Channeled Scablands are a relatively barren and soil-free region
of interconnected relict and dry flood channels, coulees and cataracts
eroded through Palouse loess and into typically flat-lying basalt
flows by cataclysmic floods within eastern part of the
U.S. state of
Washington. The channeled scablands were scoured by over 40
cataclysmic floods during the
Last Glacial Maximum
Last Glacial Maximum and innumerable
more older cataclysmic floods over the last two million
years. These cataclysmic floods were repeatedly unleashed
when a large glacial lake repeatedly drained and swept across eastern
Washington and down the
Columbia River Plateau
Columbia River Plateau during the Pleistocene
epoch. The last of the cataclysmic floods occurred between 18,200 and
14,000 years ago.
J Harlen Bretz
J Harlen Bretz coined the term "channeled scablands" in a
series of papers written in the 1920s. The debate on the origin of the
Scablands that ensued for four decades became one of the great
controversies in the history of earth science. The Scablands are also
important to planetary scientists as perhaps the best terrestrial
analog of the Martian outflow channels.
3 See also
6 External links
Bretz conducted research and published many papers during the 1920s
describing the Channeled Scablands. His theories of how they were
formed required short but immense floods – 500 cubic miles
(2,100 km3) – for which Bretz had no explanation. Bretz's
theories met with vehement opposition from geologists of the day, who
tried to explain the features with uniformitarian theories.
J.T. Pardee first suggested in 1925 to Bretz that the draining of a
glacial lake could account for flows of the magnitude needed. Pardee
continued his research over the next 30 years, collecting and
analyzing evidence that eventually identified Lake Missoula as the
source of the
Missoula Floods and creator of the Channeled Scablands.
Pardee's and Bretz's theories were accepted only after decades of
painstaking work and fierce scientific debate. Research on
open-channel hydraulics in the 1970s put Bretz's theories on solid
scientific ground. In 1979 Bretz received the highest medal of the
Geological Society of America, the Penrose Medal, to recognize that he
had developed one of the great ideas in the earth sciences.
The term scabland refers to an area that has experienced fluvial
erosion resulting in the loss of loess and other soils, leaving the
land barren. River valleys formed by erosional downcutting of
rivers create V-shaped valleys, while glaciers carve out U-shaped
Channeled Scablands have a rectangular cross section,
with flat plateaus and steep canyon sides, and are spread over immense
areas of eastern Washington. The morphology of the scablands is
butte-and-basin. The area that encompasses the Scablands has been
estimated between 1,500 and 2,000 square miles (3,900 and
5,200 km2), though those estimates still may be too
They exhibit a unique drainage pattern that appears to have an
entrance in the northeast and an exit in the southwest. The
Cordilleran Ice Sheet
Cordilleran Ice Sheet dammed up
Glacial Lake Missoula
Glacial Lake Missoula at the Purcell
Trench Lobe. A series of floods occurring over the period of 18,000
and 13,000 years ago swept over the landscape when the ice dam broke.
The eroded channels also show an anastomosing, or braided, appearance.
The presence of Middle and Early
Pleistocene Missoula flood deposits
have been documented within the Channeled Scabland as other parts of
the Columbia Basin, e.g. the Othello Channels, Columbia River Gorge,
Quincy Basin, Pasco Basin, and the Walla Walla Valley. Based on the
presence of multiple interglacial calcretes interbedded with
glaciofluvial flood deposits, magnetostratigraphy, optically
stimulated luminescence dating, and unconformity truncated clastic
dikes, it has been estimated that the oldest of these megafloods
flowed through the Channel Scablands sometime before 1.5 million years
ago. Because of the fragmentary nature of older glaciofluvial
deposits, which have been largely removed by subsequent Missoula
floods, the exact number of older Missoula floods, which are known as
Ancient Cataclysmic Floods, that occurred during the Pleistocene
cannot be estimated with any confidence. As many as 100
separate, cataclysmic Ice Age floods may have occurred during the last
glaciation. There have been at least 17 complete
interglacial-glacial cycles since about 1.77 million years ago, and
perhaps as many as 44 interglacial-glacial cycles since the beginning
Pleistocene about 2.58 million years ago. Presuming a dozen (or
more) floods were associated with each glaciation, the total number of
cataclysmic Ice Age Missoula floods that flowed through the Channeled
Scablands for the entire
Pleistocene Epoch could possibly number in
the hundreds, perhaps exceeding a thousand Ancient Cataclysmic
There are also immense potholes and ripple marks, much larger than
those found on ordinary rivers. When these features were first
studied, no known theories could explain their origin. The giant
current ripples are between 3.3 and 49.2 feet (1 and 15 m) high
and are regularly spaced, relatively uniform hills. Vast volumes of
flowing water would be required to produce ripple marks of this
magnitude, as they are larger-scale versions of the ripple marks found
on streambeds that are typically only centimeters high. Large potholes
were formed by swirling vortexes of water called kolks scouring and
plucking out the bedrock.
The Scablands are littered with large boulders called glacial erratics
that rafted on glaciers and were deposited by the glacial outburst
flooding. The lithology of erratics usually does not match the rock
type that surrounds it, as they are often carried very far from their
Glacial lake outburst flood
Drumheller Channels National Natural Landmark
Giant current ripples
Turnbull National Wildlife Refuge
^ Bjornstad, B., and Kiver, E., 2012, On the Trail of the Ice Age
Floods: The Northern Reaches: A geological field guide to northern
Idaho and the Channeled Scabland. Keokee Books, Sandpoint, Idaho. 480
pp. ISBN 978-1879628397
^ Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005)
Glossary of Geology (5th ed.). Alexandria, Virginia, American
Geological Institute. 779 pp. ISBN 0-922152-76-4
^ a b Medley, E. (2012) Ancient Cataclysmic Floods in the Pacific
Northwest: Ancestors to the Missoula Floods. Unpublished Masters
thesis, Portland State University, Portland, Oregon. 174 pp.
^ a b Spencer, P. K., and M. A. Jaffee (2002) Pre-Late Wisconsinan
Glacial Outburst Floods in Southeastern Washington—The Indirect
Record. Washington Geology. vol. 30, no. 1/2, pp. 9-16.
^ a b Bjornstad, B. (2002) Standardized Stratigraphic Nomenclature for
Post-Ringold-Formation Sediments Within the Central Pasco Basin.
Report DOE/RL-2002-39 Rev. 0.
Pacific Northwest National Laboratory,
U.S. Department of Energy, Richland, Washington.
^ Balbas, A.M., Barth, A.M., Clark, P.U., Clark, J., Caffee, M.,
O’Connor, J., Baker, V.R., Konrad, K. and Bjornstad, B., 2017. 10Be
dating of late
Pleistocene megafloods and Cordilleran Ice Sheet
retreat in the northwestern United States. Geology, 45(7), pp.
^ Carr, M. H. (2006), The Surface of Mars. Cambridge Planetary Science
Series, Cambridge University Press.
^ a b c Baker (2008)
^ a b c d Foster (2011)
^ Waitt, RB, Jr. (1994) Scores of Gigantic, Successively Smaller Lake
Missoula Floods Through Channeled Scabland and Columbia Valley, in
Geologic Field Trips in the Pacific Northwest: 1994 Geological Society
of America Meeting, Chapter 1K, D. A. Swanson and R. A. Haugerud
(eds.), Geological Society of America, Boulder, Colorado.
Allen, John Eliot; Marjorie Burns; and Sam C. Sargent. (1986)
Cataclysms on the Columbia. Portland, Oregon: Timber Press,
Baker, Victor R.. "The Channeled Scabland: A Retrospective." Reviews
in Advance. Annual Reviews, 30 Dec 2008. Web. 9 Oct 2013.
Bjornstad, Bruce: and Eugene Kiver. (2012) "On the Trail of the Ice
Age Floods: The Northern Reaches", Keokee Co. Publishing, Inc.,
Sandpoint, Idaho, ISBN 978-1-879628-39-7.
Bjonstad, Bruce; Ice Age Floodscapes YouTube Channel
Bretz, J Harlen (1923), "The Channeled Scabland of the Columbia
Plateau." Journal of Geology, v.31, p. 617-649.
Bretz, J Harlen (1925), "The Spokane flood beyond the Channeled
Scablands." Journal of Geology, v.33, p. 97-115, 236-259.
Bretz, J H.; Smith, H.T.U.; and Neff, G.E., (1956) "Channeled Scabland
of Washington — New Data and Interpretations." Geological Society of
America Bulletin, v.67, p. 957-1049.
Channeled Scablands Theory." Spokane Outdoors. N.p., n.d. Web. 9 Oct
Foster, Tom. "Channeled Scabland." Huge Floods. N.p., n.d. Web. 9 Oct
Soennichsen, John (2008), "Bretz's Flood: The Remarkable Story of a
Geologist and the World's Greatest Flood", Seattle, Washington,
Sasquatch Books, ISBN 978-1-57061-505-4
United States Geological Survey The
Channeled Scablands of Eastern
Steven Dutch, University of Wisconsin - Green Bay, Channeled
PBS's NOVA: Mystery of the Megaflood
Scablands in Google Maps
Online book from the
National Park Service
National Park Service about the geologic origins
of the scablands.
Dry Falls State Park in the Channeled Scablands
Columbia Plateau Trail StatePark in the Channeled Scablands
The Seattle Times' Pacific NW magazine - "Trailing an Apocalypse" -
The channeled scabland: a guide to the geomorphology of the Columbia
Basin, Washington : prepared for the Comparative Planetary
Geology Field Conference held in the Columbia Basin, June 5–8, 1978
/ sponsored by Planetary Geology Program, Office of Space Science,
National Aeronautics and Space Administration ; edited by Victor
R. Baker and Dag Nummedal.
Keenan Lee. Altai Flood
Rojas-Burke, Joe (2010-02-20). "Geologists find a way to simulate the
great Missoula floods". The Oregonian.
Ice Age Floods National Geologic Trail
Ice Age Floods National Geologic Trail in the Pacific Northwest
Ice Age Glacial Floods
Glacial Lake Missoula
Glacial Lake Columbia
Ice Age Floods Glacial Residue
Sims Corner Eskers and Kames
Ice Age Floods Erosion & Deposition Features
Columbia River Gorge
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