A landform is a feature on the Earth’s surface that is part of the terrain.
Mountains, hills, plateaus, and plains are the four major types of landforms. Minor landforms include buttes, canyons, valleys, and basins.
Tectonic plate movement under the Earth can create landforms by pushing up mountains and hills. Erosion by water and wind can wear down land and create landforms like valleys and canyons. Both processes happen over a long period of time, sometimes millions of years.
Classification of landforms:
In terms of origin, oceans and continents have certain differences. Generally, the materials which constitute the ocean bottom are harder and heavier than those which constitute the continents. Though the interior of the earth is still in a hot and molten state, it is still undergoing contraction.
The contractions could be slow or sudden. Whether slow or sudden, the contractions are continuously altering the form of the earth’s surface. Such changes on the earth’s surface are therefore caused by the actions of internal force.
Since the very beginning of the earth, its surface has been continuously subjected to change by the action of river, glaciers, winds, sea waves, earthquakes, etc. Such changes are, therefore, caused by the actions of external force.
Based on the order of relief development landforms can be classified into:
First order, second order and third order landforms
- Landforms of First Order: By the actions of internal forces anticlines and synclines were formed and in course of time these have been identified as continents and oceans. That is why, they are called as Landforms of First Order or Primary landforms.
The continental landforms consist of Americas, Eurasia, Africa, Australia and Antarctica. The total area is nearly 148 million sq km, i.e., 28 per cent of the earth’s surface and average height is 830 metres.
- Landforms of Second Order:
The plateaus, mountains, plains and extensive deserts of the continents are the example of the landforms of second order on the continents.
- Landform of Third Order:
Various features which are generally smaller parts of second order landforms or which form on the second order landforms are known as landforms of third order. There are innumerable such landforms over the continents and at the sea floor.
Peaks, cols, cirques, gorge, morains, alluvial fans, floodplains, ox-bow lakes, levees, deltas, ocean islands, volcanoes and ridges are some of the many features of third order landforms.
The landforms that are found on the surface of the Earth can also be grouped into 4 of the following categories:
(a) Structural Landforms – landforms that are created by the solidification of large quantities of magma or by massive movements due or rock because of plate tectonics. This includes landforms like: shield, fold mountains, rift valleys, and volcanoes.
(b) Weathering Landforms – landforms that are created by the physical, chemical or biological decomposition of rock through weathering. Weathering produces landforms where rocks and sediments are decomposed and disintegrated. This includes landforms with some of the following geomorphic features: karst, patterned ground, and soil profiles.
(c) Erosional Landforms – landforms formed from the removal of weathered and eroded surface materials by wind, water, glaciers, and gravity. This includes landforms with some of the following geomorphic features: river valleys, glacial valleys, and coastal cliffs.
(d) Depositional Landforms – landforms formed from the deposition of weathered and eroded surface materials. On occasion, these deposits can be compressed, altered by pressure, heat and chemical processes to become sedimentary rocks. This includes landforms with some of the following geomorphic features: beaches, deltas, flood plains, and glacial moraines.
Many landforms show the influence of several of the above processes. These landforms are called polygenetic. Processes acting on landforms can also change over time, and a single landscape can undergo several cycles of development. This type of landscape development is called polycyclic.