East-central Washington and most of eastern Oregon are characterized by vast flood basalts of Cenozoic age. The volcanic section ranges from a few hundred feet to more than 20,000 ft (6,100 m) and unconformably overlies older rocks including some potential marine source and reservoir beds. Outcrops of these older rocks in the structural complex of the John Day uplift and in the Wenatchee region of north-central Washington provide clues to the subvolcanic geology elsewhere in the region. Possible oil shows and gas (including the abandoned Rattlesnake Hills gas field) have been found in sedimentary interbeds in the volcanic section and in Pliocene nonmarine beds in structural lows such as the Harney and Lakeview basins, and the Snake River basin of western Idaho and eastern Oregon. Thus, the oil and gas potential of the region is not altogether negligible; particularly the Cretaceous marine section and the Pliocene lake basins will remain prospective in spite of the presence of volcanic rocks.