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
Etzikom Coulee of at its origin east of Stirling Lake (to which it is connected by the Sluice Gate Channel) to an elevation of at its mouth at Pakowki Lake, over a length of more than . The coulee builds a canyon up to deep. Etzikom Coulee Etzikom Coulee is a coulee located in Southern Alberta, Canada. The waterway was formed as a glacial spillway channel at the end of the last ice age. The Etzikom Coulee begins northeast of the town of Stirling, and makes its way southeast of the Hamlet of Wrentham, after that it passes by the Hamlet of