Dry Falls is a 3.5 mile long scalloped precipice in central Washington, ten times the size of Niagara, Dry Falls is thought to be the greatest known waterfall that ever existed. According to the current geological model, catastrophic flooding channeled water at 65 miles per hour through the Upper Grand Coulee and over this 400-foot (120 m) rock face at the end of the last ice age.
If you want to know more: Dry Falls is part of the channeled Scablands which are a unique geological erosion feature created by the cataclysmic Missouila Floods that swept periodically across eastern Washington and down the Columbia River Plateau during the Pleistocene epoch.
River valleys formed by erosion normally have a 'V' cross section, and glaciers leave a 'U' cross section. The Channeled Scablands have a rectangular cross section and are spread over immense areas of eastern Washington. They exhibit a unique drainage pattern that appears to have an entrance in the northeast and an exit in the southwest.