****************************************************************************
GVP/USGS Weekly Volcanic Activity Report
25-31 July 2007
25-31 July 2007
http://www.volcano.si.edu/reports/usgs/
****************************************************************************
New Activity/Unrest: | Cleveland, Alaska | Gamkonora, Indonesia | Kilauea, USA | Ol Doinyo Lengai, Tanzania USA | Raung, Indonesia
Ongoing Activity: | Karymsky, Russia | Sangay, Ecuador | Shiveluch, Russia | Soufrière Hills, Montserrat | St. Helens, USA | Suwanose-jima, Japan | Tungurahua, Ecuador | Ubinas, Perú
New Activity/Unrest
CLEVELAND Aleutian Islands, USA 52.82°N, 169.95°W; summit elev. 1,730 m
A thermal anomaly in the crater of Cleveland was visible on satellite imagery during 25-26 July.
The Volcanic Alert Level remained at Watch and the Aviation Color Code remained at Orange through at least 30 July. On the 27th AVO noted that low-level eruptive activity continued. Three small SO2 clouds produced by small explosions on 20 July were detected in OMI satellite data provided by the University of Maryland Baltimore County. No further explosive activity had been detected by the OMI sensor since that time. AVO is unable to track local earthquake activity related to volcanic unrest.
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.
Sources: Alaska Volcano Observatory http://www.avo.alaska.edu/
Volcanic Emissions Group, Ozone Monitoring Instrument (OMI)-Total Ozone Monitoring Spectrometer (TOMS) http://toms.umbc.edu/
Cleveland Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1101-24-
GAMKONORA Halmahera, Indonesia 1.38°N, 127.53°E; summit elev. 5,364 m
CVGHM lowered the Alert Level for Gamkonora from 3 to 2 (on a scale of 1-4) on 24 July based on visual observations and a decrease in seismicity. That followed a sharp drop in seismicity during 8-23 July, a decline both in terms of the number of events and their energy. Later, during 16-23 July, when breaks in inclement weather took place, observers saw white plumes rising to altitudes of 5.6 km (18,400 ft) a.s.l. Available CVGHM reports issued through the 26th did not disclose more recent events.
Geologic Summary. The shifting of eruption centers on Gamkonora, at 1,635 m the highest peak of Halmahera, has produced an elongated series of summit craters along a N-S trending rift. Youthful-looking lava flows originate near the cones of Gunung Alon and Popolojo, S of Gamkonora. Since its first recorded eruption in the 16th century, Gamkonora has typically produced small-to-moderate explosive eruptions. Its largest historical eruption, in 1673, was accompanied by tsunamis that inundated villages.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id /joomla/
Gamkonora information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0608-04=
KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m
An important new eruption initiated at Kilauea very early on 21 July. It occurred along the E rift zone from fissures trending ENE for several kilometers from Pu'u O'o. The fissures caused drainage of both the West Gap lava lake and the Puka Nui pit. These and following events have come to be called the 21 July eruption and an associated fissure system by the same name.
As of 25 July, the 21 July eruption included instability at Pu'u O'o, fissuring along an NE-trending zone stretching a bit over 2 km in length, and lava flows over an area of a little over 1 km2.
A noteworthy feature of this eruption during the week 25-31 July was the formation of a series of perched ponds of lava. These formed as the edges of pools of lava hardened to create confining walls. These walls enable the pond's surface to be much higher--in some cases as much as 5 m (15 feet) higher than the surrounding land--like a volcanic above-ground swimming pool. During the 21 July eruption the walls of these perched ponds breached repeatedly, allowing lava to suddenly flood surrounding terrain. For example, at least three perched lava ponds breached by the 25th, each breakage spawning radially directed lava flows. Other small lava flows also emerged from fissures during the week as well.
The behavior of the perched ponds is difficult to judge and accordingly, around the start of this week the area was closed to the public. The eruption resided completely within the Kahauale'a Natural Area Reserve (just NE of the Hawai'i Volcanoes National Park).
On the morning of the 26th, an M 3.2 earthquake occurred on the lower E rift zone, beneath Pu`ulena crater, at a depth of 3 km (2 miles). Lava ponds again formed in the area surrounding the fissures but views of the process were hampered by foul weather. The HVO update for 31 July noted two prominent lava ponds then. In addition, one of the fissures fed an `a`a flow advancing to the NE around the N side of Kupaianaha.
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
Ol Doinyo Lengai is frequently the scene of fluid but very small volume lava flows in its summit crater, including a few that passed over the crater rim and begun the long descent down the mountain. As noted here last week, news reports had indicated that products of the volcano's 19-July eruption had entered inhabited areas. Subsequent investigations have cast doubt on those earlier claims.
Discussions this week by volcanologist Gerald Ernst with contacts in the region revealed that neither aviators, guides, scientists, nor locals had seen dramatic eruptive events at the mountain. The summit crater was intact, but eruptions were confined to the summit area. What was interpreted from a distance as a modest landslide in the crater may have sent out a dust cloud. That cloud could have been confused with ash from a large flank eruption.
To help shed light on the situation, Greg Vaughan of the Jet Propulsion Labs had a preliminary look at some ASTER satellite data of the volcano and concluded that in mid-June through late July the summit crater was likely to have continued to emit lava. The 20 July thermal emissions appeared no larger than those on 18 June. Those from 15 April appeared weaker. The images supported summit lava eruptions but failed to document any lava that had spilled over the crater rim.
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: Gerald Ernst, Centre for Environmental & Geophysical Flows, Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
Greg Vaughan, Jet Propulsion Laboratory, Mail Stop 183-501, 4800 Oak. Grove Dr., Pasadena, CA 91109
Ol Doinyo Lengai Reports from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0202-12=
RAUNG Java, Indonesia 8.12°S, 114.04°E; summit elev. 3,332 m
Based on a pilot report, the Darwin VAAC reported that an ash plume possibly from Raung rose to an altitude of 1.5 km (5,000 ft) a.s.l. Ash was not visible on satellite imagery.
Geologic Summary. Raung, one of Java's most active volcanoes, is a massive stratovolcano in easternmost Java that was constructed SW of the rim of Ijen caldera. The 3,332-m-high, unvegetated summit of Gunung Raung is truncated by a dramatic steep-walled, 2-km-wide
caldera that has been the site of frequent historical eruptions. A prehistoric collapse of Gunung Gadung on the W flank produced a large debris avalanche that traveled 79 km from the volcano, reaching nearly to the Indian Ocean. Raung contains several centers constructed along a NE-SW line, with Gunung Suket and Gunung Gadung stratovolcanoes being located to the
NE and W, respectively.
Source: Darwin VAAC http://www.bom.gov.au/info/vaac/advisories.shtml
Raung Reports from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-34=
Ongoing Activity
KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m
A KVERT report issued for Karymsky on 27 July stated the following, "The eruption of the volcano continues. Ash explosions up to 6 km (or 19,700 ft.) a.s.l. are possible at any time. The activity of the volcano could affect low-flying aircraft in the vicinity of the volcano.
Based on a report from unstated source and posted by the Tokyo VAAC, on 28 July ash plumes rose to estimated altitudes of ~6 km (20,000 ft) a.s.l., but the plume could not be identified in satellite analysis. The Level of Concern Color Code remained at 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.
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=
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 6.7-8.2 km (22,000 to 27,000 ft) a.s.l. on 28 July. Ash was not detected on satellite imagery but a weak hotspot could be seen.
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 reports noted that seismic activity at Shiveluch continued above background levels during 20-27 July. Based on seismic interpretation, during this interval ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. Gas-and-steam plumes with some ash rose to altitudes of 3.0-4.5 km (9,800-14,800 ft) a.s.l. during 20-24 July. Based on satellite imagery, gas-and-steam plumes drifted S on 22 July and a large thermal anomaly was detected in the crater during 20-27 July. Through at least 27 July, the Level of Concern Color Code remained at Orange.
<http://www.avo.alaska.edu/color_codes.php>.
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 based on visual observations, the lava dome at Soufrière Hills changed very little during 25-26 July. Seismic activity was very low and low-level rockfall activity continued. 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 25-31 July lava-dome growth at Mount St. Helens continued. Seismicity persisted at low levels.
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 and a pilot report, the Tokyo VAAC reported that an ash plume from Suwanose-jima rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted SW on 26 July. Ash was not visible 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 (VAAC) 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=
TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m
As noted by the IG in their daily reports covering 25-31 July, Tungurahua emitted a substantial number of small ash-bearing explosions and several unusually large ones as well. Based on ground observer estimates, many plumes during the reporting interval rose to 2-3 km above the crater rim (up to ~ 1 mile above the crater) and dropped ash on towns located on the volcano's flanks.
On the 26th, the IG reported one of the larger explosions, the biggest since March 2007 (its seismic signal yielded a reduced displacement of 9.2 cm2). Associated ashfalls affected some parts of the volcano. The explosion took place at night and the plume height was not estimated.
On the 30th IG observers witnessed another strong explosion that generated a heavily ash-laden plume. The dense portion of the plume rose 400 m above the crater rim. A similar plume had not been seen since 16 August 2006. The associated column of less dense material rose to 3 km and visible portions of dense material appeared as a curtain of ash deposited to the W. Some blocks associated with the outburst rolled up to 0.5 km below the crater's rim. Visibility hampered further observations that day but the many emission noises included the hammering of bouncing blocks.
Tungurahua's 25-31 July activity spurred numerous VAAC reports, but satellite analysts generally had great difficulty with cloudy conditions and few if any plumes were clearly detected.
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 ash plumes from Ubinas rose to an altitude of 5.8 km (19,000 ft) a.s.l . on 23 and 25 July. The plumes drifted SE and S, respectively. Ash was not identified on satellite imagery. On 24 July, a diffuse plume was visible on satellite imagery at an altitude of 6.1 km (20,000 ft) a.s.l.
Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)
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=
==============================================================
To unsubscribe from the volcano list, send the message:
signoff volcano
to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx
****************************************************************************
New Activity/Unrest: | Cleveland, Alaska | Gamkonora, Indonesia | Kilauea, USA | Ol Doinyo Lengai, Tanzania USA | Raung, Indonesia
Ongoing Activity: | Karymsky, Russia | Sangay, Ecuador | Shiveluch, Russia | Soufrière Hills, Montserrat | St. Helens, USA | Suwanose-jima, Japan | Tungurahua, Ecuador | Ubinas, Perú
New Activity/Unrest
CLEVELAND Aleutian Islands, USA 52.82°N, 169.95°W; summit elev. 1,730 m
A thermal anomaly in the crater of Cleveland was visible on satellite imagery during 25-26 July.
The Volcanic Alert Level remained at Watch and the Aviation Color Code remained at Orange through at least 30 July. On the 27th AVO noted that low-level eruptive activity continued. Three small SO2 clouds produced by small explosions on 20 July were detected in OMI satellite data provided by the University of Maryland Baltimore County. No further explosive activity had been detected by the OMI sensor since that time. AVO is unable to track local earthquake activity related to volcanic unrest.
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.
Sources: Alaska Volcano Observatory http://www.avo.alaska.edu/
Volcanic Emissions Group, Ozone Monitoring Instrument (OMI)-Total Ozone Monitoring Spectrometer (TOMS) http://toms.umbc.edu/
Cleveland Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1101-24-
GAMKONORA Halmahera, Indonesia 1.38°N, 127.53°E; summit elev. 5,364 m
CVGHM lowered the Alert Level for Gamkonora from 3 to 2 (on a scale of 1-4) on 24 July based on visual observations and a decrease in seismicity. That followed a sharp drop in seismicity during 8-23 July, a decline both in terms of the number of events and their energy. Later, during 16-23 July, when breaks in inclement weather took place, observers saw white plumes rising to altitudes of 5.6 km (18,400 ft) a.s.l. Available CVGHM reports issued through the 26th did not disclose more recent events.
Geologic Summary. The shifting of eruption centers on Gamkonora, at 1,635 m the highest peak of Halmahera, has produced an elongated series of summit craters along a N-S trending rift. Youthful-looking lava flows originate near the cones of Gunung Alon and Popolojo, S of Gamkonora. Since its first recorded eruption in the 16th century, Gamkonora has typically produced small-to-moderate explosive eruptions. Its largest historical eruption, in 1673, was accompanied by tsunamis that inundated villages.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id /joomla/
Gamkonora information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0608-04=
KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m
An important new eruption initiated at Kilauea very early on 21 July. It occurred along the E rift zone from fissures trending ENE for several kilometers from Pu'u O'o. The fissures caused drainage of both the West Gap lava lake and the Puka Nui pit. These and following events have come to be called the 21 July eruption and an associated fissure system by the same name.
As of 25 July, the 21 July eruption included instability at Pu'u O'o, fissuring along an NE-trending zone stretching a bit over 2 km in length, and lava flows over an area of a little over 1 km2.
A noteworthy feature of this eruption during the week 25-31 July was the formation of a series of perched ponds of lava. These formed as the edges of pools of lava hardened to create confining walls. These walls enable the pond's surface to be much higher--in some cases as much as 5 m (15 feet) higher than the surrounding land--like a volcanic above-ground swimming pool. During the 21 July eruption the walls of these perched ponds breached repeatedly, allowing lava to suddenly flood surrounding terrain. For example, at least three perched lava ponds breached by the 25th, each breakage spawning radially directed lava flows. Other small lava flows also emerged from fissures during the week as well.
The behavior of the perched ponds is difficult to judge and accordingly, around the start of this week the area was closed to the public. The eruption resided completely within the Kahauale'a Natural Area Reserve (just NE of the Hawai'i Volcanoes National Park).
On the morning of the 26th, an M 3.2 earthquake occurred on the lower E rift zone, beneath Pu`ulena crater, at a depth of 3 km (2 miles). Lava ponds again formed in the area surrounding the fissures but views of the process were hampered by foul weather. The HVO update for 31 July noted two prominent lava ponds then. In addition, one of the fissures fed an `a`a flow advancing to the NE around the N side of Kupaianaha.
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
Ol Doinyo Lengai is frequently the scene of fluid but very small volume lava flows in its summit crater, including a few that passed over the crater rim and begun the long descent down the mountain. As noted here last week, news reports had indicated that products of the volcano's 19-July eruption had entered inhabited areas. Subsequent investigations have cast doubt on those earlier claims.
Discussions this week by volcanologist Gerald Ernst with contacts in the region revealed that neither aviators, guides, scientists, nor locals had seen dramatic eruptive events at the mountain. The summit crater was intact, but eruptions were confined to the summit area. What was interpreted from a distance as a modest landslide in the crater may have sent out a dust cloud. That cloud could have been confused with ash from a large flank eruption.
To help shed light on the situation, Greg Vaughan of the Jet Propulsion Labs had a preliminary look at some ASTER satellite data of the volcano and concluded that in mid-June through late July the summit crater was likely to have continued to emit lava. The 20 July thermal emissions appeared no larger than those on 18 June. Those from 15 April appeared weaker. The images supported summit lava eruptions but failed to document any lava that had spilled over the crater rim.
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: Gerald Ernst, Centre for Environmental & Geophysical Flows, Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ, UK
Greg Vaughan, Jet Propulsion Laboratory, Mail Stop 183-501, 4800 Oak. Grove Dr., Pasadena, CA 91109
Ol Doinyo Lengai Reports from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0202-12=
RAUNG Java, Indonesia 8.12°S, 114.04°E; summit elev. 3,332 m
Based on a pilot report, the Darwin VAAC reported that an ash plume possibly from Raung rose to an altitude of 1.5 km (5,000 ft) a.s.l. Ash was not visible on satellite imagery.
Geologic Summary. Raung, one of Java's most active volcanoes, is a massive stratovolcano in easternmost Java that was constructed SW of the rim of Ijen caldera. The 3,332-m-high, unvegetated summit of Gunung Raung is truncated by a dramatic steep-walled, 2-km-wide
caldera that has been the site of frequent historical eruptions. A prehistoric collapse of Gunung Gadung on the W flank produced a large debris avalanche that traveled 79 km from the volcano, reaching nearly to the Indian Ocean. Raung contains several centers constructed along a NE-SW line, with Gunung Suket and Gunung Gadung stratovolcanoes being located to the
NE and W, respectively.
Source: Darwin VAAC http://www.bom.gov.au/info/vaac/advisories.shtml
Raung Reports from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-34=
Ongoing Activity
KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m
A KVERT report issued for Karymsky on 27 July stated the following, "The eruption of the volcano continues. Ash explosions up to 6 km (or 19,700 ft.) a.s.l. are possible at any time. The activity of the volcano could affect low-flying aircraft in the vicinity of the volcano.
Based on a report from unstated source and posted by the Tokyo VAAC, on 28 July ash plumes rose to estimated altitudes of ~6 km (20,000 ft) a.s.l., but the plume could not be identified in satellite analysis. The Level of Concern Color Code remained at 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.
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=
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 6.7-8.2 km (22,000 to 27,000 ft) a.s.l. on 28 July. Ash was not detected on satellite imagery but a weak hotspot could be seen.
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 reports noted that seismic activity at Shiveluch continued above background levels during 20-27 July. Based on seismic interpretation, during this interval ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. Gas-and-steam plumes with some ash rose to altitudes of 3.0-4.5 km (9,800-14,800 ft) a.s.l. during 20-24 July. Based on satellite imagery, gas-and-steam plumes drifted S on 22 July and a large thermal anomaly was detected in the crater during 20-27 July. Through at least 27 July, the Level of Concern Color Code remained at Orange.
<http://www.avo.alaska.edu/color_codes.php>.
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 based on visual observations, the lava dome at Soufrière Hills changed very little during 25-26 July. Seismic activity was very low and low-level rockfall activity continued. 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 25-31 July lava-dome growth at Mount St. Helens continued. Seismicity persisted at low levels.
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 and a pilot report, the Tokyo VAAC reported that an ash plume from Suwanose-jima rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted SW on 26 July. Ash was not visible 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 (VAAC) 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=
TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m
As noted by the IG in their daily reports covering 25-31 July, Tungurahua emitted a substantial number of small ash-bearing explosions and several unusually large ones as well. Based on ground observer estimates, many plumes during the reporting interval rose to 2-3 km above the crater rim (up to ~ 1 mile above the crater) and dropped ash on towns located on the volcano's flanks.
On the 26th, the IG reported one of the larger explosions, the biggest since March 2007 (its seismic signal yielded a reduced displacement of 9.2 cm2). Associated ashfalls affected some parts of the volcano. The explosion took place at night and the plume height was not estimated.
On the 30th IG observers witnessed another strong explosion that generated a heavily ash-laden plume. The dense portion of the plume rose 400 m above the crater rim. A similar plume had not been seen since 16 August 2006. The associated column of less dense material rose to 3 km and visible portions of dense material appeared as a curtain of ash deposited to the W. Some blocks associated with the outburst rolled up to 0.5 km below the crater's rim. Visibility hampered further observations that day but the many emission noises included the hammering of bouncing blocks.
Tungurahua's 25-31 July activity spurred numerous VAAC reports, but satellite analysts generally had great difficulty with cloudy conditions and few if any plumes were clearly detected.
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 ash plumes from Ubinas rose to an altitude of 5.8 km (19,000 ft) a.s.l . on 23 and 25 July. The plumes drifted SE and S, respectively. Ash was not identified on satellite imagery. On 24 July, a diffuse plume was visible on satellite imagery at an altitude of 6.1 km (20,000 ft) a.s.l.
Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)
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=
To contribute to the volcano list, send your message to: volcano@xxxxxxxx Please do not send attachments. ==============================================================
