Mesa, << MAY suh, >> is an isolated hill or mountain that has a flat, tablelike top and steep sides. Mesa is a Spanish word meaning table. Mesas are found in dry climates. In the United States, they are common in Arizona, Colorado, New Mexico, and Utah.
Mesas range in size from a few acres or hectares to hundreds of square miles or kilometers. Mesas were once part of larger plateaus or upland areas that were worn away by erosion over a long period of time. The top of a mesa consists of lava, sandstone, or other types of rock that resist erosion. Beneath it lie layers of less resistant rocks, such as siltstone and shale. The lower slopes of a mesa are covered with large blocks of resistant rock, which broke off from the edges of the mesa when the underlying rock eroded.
