GVP/USGS Weekly Volcanic Activity Report

16-22 August 2006

http://www.volcano.si.edu/reports/usgs/

New Activity/Unrest: | Mayon, Philippines | Tungurahua, Ecuador

Ongoing Activity: | Fuego, Guatemala | Karymsky, Russia | Kilauea, USA |
Manam, Papua New Guinea | Pacaya, Guatemala | Rabaul, Papua New Guinea |
Soufriere Hills, Montserrat | St. Helens, USA | Sulu Range, Papua New
Guinea | Ubinas, Perú

New Activity/Unrest

MAYON southeastern Luzon, Philippines 13.257°N, 123.685°E; summit elev.
2,462 m

PHIVOLCS reported that explosions from Mayon continued during 16-19
August. On 17 August, ash-and-steam plumes drifted at least 5.3 km NE
and reached the town Calbayog, where light ashfall was reported. Lava
extrusion and collapsing lava-flow fronts that produced blocks and small
fragments on the SE slopes continued during the reporting period. On 18
August, the Mibinit/Bonga valley lava flows reached ~6.8 km SE from the
summit. The following day, PHIVOLCS estimated that the volume of erupted
volcanic deposits was 36 to 41 million cubic meters.

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; All times are
local (= UTC -5 hours)

A large eruption of Tungurahua began on 16 August at 1900 and continued
to 17 August at 0200, when activity began to diminish. According to the
Instituto Geofísico, seismic activity increased on 16 August and
clinometer measurements indicated a bulge on the N flank as compared to
11 August measurements. Ash-and-gas plumes reached heights of 3 km above
the summit (26,300 ft a.s.l.) and drifted W and NW. About 3,200 people
were evacuated from at-risk areas. On 17 August, about 20 pyroclastic
flows traveled NW through the Achupashal, La Hacienda, and Mandur
drainages, and NNW towards the Juive and Vazcún drainages. The Chambo
and Puela rivers and several roads to the W and S were blocked by
pyroclastic-flow debris. Tephra fall (3 cm in diameter) was reported
from several areas in a zone that extended from Penipe in the SW to
about 15 km NW. Ash plumes reached estimated heights of 10 km above the
summit (49,000 ft a.s.l.) and covered the central part of Ecuador,
forming a cloud ~742 km long and ~185 km wide trending NNW and SSE.

On 18 August, incandescent blocks were ejected from the summit and
descended about 1.7 km down the flanks. Based on seismic interpretation,
one of the blockages damming part of the Chambo River had been breached.
During 18-19 August, the N flank continued to inflate. During 20-21
August, steam emissions were observed during breaks in the cloud cover
and the N flank exhibited deflation. On 23 August, two lava flows were
identified on the NW slope moving at a slow rate.

According to news reports, ash and debris fall caused fires and severe
damage to five villages. An estimated 20,000 hectares (50,000 acres) of
crops were destroyed. At least five people are dead or missing, and
several more were injured. An estimated 4,000 people have been relocated
to shelters.

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,

Agence France-Presse
http://news.yahoo.com/s/afp/20060817/sc_afp/ecuadorvolcano_060817221429,

Relief Web
http://www2.reliefweb.int/rw/RWB.NSF/db900SID/LSGZ-6SSGAR?OpenDocument&rc=2,

Associated Press
http://www.columbian.com/news/localNews/08182006news51992.cfm,

Relief Web
http://www.reliefweb.int/rw/rwb.nsf/db900SID/EKOI-6SW5DM?OpenDocument&rc=2&cc=ec

Tungurahua Information from the Global Volcanism Program

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

Ongoing Activity

FUEGO Guatemala 14.47°N, 90.88°W; summit elev. 3,763 m

Ash explosions from Fuego reached 300-800 m above the summit
(13,300-15,000 ft a.s.l.) on 16 and 21 August. Explosions of
incandescent material on 16, 18, and 21 August produced avalanches that
descended 300-500 m SW towards the Ceniza, Taniluyá, and Santa Teresa
river valleys.

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.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meterologia, e
Hidrologia, http://www.insivumeh.gob.gt/geofisica/boletin%20formato.htm

Fuego Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-09=

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

Activity at Karymsky continued during 12-18 August, with 60-500 shallow
earthquakes occurring daily. Based on interpretations of seismic data,
ash plumes reached altitudes of 3.7 km (12,140 ft) a.s.l. According to
the Airport Meteorological Center (AMC) in Yelizovo, on 16 August a
pilot saw an ash plume rise to ~6.5 km (21,300 ft.) a.s.l. and drift NE.
Karymsky remained at Concern Color Code Orange
.

Geologic Summary. Karymsky, the most active volcano of Kamchatka's
eastern volcanic zone, is a symmetrical stratovolcano constructed within
a 5-km-wide caldera that formed about 7,600-7,700 radiocarbon years ago.
Construction of the Karymsky stratovolcano began about 2,000 years
later. The latest eruptive period began about 500 years ago, following a
2,300-year quiescence. Much of the cone is mantled by lava flows less
than 200 years old. Historical eruptions have been Vulcanian or
Vulcanian-Strombolian with moderate explosive activity and occasional
lava flows from the summit crater. Most seismicity preceding Karymsky
eruptions has originated beneath Akademia Nauk caldera, which is located
immediately S of Karymsky volcano and erupted simultaneously with
Karymsky in 1996.

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 16-22 August, 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 visible from the East Pond and January vents, South
Wall complex, and Drainhole vent in Pu'u 'O'o's crater during most of
the reporting period.

A recent leveling survey revealed an inflationary trend at the summit of
Kilauea, in areas S of Halema'uma'u crater. Elevations have increased 11
cm in the past 6 months and continued to increase during the reporting
period.

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

The RVO reported continuous emissions of ash clouds from Manam’s Main
Crater during 14-17 August. On 14 August, dense pale gray-to-brown ash
clouds rose to less than 1 km above the summit (~9,200 ft a.s.l.) and
drifted WNW. During 15-17 August, the emissions decreased to diffuse
pale gray ash clouds and weak incandescence was observed at night.

Based on pilot reports and satellite imagery, the Darwin VAAC reported
continuous emissions during 17-21 August. The plumes reached altitudes
of 3.7 km (12,000 ft) a.s.l. and drifted NW.

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.

Sources: Herman Patia, Rabaul Volcano Observatory,

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=

PACAYA southern Guatemala 14.38°N, 90.60°W; summit elev. 2,552 m

Fumarolic emissions from Pacaya’s Mackenney Cone drifted S and SW on 16
and 21 August. Lava flows advanced N and NW towards Cerro Chino, NE
towards Cerro Grande, and SW from Mackenney Cone during 16-21 August.

Geologic Summary. Eruptions from Pacaya, one of Guatemala's most active
volcanoes, are frequently visible from Guatemala City, the nation's
capital. Pacaya is a complex volcano constructed on the southern rim of
the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava
domes occupies the caldera floor. The Pacaya massif includes the Cerro
Grande lava dome and a younger volcano to the SW. Collapse of Pacaya
volcano about 1,100 years ago produced a debris-avalanche deposit that
extends 25 km onto the Pacific coastal plain and left an arcuate somma
rim inside which the modern Pacaya volcano (MacKenney cone) grew. During
the past several decades, activity at Pacaya has consisted of frequent
Strombolian eruptions with intermittent lava flow extrusion on the
flanks of MacKenney cone, punctuated by occasional larger explosive
eruptions.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meterologia, e
Hidrologia, http://www.insivumeh.gob.gt/geofisica/boletin%20formato.htm

Pacaya Information from the Global Volcanism Program

http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-11=

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

RVO reported that during 11-20 August, Rabaul caldera's Tavurvur cone
continued with mild eruptive activity. Variable amounts of diffuse gray
ash-clouds were emitted from the summit area and rose to less than 150 m
above the summit (~2,750 ft a.s.l.). The plumes drifted N and NW
depositing small amounts of ash in Rabaul Town. Based on GPS and Tide
Gauge measurements, an overall inflationary trend that began in
mid-February continued through the reporting period.

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=

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

Lava dome growth continued at Soufrière Hills during 11-18 August. The
activity was concentrated in the N half of the dome. Based on
information from the MVO, pilot reports, and the Piarco MWO, the
Washington VAAC reported continuous ash emissions on 18 and 19 August.
The plumes reached altitudes of 2.4 km (8,000 ft) a.s.l. and drifted W.

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 16-22 August, the lava dome at Mount St. Helens continued to
grow. Based on interpretations of seismic data, spine extrusion from the
dome continued in conjunction with small earthquakes and rockfalls.

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-

SULU RANGE New Britain Island, Papua New Guinea 5.50°S, 150.942°E

The RVO reported that during 10-15 August, seismic activity in the Sulu
Range fluctuated but remained at low levels. Epicenters of occasional
high frequency earthquakes were located between the Sulu Range and the
Silanga area, approximately 10 km to the SW. Vapor plumes were emitted
from the Silanga Hotsprings and on 15 August an explosion was heard from
Mato Hotspring.

Geologic Summary. The Sulu Range consists of a group of partially
overlapping small stratovolcanoes in west-central New Britain off
Bangula Bay. The 610-m Mount Malopu forms the high point of the
basaltic-to-rhyolitic complex at its SW end. Lava Point forms a
peninsula extending about 1 km into Bangula Bay at the NW side of the
Sulu Range. The Walo hydrothermal area, consisting of solfataras and mud
pots, lies on the coastal plain west of the SW base of the Sulu Range.
Prior to 2006, no historical eruptions had occurred from the Sulu Range,
although some of the cones display a relatively undissected morphology.

Source: Herman Patia, Rabaul Volcano Observatory

Sulu Range Information from the Global Volcanism Program

http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-09=

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

Based on pilot reports and satellite imagery, the Buenos Aires VAAC
reported continuous emissions of ash plumes from Ubinas during 17-21
August. The plumes reached altitudes of ~5.5-7.9 km (~18,000-26,000 ft)
a.s.l. and drifted NE, SE, and S.

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