Mesa

thumb|Aerial view of mesas in [[Monument Valley, on the Colorado Plateau]]

thumb|right|Har Qatum, a mesa located on the southern edge of [[Makhtesh Ramon, Israel]]

thumb|[[Ingleborough in North Yorkshire, England]]

thumb|[[Mount Garfield (Mesa County, Colorado)|Mount Garfield, a mesa in Colorado]]

A mesa is an isolated, flat-topped elevation, ridge, or hill, bounded from all sides by steep escarpments and standing distinctly above a surrounding plain. Mesas consist of flat-lying soft sedimentary rocks, such as shales, capped by a resistant layer of harder rock, like sandstone or limestone, forming a caprock that protects the flat summit. The caprock may also include dissected lava flows or eroded duricrust.

Unlike a plateau, which is a broader, elevated region that may not have horizontal bedrock (e.g., Tibetan Plateau), a mesa is defined by flat-lying strata and steep-sided isolation. Large, flat-topped plateaus with horizontal strata, less isolated and often part of extensive plateau systems, are called tablelands. A butte is a smaller, eroded mesa with a limited summit, while a cuesta has a gentle dip slope and one steep escarpment due to tilted strata.

Names, definition and etymology

As noted by geologist Kirk Bryan in 1922, mesas "...stand distinctly above the surrounding country, as a table stands above the floor upon which it rests". It is from this appearance that the term mesa was adopted from the Spanish word mesa, meaning "table".

A mesa is similar to, but has a more extensive summit area than, a butte. There is no agreed size limit that separates mesas from either buttes or plateaus. For example, the flat-topped mountains which are known as mesas in the Cockburn Range of North Western Australia have areas as large as . In contrast, flat topped hills with areas as small as in the Elbe Sandstone Mountains, Germany, are described as mesas.

Less strictly, a very broad, flat-topped, usually isolated hill or mountain of moderate height bounded on at least one side by a steep cliff or slope and representing an erosion remnant also have been called mesas. Similar landforms in Australia are known as tablehills, table-top hills, tent hills, or jump ups (jump-ups). The German term Tafelberg has also been used in the English scientific literature in the past.

Formation

Mesas form 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 resist weathering and erosion cause the weaker types of rocks to be eroded away, leaving the more resistant types of rocks topographically higher than their surroundings. This process is called differential erosion. The most resistant rock types include sandstone, conglomerate, quartzite, basalt, chert, limestone, lava flows and sills. As the underlying shale erodes away, it can no longer support the overlying cliff layers, which collapse and retreat. When the caprock has caved away to the point where only little remains, it is known as a butte.

Examples and locations

Australia

Cockburn Range, Western Australia
Mount Conner, Northern Territory

File:Mount Conner - panoramio.jpg|Mount Conner, a mesa located in Northern Territory, Australia

File:Cockburn Range.jpg|Cockburn Range, Kimberley, Western Australia, Australia

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Czechia

Děčínský Sněžník, Ústí nad Labem Region

France

Mont Aiguille, Auvergne-Rhône-Alpes

Germany

Königstein, Saxony
Lilienstein, Saxony
Papststein, Saxony
Quirl, Saxony
Knocknarea, County Sligo
Har Qatum

Italy

Monte Santo, Sardinia

Poland

Szczeliniec Wielki, Lower Silesian Voivodeship

United Kingdom

England

Castle Folds, Cumbria
Cross Fell, Cumbria
Goldsborough Carr, County Durham
Higger Tor, South Yorkshire
Ingleborough, North Yorkshire
Shacklesborough, County Durham

United States

Many but not all American mesas lie within the Basin and Range Province.

Arizona

Anderson Mesa
Black Mesa (Apache-Navajo Counties)
Black Mesa (Navajo County)
Black Mesa (Warm Springs)
Black Mountain
Cummings Mesa
First Mesa
Horseshoe Mesa
Indian Mesa
Second Mesa

Arkansas

Mount Magazine

California

Redonda Mesa

Colorado

Battlement Mesa
Grand Mesa - largest flat-topped mountain in the world.
Green Mountain
Log Hill Mesa
North Table Mountain
Raton Mesa

Nevada

Mormon Mesa
Pahute Mesa

Oklahoma

Black Mesa
Mesa de Maya

Texas

Floating Mesa
Llano Estacado

Utah

Checkerboard Mesa
Crazy Quilt Mesa
Hurricane Mesa
Sams Mesa
Smith Mesa
South Caineville Mesa
Thompson Mesa
Wildcat Mesa
Wingate Mesa

Wisconsin

Gibraltar Rock
Grandad Bluff
Mile Bluff
Quincy Bluff
Rattlesnake Mound

On Mars

thumb|A mesa in [[Noctis Labyrinthus on Mars, viewed by HiRISE]]

A transitional zone on Mars, known as fretted terrain, lies between highly cratered highlands and less cratered lowlands. The younger lowland exhibits steep walled mesas and knobs. The mesa and knobs are separated by flat lying lowlands. They are thought to form from ice-facilitated mass wasting processes from ground or atmospheric sources. The mesas and knobs decrease in size with increasing distance from the highland escarpment. The relief of the mesas range from nearly to depending on the distance they are from the escarpment.