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Coulee) is 150 feet (46 m) high and had three alcoves over more than 1 mile (1.6 km). There is no channel as the water arrived in a broad sheet. The gravel deposits of Quincy Basin represent only a third or a fourth of the estimated 11 cubic miles of rock excavated from the Grand Coulee and its smaller other related coulees (Dry, Long Lake, Jasper, Lenore, and
Unnamed). Most of the debris was carried on through and beyond
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boulders from as far away as
Montana and Canada. At present day Portland, the water measured 400 feet (120 m) deep. A canyon 200 feet (61 m) deep is carved into the far edge of the continental shelf. The web-like formation can be seen from space. Mountains of gravel as tall as 40-story buildings were left behind; boulders the size of small houses and weighing many tons were strewn about the landscape.
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This mass of water and ice, 2,000 feet (610 m) high near the ice dam before release, flowed across the
Columbia Basin, moving at speeds of up to 65 miles per hour (105 km/h). The deluge stripped away soil, cut deep canyons and carved out 50 cubic miles (210 km) of earth, leaving behind
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is at the head of Lower Grand Coulee. The Great
Cataract forms the divide from the upper to lower coulees. The Lower Coulee tends along the monoclinal flexure to Soap Lake where the canyons end and the water flowed out into Quincy Basin. Quincy Basin is filled with the eroded gravels and silts from
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Evidence of the waterfalls includes a plunge basin where the falls began, immediately south of Coulee City. It contains at least 300 feet (91 m) of gravel lower than the open flooring of the land. The river above the falls was shallow and much wider than the gorge. Thus, it wrapped around the
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Grand Coulee is the longest and deepest of eastern
Washington canyons. Its unique characteristics include a lower floor at the head of the channel than at its outlet and the widest and highest dry falls cliff in the middle. It was created through the process of cataract recession, which included a
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It is probable that humans were witnesses, and victims, of the immense power of the Ice Age Floods. Archeological records date human presence back to nearly the end of the Ice Age, but the raging torrents erased the land of clear evidence, leaving us to question who, if anyone, may have survived.
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from Dry Falls to Park Lake. Numerous canyons acted as a distribution system for the volume of water flowing out of the upper coulee. The distribution begins in the uncanyoned basin below Dry Falls and expanded to over 15 miles (24 km) before reaching Quincy Basin. One cataract (Unnamed
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Over nearly 2500 years the cycle was repeated many times. Most of the displaced soil created new landforms, but some was carried far out into the
Pacific Ocean. In Oregon's Willamette Valley, as far south as Eugene, the cataclysmic flood waters deposited fertile soil and icebergs left numerous
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Upper Grand Coulee began as an 800-foot (240 m) cascade just north of Coulee City. As the rush of water eroded the surface, it steepened into a waterfall. The falls continued to erode backward (northward) creating the canyon. When the falls reached the divide into Lake
Columbia, i.e.,
382:, a steep warping up of 1,000 feet (300 m) toward the northwest. Lake Columbia topped the ridge at the higher side of the flexure. Encountering the steep slope of the monocline, the new river would have cascaded off the rim, 800 feet (240 m) down onto a broad plain where
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and three times as high. Steamboat Rock, 880 feet (270 m) high and a 1 square mile (2.6 km) in area, now stands as an isolated rise, but for a time it created two cataracts. When the falls passed north of
Steamboat Rock, it found a granite base beneath the basal flows.
498:. The lake is filled by pumps from the Grand Coulee Dam and forms the first leg of a one-hundred-mile (160 km) irrigation system. Canals, siphons, and more dams are used throughout the Columbia Basin, supplying over 600,000 acres (240,000 ha) of farm land.
259:
took place in the area. Large parts of northern North
America were repeatedly covered with glacial ice sheets, at times reaching over 10,000 feet (3,000 m) in thickness. Periodic climate changes resulted in corresponding advances and retreats of ice.
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with water up to 1,970 feet (600 m) deep, in northwest
Montana and in 1940 he reported his discovery that giant dunes 50 feet (15 m) high and 200–500 feet (61–152 m) feet apart had formed the lake bed. In the 1920s,
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drainage, thus creating an enormous lake reaching far back into mountain valleys of western Montana. Leaks may have developed around and under the ice, causing the dam to fail. The 500 cubic miles (2,100 km) of water in
330:
With the end of the last glacial advance, the Columbia settled into its present course. The river bed is about 660 feet (200 m) below the Grand Coulee. Walls of the coulee reach 1,300 feet (400 m) in height.
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From about 10 to 18 million years ago, a series of volcanic eruptions from the Grand Ronde Rift near the Idaho/Oregon/Washington/Montana border began to fill the inland sea with lava. In some places the volcanic
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bedrock, formed deep in the Earth's crust 40 to 60 million years ago. The land periodically uplifted and subsided over millions of years giving rise to some small mountains and, eventually, an inland sea.
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The river at Grand Coulee found no existing valley and thus forged its own pathway across the divide, creating the Upper Coulee. The plateau is not level, but is marked with wrinkles and upfolds of the
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and leads southward, through the surrounding highlands. The entry to the coulee is 650 feet (200 m) above the Columbia. It began as the course of a Glacial Columbia River. The
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preglacial Columbia Valley, it disappeared, leaving the elongated notch. Today, the waters of the Lake Roosevelt are pumped 280 feet (85 m) from the Grand Coulee Dam, into
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into what became the Grand Coulee and that normal flows caused the erosion observed. In 1910 Joseph T. Pardee described a great Ice Age lake, "Glacial Lake Missoula", a
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Washington’s Channeled Scabland; Bulletin No. 45; J Harlen Bretz; Division of Mines and Geology, Department of Conservation, State of Washington; April 15, 1959
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state parks are both found in the Grand Coulee. However, the lake has also flooded a large area of natural habitat and native hunting grounds, displacing local
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and resisted the erosion from the cataract's plunge. It remains as hills on the broad floor of the Coulee. Some gravel-bar deposits are visible along the
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the Coulee. The Lower Coulee also created its own path across the plains. Evidence of this is found in the tilted flows visible at Hogback islands in
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habitat, with an average annual rainfall of less than twelve inches (300 mm). The Lower Grand Coulee contains Park, Blue, Alkali, Lenore, and
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changed this in 1952, using the ancient river bed as an irrigation distribution network. The Upper Grand Coulee was dammed and turned into
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About 18,000 years ago a large finger of ice advanced into present-day Idaho, forming an ice dam known as the Purcell lobe at what is now
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lip of the main falls creating lateral falls. These flowed until the recession of the main falls denied them water. Northrup Canyon in
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505:. Recreation is a side benefit and includes several lakes, mineral springs, hunting and fishing, and water sports of all kinds.
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470:") is a gravel fan formed when floodwaters from the lower Grand Coulee entered the Quincy Basin during the formation of the
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was released in just 48 hours—a torrential flood equivalent to ten times the combined flow of all the rivers in the world.
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Grooves in the exposed granite bedrock are still visible in the area from the movement of glaciers, and numerous
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Okanogan lobe extended southward across the Columbia Rivers pathway and onto the southern plateau creating an
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Includes 146 images (ca. 1938–1958) of the Columbia River, Eastern Washington and the Grand Coulee region.
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is 6,600 feet (2.0 km) thick. In other areas granite from the earlier mountains is still exposed.
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Water has turned the Upper Coulee and surrounding region into a haven for wildlife, including
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University of Washington Libraries Digital Collections – Lawrence Denny Lindsley Photographs
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Grand Coulee is two canyons, with an open basin in the middle. The Upper Coulee, filled by
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Channeled Scablands: A Megaflood Landscape, in Geomorphological Landscapes of the World
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562: – Lake formed by the Missoula Floods in the lower Coulee in Washington state
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looked deeper into the landscape and put forth his theory of the dam breaches and
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On the Trail of the Ice Age Floods: A Geological Guide to the Mid-Columbia Basin
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Part of the Grand Coulee has been dammed and filled with water as part of the
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J Harlen Bretz, (1923), The Channeled Scabland of the Columbia Plateau.
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forced those waters into eastern Washington, creating the Scablands.
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are found in the elevated areas to the northwest of the coulee.
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to act as an Equalizing Reservoir and irrigation water source.
44:. The layering effect of periodic basalt lava flows is visible.
362:. This dam backed up the waters of the Columbia into Glacial
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WDFW - Wildlife of Eastside Shrubland and Grassland Habitats
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stretches for about 60 miles (100 km) southwest from
378:. The diverted waters of the Columbia encountered the
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lakes. Until recently, the Upper Coulee was dry. The
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Pages displaying wikidata descriptions as a fallback
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Pages displaying wikidata descriptions as a fallback
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Pages displaying wikidata descriptions as a fallback
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Early theories suggested that glaciers diverted the
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785:The Geologic Story of the Columbia Basin, BPA site
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339:cataract twice as high as its existing Dry Falls.
251:Starting about two million years ago, during the
23:Ancient river bed in the U.S. state of Washington
1091:National Natural Landmarks in Washington (state)
967:Ice Age Floods Erosion & Deposition Features
621:Glacial Lake Missoula & its Humongous Floods
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195:is an ancient river bed in the U.S. state of
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553: – dam in Grant County, Washington, USA
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756:Baker, Victor (2010). Migon, Piotr (ed.).
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568: – Lake in Washington, United States
482:The area surrounding the Grand Coulee is
1106:Canyons and gorges of Washington (state)
797:3D images of the Grand Coulee, USGS site
1096:Landforms of Douglas County, Washington
1081:Geography of Douglas County, Washington
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535: – dam in Grant County, Washington
856:Ice Age Floods National Geologic Trail
1101:Landforms of Grant County, Washington
1086:Geography of Grant County, Washington
623:. Mountain Press Publishing Company.
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7:
544: – reservoir in Washington, USA
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714:Bretz, 1932; Bretz and others, 1956
529: – American irrigation project
428:lacks the close vertical joints of
419:contains a dry cataract as wide as
648:. Keokee Books; San Point, Idaho.
165:Looking northward in Grand Coulee.
14:
61:
54:
34:
682:Mueller, Ted and Marge (1997).
267:. The Purcell lobe blocked the
215:into the Upper and Lower Grand
1043:Related contemporaneous events
941:Ice Age Floods Glacial Residue
137:U.S. National Natural Landmark
1:
1071:Geology of Washington (state)
18:Grand Coulee (disambiguation)
958:Sims Corner Eskers and Kames
760:. Springer. pp. 21–28.
820:JSTOR - Geographical Review
235:. This area has underlying
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15:
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692:University of Idaho Press
686:Fire, Faults & Floods
644:Bjornstad, Bruce (2006).
464:The Ephrata Fan (a.k.a. "
417:Steamboat Rock State Park
402:Formation of Grand Coulee
280:areas of stark scabland.
201:National Natural Landmark
155:
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227:Grand Coulee is a large
452:and tilted flows along
356:Cordilleran ice sheet's
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867:Ice Age Glacial Floods
527:Columbia Basin Project
492:Columbia Basin Project
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309:massive glacial floods
233:Columbia River Plateau
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186:Columbia Basin Project
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906:Glacial Lake Columbia
901:Glacial Lake Missoula
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595:National Park Service
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366:and later during the
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1029:Columbia River Gorge
388:Dry Falls State Park
211:, being bisected by
176:in the Grand Coulee.
40:Grand Coulee, below
16:For other uses, see
999:Drumheller Channels
989:Channeled Scablands
619:Alt, David (2001).
467:Ephrata Erratic Fan
320:Channeled Scablands
300:glacier dammed lake
111: /
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802:2010-06-09 at the
790:2009-11-05 at the
670:Journal of Geology
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380:monoclinal flexure
223:Geological history
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115:47.62°N 119.3075°W
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1019:Touchet Formation
860:Pacific Northwest
694:, Moscow, Idaho.
672:, v.31, p.617-649
655:978-1-879628-27-4
394:Waterfall Erosion
265:Lake Pend Oreille
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932:Lake Allison
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603:. Retrieved
599:the original
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459:Quincy Basin
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440:Lower Coulee
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193:Grand Coulee
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29:Grand Coulee
1024:Wallula Gap
1009:Corfu Slide
927:Lake Condon
560:Lenore Lake
478:Modern uses
450:Lake Lenore
390:now stand.
384:Coulee City
253:Pleistocene
118: /
106:119°18′27″W
94:Coordinates
1065:Categories
1004:Crab Creek
922:Lake Lewis
605:2013-03-31
573:References
542:Banks Lake
503:bald eagle
496:Banks Lake
409:Banks Lake
344:Banks Lake
257:glaciation
197:Washington
144:Designated
103:47°37′12″N
87:Washington
72:Washington
994:Dry Falls
566:Soap Lake
533:North Dam
507:Sun Lakes
472:Scablands
445:Dry Falls
434:Route 155
324:Dry Falls
213:Dry Falls
209:Soap Lake
42:Dry Falls
800:Archived
788:Archived
521:See also
289:erratics
83:Location
858:in the
591:nps.gov
426:Granite
360:ice dam
318:Of the
255:epoch,
237:granite
231:on the
199:. This
70:Map of
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698:
652:
627:
430:basalt
376:basalt
246:basalt
229:coulee
217:Coulee
311:from
89:state
74:state
762:ISBN
696:ISBN
650:ISBN
625:ISBN
509:and
488:Soap
386:and
147:1965
350:at
207:to
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219:.
848:e
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834:v
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188:.
20:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
