Under the process of erosion, there are activities in the upper parts of the earth's crust. They try to level the earth's crust. These actions come under exogenous force. In this article, we will study the various topographies made by river erosion and deposition.
Landforms Formed By River or Running Water
- Flow Area or River Basin or Catchment Area – The area or place where rivers take water and move forward, that place is called river basin. In this the rivers move along with their tributaries.
- Watershed – The high land area situated between any two river basins is called watershed, that is, the high plateau or mountain due to which two rivers flow in different areas.
A. Topographies Formed By River Erosion
- V shaped Canyons – Gorges and Canyons
- Waterfall and Rapids
- Water Socket
- River Meanders
- River Meanders
- Structural Benches
- Peneplain
1. V - Shaped Canyons – Gorges and Canyons
When a river flows from high places to low places, the river valley becomes deep and thin due to vertical cut. It looks similar to the letter V in English. This is called V shaped valley. In this the slope of the river is convex and sharp. Two types of topographies are formed in V shaped valley.
- Gorges : When the water falls move rapidly backwards, a very deep and narrow V-shaped valley is formed, which is called a gorge or kandara.
- Canyons : It is a relatively steep slope, a wide form of gorge or ravine. The Grand Canyon located on the Colorado River in America is the best example of this.
2. Waterfall and Rapids
When rivers fall downwards from a great height and with a very rapid velocity, it is called a waterfall. Such waterfalls whose height is less are called Kshiprika or Rapids. The waterfall also comes under this, whose height is very less. In common parlance, it is called a waterfall.
They are formed due to upliftment of land during fold and fault activities, formation of fault edges and heterogeneity in rock structure.
3. Pot Holes or Water Socket
In the plains, troughs are formed due to whirlpools in the bottom of a fast flowing river, these troughs are called water sockets. At first these sockets are small, whose diameter and depth increase later. These troughs can be large and deep from a few cm to several meters. They are formed as a result of the erosion of pebbles, stones and gravel moving along with the water whirlpool. They are also built at the bottom of the waterfall.
Statue of Equality4. River Terraces or Alters
Tiered altars are built on both the banks of the river in the flood plain, which are parallel to the river. Their number can be one or more. The height difference between two platforms can be from a few meters to 20 – 30 meters, while their width can be from a few meters to several kilometers.
5. River Meanders
The movement of rivers through zigzag paths is called river meanders. Due to excessive erosion and low velocity in the plains, they start leaving the eroded materials on their sides, due to which their stream sometimes turns to the left and sometimes to the right.
6. Structural Benches
When layers of hard and soft rocks are successively mixed in the course of a river, the erosion of soft rocks takes place at a rapid rate. As a result of erosion, step-like structures are formed on both the banks of the river, which are called structural benches.
7. Peneplain
Rivers form this type of plain in the last stage of their erosion cycle. Here and there in these plains, the remains of resistant rocks are present in the form of mounds, which are called monadnak.
Lokpal : Structure & It's FunctionB. Topographies Formed By River Deposition
When the amount of weathered materials in the rivers increases, then the rivers start taking these extra materials out of their flow path after a limit. This is called deposition. For example, piles of sand on the banks of rivers after floods etc.
- Alluvial Fans
- Alluvial Cone
- Flood Plain
- Gokhur Lake or Oxbow Lake
- Natural Embankment
- Delta
1. Alluvial Fans
At the time of leaving the mountainous parts, the sediments of the rivers spread far and wide, due to which feather like plains are formed. This is called Alluvial Fans. Terai region or Giripad plain is formed by joining of many alluvial fans.
2. Alluvial Cone
When rivers leave the mountains and enter the plains, large depressions of rocks are left behind. The shape made by these rocks is called Alluvial Cone. Bhabar region is formed by the meeting of many alluvial cones.
Ocean Current - Part 3, Pacific Ocean Currents3. Flood Plain
When the carrying power of the river becomes too low, it starts depositing excessive sediments. Due to the deposition of excessive sediments at its bottom, its flow stops and the water of the river spreads in the surrounding areas. This flat and square plain is called flood plain. In these plains, new sediments are deposited every year due to floods.
4. Oxbow Lake
When the river takes a straight path again leaving its meander made due to sediments. Then the residual part of the river, which has been abandoned by the river, is called Gokhur Lake.
5. Natural Levees
When the rivers move further, they also deposit large sediments on the banks along with erosion. Due to this deposition, dam-like structures are formed on the banks of the rivers. Which is called Natural Levees.
6. Delta
Due to the low slope of the land in the lower part, the speed of the river also decreases. Also, due to the realization of the erosive substances present in the rivers, they slow down further. Therefore, they start depositing erosive substances on their bottom, due to which the river streams are divided into thin sub-streams. This region formed in this way is called delta. Delta is formed at the mouth of the river. Delta is divided into several types on the basis of its type –
- Arcuate Delta : Ganga-Brahmaputra Delta, Nile River Delta, Rhine River Delta, Indus River Delta
- Birdfoot Delta : Mississippi – Missouri Delta
- Estuary Delta : Amazon River Delta, Seine River Delta in France, Narmada and Tapti Delta in India
- Cuspate Delta : Tiber River Delta of Italy, Ebro River Delta of Spain.
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