Mountains

A rare kind of mountain is the individual volcano with no known relationship to a volcanically active region. Solitary volcanos like these have erupted in tectonically quiet landscapes, such as east Texas of the Cretaceous period, and their cause remains a mystery.

Mesas are flat-topped mountains. They form when a solid sheet of hard rock sits on top of softer rock. The hard rock layer on top, called the "caprock," once covered a wide area. The caprock is cut up by the erosive action of streams. Where there is no more caprock, the softer rock beneath washes away relatively quickly. Mesas are left wherever a remnant of the caprock forms a roof over the softer rock below. A cuesta is a mesa that has been tilted, so the caprock forms a slope.