AVO Staff Directory:

Gareloi Volcano (178.794 deg W and 51.790 deg N) is located on Gareloi Island in the Delarof Islands group of the Aleutian Islands, about 2,000 kilometers west-southwest of Anchorage and about 150 kilometers west of Adak, the westernmost community in Alaska. This small (about 10 kilometer) volcano has been one of the most active in the Aleutians since its discovery by the Bering expedition in the 1740s, though because of its remote location, observations have been scant and many smaller eruptions may have gone unrecorded. Eruptions of Gareloi commonly produce ash clouds and lava flows. Scars on the flanks of the volcano and debris-avalanche deposits on the adjacent seafloor indicate that the volcano has produced large landslides in the past, possibly causing tsunamis. Such events are infrequent, occurring at most every few thousand years. The primary hazard from Gareloi is airborne clouds of ash that could affect aircraft. In this report, we summarize and describe the major volcanic hazards associated with Gareloi.

Coombs, M.L., McGimsey, R.G., and Browne, B.L., 2008, Preliminary volcano-hazard assessment for Gareloi Volcano, Gareloi Island, Alaska: U.S. Geological Survey Scientific Investigations Report 2008-5159, 29 p., 1 sheet, available at http://pubs.usgs.gov/sir/2008/5159/ .
link to USGS website containing PDFs of report and map

Along the 450-km-long stretch of the Aleutian volcanic arc from Great Sitkin to Kiska Islands, edifice failure and submarine debris-avalanche deposition have occurred at seven of ten Quaternary volcanic centers. Reconnaissance geologic studies have identified subaerial evidence for large-scale prehistoric collapse events at five of the centers (Great Sitkin, Kanaga, Tanaga, Gareloi, and Segula). Side-scan sonar data collected in the 1980s by GLORIA surveys reveal a hummocky seafloor fabric north of several islands, notably Great Sitkin, Kanaga, Bobrof, Gareloi, Segula, and Kiska, suggestive of landslide debris. Simrad EM300 multibeam sonar data, acquired in 2005, show that these areas consist of discrete large blocks strewn across the seafloor, supporting the landslide interpretation from the GLORIA data. A debris-avalanche deposit north of Kiska Island (177.6° E, 52.1° N) was fully mapped by EM300 multibeam revealing a hummocky surface that extends 40 km from the north flank of the volcano and covers an area of 380 km2. A 24-channel seismic reflection profile across the longitudinal axis of the deposit reveals a several hundredmeter- thick chaotic unit that appears to have incised into well-bedded sediment, with only a few tens of meters of surface relief.

Coombs, M.L., White, S.M., and Scholl, D.W., 2007, Massive edifice failure at Aleutian arc volcanoes: Earth and Planetary Science Letters, v. 256, p. 403-418, doi: 10.1016/j.epsl.2007.01.030.

The Tanaga volcanic cluster lies on the northwest part of Tanaga Island, about 100 kilometers west of Adak, Alaska, and 2,025 kilometers southwest of Anchorage, Alaska. The cluster consists of three volcanoes from west to east, they are Sajaka, Tanaga, and Takawangha. All three volcanoes have erupted in the last 1,000 years, producing lava flows and tephra (ash) deposits. A much less frequent, but potentially more hazardous phenomenon, is volcanic edifice collapse into the sea, which likely happens only on a timescale of every few thousands of years, at most. Parts of the volcanic bedrock near Takawangha have been altered by hydrothermal activity and are prone to slope failure, but such events only present a local hazard. Given the volcanic cluster's remote location, the primary hazard from the Tanaga volcanoes is airborne ash that could affect aircraft. In this report, we summarize the major volcanic hazards associated with the Tanaga volcanic cluster.

Coombs, M.L., McGimsey, R.G., and Browne, B.L., 2007, Preliminary volcano-hazard assessment for the Tanaga Volcanic Cluster, Tanaga Island, Alaska: U.S. Geological Survey Scientific Investigations Report 2007-5094, 36 p., available online at: http://pubs.usgs.gov/sir/2007/5094/ .
USGS website with links to PDF of report and map sheet

Augustine volcano, in south central Alaska, ended a 20-year period of repose on 11 January 2006 with 13 explosive eruptions in 20 days. Explosive activity shifted to a quieter effusion of lava in early February, forming a new summit lava dome and two short, blocky lava flows by late March (Figure 1). The eruption was heralded by eight months of increasing seismicity, deformation, gas emission, and small phreatic eruptions, the latter consisting of explosions of steam and debris caused by heating and expansion of groundwater due to an underlying heat source.

Power, J.A., Nye, C.J., Coombs, M.L., Wessels, R.L., Cervelli, P.F., Dehn, J., Wallace, K.L., Freymueller, J.T., and Doukas, M.P., 2006, The reawakening of Alaska's Augustine Volcano: Eos, v. 87, n. 37, p. 373, 377.

Mount Spurr, a 3,374-m-high stratovolcano in the Cook Inlet region of Alaska, showed signs of volcanic unrest beginning in 2004 and lasting through 2006. These signs included increases in heat flow, seismicity, and gas flux, which we interpret as the results of a magmatic intrusion in mid-2004. In response, debris-laden meltwater beneath the glacier in Mount Spurr's geothermally active summit basin accumulated as the overlying snow and ice melted. As heat output increased, the icecap subsided into a growing cavity over a meltwater lake, similar to that observed during subglacial volcanic activity in Iceland.

Coombs, M.L., Neal, C.A., Wessels, R.L., and McGimsey, R.G., 2006, Geothermal disruption of summit glaciers at Mount Spurr Volcano, 2004-6: an unusual manifestation of volcanic unrest: U.S. Geological Survey Professional Paper 1732-B, 33 p., available at http://pubs.usgs.gov/pp/pp1732/pp1732b/index.html .
website with link to full-text PDF

From 1998 to 2002, four cruises by Japan Marine Science and Technology Center (JAMSTEC) research vessels explored the submarine flanks of the Hawaiian Islands. This collaborative Japan-USA research program resulted in new multibeam mapping of the seafloor around Hawai'i, and seafloor observation and sample collection during 53 manned submersible and 25 remotely-operated vehicle (ROV) dives. In this report, we present major element, S, and Cl compositions of volcanic glasses collected from the submarine flanks of Kilauea Volcano during the JAMSTEC research program. The compositions were determined by electron probe microanalysis (EPMA) at the USGS in Menlo Park, California.

Coombs, M., Sisson, T., and Lipman, P., 2004, Major-element, sulfur, and chlorine compositions of glasses from the submarine flank of Kilauea Volcano, Hawaii, collected during 1998-2002 Japan Marine Science and Technology Center cruises: U.S. Geological Survey Open-File Report 2004-1378, 7 p.
website with links to PDF and Excel

Between 1953 and 1974, approximately 0.5km^3 of andesite and dacite erupted from a new vent on the southwest flank of Trident volcano in Katmai National Park, Alaska, forming an edifice now known as Southwest (or New) Trident. Field, analytical, and experimental evidence shows that the eruption commenced soon after mixing of dacite and adesite magmas at shallow crustal levels.

Coombs, M. L., Eichelberger, J. C., and Rutherford, M. J., 2000, Magma storage and mixing conditions for the 1953-1974 eruptions of Southwest Trident volcano, Katmai National Park, Alaska: Contributions to Mineralogy and Petrology, v. 140, n. 1, p. 99-118, 1 sheet, scale unknown.

Miller, T. P., Chertkoff, D. G., Eichelberger, J. C., and Coombs, M. L., 1999, Mount Dutton volcano, Alaska: Aleutian arc analog to Unzen volcano, Japan: in Nakada, S., Eichelberger, J. C., and Shimizu, H., (eds.), Unzen eruption: Magma ascent and dome growth, Journal of Volcanology and Geothermal Research, v. 89, n. 1, p. 275-301.