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CHAPTER II
COULEE CITY AND GEOLOGICAL CHARACTERISTICS
OF THE BIG BEND
Location
Coulee City, Washington, is a small rural farm community located 100 miles west of Spokane on U. S. Highway 2 near the junction of State Highway 17. The town is situated on an alkali flat at the south end of Banks Lake, a 25-mile long man-made reservoir that covers the floor of the upper Grand Coulee. The South Dam that forms the southwest end of the reservoir, extends in a westerly direction from the outskirts of Coulee City. Coulee City is the oldest town in Grant County. The name is apparent because of the location at the middle crossing of the Grand Coulee. 1 This middle crossing of the Grand Coulee is situated at the center of the upper part of the Columbia Plateau that has been called the Big Bend country.
The two major cross-state highways that intersect two miles west of Coulee city give some insight into the significance of the location of Coulee City. U. S. Highway 2 is a main route of travel west from Spokane to Wenatchee across the Big Bend. State Highway 17 is the principal north-south route of travel from Pasco to the Okanogan Valley.
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1 Edmond S. Meany, Origin of Washington Geographic Names (Seattle: University of Washington Press, 1923), p. 58
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| Fig. 2 -- Location of Coulee City |
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| Google Maps |
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The Two most significant geological features of the region around Coulee City are the Grand Coulee and Dry Falls. These two scenic wonders of nature attract thousands of tourists each year. In 1967 the car count of visitors to Dry Falls numbered 468,854; July was the largest month, having a total of 107,044. 2
Other Geological features that attract interest are the talus slopes, basaltic columns, monoclines, caves, lava strata, and haystack rocks. Each of these features shows evidence of the great geological changes that the area has experienced during the past 20 million years. For one to try to understand this geology it is necessary to go back about 20 million years when the landscape of central Washington consisted of mountains, valleys, streams, and lakes. The sequoia, oak, elm, cypress, chestnut, and sacred ginkgo grew over what is now the Columbia Basin. This growth took place during the Miocene period of the geological time scale. 3
Geological Change
At the close of the Miocene period and during the early Pliocene that followed, a great basaltic lava flood engulfed approximately 250,000 square miles of the Pacific Northwest. For perhaps 10 to 15 million years a succession of lava floods poured out over the granite base rock from fissures or cracks in the earth's crust. 4 Eventually this lava accumulated a thickness
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2 This information was obtained from the ranger at Sun Lakes Park in 1968.
3 This information was obtained from a pictorial display at Ginkgo State Park, Vantage, Washington.
4 Joseph G. McMacken, Geology of the Grand Coulee and the Columbia Basin Project (Spokane: Joseph G. McMacken, 1937), p. 3
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of over 4,000 feet in places, and a large depressed lava plain, now known as the Columbia Plateau was formed. 5 The flood of lava appears to have advanced in a northeasterly direction forcing the Columbia River into its present course between the plateau and the granite mountains of the Okanogan Highlands. The lava floods impounded ancient lake beds where fossil leaf impressions, petrified wood, and fossils are found today. One of the most unusual fossils to be found was the Blue Lake Rhino that was discovered in a cave near Blue Lake on July 10, 1935. 6
The weight of the lava and other forces deep within the earth have warped the plateau in several places, causing the plateau to tilt slightly to the south. This tilting resulted in a series of stairstep rockfolds, called monoclines, in the vicinity of Coulee City and Soap Lake. Following the Pliocene Era and about 1,000,000 years ago, the earth began to experience a cooling trend, which was favorable for the creation of great sheets of ice. during the Pleistocene Era or the Ice Age, scientists estimate that about one-third of the earth's surface was covered by ice. As the snowfall exceeded melting and evaporation, the glaciers started pushing southward out of present-day Canada and blocked the Columbia River near the present site of grand Coulee Dam. The river changed its course when the water that backed up behind the ice jam spilled out across the
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5 Editorial Staff, "Grand Coulee Country," Sunset Discovery Trips in Washington (Menlo Park, Calif.: Lane Publishing Co., 1956), p. 85
6 Coulee City Dispatch, August 22, 1935, p. 1
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sloping lava plateaus and ultimately, by following the lines of least resistance, formed the coulees which characterize the region today. 7 *
This glacial river carried a great deal of sediment that gave erosive power as the gradient was somewhere between 20 and 30 feet per mile. 8 Many of the eroded materials were dropped by the flood waters and later helped to form the fertile soils of the Quincy Basin.
Dry Falls and the Grand Coulee
The largest of the coulees and the one that was the main stream bed is the Grand Coulee. As the Columbia moved along southward, two major cataracts were formed along its course. One of these was north of Coulee City in the vicinity of Steamboat Rock and the other was south near Blue Lake. The larger cataract was in the upper coulee, but Dry Falls in the lower coulee has become the most famous tourist attraction. Here the tremendous erosive power of the current caused the basaltic layers to wear away and the falls retreated to its present location four miles west of Coulee City. Dry Falls is three and one-half miles wide with a drop of 400 feet, making it the greatest waterfall skeleton in geologic history. 9
The Coulee walls show evidence of at least seven major lava floods separated by intervals of time. McMacken points out
____________7 Information obtained from the pictorial display at the Dry Falls Museum, Coulee City, Washington.
* More recent scientific investigation points to ice age floods from a glacial Lake Missoula as what carved out the Grand Coulee. At PBS.org, Mystery of the MEGAFLOOD provides links to much more information. The Cheney-Spokane Chapter of the Ice Age Floods Institute includes pictures and information on the Big Bend and Grand Coulee area.
8 McMacken, p. 5
9 Information obtained from the pictorial display at the Dry Falls Museum.
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Dry Falls
Air View of Dry Falls
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| The Upper Grand Coulee |
Coulee Monocline
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that there is evidence that the Columbia was dammed again at a later date by the okanogan Lobe of the Wisconsin Glacier, causing the Grand Coulee to experience more erosive power of glacial water that deepened the Coulee 50 feet or more. 10 Hodge, in his paper Origin of the Washington Scablands, tends to support McMacken's theory. 11 Southwest of Coulee City extend a series of eroded coulees that J. Harlen Bretz named scablands. He defines these coulees as "a multiplicity of irregular and commonly anastomosing channels and rock-basins eroded in basalt containing meadows, swamps and lakes." 12 These scabland channels are abandoned glacial spillways of the Columbia as it cut its way across the plateau. The plateau to the west of the Grand Coulee was glaciated to the edge of the Coulee during the Wisconsin Epoch. After the retreeat of the glacier large haystack rocks were left as evidence of the glacier's passing. 13.
During the latter part of the Pleistocene Era the climate moderated and the ice slowly retreeated northward, causing the ice dam to disintegrate and allow the columbia to return to its original channel along the northern edge of the lava plateau.
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10 McMacken, p. 12
11 Edwin T. Hodge, "Origin of the Washington Scablands," Northwest Science, VIII (September, 1934), 9-10.
12 J. Harlen Bretz, "Glacial Drainage on the Columbia Plateau," Bulletin of the Geological Society of America, XXXIV (September, 1913), 591
Also, Otis W. Freeman, Howard H. Martin, The Pacific Northwest: A Regional, Human, and Economic Survey of resources and Development (New York: John Wiley and Sons, Inc., 1942), pp. 63-64.
13 Ibid., p. 62.
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The river bed was left high and dry to become the largest abandoned river channel in the lava plateau of eastern Washington and represents the greatest example of canyon excavation by glacial waters in existence. The Grand Coulee is one and one-half miles wide at the south end and four miles wide at the north end, according to information obtained from the earliest geoligical survey made of the Coulee in 1892. 14 Jones wrote that "in comparison to the time it took nature to do this work, a man's life is no more than the whispering of a breeze along these canyon walls." 15 See Appendix A for geologic time scale.
In searching for the origin of the name Grand Coulee, one finds two different definitions. jones, in his Evergreen Land, claims that Coulee is a French word meaning a deep dry river bed of lava rock. 16 Hawthorne, in History of Washington, says that "Coulee is a term corrupted from the French word 'Couler,' meaning a cut off." 17 Meany, in his Origin of Washington Geographic Names, does not define the term Grand Coulee. He mentions that the name appeared in literature regarding the area as Grand Coolly in 1825 and Grande Coulle in 1841. 18
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14 Israel C. Russell, "A Geological Reconnaissance in Central Washington," Bulletin of the U. S. Geological Survey, No. 108 (Washington, D. C.: U. S. Government Printing Office, 1893), p. 90.
15 Nard Jones, Evergreen Land (New York: Dodd, Mead and Company, 1947), p. 57.
16 Ibid., p. 58.
17 Julian Hawthorn (ed.), History of Washington, Vol. II (New York: American Historical Publishing Co., 1893), p. 202.
18 Meany, p. 100.
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Alexander Ross labeled this chasm as the Grand Coulee in 1814. 19 On an 1838 map showing the important fur trading posts in the Oregon Country the chasm is called the Gr. Coallee.
The Coulee is divided into an upper and lower coulee by a break in the canyon walls at Coulee City. This break is represented by the two monoclines located near Coulee City -- one lying four miles north along the east wall of the coulee; the other, four miles west where U. S. Highway 2 climbs up the west wall on its route to Waterville. these monoclines form a sag in the coulee walls that provide the only place within 60 miles where the Grand Coulee can be crossed without great difficulty. This break provides a route which people have travelled since primitive man moved across the Big Bend Country.
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19 Alexander Ross, The Fur Hunters of the Far West, ed. Kenneth A. Spalding (Norman: University of Oklahoma Press, 1953), pp. 31-32.
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(page 11 is fig. 2, above)
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(page 10 is fig 3, above)
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