Mount Churchill is a volcano in the
Saint Elias Mountains
Saint Elias Mountains and the
Wrangell Volcanic Field
Wrangell Volcanic Field of eastern Alaska. Churchill and its higher
Mount Bona about 2 mi (3 km) to the southwest are
both large ice-covered stratovolcanoes, with Churchill being the
fourth highest volcano in the
United States and the seventh highest in
1 Volcanic eruptions
4 External links
Mount Churchill is most noteworthy as the source of the White River
Ash, deposited during two of the largest volcanic eruptions in North
America during the past two millennia. This twin-lobed tephra deposit
covers more than 130,000 square miles (340,000 km2) of eastern
Alaska and northwestern Canada, with the northern lobe deposited 1900
years ago and extending over 250 miles (400 km) and the larger
eastern lobe about 1,250 years ago and stretching over 500 miles
(800 km). The total volume of the ash exceeds 12 cubic miles
(50 km3), or roughly 50 times the volume of the 1980 eruption of
Mount St. Helens, and ash layers up to 2 feet (61 cm) thick can
be seen just below the surface in many roadcuts along the Alaska
The extensive ash deposits in the lowlands near the White and Yukon
Rivers were first recognized in 1883, but their source remained a
mystery for the next century. Geologists in the 1960s traced the two
lobes of the ash back into the Saint Elias Mountains, and postulated
that the ash may have come from a vent now buried under the Klutlan
Glacier, which flows east for over 40 mi (64 km) from the
Bona-Churchill massif into the
Yukon Territory of Canada. More
detailed studies in the 1990s by the
U.S. Geological Survey
U.S. Geological Survey finally
produced the definitive answer. Aerial photos showed a 2.6 by 1.7
miles (4.2 km × 2.7 km) elliptical, gently sloping,
ice-filled depression at 14,500 feet (4,400 m) just east of the
present summit of Mount Churchill. This was identified as a caldera,
which had formed by the collapse of the volcano's previous summit
during the cataclysmic eruptions. The geological field work revealed
thick young pumice deposits along the rim of the caldera which are
mineralogically and chemically identical to the White River Ash.
U.S. Geological Survey
U.S. Geological Survey climbing party reaching the east rim of the
summit caldera on Mount Churchill. Blocky debris in the photo consists
of pumice and lithic fragments ejected 1,250 years ago, during the
eruption which formed the eastern lobe of the White River Ash.
Mount Churchill was first climbed in 1951 by R. Gates and J. Lindberg,
but the peak was merely an unnamed satellite of
Mount Bona at the
time. The mountain was named in 1965 by the
Alaska State Legislature
for English statesman Winston Churchill.
In terms of elevation, it is a major North American peak, at well over
15,000 feet (4,600 m); however, in terms of topographic
prominence or isolation, it is less significant, with less than a
1200-foot drop from its summit to the saddle with Bona. Churchill also
lies on the northern, gentler side of the Bona massif, making it a
less visually spectacular peak than some of the lower outliers of Bona
such as University Peak or Aello Peak. The current standard climbing
route is the South Ridge, usually as part of a climb of Mount Bona
from the east starting from a ski-equipped bush plane landing at
around 10,000 feet (3,000 m) on the Klutlan Glacier.
McGimsey, R. G.; Richter, D. H.; DuBois, G. D.; Miller, T. P. (1992).
"A postulated new source for the White River Ash, Alaska". Geological
Survey Bulletin. 1999: 212–218.
Richter, D. H.; Preece, S. J.; McGimsey, R. G.; Westgate, J. A.
(1995). "Mount Churchill, Alaska; source of the late Holocene White
River Ash". Canadian Journal of Earth Sciences. 32 (6): 741–748.
"Churchill". Global Volcanism Program. Smithsonian Institution.
Wood, Charles A.; Kienle, Jürgen, eds. (1990). Volcanoes of North
America. Cambridge University Press. ISBN 0-521-43811-X.
Richter, Donald H.; Rosenkrans, Danny S.; Steigerwald, Margaret J.
(1995). Guide to the Volcanoes of the Western Wrangell Mountains,
USGS Bulletin 2072.
Winkler, Gary R. (2000). A Geologic Guide to Wrangell—Saint Elias
National Park and Preserve, Alaska: A Tectonic Collage of Northbound
USGS Professional Paper 1616. ISBN 0-607-92676-7.
Richter, Donald H.; Preller,Cindi C.; Labay, Keith A.; Shew, Nora B.
(2006). Geologic Map of the Wrangell-Saint Elias National Park and
USGS Scientific Investigations Map 2877.
Wood, Michael; Coombs, Colby (2001). Alaska: A Climbing Guide.
Mountaineers Books. ISBN 0-89886-724-X.
^ "Mount Churchill". Geographic Names Information System. United
States Geological Survey. Retrieved 2007-03-10.
"Mount Churchill". Bivouac.com. Retrieved 2014-