Sims Corner Eskers and Kames million years ago. These lava flows have been extensively exposed by the erosion resulting from the Missoula Floods, which laid bare many layers of the basalt flows on the edges of the plateau at Grand Coulee and Moses Coulee. Two million years ago the Pleistocene epoch began and ice age glaciers invaded the area. They scoured the Columbia River Plateau, reaching as far south as the middle of the Waterville Plateau highlands above the Grand Coulee and south to the head of Moses Coulee. In some areas north of the Grand Coulee they were as much as 3 km (10,000
Grand Coulee pumped from the Grand Coulee Dam, into Banks Lake to act as an Equalizing Reservoir and irrigation water source. Evidence of the waterfalls includes a plunge basin where the falls began, immediately south of Coulee City. It contains at least 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 lip of the main falls creating lateral falls. These flowed until the recession of the main falls denied them water. Northrup Canyon in Steamboat Rock State Park, contains a dry cataract as