Plains And Straits
Plains and Its Types
The plain has the most important place in the relief of the secondary category. 41% of the world's lithosphere is covered by plains, 33% by plateaus and 26% by mountains and hills.
Participation of various reliefs in the lithosphere – plains – 41%
Plateau part – 33%
Mountains and hills – 26%
The flat and relatively low land, whose local gradient is very less, is called plain. Some plains are higher than the plateaus. For example, the plains of Mississippi are higher than the Appalachian Plateau. While some plains may be below sea level. Like – in the Netherlands.
Types of Plain
- By Origin
- Structural or Geomorphological
- Erosive plains
- River Erosion
- Glacial Erosion
- Wind Erosion
- Karst Plain
- Depositional Plains
- Alluvial Plains
- Deposited By Glaciers
- Submitted By Wind
- Lake Plains
- Lava Plains
1. By Origin
- Structural or Geomorphological – eg – Karnataka and East Coastal Plains.
- Erosive plains : Erosive plains are following types -
- River Erosion – common ground, final stage of erosion cycle. Example – Chota Nagpur Plateau.
- Glacial Erosion – Ladakh plains in India (east of Shyok river and north of Changchenmo river).
- Wind Erosion – Peniplane |
- Karst Plain – formed as a result of the action of rain water or underground water in the limestone area. The mounds made in these are called Humes. Example – Karst region of Yugoslavia, Chitrakoot in India.
2. Depositional Plains
- Alluvial Plains – plains of the Ganges.
- Deposited By Glaciers – depositional plains, tills or outwash plains.
- Submitted By Wind - Loyce
- Lake Plains – Plains formed by the filling of lakes like – Valley of Kashmir.
- Lava Plains – Deccan Region of India
Island
The land area surrounded by water from all sides is called an island. The islands are divided into several parts on the basis of their origin.
- Tectonic Islands
- Sedimentary Islands
- Erosional Islands
- Volcanic Islands
- Coral Islands
1. Tectonic Islands
Due to geological movements, they are originated as a result of land subsidence or rise of land in oceanic parts, development of rift valleys or fragmentation of continents. Example – West Indies
2. Sedimentary Islands
Made of materials deposited by rivers, glaciers.
3. Erosional Islands
Islands formed by the erosion of glaciers come under this category. Example – Greenland
4. Volcanic Islands
Islands formed as a result of volcanic activity. Example – Hawaiian Islands and Aleutian Islands.
5. Coral Islands
Islands made by corals in the ocean. Example – Lakshadweep, Maldives, Bermuda etc.
Isthmus
The isthmus connects two water bodies and separates two landmasses. Like – Gibraltar, Bering etc.
- Gibraltar is called the key to the Mediterranean Sea.
- The International Date Line passes through the Bering Strait.
Strait
Unlike an isthmus, it separates two water bodies and connects two landmasses. Like – Sunda Strait (Java).
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