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Mountains, Plateaus and Plains

Study Material > Geography
  • There are three major landforms Mountains, Plateaus and Plains. Mountains, Plateaus, Hills, and Plains cover about 12, 14, 33 and 41 percent of total surface area of the global respectively.

Orogeny

  • Orogeny (Geology) is a process in which a section of the earth’s crust is folded and deformed by lateral compression to form a mountain range.
  • Orogenic movements are ‘Tectonic movements’ of the earth which involve the folding of sediments, faulting and metamorphism [Geology (of rock) that has undergone transformation by heat, pressure, or other natural agencies].

Mountain System

  • A mountain is a large landform that stretches above the surrounding land in a limited area, usually in the form of a peak.
  • A mountain is generally steeper than a hill. Mountains are formed through tectonic forces or volcanism.
  • Generally, the mountains are more than 1000 metres high. The mountains whose height is less than 1000 metres, called Hills.
  • Cordillera: A cordillera is an extensive chain of mountains or mountain ranges formed in different period and by different process. Mountain ranges of this type have a complex structure, usually the result of folding and faulting accompanied by volcanic activity. g., cordillera of the Western United States and British Columbia.

Types of Mountains

  • Fold Mountains (Folded Mountains): These are the most common Mountain types. The world’s largest Mountain ranges are Fold Mountains. These ranges were formed over millions of years. Fold mountains formed when a thickly bedded sedimentary layer are subjected to horizontal compressional forces for millions of years. The sediments get bend into up and down Falls. This leads to the formation of anticlines and synclines. These Mountains are characterized by more developed system of anticlines and synclines wherein folds are arranged in a wave-like pattern.

  • Types of Fold mountain
    1. Young Fold Mountain:  The Himalayas, the Alps, the Rockies, Andies etc.
    2. Mature Fold Mountains:  The Pennines, the Appalachians, and the Cape range of South Africa were formed during the carboniferous age.
    3. Old Fold Mountains: The high mountains of Scotland and Norway, the Sayan and Stanovai Mountains of Soviet Russia, and the Aravali and the Mahadev mountains of India.
  • Block Mountains: These mountains originate due to the forces of tension leading to the formation of Rift Valley. The Block mountain or horst represents upstanding part of the ground between two faults or on either side of a Rift Valley or a Graben. The Vosges in France, Black Forest mountains in Germany and Sierra Nevada in North America are the typical examples of Block mountains.

  • Dome mountains: Dome Mountains are formed when a large amount of magma pushes up from below the Earth's crust, but it never actually reaches the surface and erupts. Instead of bursting, the magma pushes up overlaying rock layers. After some time the magma cools and forms a dome shape rock. The uplifted area created by rising magma looks like the top half of a sphere or ball, thereby giving it the name Dome Mountain. E.g., The Henry Mountain in North America.

  • Volcanic Mountains: Volcanic Mountains are created when magma (molten rock) deep within the Earth, erupts, and piles upon the surface. When the ash and lava cools, it builds a cone of rock. This material builds up around the Volcanic Vent is known as Volcanic Mountain. Some of the Volcanic Mountains:
    1. Mount St. Helens in North America.
    2. Mount Pinatubo in the Philippines.
    3. Mount Kea and Mount Loa in Hawaii.

  • Plateau Mountains: Plateau Mountains are created when running water carves deep channels into a region, creating Mountains. Over billions of years, the rivers can cut deep into a Plateau and make tall Mountains. Plateau Mountains are usually found near Mountain. Because they are formed by erosion they are also known as Erosion Mountains. The Mountains in New Zealand are examples of Plateau Mountains.
  • Relict mountains: They are the remnants of former old mountains and plateaus, which have been subjected to severe denudation thus exposing the base of mountains.
  • Vindhyas, Aravallis, Satpura, Western Ghats, Eastern Ghats are the examples of relict mountains.

Classification of mountains based on the period of their origin

  • Pre-Cambrian Mountains: They belong to the Pre-Cambrian period, a period that extended for more than 4 billion years. The rocks have been subjected to upheaval, denudation and metamorphosis. So the remnants appear as ‘residual mountains’. Some of the examples are Laurentian mountains of USA, Algoman mountains, Aravalli Mountains of India belong to this period.
  • Caledonian Mountains: They originated due to the great mountain-building movements and associated tectonic movements of the late Silurian and early Devonian periods. Caledonian mountains came into existence between approximately 430 million years and 380 million years ago. Examples are the Taconic mountains of the  Appalachian system,  Aravallis,  Mahadeo, Vindhyachal, Satpura of India etc.
  • Hercynian Mountains: These mountains originated during the upper Carboniferous to Permian Period in Europe. Hercynian mountains came into existence between approximately 340 million ears and 225 million years ago. Some examples are the mountains of Vosges and Black Forest, Altai, Tien Shan mountains of Asia, Ural Mountains etc.
  • Alpine Mountains: Has its origin in the Tertiary Period which consists of the Palaeocene, Eocene, Oligocene, Miocene and Pliocene epochs. The mountains formed during this period are called Alpine after the Alps Mountains of Europe. Examples are the Rockies of North America, the Alpine mountains of Europe, the Atlas mountains of north-western Africa, the Himalayas of the Indian subcontinent in mountains radiating from Pamir knot like Pauntic, Taurus, Elburz, Zagros and Kunlun etc. Being the most recently formed, these ranges, such as the Alps, Himalayas, Andes and Rockies are the loftiest with rugged terrain.

Plateaus

  • A plateau, also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain that is raised significantly above the surrounding area, often with one or more sides with steep slopes. Plateaus can be formed by a number of processes, including upwelling of volcanic magma, extrusion of lava, and erosion by water and glaciers. Plateaus are classified according to their surrounding environment as intermontane, Piedmont, or continental. Plateaus are found on every continent, with Asia hosting the largest and highest i.e., the Tibetan Plateau.
  • Types of plateaus: 
    1. Intermontane Plateau: These plateaus are surrounded by hills and mountains from all sides. The Tibetan Plateau, with a height of about 5000 mts, is the most striking example of this type. Other Examples: Bolivian Plateau, Peruvian Plateau, Columbian Plateau, Mexican Plateau.
    2. Piedmont Plateaus: Plateau formed at the foothill of extensive mountains is called Piedmont Plateau. Piedmont plateaus are bordered on one side by mountains and on the other by a plain or a sea. Eastern margins of the Appalachian Mountains (USA) and the Atlantic Coastal Plain is an example.
    3. Dome Shaped Plateaus:  These plateaus are formed when the landmass is uplifted in such a manner that the middle portion is raised and the sides are rounded. E.g., Chhotanagpur Plateau, Ozark Plateau.
    4. Continental Plateau: These plateaus are formed either due to the upliftment or extensive spreading of lava on the Earth surface. Continental plateaus are bordered on all sides by plains or oceans, forming away from the mountains. An example of a continental plateau is the Antarctic Plateau or Polar Plateau in East Antarctica.
    5. Volcanic Plateaus: These plateaus are formed due to accumulation of thick layers of basaltic lavas. Fissure eruption of volcanoes is the main cause for the formation of these plateaus. Deccan plateau of India and Columbian plateau of USA are the best example.

Plains

  • A plain is an area of lowland, either level or undulating. Plains seldom rise more than a hundred meters above sea level. Plains are one of the major landforms on earth, where they are present on all continents, and would cover more than one-third of the world’s land area. On the basis of their mode of formation, the plains can be various types. Some of them are: 
    1. Structural plains: Structural plains are relatively undisturbed horizontal surfaces of the Earth. They are structurally depressed areas of the world that make up some of the most extensive natural lowlands on the Earth's surface.
    2. Erosional plains: Erosional plains have been leveled by various agents of denudation such as running water, rivers, wind and glacier which wear out the rugged surface and smoothens them. Plain resulting from the action of these agents of denudation are called peneplains (almost plain) while plains formed from wind action are called pediplains.
    3. Depositional Plains: Depositional plains formed by the deposition of materials brought by various agents of transportation such as rivers, wind, waves, and glaciers. Types of depositional plains are: 
      1. Riverine Alluvial Plains: Formed by the deposition of sediments brought down by rivers. It includes piedmont alluvial plains, flood plains and delta plains. 
      2. Glacial Plains: Formed by the deposition of unsorted sands and gravels brought down by glaciers. Glacial plains are divided into three types on the basis of composition and structure- Till Plains, Morainic Plains, Outwash Plains.
      3. Loess Plains : These plains are formed due to the deposition of sand and clay brought by the winds. These plains lack in layers but are highly porus. The soil of these plains is very fertile. E.g., the Great plain of Northern China.
    4. Lacustrine Plains: These are the plains formed by lakes filled up by the sediments brought down by the rivers. The Valley of Kashmir is an example of this type.


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