A landform is a feature on the Earth's surface that is part of the terrain. Mountains, hills, plateaus, and plains are the major types of landforms.
Mountain
The uplifted portions of the earth's surface with steep slopes and small summit area rising above 1000 metres and formed over a period of million of years are called mountains. About 27% of the earth’s surface is covered by the mountains.
On the basis of their mode of formation, the mountains have been classified as:
(a) Fold Mountains: Mountain ranges mainly consisting of uplifted folded sedimentary rocks are called fold mountains. When two plates move together (a compression plate margin), the movement of the two plates forces sedimentary rocks upwards into a series of folds. Fold mountains are usually formed from sedimentary rocks.
(b) Block Mountains: Block mountains are also formed by the internal earth movements. When the forces of tension act on the rocks, they create faults in them. When the land between the two almost parallel faults is raised above the adjoining areas, it forms a block mountain.
(c) Volcanic Mountains: When this molten rock material is ejected to the earth's surface during volcanic eruption, it accumulates around the vent and may take the form of a cone. The height of the cone increases with each eruption and it takes the form of a mountain.
(d) Residual Mountains: The weathering and different agents of erosion constantly act on the earth's crust. These agents level down the elevated mountain ranges on the earth's surface. After thousands of years, soft rocks are worn down and the hard rocks are left but have been reduced in height. These are called residual mountains.
Plateau
The plateaus cover about 18% of the earth's surface. This landform has a large elevated area on its top unlike a mountain and has nearly even surface out there and affected by rivers or streams to cut out deep valleys and gorges.
Though normally 600 metres above sea level, there are plateau of Tibet and Bolivia, more than 3600 metres above sea level.
Classification of Plateaus
Intermontane Plateaus: Wide tablelands that are situated between mountain ranges, when a plateau is surrounded by mountains on all sides.
Piedmont Plateaus: Situated at the foot of the mountains and are bounded on other sides by a plain or an ocean are called piedmont plateau.
Continental Plateaus: These are formed either by an extensive continental uplift or by the spread of horizontal basic lava sheets completely covering the original topography to a great depth.
Plains
A low lying relatively flat or slightly rolling land surface with very gentle slope and minimum local relief is called a plain. Plains occupy about 55% of the earth’s surface. Plains have an average height of less than 200 metres.
Classification of Plains
Structural plains: These plains are mainly formed by the uplift of a part of the sea-floor or continental shelf.
Erosional plains: These plains are formed by the continuous and a long time erosion of all sorts of upland.
Depositional plains: Fragments of soil, regolith and bedrock that are removed from the parent rock mass are transported and deposited elsewhere to make on entirely different set of surface features, these are depositional landforms.