Plains of Rajasthan
Definition
A plain is a broad area of relatively flat land. Plains are one of the major landforms or types of land on Earth. They cover more than one-third of the world’s land area. The plains exist on every continent.
How the Plain formed?
Plains form in many different ways. Some plains form as ice and water erodes or wears away the dirt and rock on higher land. Water and ice carry the bits of dirt, rock and other material called sediment, down hillsides to be deposited elsewhere. As layer upon layer of this sediment is laid down and formed the plains.
Volcanic activity can also form plains. Lava plains form when lava pushes up from below ground and flows across the land. The land area in a lava plain is often much darker than the surrounding soil. The dark land is a result of the lava, mostly dark-colored mineral called basalt that is broken down into tiny particles over millions of years.
The movement of rivers sometimes formed plains. Many rivers run through valleys. As rivers move from side to side they gradually erode the valley and creating broad plains.
As a river flood overflows the bank. The flood carries mud, sand and other sediment out over the land. After the water withdraws, the sediment remains. If a river floods repeatedly, over time this sediment will build up into a flood plain. Flood plains are often rich in nutrients and create fertile farmland.
Alluvial plains form at the base of mountains. Water carrying sediment flows downhill until it hits flat land. There it spreads out, depositing the sediment in the shape of a fan.
Many rivers deposit their sediment in the ocean. As the sediment builds up, it might eventually rise above sea level and forming a coastal plain.
Sediments:Sediment is a naturally occurring substance composed of small particles. It can be broken down by various processes such as erosion and weathering. Sediments can be transported through forces of water, wind, gravity, ice and the action of the particle.
Abyssal plains are found at the bottom of the ocean. These plains are 5,000 to 7,000 meters (16,400 to 23,000 feet) below sea level so scientists have a hard time studying them. But scientists say abyssal plains are among the flattest, smoothest places on Earth.
What are the Abyssal plains? – Large, relatively flat areas of ocean floor found at 5,000-6,000m below sea level. If sediments are discharged from a river and deposit relatively quick onto the plain they may form an abyssal plain.
Eastern Plains: The area on the northeast, east and southeast of the Aravalli range is known as the Eastern Plain and it covers 23% of the total area of Rajasthan.
The Vindhyan Plateau marks the southeastern limit of the plain and the western boundary is demarcated by the eastern edge of the Aravalli up to north of Udaipur.
This Plain is further subdivided into two physiographic units-
(i) The Banas Basin
(ii) The Chappan Plain
What is Basin?
A basin is a depression or dip in the earth’s surface. Basins are shaped like bowls with sides higher than the bottom. They can be oval or circular in shape similar to a sink or tub you might have in your own bathroom. The basins are filled with water or may be empty.
Basins are formed by forces above the ground (like erosion) or below the ground (like earthquakes). They can be created over thousands of years or almost overnight.
The major types of basins are river drainage basins, structural basins and ocean basins.
What is a River drainage basin?
- A river drainage basin is an area drained by a river and all of its tributaries. The river basin is made up of many different watersheds.
- A watershed is small version of a river basin. Every stream and tributary has its own watershed which drains to a larger stream or wetland. These streams, ponds, wetlands and lakes are part of a river basin.
(i) Banas River Basin
The great watershed of india runs in an easterly direction starting from Udai Sagar, east of Udaipur. The watershed acts as the southern boundary of the Mewar Plains and southern area of this watershed is known as the Chappan Plain. The region is marked by various types of erosional features produced in the granite and gneiss rocks mark the topography of the area. The soil is stony and the annual rainfall is about 73cm. It is a Peneplane rather than alluvial plain drained by Banas and its tributaries having an elevation of about 300 metre normally. The plain has been formed on the Archean gneiss and its slope gradually decreases toward east and north east. The Banas is super-imposed in a most striking manner.
This plain is poor; having thin soil but the numerous pegmatite and quartzite dykes facilitates the construction of tanks.
- The area- 187400 Km³ is an elevated plain drained by Banas & its tributaries and it is essentially Peneplains (Peneplain is a low-relief plain formed by protracted erosion or it is a more or less level land surface produced by erosion over a long period, undisturbed by crustal movement).
- It is a dissected in Mewar and flat in Malpura plain region.
- Mewar plain gradually slope towards the east & north east.
- The Banas & its tributaries Berach, Menal, Bandi, Mansi, Kothari and Khori flow through this plain.
- It is flat upland which recognized a ―Tertiary Peneplane.
- It is composed of schist & guess.
- Banas plain slopes gradually towards northeast from the foot of the Aravalli range.
(ii) The Chappan Plains
- It is lying east of the Mewar hills & south of the Banas plain in Dungarpur district.
- The central & eastern parts known as Chhappan
- Average elevation is approximate 200-400 m
- This dissected plain along with hill tracts of Banswara and Dungarpur are locally known as Bagar.
- This plain drained by the tributaries of the Mahi River lies south of the great indian watershed in southeastern Udaipur, Banswara and the southern part of Chittorgarh district.
The Chappan area is deeply and intricately eroded resulting in the formation of separate hillocks, which is not identical to the Mewar plain in the north. This deeply dissected area is locally known as ‘Bagar’ and includes the hilly tracts of Banswara and Dungarpur.