Challis Volcanics, Central Idaho Copyright © Ralph Maughan Cliffs composed of Challis volcanics along the Salmon River between Challis and Salmon, Idaho.  The usually colorful Challis volcanics cover a good portion of east central Idaho. They consist of latite-andesite flows, basalts, tuffs, and rhyolites. In many places they have eroded into eye-catching cliffs, pinnacles, and buttresses.