One of many impressive tributaries of the Imnaha Canyon in Hells Canyon National Recreation Area. Exposed in the canyon walls is the stack of flood basalt lavas which make up the Columbia River Basalt Formation. It was here in northeast Oregon that most of this material was erupted and flowed outward-- mostly westward--for vast distances to what is now Spokane, Wenatchee, and the Pacific Ocean at Astoria and Cannon Beach. Photographed on 4x5.