Mesa

A mesa is a flat-top tableland with one or more steep sides commonly found in Colorado Plateau regions of the United States. Mesas consist of flat-lying soft sedimentary rocks covered by more resistant layers or layers of hard rock. For example, shales overlaminated by sandstones. The resistant layer functions as a caprock that forms the flat summit of the mesa. The caprock can consist of either sedimentary rock such as sandstone or limestone or a deeply eroded duricrust. 

A butte is also a flat-topped hill with steep sides, though smaller in area than a Mesa. However, there is no acceptable way to separate mesa from butte or the plateaus. For example, the flat-topped mountain known as mesa, in the Cockburn range of North-Western Australia has an area as much as 350 km (220 mi) in opposition to flat-topped hills which is as small as 0.1 kilometers (0.062 mi) in area, in the Elbsandsteingebirge, Germany.

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Define Mesa

A mesa is an isolated, high plateau with a flat top and steep slides that has been separated by the broadening of canyons. Mesas are mostly found in the drier southwestern states of New Mexico, Colorado, Utah, and Arizona.

Mesa Formation

Mesas are generally formed when the horizontal stratification of rock is pushed upwards by tectonic force. Erosion and weathering then act on these rocks, and the weaker layer of rocks are eroded away, leaving behind more resistant rocks which become elevated above their surroundings in a process known as differential erosion. The more resistant rock types include conglomerate, sandstone, quartzite, basalt, limestone, lava flows, chert, and sills. Lava and sills, in general, are very resistant to weathering and erosion, and often form the flat top, or caprock of the mesa. The less resistant rock layers are generally made up of shale, a softer rock that weathers and erodes easily. 

The mesa formation is quite a lengthy process and can take millions of years. The variation in different types of rocks during the formation of mesa also affects the steepness and sides of mountains. More resistant rock layers form cliffs whereas less resistant rock types form gentle slopes. Eventually, the basal sapping causes the cliffs to be cut off from the mesa. 

Mesa on Mars

Mesas are not restricted to Planet Earth, as these geographical features have been found on an extraterrestrial location known as Mars.  A translation zone on Mars lies between highly cratered highlands and low cratered lowlands. The younger lowland manifests steep-walled mesas and knobs. The mesas and knobs are departed by flat-lying lowlands. They are considered to form from ice-facilitated mass wasting processes from the ground or atmospheric sources. The mesas and knobs diminish in size with escalating distance from the highland escarpment. The relief of the mesas ranges from nearly 2 km to 100 m depending on the distance they are from the escarpment. 

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How Mesas are Related to Two Landforms: Butte and Plateaus?

Mesas are closely related to two landforms known as butte and plateaus. The basic difference between these landforms is size. The surface area of mesas ranges between 11.251 square feet and four square miles whereas plateaus are larger, i.e., more than 4 square miles, and buttes are smaller (11,250 square feet or less).

The simple difference between mesa and butte is that some say mesa has more width than its height whereas others say a butte has more height than its width.

The three landforms mesa, butte, and plateaus are also related to the sense that over time, one landform can transform into another. For example, a plateau can be eroded into various forms. Similarly, a mesa can be eroded multiple times until its height is greater than its width, at this point it is considered a butte. A butte will ultimately erode into a peak, which will ultimately crumble and fall to the surface.

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Did You Know?

• The largest mesa in the world is Grand Mesa, found in Western Colorado in the United States.

• A mesa on Mars can be viewed easily from satellites.

• The term Mesa is used to describe flat-topped mountains in the Southwestern United States.