THE GRAND COULEE 



By WINTHROP P. HAYNES 



IN the heart of the vast lava plains 

 which occupy a large part of the 

 States of Washington, Idaho and 

 Oregon,, lies the Grand Coulee, 

 an unsurpassed natural feature of 

 grandeur and wild beauty, which is well 

 worthy of a place among the wonder 

 sights of America, but which is practi- 

 cally unknown and unvisited at the pres- 

 ent time. 



The Grand Coulee is a great dry 

 gorge or canyon cut by the Columbia 

 river when it was diverted from its 

 course ages ago in the glacial period, by 

 an obstruction of ice, and made this 

 channel across the lava plains in central 

 Washington, in a general southwest di- 

 rection. It extends nearly one hundred 

 miles across a part of the so-called "Big 

 Bend' region of the Columbia River, 

 where the river turns west, then south 

 and east, before making its final swing 

 to the west which it holds to the sea. 

 The Big Bend region is bounded on the 

 north and west by mountainous areas. 



The name "Coulee" is frequently ap- 

 plied all through this part of the coun- 

 try to any dry gully or canyon where 

 water may flow during a small part of 

 the year. In the Big Bend district there 

 are many coulees, but the largest and 

 most interesting is the Grand Coulee. 



The northern part of the Grand 

 Coulee extends for about thirty miles 

 from the Columbia River to just south 

 of Coulee City. This portion may be 

 called the Upper Coulee, since it lies at 

 a higher level than any of the coulees 

 farther south. This Upper Coulee is a 

 flat-bottomed, vertical-walled canyon, 

 with several small lakes, some alkaline, 

 along the western margin, which is pre- 

 vailingly low and marshy. The depth 

 of the floor below the level of the plains 

 is from 400 to 500 feet, and the average 

 width is about one and a half miles, but 

 the coulee is very much wider in the 

 vicinity of Steamboat Rock, a flat- 

 topped me^a ten miles south of the Co- 

 lumbia River, which rises about 400 feet 



346 



above the floor of the Coulee. The east- 

 ern wall dies out about five miles north 

 of Coulee City, and the level floor rises 

 and merges with the slightly undulating 

 plain which extends eastward for many 

 miles. The western wall, although 

 somewhat broken and eroded back 

 about three miles southwest of the town, 

 continues for about twenty miles to the 

 south in the Lower Coulee. 



There is a precipitous drop of about 

 400 feet in the floor of the Coulee four 

 miles southwest of the town, and the 

 top of the east wall in the Lower Coulee 

 is continuous with the floor of the Up- 

 per Coulee. The floor of the Lower 

 Coulee is uneven, and most of the de- 

 pressions are occupied by lakes which 

 are fresh in the northern part and 

 strongly alkaline in the southern part 

 of the Coulee. The walls of the Lower 

 Coulee south of Moses Lake become 

 less distinct, but the course of the 

 former drainage channel is still clearly 

 visible as it swings to the west and 

 finally joins the Columbia River. The 

 length of the Lower Coulee is about 

 seventy miles. 



GEOLOGIC HISTORY OF THE REGION 



Many ages ago there was great vol- 

 canic activity in this region, and ex- 

 tensive flows of basaltic lava were 

 poured forth and covered the rather 

 subdued old land surface of the Big 

 Bend to a varying depth. In the north- 

 ern part the cover is relatively thin, and 

 the granite of the old land surface is 

 often exposed, but to the south it be- 

 comes increasingly thicker. 



Following the volcanic activity the 

 region was irregularly uplifted, caus- 

 ing dislocations of the lava flows and a 

 warping of the surface. After a long 

 period of erosion in which the region 

 was nearly reduced to a plain, the land 

 was again uplifted and the main streams 

 had cut deep channels before the Glacial 

 Period commenced. In the Glacial 

 Period an ice sheet advanced down the 



