Lake Mead - Malpais Flattop Mesa

This zoomed-in view shows Malpais Flattop Mesa in the Black Mountains beyond the Black Canyon gorge flooded by Lake Mohave. The mesa is capped by a horizontal layer of a massive volcanic flow that formed about 12 million years ago. The Black Mountains consist of a thick sequence of Miocene-age volcanic rocks and alluvial sediments that overlie ancient Precambrian-age metamorphic rocks. These rocks have been folded and faulted by ongoing regional tectonic forces shaping the eastern margin of the Basin and Range Province (Beard and others, 2007).