A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a more resistant layer or layers of harder rock, e.g. shales overlain by sandstones. The resistant layer acts as a caprock that forms the flat summit of a mesa. The caprock can consist of either sedimentary rocks such as sandstone and limestone; dissected lava flows; or a deeply eroded duricrust. Unlike plateau, whose usage does not imply horizontal layers of bedrock, e.g. Tibetan Plateau, the term mesa applies exclusively to the landforms built of flat-lying strata. Instead, flat-topped plateaus are specifically known as tablelands.[1][2][3]

Aerial view of mesas in Monument Valley, on the Colorado Plateau
Cockburn Range, Kimberley, Western Australia, Australia

Names, definition and etymology edit

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".[4] It is from this appearance that the term mesa was adopted from the Spanish word mesa, meaning "table".[2]

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 350 km2 (140 sq mi). In contrast, flat topped hills with areas as small as 0.1 km2 (0.039 sq mi) in the Elbe Sandstone Mountains, Germany, are described as mesas.[1][2][3]

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.[3]

In the English-language geomorphic and geologic literature, other terms for mesa have also been used.[1] For example, in the Roraima region of Venezuela, the traditional name, tepui, from the local Pomón language, and the term table mountains have been used to describe local flat-topped mountains.[5][6] Similar landforms in Australia are known as tablehills, table-top hills, tent hills, or jump ups (jump-ups).[7][8][9] The German term Tafelberg has also been used in the English scientific literature in the past.[10]

Formation edit

Har Qatum, a mesa located on the southern edge of Makhtesh Ramon, Israel

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.[11] This process is called differential erosion. The most resistant rock types include sandstone, conglomerate, quartzite, basalt, chert, limestone, lava flows and sills.[11] Lava flows and sills, in particular, are very resistant to weathering 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.[11]

The differences in strength of various rock layers are what give mesas their distinctive shape. Less resistant rocks are eroded away on the surface into valleys, where they collect water drainage from the surrounding area, while the more resistant layers are left standing out.[11] A large area of very resistant rock, such as a sill, may shield the layers below it from erosion while the softer rock surrounding it is eroded into valleys, thus forming a caprock.

Differences in rock type also reflect on the sides of a mesa, as instead of smooth slopes, the sides are broken into a staircase pattern called "cliff-and-bench topography".[11] The more resistant layers form the cliffs, or stairsteps, while the less resistant layers form gentle slopes, or benches, between the cliffs. Cliffs retreat and are eventually cut off from the main cliff, or plateau, by basal sapping. When the cliff edge does not retreat uniformly but instead is indented by headward eroding streams, a section can be cut off from the main cliff, forming a mesa.[11]

Basal sapping occurs as water flowing around the rock layers of the mesa erodes the underlying soft shale layers, either as surface runoff from the mesa top or from groundwater moving through permeable overlying layers, which leads to slumping and flowage of the shale.[12] 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 edit

Australia edit

Mount Conner, a mesa located in Northern Territory, Australia
Amadiya, Iraq, a city in its entirety built on a mesa

Czech Republic edit

France edit

Germany edit

Iraq edit

Ireland edit

Israel edit

Italy edit

United Kingdom edit

England edit

Ingleborough in North Yorkshire, England

Scotland edit

United States edit

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

Arizona edit

Arkansas edit

California edit

Colorado edit

Mount Garfield, a mesa in Colorado

Nevada edit

Oklahoma edit

Texas edit

Utah edit

Wisconsin edit

On Mars edit

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 2 km (1.2 mi) to 100 m (330 ft) depending on the distance they are from the escarpment.[28]

See also edit

  • Amba – Steep-sided, flat-topped mountain in Ethiopia, usually harboring various settlement
  • Archipelago – Collection of islands
  • Butte – Isolated hill with steep, often vertical sides and a small, relatively flat top
  • Dissected plateau – Plateaus area that has been severely eroded so that the relief is sharp
  • Mensa – Flat-topped prominence with cliff-like edges
  • Mesa Verde National Park – U.S. national park in Colorado
  • Nor'Wester Mountains – Mountain range in Ontario, Canada – Group of mountains immediately south of Thunder Bay, Ontario, Canada
  • Pingdingshan – prefecture-level city in Henan, China – Chinese city named after a local mesa
  • Potrero – Long mesa that at one end slopes upward to higher terrain
  • Table hill – Raised landform with a flat top
  • Table Mountain – Flat-topped mountain overlooking the city of Cape Town, South Africa
  • Tepui – Table-top mountain or mesa in the Guiana Highlands of South America
  • Tundra – Biome where plant growth is hindered by frigid temperatures
  • Tuya – Flat-topped, steep-sided volcano formed when lava erupts through a thick glacier or ice sheet

References edit

  1. ^ a b c Duszyński, F., Migoń, P. and Strzelecki, M.C., 2019. Escarpment retreat in sedimentary tablelands and cuesta landscapes–Landforms, mechanisms and patterns. Earth-Science Reviews,' no. 102890. doi.org/10.1016/j.earscirev.2019.102890
  2. ^ a b c Migoń, P., 2004a. Mesa. In: Goudie, A.S. (Ed.), Encyclopedia of Geomorphology. Routledge, London, pp. 668. ISBN 9780415272988
  3. ^ a b c Neuendorf, Klaus K.E. Mehl, James P., Jr. Jackson, Julia A.. (2011). Glossary of Geology (5th Edition). American Geosciences Institute. ISBN 9781680151787
  4. ^ Bryan, K. (1922). "Erosion and Sedimentation in the Papago Country, Arizona". US Geological Survey Bulletin (730): 19–90.
  5. ^ Briceño, H.O. and Schubert, C., 1990. Geomorphology of the Gran Sabana, Guayana Shield, southeastern Venezuela. Geomorphology, 3(2), pp.125-141.
  6. ^ Doerr, S.H., 1999. Karst-like landforms and hydrology in quartzites of the Venezuelan Guyana shield: Pseudokarst or" real" karst?. Zeitschrift fur Geomorphologie, 43(1), pp.1-17.
  7. ^ Jack, R.L., 1915. The Geology and prospects of the Region to the South of the Musgrave Ranges, and the Geology of the Western Portion of the Great Australian Artesian Basin. Geol. Survey South Australia Bulletin 5, pp. 72.
  8. ^ Macquarie dictionary : Australia's national dictionary online, Macquarie Library, 2021, retrieved 11 March 2021
  9. ^ "Land Zones of Queensland". Queensland Government. 2012. pp. 62–63. Retrieved 11 March 2021.
  10. ^ King, L.C., 1942. South African Scenery. A Textbook of Geomorphology. Oliver and Boyd, Edinburgh, London (340 pp.).
  11. ^ a b c d e f Easterbrook, Don J. (1999). Surface Processes and Landforms. Upper Saddle River, NJ: Prentice Hall. ISBN 9780138609580.
  12. ^ Choreley, Richard J.; Stanley A. Schumm; David E. Sugden (1985). Geomorphology. New York: Methuen.
  13. ^ Burbridge, Andrew; Mckenzie, NL; Kenneally, Kevin F (1991). Nature Conservation Reserves in the Kimberley, Western Australia. Department of Conservation and Land Management. ISBN 9780646033747. Retrieved 4 July 2021.
  14. ^ Report. The Department. 1966.
  15. ^ Kindred by Choice Germans and American Indians Since 1800, Glenn H Penny, 2013
  16. ^ Lilienstein – a mesa with a symbolic character
  17. ^ a b c Jancewicz, Kacper. "Morphological diversity of mesas in Elbsandsteingebirg". ResearchGate. Retrieved 4 July 2021.
  18. ^ a b c Journal of Earth Sciences Royal Dublin Society. (1980). Ireland: The Society.
  19. ^ "Masada - Definition, History, Siege & Facts". Encyclopedia Britannica. Retrieved 4 July 2021.
  20. ^ Karst Rock Features. Karren sculpturing: Karren sculpturing. Zalozoba ZRC. 2009. p. 286. ISBN 9789612541613. Retrieved 4 July 2021.
  21. ^ Lakeland - The Wildlife of Cumbria, Derek A Ratcliffe
  22. ^ a b Reading, H. G. (1954) The stratigraphy and structure of the syncline of stainmore, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/9349/
  23. ^ "Bulletin of the Centre of Excellence in Geology". University of Peshawar - Bulletin of the Centre of Excellence in Geology. 7–8: 3. 1975.
  24. ^ a b Wood, Harold; Preece, Dorothy (1948). Modern Geography ...: The British Isles. Retrieved 9 July 2022.
  25. ^ Reid, T.R. (2 November 2000). "A Lord's Leaky Roof vs. a Changing Scotland". The Washington Post. Retrieved 10 August 2022.
  26. ^ National Geographic Encyclopedia (2016)
  27. ^ "Floating Mesa, Bushland, Texas". Atlas Obscura. Retrieved 19 October 2021.
  28. ^ Baker, David M. Morphological Analyses of Mesas and Knobs in the Northwest Fretted Terrain of Mars; Constraints on the Presence and Distribution of Ice-Facilitated Mass-Wasting. Ed. Alexander K. Stewart and James W. Head. Vol. 40. Issue 2. pp. 72. United States: Geological Society of America (GSA) : Boulder, CO, United States, 2008.