Continuing through the Snake River valley we visited the Craters of the Moon National Monument. The Craters of the Moon National Monument is an area where considerable recent volcanic activity has occurred providing vast areas of lava flows and cinder cones. Indeed, the Columbia Plateau, Craters of the Moon and Yellowstone are all linked to a ‘hot-spot’ in the earth’s interior thought, perhaps to have been created when a massive asteroid or comet hit the earth at the point of the Columbia Plateau. The plateau was created from the out pouring of magma from the fracture. Since that time, the continental plate has been sliding over-top of the hot-spot in a westward direction taking it successively underneath Craters of the Moon and, now, Yellowstone.