Dissected plateau
Encyclopedia
Plateau
In geology and earth science, a plateau , also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain. A highly eroded plateau is called a dissected plateau...
area that has been severely eroded so that the relief is sharp. Such an area may be referred to as mountainous, but dissected plateaus are distinguishable from orogenic mountain belts by the lack of folding, metamorphism
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
, extensive faulting, or magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
tic activity that accompanies orogeny
Orogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
.
The Allegheny Plateau
Allegheny Plateau
The Allegheny Plateau is a large dissected plateau area in western and central New York, northern and western Pennsylvania, northern and western West Virginia, and eastern Ohio...
, the Cumberland Plateau
Cumberland Plateau
The Cumberland Plateau is the southern part of the Appalachian Plateau. It includes much of eastern Kentucky and western West Virginia, part of Tennessee, and a small portion of northern Alabama and northwest Georgia . The terms "Allegheny Plateau" and the "Cumberland Plateau" both refer to the...
, the Ozark Plateau
The Ozarks
The Ozarks are a physiographic and geologic highland region of the central United States. It covers much of the southern half of Missouri and an extensive portion of northwestern and north central Arkansas...
, the Catskill Mountains
Catskill Mountains
The Catskill Mountains, an area in New York State northwest of New York City and southwest of Albany, are a mature dissected plateau, an uplifted region that was subsequently eroded into sharp relief. They are an eastward continuation, and the highest representation, of the Allegheny Plateau...
, and the Blue Mountains are examples of dissected plateaus formed after regional uplift. These older uplift
Tectonic uplift
Tectonic uplift is a geological process most often caused by plate tectonics which increases elevation. The opposite of uplift is subsidence, which results in a decrease in elevation. Uplift may be orogenic or isostatic.-Orogenic uplift:...
s have been eroded by creeks and river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s to develop steep relief not immediately distinguishable from mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...
s. Many areas of the Allegheny Plateau and the Cumberland Plateau, which are at the western edge of the Appalachian Mountains
Appalachian Mountains
The Appalachian Mountains #Whether the stressed vowel is or ,#Whether the "ch" is pronounced as a fricative or an affricate , and#Whether the final vowel is the monophthong or the diphthong .), often called the Appalachians, are a system of mountains in eastern North America. The Appalachians...
of eastern North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, are called "mountains" but are actually dissected plateaus. One can stand on the top of one of these high "mountains" and note that all the other tops are nearly the same height, which represents the original elevation profile of the plain
Plain
In geography, a plain is land with relatively low relief, that is flat or gently rolling. Prairies and steppes are types of plains, and the archetype for a plain is often thought of as a grassland, but plains in their natural state may also be covered in shrublands, woodland and forest, or...
before uplift, and thereafter the subsequent weather erosion.
A dissected plateau may also be formed, or created, usually on a comparatively small scale, by the levelling of terrain by planing and deposition beneath an ice sheet
Ice sheet
An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...
or perhaps, an ice cap
Ice cap
An ice cap is an ice mass that covers less than 50 000 km² of land area . Masses of ice covering more than 50 000 km² are termed an ice sheet....
. Subsequently, during the same or a later glacial, the margins of the glacial till
Till
thumb|right|Closeup of glacial till. Note that the larger grains in the till are completely surrounded by the matrix of finer material , and this characteristic, known as matrix support, is diagnostic of till....
plain are removed by glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
s, leaving the plateau into which erosion by water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
incises valley
Valley
In geology, a valley or dale is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys...
s. Such a plateau may be level or gently sloping but may be distinguished by the till caps on its hills. Glacial till is still widely known in Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
by the older name of boulder clay.
Dissected volcanic plateau
Volcanic plateau
A volcanic plateau is a plateau produced by volcanic activity. There are two main types: lava plateaus and pyroclastic plateaus.-Lava plateau:...
s include the Pajarito Plateau
Pajarito Plateau
The Pajarito Plateau is a volcanic plateau in north central New Mexico, United States. The plateau, part of the Jemez Mountains, is bounded on the west by the Valles Caldera and on the east by the White Rock Canyon of the Rio Grande...
in New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
, on the skirt of the enormous Valles Caldera. Isolated portions of this plateau are known as mesa
Mesa
A mesa or table mountain is an elevated area of land with a flat top and sides that are usually steep cliffs. It takes its name from its characteristic table-top shape....
s, and long, connected portions are known as potrero
Potrero (landform)
A potrero is a long mesa that at one end slopes upward to higher terrain. This landform commonly occurs on the flanks of a mountain, as part of a dissected plateau....
s.
See also
- SyrtSyrtA syrt is a kind of an elevated landform in Russia and Central Asia.The word means "highland", "ridge" or "backbone" in Turkic languages and is present in Turkic toponymy in the mentioned areas: in Tien Shan, Pamirs, South Urals, such as Obshchiy Syrt by Urals, Uzun-Syrt plateau by Koktebel in...
, denudationDenudationIn geology, denudation is the long-term sum of processes that cause the wearing away of the earth’s surface leading to a reduction in elevation and relief of landforms and landscapes...
al uplands or dissected plateaus in Turkic toponymy of RussiaRussiaRussia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
and Central AsiaCentral AsiaCentral Asia is a core region of the Asian continent from the Caspian Sea in the west, China in the east, Afghanistan in the south, and Russia in the north...