Mt. SpurrKylie Walters and Danielle GouldDept. of Geology, Colby College

Geographic and Volcanic Setting

● Northeastern end of Aleutian volcanic arc● Zone where denser Pacific oceanic plate subducts

under North American plate● Pacific Ring of Fire

Volcanic Form and Dimensions

● Stratovolcano grown in center of caldera~12 miles (19 km) around

● Highest volcano in the Aleutian Arc (3,374 m summit, 11,067 ft elevation)

● Mostly two-pyroxene andesite composition● Base covered by thick ash flows, pyroclastic

deposits

Mt. Spurr’s Caldera★ Inferred Caldera

-5-6 km wide-controversy →

coincidental or formation from Bezymianny- type eruption at the end of the last ice age?

-dome houses new Mt. Spurr

Vents and Craters● Crater Peak Vent

-3.2 miles southon Caldera rim-small stratocone-summit crater

(w/lake)

Eruptive History

● Ash eruption on July 9, 1953 from Crater Peak on South Flank

● Crater Peak erupted again three times in 1992 following 10 months of heightened seismicity (June 27, August 18 & Sept. 16)

● VEIs of 4● Became forming ~255,000 yrs ago● 5 prior eruptions dated by scientists

Eruptive Style● Sub-Plinian

-Explosive-Pyroclastic flows-Lava Bombs-Lahars-Viscous andesitic lava flows-Debris avalanches-Ash <5mm→ closed airports, damaged equipment, economic losses

Volcanic Hazards● Eruption column from

August 18, 1992 (~13.5 km)

● Disruption to U.S. air travel

● Ashfall on Anchorage - $2 million in damage

● Melting snow and ice● Ash trouble in dry season● Lava bombs can travel

more than 30 Km

Volcanic Deposits - 1953● Pre-1953 → Caldera’s

collapse led to avalanche deposits

● ~6 mm of Andesitic ash fell on Anchorage ~125 km to the East

● Large lahars (100,000 m3) due to glaciers-blocked the Chakachatna River (in 1992 as well)

Volcanic Deposits - 1992

★ June 27-Ash went 9 Km high and 200 Km wide SO2 500 Km★ August 18-Ash went 13.5 Km high and 600 Km away at

Beaver Creek; 5 mm thick★ Lava bombs-8mm to 2 m large fell 2-4 Km from Crater

Peak, some, 8 Km★ September 16-400,000 tons of SO2 and 12,000 tons of

CO2

Petrology● Major: Andesite, Basaltic Andesite● Minor: Dacite, Basalt/Picro-Basalt, Rhyolite

-SiO2 = 57%-plagioclase, pyroxene, hornblende

-very little glass● Small pieces of metamorphic rock● From pyroclastic flows

Hydrothermal Activity and Tourism

● Fumaroles-steam vents near volcano base● Alaska Flightseeing Tour of the Triumvirate Glacier and Mt.

Spurr● Not a major site for tourists

○ Hiking April through October

Active Monitoring

● Alaska Volcano Observatory (AVO)

● 8 seismographs-1 on crater rim before 1992

eruption-monitored for past 33 years ~10 earthquakes per month!

● Gas levels are monitored

Works CitedAVO Web Team, 2014: Mount Spurr Description and Information, at

http://www.avo.alaska.edu/volcanoes/volcinfo.php?volcname=Spurr (accessed 24 January, 2015)Crossen, Kristine J., 2001: Aleutian Volcanoes and Plate Tectonics on the Pacific Rim, at http://www.pbs.org/harriman/explog/lectures/crossen1.html (accessed 25 January, 2015)March, Rod, 2010: Snow and Ice on Volcanoes in Alaska, athttp://ak.water.usgs.gov/glaciology/volcanoes/ (accessed 25 January, 2015)McGimsey, Robert G., Neal, Christina A., Riley, Colleen M., 2001: Areal Distribution, Thickness, Mass, Volume, and Grain Size of Tephra-Fall

Deposits from the 1992 Eruptions of Crater Peak Vent, Mt. Spurr Volcano, Alaska: U.S. Geological Survey Open-File Report 01-370, at http://pubs.usgs.gov/of/2001/0370/ (accessed 23 January, 2015)Mount Spurr Mountain Information, 2015: Mount Spurr – Climbing, Hiking & Mountaineering, at

http://www.mountain-forecast.com/peaks/Mount-Spurr (accessed 23 January, 2015)

Regal Air, 2010: Triumvirate Glacier and Mt. Spurr Volcano Flightseeing Tour, at http://regal-air.com/alaska-flightseeing/triumvirate-mtspurr-flightseeing/ (accessed 25 January, 2015)Smithsonian Institution, 2013: Spurr, athttp://www.volcano.si.edu/volcano.cfm?vn=313040 (accessed 25 January, 2015)The Regents of the University of California, 2015: The Holocene Epoch, at http://www.ucmp.berkeley.edu/quaternary/holocene.php (accessed 24 January, 2015)

Works Cited (cont.)Waythomas, Christopher F., and Christopher J. Nye. Preliminary Volcano-Hazard Assessment for Mount Spurr Volcano, Alaska. Publication no.

01-482. Anchorage: US Geological Survey, 2002. Print.Wood, Charles A. and Kienle, Jurgen, "Volcanoes of North America United States and Canada," Cambridge University Press, New York, 354 pp., 1990. USGS. Alaska Volcano Observatory

Imageshttp://www.akenergyauthority.org/Useful%20pics/Geothermal/Mt%20Spurr.jpghttp://www.jochemnet.de/fiu/earth3.jpghttps://www.ngdc.noaa.gov/hazardimages/picture/show/1497 http://pubs.usgs.gov/fs/fs030-97/SatelliteSpurr.gif https://volcanocafe.files.wordpress.com/2013/11/image013.jpgAssorted images from USGS sites.