Mesa

A mesa (Spanish and Portuguese for "table") is the American English term for tableland, an elevated area of land with a flat top and sides that are usually steep cliffs. It takes its name from itscharacteristic table-top shape.

It is a characteristic landform of arid environments, particularly the Southwestern United States. Many examples are also found in Spain, Sardinia, North and SouthAfrica, Arabia, India, Australia, badlands and in the mountainous parts of Wyoming, Idaho, Montana, Texas, and Oklahoma. Grand Mesa is a large mesa located in western Colorado in the Southwest UnitedStates.

The term "mesa" is used throughout the United States to describe a flat-topped mountain or hill. In Spanish such a landform is more usually known as a meseta.[1]





Contents[hide] 1 Formation
2 Mesas on Mars
3 See also
4 References


[edit] Formation





Mesas in the region of Logudoro in northern Sardinia.




Cerro Negro one of a few mesas nearZapala, Argentina.
Mesas are formed by weathering and erosion of horizontally layered rocks that have been uplifted by tectonic activity. Variations in the ability of different types of rock to resistweathering and erosion cause the weaker types of rocks to be eroded away, leaving the more resistant types of rocks topographically higher than their surroundings.[2] This process is calleddifferential erosion. The most resistant rock types include sandstone, conglomerate, quartzite, basalt, chert, limestone, lava flows and sills.[2] Lava flows and sills, in particular, are very resistant toweathering and erosion, and often form the flat top, or caprock, of a mesa. The less resistant rock layers are mainly made up of shale, a softer rock that weathers and erodes more easily.[2]

Thedifferences in strength of various rock layers is what gives mesas their distinctive shape. Less resistant rocks are eroded away on the surface into valleys, where they collect water drainage from the...