· The landscape is continuously being worn away by two processes:
- It is the breaking up of rocks on the earth’s surface. It creates rock fragments.
- As mentioned earlier, it is the wearing away of landscape by different agents like wind, water and ice.
- The eroded material is carried away or transported by water, wind, etc. and eventually deposited.
- Different landforms are created on the earth’s surface because of erosion and deposition.
Role of water in erosion/ deposition :
- The running water of the river erodes the landscape.
- A waterfall is formed when the river tumbles at steep angle:
- over very hard rocks or
- down a steep valley side
3.Ox Bow Lake :
- As the river enters the plain, it twists and turns forming large bends called meanders.
- Due to continuous erosion and deposition along the sides of the meander, the ends of the meander loop come closer and closer.
- When this happens, over a course of time, the meander loop cuts off from the river and forms a cut – off lake.
- Such a lake is also called an ox-bow lake
- When the river overflows its banks, the neighbouring areas get flooded.
- When the river floods, it deposits layers of fine soil and other material called sediments along its banks.
- This leads to the formation of a floodplain.
- A floodplain is flat and fertile.
- When the river approaches the sea, it becomes very slow in its flow and begins to break up into a number of streams called distributaries.
- The speed of the river water is so less that it starts depositing its load.
- Each distributary forms its own mouth.
- A collection of sediments from all the mouths forms a delta.
7.Sea Waves :
- The erosion and deposition by water in the form of sea waves leads to the formation of coastal landforms.
- Some coastal landforms are as follows:
- Sea Caves
- Sea Arches
- Sea Cliff
- Seawaves continuously strike at the rocks. This leads to cracks. The cracks become larger and wider overtime.
- Thus hollow like caves are formed on the rocks. They are called sea caves.
- As these cavities become bigger and bigger, only the roof of the caves remains, hence forming sea arches.
- The erosion further breaks the roof and only the walls remain. These wall-like features are called stacks.
- Sea cliff is the steep rocky coast rising almost vertically above sea water.
- The sea waves deposit sediments along the shores forming beaches.
8. Role of ice in erosion/ deposition:
Glaciers are ‘rivers’ of ice that too erode the landscape by bulldozing soil and stones to expose the solid rock below. They create
- Deep hollows .
- Lakes in mountains: These are formed when the ice melts and the deep hollows get filled up with water
- Glacial moraines: These are formed by the deposition of the material carried by the glacier such as rocks big and small, sand and silt.
9. Role of wind in erosion/ deposition :
- An active agent of erosion and deposition in the deserts is the wind. The landforms in the desert are
a. Mushroom Rocks:
- In deserts, we can see rocks in the shape of mushrooms called mushroom rocks.
- The mushroom has a narrow base and a wider top.
- These rocks also have such a shape because the winds erode the lower section of the rock more than the upper part.
- When the wind blows, it lifts and transports sand from one place to another.
- When it stops blowing the sand falls and gets deposited in low hill – like structures called sand dunes.
· When the grains of sand are very fine and light, the wind can carry it over very long distances.
· When such sand is deposited in large areas, it is called loess.
· Large deposit of loess is found in China.