Plateaus

Plateau is extensive area of flat upland usually bounded by an escarpment (i.e., steep slope) on all sides but sometimes enclosed by mountains. The essential criteria for plateaus are low relative relief and some altitude.

Although plateaus stand at higher elevation than surrounding terrain, they differ from mountain ranges in that they are remarkably flat.

Some plateaus, like the Altiplano in southern Peru and western Bolivia, are integral parts of mountain belts. Others, such as the Colorado Plateau (across which the Colorado River has cut the Grand Canyon), were produced by processes very different from those that built neighbouring mountain ranges.

Some plateaus—for example, the Deccan plateau of central India—occur far from mountain ranges. The differences among plateaus can be ascribed to the different geologic processes that have created them.

The formation of a plateau requires one of the same three types of tectonic processes that create mountain ranges—volcanism, crustal shortening (by the thrusting of one block or slice of crust over another or by the folding of layers of rock), and thermal expansion. The simplest of these is thermal expansion of the lithosphere (or the replacement of cold mantle lithosphere by hot asthenosphere).

Volcanism:

This type of plateau can form where extensive lava flows (called flood basalts or traps) and volcanic ash bury preexisting terrain, as exemplified by the Columbia Plateau in the northwestern United States, Deccan Traps of peninsular India, Laurentian plateau or The Canadian Shield and the Siberian Traps of Russia.

Volcanic plateaus are commonly associated with eruptions that occurred during the Cenozoic or Mesozoic.

Eruptions on the scale needed to produce volcanic plateaus are rare, and none seems to have taken place in recent time.

The volcanism involved in such situations is commonly associated with hot spots. The lavas and ash are generally carried long distances from their sources, so that the topography is not dominated by volcanoes or volcanic centers.

 For example, the basalts of the Deccan Traps, which cover the Deccan plateau in India, were erupted 60–65 million years ago when India lay in the Southern Hemisphere, probably over the same hot spot that presently underlies the volcanic island of Reunion.

The thickness of the volcanic rock can be tens to even hundreds of metres, and the top surface of flood basalts is typically very flat but often with sharply incised canyons and valleys.

In North America the Columbia River basalts may have been ejected over the same hot spot that underlies the Yellowstone area today. Lava plateaus of the scale of those three are not common features on Earth.

Crustal Shortening:

Crustal shortening is the process of plateau formation by the thrusting of one block or slice of crust over another or by the folding of layers of rock.

The great heights of some plateaus, such as the Plateau of Tibet is due to crustal shortening.

Crustal shortening, which thickens the crust as described above, has created high mountains along what are now the margins of such plateaus.

Plateaus that were formed by crustal shortening and internal drainage lie within major mountain belts and generally in arid climates. They can be found in North Africa, Turkey, Iran, and Tibet, where the African, Arabian, and Indian continental masses have collided with the Eurasian continent.

Thermal expansion:

When the lithosphere underlying a broad area is heated rapidly—e.g., by an upwelling of hot material in the underlying asthenosphere—the consequent warming and thermal expansion of the uppermost mantle causes an uplift of the overlying surface.

If the uplifted surface had originally been low and without prominent relief, it is likely to remain relatively flat when uplifted to a relatively uniform elevation.

The high plateaus of East Africa and Ethiopia were formed due to thermal expansion. As in parts of Africa, plateaus of that sort can be associated with volcanism and with rift valleys, but those features are not universal.

Plateaus are of classified into three different types based on their locations in the world.

• The Intermontane plateaus
• The Piedmont plateaus
• The Continental plateaus

The Intermontane plateau

When a plateau is surrounded by mountains on all sides, it is called an Intermontane plateau. The Tibetan plateau, the Bolivian plateau are examples of the Intermontane plateau.

The Piedmont plateaus

A Piedmont plateau has a mountain on one side. The best examples of Piedmont plateaus are the Malwa plateau in India, the Patagonian plateau in Argentina and the Piedmont plateau in America.

The Continental plateaus

A Continental plateau is surrounded by oceans or plains. These plateaus are very vast. The plateaus of western Australia and Africa are examples of Continental plateaus.Plateaus are important geological structures though few people live here.

There are two kinds of plateaus: dissected plateaus and volcanic plateaus.

Dissected Plateaus:

A dissected plateau forms as a result of upward movement in the Earths crust. The uplift is caused by the slow collision of tectonic plates.

 Through the continental process of weathering and erosion by running water, ice and winds, high and extensive plateaus are gradually worn down and their surfaces made irregular in the humid highlands stream action and sometimes glaciers cuts deep narrow valleys in the plateau and are also called dissected plateaus. An example of dissected plateaus is Scottish Highlands.

In drier countries, vertical corrosion by rivers and abrasion by winds dissect the plateaus into steep sided tabular masses termed mesas and butters intersected by deep canyons. This is a common feature of arid and semi-arid areas.

Volcanic Plateaus:

These kinds of plateaus are formed by molten lava. When molten lava erupts from the earth’s crust, it spreads onto its surface to form successive sheets of basaltic lava. These solidify to form the lava plateau.

Some of the well-known lava plateaus include the Antrim plateau of Northern Ireland and the North Western Plateau of the Deccan Plateau.

The most remarkable plateau built by lava is the Columbia-Snake Plateau, which covers an area almost twice as big as Malaysia. Each layer of the lava flow is 100 feet thick and the entire depth of such successive lava layers is estimated to be almost a mile.

The Tibetan plateau– this is the highest, largest and most famous plateau in the world; it is located in South-Central Asia and Stretches through the countries of Tibet, China, and India. It is 1,000 km. north to south and 2,000 km. east to west and covers an area of 2,500,000km2(970,000sq mi); with a flat valley floor which at about 16,000 feet above sea level.

The Columbia Plateau– The Columbia Plateauis located in parts of Washington, Oregon, and Idaho states of the U.S. It is surrounded by the Cascade Range and Rocky Mountains and it is divided by the Columbia River.

The Hardangervidda Plateau– The Hardangervidda Plateau has elevation covers an area of about 6,500km²and has an average elevation of 1,100 meters and 1,690mwhen viewed from a central position. It is one of the largest plateaus in Europe located at a distance of about 200 km to the west of Oslo in the Hardanger region of western Norway. Northwest of the plateau is bordered by one of the largest glaciers of Norway.

The Antarctic Plateau–This plateau is located in Central Antarctica and cuts across parts of the South Pole and the Amundsen Scott Station. This plateau covers an area of 1,000km²and has its highest elevation of about 3,000m above sea level.

The Colorado Plateau– TheColorado Plateau includes Utah, Arizona, and New Mexico. It is divided by the Colorado River and the Grand Canyon. It is the largest plateau in America, and it covers an area of 337,000km²and its highest elevation is about 2,450m above sea level.

Ethiopian Highland– This the highest plateau in Africa, it covers the central part of Ethiopia and forms the largest continuous area of its altitude in the continent, with little of its surface falling below 1500m (4,921ft), above sea level. Ethiopian Highland has its height at 4550m above sea level.

Table Mountain– Table Mountainis a prominent landform located in Cape Town in South Africa. It is located at the northern end of the Sandstone Mountain Range. To its south is the part of the range known as the Back Table. It is a level plateau measuring 3m from side to side.

TheDeccan Plateau– The Deccan Plateau covers an area of 500,000km²; it is a large plateau, which cuts across eight states of India. It is bordered by two mountain ranges, the Western Ghats and the Eastern, it is 100m in the north, but higher in the south.

The Atherton Tableland– TheAtherton Tablelandis located in Queensland, Australia. It covers an area of 32,000km²and has an elevation of 500 to 1,280m above sea level.

The Potohar Plateau– ThePotohar Plateau is located in the northeastern part of Pakistan. The plateau is bordered by the Jehlum River to the east, by the Indus River to the west, by the Margalla Hills and the Kala Chitta Range to the north, and by the Salt Range to the south. The plateau encompasses four districts which include Jehlum, Chakwal, Rawalpindi and Attock.

The Brazilian Plateau– the Brazilian Plateauis a large plateau that covers almost half of Brazil. The Brazilian Highland is divided into three plateaus. The Atlantic Plateau located at the eastern coast of Brazil.

There are lots of benefits of the world’s plateaus both to man and to the subjective well-being of the earth’s surface. Some of the significant benefits of plateaus are:

• Mineral deposits: Plateaus are rich in mineral deposits that can be mined by man to earn a living. Most minerals that are found on plateaus are valuable and have a monetary value such as gold and diamond. The minerals can be sold to earn money which can then be used to make a living.
• Waterfalls: In most areas occupied by plateaus, there are waterfalls as well as river falls. As water is a basic human need, such places will act as sources of drinking waters as well as water for other valuable activities.
• Extensive grasslands: Most plateaus are characterized by plenty of grass. The places are therefore crucial for the nomadic lifestyle since the grass is essential animal food. The green pastures on the plateaus are a perfect match for the growth and rearing of domestic animals.
• Fertile soils: The volcanic plateaus which are formed as a result of the flow of lava are known to be very productive. Volcanoes consist of fertile soils which are suitable for farming and other agricultural activities.
• Tourist attraction: Most plateaus have scenic spot-like features which act as tourist attraction sites. The grand cannons, as well as the numerous waterfalls which are found in most high plateaus, are the perfect examples of tourist attraction features on plateaus. With the attractions, the residents of such areas can earn foreign revenues from the sites.