********************************************************* GVP/USGS Weekly Volcanic Activity Report 21-27 June 2006 ********************************************************* From: Sally Kuhn <kuhns@xxxxxx> GVP/USGS Weekly Volcanic Activity Report 21-27 June 2006 http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Bulusan, Philippines Ongoing Activity: | Anatahan, Mariana Islands | Canlaon, Philippines | Karymsky, Russia | Kilauea, USA | Merapi, Indonesia | Santa María, Guatemala | Semeru, Indonesia | Soufriere Hills, Montserrat | St. Helens, USA | Tungurahua, Ecuador New Activity/Unrest BULUSAN Luzon, Philippines 12.770°N, 124.05°E; summit elev. 1,565 m According to news reports, on 24 June rocks and large boulders that were mobilized on the flanks of Bulusan by heavy rains prompted 100 residents of Cogon village to evacuate. On 26 June, lahars occurred along a tributary leading to the Gulang-Gulang River in Irosin town. 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. Sources: Philippine Institute of Volcanology and Seismology http://www.phivolcs.dost.gov.ph/news/bulusan_bul_31May2006.html, The Associated Press http://www.chron.com/disp/story.mpl/ap/world/3999754.html Bulusan Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0703-01= Ongoing Activity ANATAHAN Mariana Islands, central Pacific Ocean 16.35°N, 145.67°E; summit elev. 788 m According to the Washington VAAC, a pilot reported that on 26 June an ash cloud from Anatahan reached altitudes of 3 km (10,000 ft) a.s.l. and drifted W. Geologic Summary. The elongate, 9-km-long island of Anatahan in the central Mariana Islands consists of large stratovolcano with a 2.3 x 5 km, E-W-trending compound summit caldera. The larger western caldera is 2.3 x 3 km wide, and its western rim forms the island's 790-m high point. Ponded lava flows overlain by pyroclastic deposits fill the floor of the western caldera, whose SW side is cut by a fresh-looking smaller crater. The 2-km-wide eastern caldera contained a steep-walled inner crater prior to the 2003 eruption whose floor was only 68 m above sea level. Sparseness of vegetation on the most recent lava flows on Anatahan had indicated that they were of Holocene age, but the first historical eruption of Anatahan did not occur until May 2003, when a large explosive eruption took place forming a new crater inside the eastern caldera. Source: Washington Volcanic Ash Advisory Center http://www.ssd.noaa.gov/VAAC/ARCHIVE/ANAT/2006E291935.html Anatahan Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0804-20= CANLAON Philippines 10.41°N, 123.13°E; summit elev. 2,435 m Minor steam-and-ash emissions that were observed from Canlaon during 21-24 June reached a maximum height of 1.5 km above the summit (12,900 ft a.s.l.) and drifted NW and SW. Light ash fall was observed approximately 25 km SW in the municipality of La Castellana. The alert status remained at Level 1, which restricts activity within 4 km of the summit. Geologic Summary. Canlaon volcano, the most active of the central Philippines, forms the highest point on the island of Negros, about 500 km ESE of Manila. The massive stratovolcano is dotted with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The summit of Canlaon contains a broad northern crater with a crater lake and a smaller, but higher, historically active crater to the south. Historical eruptions, recorded since 1866, have typically consisted of phreatic explosions of small-to-moderate size that produce minor ashfalls near the volcano. Source: Philippine Institute of Volcanology and Seismology http://www.phivolcs.dost.gov.ph/news/bulusan_bul_31May2006.html Canlaon Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0702-02= KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m Activity at Karymsky continued during 21-27 June, with 200-700 shallow earthquakes occurring daily. Based on pilot reports, on 19 June ash plumes rose up to 4 km (13,100 ft) a.s.l. and traveled NE. A thermal anomaly in the crater was observed during 17,19, and 22 June. 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 21-27 June, lava from Kilauea continued to flow off of a lava delta into the ocean at the East Lae`apuki entry. On 24 June, lava that flowed over a 67 m wide sea cliff was fed from a breakout point about 50 m inland from the cliff on the W surface of the delta. The area of East Lae`apuki lava delta was estimated to be 20.5 hectares. On 24 June, the floor of Drainhole vent in Pu`u `O`o's crater collapsed and produced a 30 m by 25 m lava pond with dynamically active lava on the SE side of the pit. Lava from the Campout flow and tube, located on the E margin of the PKK shield, advanced 1.2 km towards the Pulama pali approximately during 19-24 June. 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 about 104 km2 of land on the S flank of Kilauea and building more than 200 hectares of new land. 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- MERAPI central Java, Indonesia 7.542°S, 110.442°E; summit elev. 2,947 m During 21-25 June, seismic signals at Merapi indicated almost daily occurrence of rockfalls and pyroclastic flows. Due to inclement weather, pyroclastic flows were only observed on 24 June and reached a maximum distance of 4 km SE along the Gendol River and 2.5 km SW along the Krasak River. Gas plumes were observed during 22-25 June and reached a maximum height of 1.5 km above the summit (14,600 ft a.s.l.) on 24 June. 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= SANTA MARÍA Guatemala 14.756°N, 91.552°W; summit elev. 3,772 m Explosions at Santa María's Santiaguito lava-dome complex on 15-16, 18, 21, and 26 June produced gas-and-steam plumes with moderate to no ash content that reached heights of 1 km above the summit (15,700 ft a.s.l.). Lahars were observed on 18 and 19 June. Geologic Summary. Symmetrical, forest-covered Santa María volcano is one of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1-km-wide crater, which formed during a catastrophic eruption in 1902 and extends from just below the summit to the lower flank. The renowned Plinian eruption of 1902 followed a long repose period and devastated much of SW Guatemala. The large dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, accompanied by almost continuous minor explosions and periodic lava extrusion, larger explosions, pyroclastic flows, and lahars. Sources: Instituto Nacional de Sismologia, Vulcanologia, Meterologia, e Hidrologia http://www.insivumeh.gob.gt/geofisica/boletin%20formato.htm, Washington Volcanic Ash Advisory Center http://www.ssd.noaa.gov/VAAC/messages.html Santa María Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-03= SEMERU Java, Indonesia 8.11°S, 112.92°E; summit elev. 3,676 m Based on a pilot report, the Darwin VAAC reported that an ash plume from Semeru reached 5.5 km (18,000 ft) a.s.l. on 25 June. 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 During 16-23 June, only brief observations of the Soufrière Hills lava dome were possible due to inclement weather. The lava dome filled the base of the crater, which suggested a high rate of growth. On 17 June, lahars reached the Belham and other valleys on the lower flanks. Wet ash accumulated NW in the Salem and Olveston areas. 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 During 21-27 June, the lava dome at Mount St. Helens continued to grow and produce small rockfalls. A small steam plume from the lava dome and dust from minor rockfalls were visible from the US Forest Service's web camera at the Johnston Ridge Observatory on 25 and 26 June. On 26 June, a pilot reported that dust and ash reached a height of ~2.4 km (8,000 ft) a.s.l. and drifted W. The volcano 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- TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m During 21-27 June, small-to-moderate explosions at Tungurahua produced plumes composed of gas, steam, and small amounts of ash that reached heights of 1 km above the crater (19,800 ft a.s.l.). Light ashfall was reported in nearby localities on 21, 24-25 June. Night-time incandescence was observed from 24 to 26 June. 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 Tungurahua Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08 ============================================================== 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. ==============================================================
