Definition: The natural features existing on the Earth’s surface like mountains, plateaus, plains, hills and glaciers are known as landforms.
Types of landforms
- A valley is defined as a hollow or surface depression in the Earth’s surface, bound by hills or mountains that slopes down to a stream, lake or ocean and is formed by water or ice erosion.
- The system of valleys extends across plains, hills and mountains. Rivers and streams flow through plains and drain the interior land regions into the ocean. Underneath most valleys lies the most fertile soil which is ideal for farming.
- The bottom of the valley is called its floor. Most floors slope downstream. The floors of mountain valleys are usually narrow. Parts of floor which lie alongside rivers are known as flood plains. The sides of a valley are called valley walls or valley slopes.
- The formation of a valley is dependent on the rate at which widening and deepening goes on in it. Erosion and rivers are largely responsible for the formation of V-shaped valleys.
- U-shaped valleys are another form of valleys which were previously occupied by glaciers. When those huge bodies of ice moved, they carved the valleys, carrying along huge amounts of debris with them.
- Deep narrow valleys are sometimes called canyons. Valleys in the mountains have deep and narrow slopes, while in the plains valleys have average slopes.
- Erosion by rivers is the main process of valley formation, others being movement of Earth’s crust and glaciers.
- The rate at which a river erodes a valley is dependent on various factors. The primary factor is at which rate the water is going down a channel. Another factor is the resistance offered by the material through which the river channel is cutting.
- While the channel cuts down the valley floor, erosion carries soil and sediments down the valley slopes towards the channel.
- A large highland area of fairly leveled land, separated from the surrounding land by steep slopes is called a plateau. Plateau is also called table land.
- Some plateaus lie between mountain ranges, like the plateau of Tibet. Plateaus are found everywhere and cover almost 45 per cent of the Earth’s land surface.
- The Deccan Plateau of India and the Columbia Plateau of the United States are amongst the largest plateaus in the world. Both are basaltic plateaus and were formed by the lava flowing for thousands of square kilometers.
- Many plateaus are a result of upward folding, while some were formed by erosion of surrounding lands. Like all elevated regions, even plateaus are subjected to erosion.
- Low plateaus are used for farming, while high plateaus serve the purpose of livestock grazing.
- Many of the world’s highest plateaus are deserts.
- A few notable plateaus of the world are the Colorado Plateau, Bolivian Plateau, plateaus of Anatolia, Arabia, Iran and Tibet.
- The Canadian Shield or Laurentian Plateau is a U-shaped region of ancient rock. It covers more than half of Canada, most of Greenland and even extends into the Unites States.
- Mountains are created by tremendous forces from within the Earth, over long periods of time. Mountains have a steep top that usually shapes up to a peak or ridge. Mountains occur more often in oceans than on land.
- Mountains are formed by volcanic activity, erosion or uplifting of the Earth’s crust due to disturbances. According to geologists most of the mountains have formed due to geological activity and movement of Earth’s crust. This movement is called plate tectonics.
- The Earth’s crust is divided into a number of rigid plates that move at a rate of a few centimeters a year. When these plates collide with each other, it leads to uplifting of the Earth’s surface, which results in formation of mountains.
- Another process that causes mountain formation is horizontal compression, which means deformation of crustal strata that produces folds or wrinkles.
- The Himalayas were formed by compression that accompanied the collision of the Indian plate with the Eurasian plate. The European Alps and Jura mountains were also formed by horizontal compression created by the collision of the African and the Eurasian plates.
- Some low mountains are also formed by non-tectonic processes, like sculpting effects of differential erosion by wind, rain or ice.
- Some mountains are also formed by volcanoes like Mount Saint Helen in United States and Mount Fuji in Japan. Such mountains can be active or dormant and might periodically emit lava, steam or debris.
- Broad, large stretches of land that are nearly level without any significant change in elevation are known as plains. Plains are generally lower than the land around them. Plains may be found along a coast or inland.
- Coastal plains normally rise up from sea level until they meet higher landforms like mountains or plateaus.
- Climate plays an important role in determining the plant life on plains.
- Thick forests are generally found on plains in humid zones. Dry planes are generally covered with grasslands. Because of the soil and terrain being good, plains are most populated landforms on Earth as they are good for farming.
Landforms created by river systems
The process of erosion and deposition by rivers creates different landforms like V-shaped valleys, interlocking spurs, waterfalls and rapids and steep gradients.
Landforms created by glaciers
Landforms created by action of glaciers are known as glacial landforms. Most of the glacial landforms were created during the Quaternary glaciations by movement of large ice sheets.
As the glaciers expanded, their accumulating weight of ice and snow crushed the rocks and bedrock. Landforms created by glaciers include stariations, cirques, glacial horns, arêtes, trim lines, U-shaped valleys, roches moutonnees and hanging valleys.
Landforms created by wind
Wind erosion is striking in arid and semi-arid zones. Wind erosion is signified with abrasions which break up rocks, producing rock pedestals, zeugens, yardangs and inselbergs. Deflation by wind erosion blows away rock waste, thus lowering desert surface, producing depressions. Deposition by wind creates sand dunes and leads to expansion of deserts.
Landforms created by groundwater
Water below the Earth’s surface is called subsurface water. Ground water could be derived from rain water that percolates down or from the water that has remained trapped within rocks.
Groundwater sinking below creates landforms like springs, artesian wells, geysers, oasis, swamp, marsh, bogs and caves.
Landforms created by sea water
Waves originating from sea are also responsible for creating landforms, called coastal landforms. Waves have brute force and can do a lot to the land they crash into. Waves create landforms like cliffs, caves, stumps, arches, beaches and stacks.