The canyon at the falls is 115 meters (377 ft) deep, exposing a large cross-section of the Columbia River Basalt Group. These falls and the canyon downstream comprise an important feature of the channeled scablands created by the great Missoula Floods that swept periodically across eastern Washington and across the Columbia River Plateau during the Pleistocene epoch.
The ancestral Palouse river flowed through the currently dry Washtucna Coulee to the Columbia River. The Palouse Falls and surrounding canyons were created when the Missoula Floods overtopped the south valley wall of the ancestral Palouse River, diverting it to the current course to the Snake River by erosion of a new channel.
The Palouse (/pəˈluːs/ pə-looss) is a region of the northwestern United States, encompassing parts of southeastern Washington, north central Idaho and, in some definitions, extending south into northeast Oregon. It is a major agricultural area, primarily producing wheat and legumes. Situated about 160 miles (260 km) north of the Oregon Trail, the region experienced rapid growth in the late 19th century, and for a brief time surpassed the population of the Puget Sound region of Washington. The region is home to two land grant universities, the University of Idaho in Moscow and Washington State University in Pullman. Located just eight miles (13 km) apart, both schools opened in the early 1890s.