Transcript Mt. Spurr Kylie Walters and Danielle Gould Dept. of Geology, Colby College.

Mt. Spurr
Kylie Walters and Danielle Gould
Dept. 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 south
on 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 Cited
AVO 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, at
http://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, at
http://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
Images
http://www.akenergyauthority.org/Useful%20pics/Geothermal/Mt%20Spurr.jpg
http://www.jochemnet.de/fiu/earth3.jpg
https://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.jpg
Assorted images from USGS sites.