Geology of the Pacific Northwest along their course. The larger cataract was that of the upper Grand Coulee, where the river roared over an waterfall. The eroding power of the water plucked pieces of basalt from the precipice, causing the falls to retreat and self-destruct by cutting through to the Columbia River valley near what is now the Grand Coulee Dam. The other major cataract is now known as Dry Falls. It started near Soap Lake in Washington State, where less resistant basalt layers gave way before the great erosive power of this tremendous torrent and waterfalls developed. As in the upper Grand Coulee, the
Moses Coulee thrasher, sage sparrow, poorwill, mountain bluebird, loggerhead shrike, canyon wren, white-throated swift, golden eagle), plants (sagebrush buttercup, shooting star, sulphur lupine, serviceberry, mock orange, slender cryptantha, Tiehm's rush, big sagebrush, bluebunch wheatgrass and sego lily) and animals (mule deer, least chipmunk, bats, and marmot). Moses Coulee Moses Coulee is a canyon in the Waterville plateau region of Douglas County, Washington. Moses Coulee is the second-largest and westernmost canyon of the Channeled Scablands, located about to the west of the larger Grand Coulee. This water channel is now dry, but during glacial periods, large outburst floods with discharges greater than carved