HOME
TheInfoList



A mesa is an isolated, flat-topped elevation,
ridge A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for some distance. The sides of the ridge slope away from narrow top on either side. The lines along the ...

ridge
or
hill A hill is a landform that extends above the surrounding terrain. It often has a distinct summit. Terminology The distinction between a hill and a mountain is unclear and largely subjective, but a hill is universally considered to be not as t ...
, which is bounded from all sides by steep
escarpment An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations. Usually ''scarp'' and ''scarp face'' are used interchangeably with ''escarpment''. S ...
s and stands distinctly above a surrounding
plain In geography, a plain is a flat expanse of land that generally does not change much in elevation. Plains occur as lowlands along valleys or on the doorsteps of mountains, as coastal plains, and as plateaus or uplands. In a valley, a plain is encl ...
. Mesas characteristically consist of flat-lying soft
sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at the Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles to ...
s capped by a more resistant layer or layers of harder
rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...
, e.g.
shale Shale is a fine-grained, clastic sedimentary rock, formed from mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite.Blatt, Harvey and Robert J. Tracy (1996) ''Petr ...
s overlain by
sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones make up about 20 to 25 percent of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) be ...
s. The resistant layer acts as a caprock that forms the flat summit of a mesa. The
caprockCaprock or cap rock is a harder or more resistant rock type overlying a weaker or less resistant rock type.Kearey, Philip (2001). ''Dictionary of Geology'', 2nd ed., Penguin Reference, London, New York, etc., p. 41.. . Common types of caprock are sa ...
can consist of either sedimentary rocks such as sandstone and
limestone Limestone is a common type of carbonate sedimentary rock. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (). Limestone forms when these minerals precipitate out of water con ...
; dissected
lava flow of pāhoehoe lava, Hawaii, United States , Iceland in 1984 Lava is molten Rock (geology), rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon. Magma is generated by the internal heat of the pla ...
s; or a deeply eroded
duricrust Duricrust is a hard layer on or near the surface of soil. Duricrusts can range in thickness from a few millimeters or centimeters to several meters. It is a general term (not to be confused with duripan) for a zone of chemical precipitation and ...
. Unlike ''
plateau In geology and physical geography, a plateau (, , or ; ; plural plateaus or plateaux), also called a high plain or a tableland, is an area of a highland consisting of flat terrain, that is raised sharply above the surrounding area on at least on ...
'', whose usage does not imply horizontal layers of
bedrock Bedrock in geology is lithified rock that lies under loose softer material called regolith within the surface of the Earth's crust or other terrestrial planets. Components of bedrock Bedrock essentially refers to the substructure composed of ...
, e.g.
Tibetan Plateau The Tibetan Plateau (), also known in China as the Qinghai–Tibet Plateau or the Qing–Zang Plateau () or as the Himalayan Plateau in India, is a vast elevated plateau in South Asia, Central Asia and East Asia, covering most of the Tibet Autono ...
, the term ''mesa'' applies exclusively to the landforms built of flat-lying
strata (Argentina). , Canada. These are Middle Cambrian marine sediments. This formation covers over half of Nova Scotia and is recorded as being 8,800 m (29,000 ft) thick in some areas. In geology and related fields, a stratum (plural: strata) is a l ...
. Instead, flat-topped plateaus are specifically known as '' tablelands''.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.2019.102890Migoń, P., 2004a. ''Mesa.'' In: Goudie, A.S. (Ed.), ''Encyclopedia of Geomorphology.'' Routledge, London, pp. 668. Neuendorf, Klaus K.E. Mehl, James P., Jr. Jackson, Julia A.. (2011). ''Glossary of Geology'' (5th Edition). American Geosciences Institute. As noted by 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 the term mesa was adopted from a
Spanish Spanish may refer to: * Items from or related to Spain: **Spaniards, a nation and ethnic group indigenous to Spain **Spanish language **Spanish cuisine Other places * Spanish, Ontario, Canada * Spanish River (disambiguation), the name of several ...
word meaning ''table.'' A mesa is similar to, but has a more extensive summit area than, a
butte __NOTOC__ In geomorphology, a butte () is an isolated hill with steep, often vertical sides and a small, relatively flat top; buttes are smaller landforms than mesas, plateaus, and tablelands. The word ''butte'' comes from a French word meaning ...
. However, 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 much as . In contrast, flat topped hills, which are as small as in area, in the
Elbsandsteingebirge The Elbe Sandstone Mountains, also called the Elbe Sandstone Highlands (german: Elbsandsteingebirge; cs, Labské pískovce) is a mountain range straddling the border between the state of Saxony in southeastern Germany and the North Bohemian region ...
,
Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official language , languages = German , demonym = German , government_type = Federal parliamentary republi ...
, 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. In the English language geomorphic and geologic literature, other terms for mesa have also been used. For example, in the Roraima region of Venezuela, the traditional name, ''
tepui A tepui , or tepuy (), is a table-top mountain or mesa found in the Guiana Highlands of South America, especially in Venezuela and western Guyana. The word tepui means "house of the gods" in the native tongue of the Pemon, the indigenous people w ...
'', from the local Pomón language, and the term ''
table mountain Table Mountain ( naq, Huriǂoaxa, lit= sea-emerging; af, Tafelberg) is a flat-topped mountain forming a prominent landmark overlooking the city of Cape Town in South Africa. It is a significant tourist attraction, with many visitors using the cabl ...
s'' have been used to describe local flat-topped mountains.Briceño, H.O. and Schubert, C., 1990. ''Geomorphology of the Gran Sabana, Guayana Shield, southeastern Venezuela.'' ''Geomorphology,'' 3(2), pp.125-141. 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. Similar landforms in Australia are known as tablehills, table-top hills, tent hills, or jump ups (jump-ups).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. The German term Tafelberg has also been used in the English scientific literature in the past.King, L.C., 1942. ''South African Scenery. A Textbook of Geomorphology.'' Oliver and Boyd, Edinburgh, London (340 pp.).


Formation

Mesas form by
weathering Weathering is the breaking down of rocks, soils, and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...
and
erosion In earth science, erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location. Erosion is distinct from ...

erosion
of horizontally layered rocks that have been uplifted by
tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents kn ...
activity. Variations in the ability of different types of rock to resist weathering and
erosion In earth science, erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location. Erosion is distinct from ...

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 Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones make up about 20 to 25 percent of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) be ...
, conglomerate,
quartzite Quartzite is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tecton ...
,
basalt Basalt (, ) is a fine-grained extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (''mafic '' lava) exposed at or very near the surface of a rocky planet or a moon. More than 90% of all volc ...
,
chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline (or cryptocrystalline) crystals of quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin but may also occur inorganica ...
,
limestone Limestone is a common type of carbonate sedimentary rock. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (). Limestone forms when these minerals precipitate out of water con ...
,
lava flows of pāhoehoe lava, Hawaii, United States , Iceland in 1984 Lava is molten Rock (geology), rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon. Magma is generated by the internal heat of the pla ...
and sills. Lava flows and sills, in particular, are very resistant to weathering and erosion, and often form the flat top, or
caprockCaprock or cap rock is a harder or more resistant rock type overlying a weaker or less resistant rock type.Kearey, Philip (2001). ''Dictionary of Geology'', 2nd ed., Penguin Reference, London, New York, etc., p. 41.. . Common types of caprock are sa ...
, of a mesa. The less resistant rock layers are mainly made up of
shale Shale is a fine-grained, clastic sedimentary rock, formed from mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite.Blatt, Harvey and Robert J. Tracy (1996) ''Petr ...
, a softer rock that weathers and erodes more easily. The differences 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 surrounding area, while the more resistant layers are left standing out. 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". The more resistant layers form the cliffs, or stair steps, 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 In geology and physical geography, a plateau (, , or ; ; plural plateaus or plateaux), also called a high plain or a tableland, is an area of a highland consisting of flat terrain, that is raised sharply above the surrounding area on at least on ...
, by basal sapping. When the cliff edge does not retreat uniformly, but instead is indented by streams, a section can be cut off from the main cliff, forming a mesa. Basal sapping occurs as water flowing around the rock layers of the mesa erodes the underlying soft shale layers, either as
surface runoff Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when the so ...
from the mesa top or from
groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The de ...
moving through permeable overlying layers, which leads to slumping and flowage of the shale. 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 a little remains, it is known as a
butte __NOTOC__ In geomorphology, a butte () is an isolated hill with steep, often vertical sides and a small, relatively flat top; buttes are smaller landforms than mesas, plateaus, and tablelands. The word ''butte'' comes from a French word meaning ...
.


On Mars

A transitional zone on
Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, being larger than only Mercury. In English, Mars carries the name of the Roman god of war and is often referred to as the "Red Planet". The latter refe ...

Mars
, known as the ''
fretted terrain Fretted terrain is a type of surface feature common to certain areas of Mars and was discovered in Mariner 9 images. It lies between two different types of terrain. The surface of Mars can be divided into two parts: low, young, uncratered plains th ...
'', lies between highly cratered highlands and less cratered lowlands. The younger lowland exhibits steep walled mesas and . 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 to 100 m depending on the distance they are from the escarpment.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.


See also

* * * * * * * * * * * * *


References

{{Authority control
Erosion landforms Landforms Landform {{CatAutoTOC ...
Geography terminology Slope landforms