Land modification depends on many factors such as internal processes, external forces, nature of rocks and the length of time these processes that have been acting upon. So there are basically two major processes as given below:
- INTERNAL PROCESSES: The internal processes include movement of tectonic plates, volcanic eruptions and Earthquakes. Internal processes may produce lava plains, plateaus, rift valleys, geysers, mud pools etc.
- EXTERNAL PROCESSES: The external processes take place on the surface of the earth. These processes work slowly. Weather, rivers, glaciers, wind waves etc are some of the major agents responsible for external processes.
Various Factors Related To These Processes:
1). WEATHERING: The wearing away or breaking dawn of rocks by agents present in the atmosphere like Temperature, Moisture and frost is known as weathering.
TYPES OF WEATHERING:
1) PHYSICAL WEATHERING: Temperature and Frost two factors responsible for physical setting.
2) CHEMICAL WEATHERING: Water is the main agent of Chemical Weathering.
3) BIO-LOGICAL WEATHERING: Plants, Trees and Animals also contribute to Weathering.
2). EROSION:Erosion is the wearing a way of rocks on the surface of the Earth by agents like running water, moving ice, wind and waves.
The rate of weathering and erosion depends on the following factors:
1) Temperature and Rainfall 2) Vegetation Cover 3) Change in Land use
4) Slope of the land 5) Type of Soil
DNUDATION: The process of weathering and erosion are called denudation.
Agents of Denudation: Running water, Wind, Glaciers, and Waves are the major agents of Denudation.
How Land Form?
i). LAND FORMS MADE BY WIND: Work of wind is more important or prominent in desert areas where soil particles are loose due to leak of moisture and vegetation. A deflation hallow and Sand Dunes are the most important landforms made by wind.
ii). LAND FORMS MADE BY GLACIERS:
GLACIER: A glacier is a huge mass of ice that moves slowly down a mountain valley.
- EROSIONAL WORK OF GLACIERS: The Cracks that appear on the glacier because of the splitting up of ice as a result of its unequal movement are known as “Crevasses”.
U-SHAPED VALLEY: Mountain Glaciers can’t dig a new valley but deepen, straighten as well as widen the persisting valley by eliminating irregularities during its passages. It is called a U – Shaped valley.
GIRGUE: A Girgue is an armchair shaped depression with a steep back wall. It is formed due to the downslape movement of glacier.
- Depositional work of a Glacier: Moraines are the result of depositional work of the glaciers.
- MORAINE: A mound of unsorted rock material left behind by a glacier is called a moraine.
iii). LANDFORMS MADE BY SEA WAVES:The sea is an active agent of gradation in coastal areas.
1) SEA CLIFF: A cliff has a sleep shape facing the sea.
2) SEA ARCH: If the rock formation along a coast differs in resistance, softer rocks are evaded first and harder rocks stand about forming distinctive coastal features as arches.
3) SEA STACK: Continued erosion of the headland may cause the arch to fall in, leaving behind an isolated column as sea stack.