Columbia River Basalts seen at Steens Mountain, Oregon

Looking southwest from the Steens Mountain summit area into the Alvord desert of eastern Oregon.  This fault-block escarpment reveals the oldest lava flows of the Columbia River Flood Basalts, which erupted about 17 million years ago.  Three or four vertical dikes that feed these flows are evident in the midground ridge where they stand as rock walls cutting across the horizontal lava flows.  The Steens Mountain eruption site is one of many volcanic provinces generated along the Yellowstone hotspot track.