that during 18-24 July, intermittently visible ash plumes
from Tungurahua rose to altitudes of 5.2-8 km (17,100-26,200 ft) a.s.l.
and drifted NW, W, and SW. Ashfall was reported from areas SW and W
during 19-21 and 24 July. On 20 July, mudflows were reported from
drainages to the NW. On 21 July, a steam-and-gas plume drifted W. On 21,
22, and 24 July, ash plumes were occasionally accompanied by roaring
sounds, “cannon shots”, or noises that resembled blocks rolling down the
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.
Source: Instituto Geofísico-Escuela Poltécnica Nacional
http://www.igepn.edu.ec/
Tungurahua Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08=
UBINAS Perú 16.355°S, 70.903°W; summit elev. 5,672 m
Based on a Significant Meteorological Information (SIGMET) advisory, the
Buenos Aires VAAC reported that an ash plume from Ubinas rose to an
altitude of 6.1 km (20,000 ft) a.s.l. and drifted SE on 22 July. Ash was
not identified on satellite imagery.
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 (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html
Ubinas Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1504-02=
---------------------------------------------------------------------------------
Sally Kuhn Sennert
SI/USGS Weekly Volcanic Activity Report Editor
Global Volcanism Program
http://www.volcano.si.edu/reports/usgs/
Smithsonian Institution, National Museum of Natural History
Department of Mineral Sciences, MRC-119
Washington, D.C., 20560
Phone: 202.633.1805
Fax: 202.357.2476
---------------------------------------------------------------------------------
==============================================================
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.
==============================================================
