Physiography of Rajasthan  :

The territory which the state covers has developed after years of denudation and erosion processes and has a very mature topography. The State can be divided into two major divisions structurally along the Aravalli range which cuts the state into East Rajasthan and West Rajasthan. These two divisions on the physiographic basis stretch into two of India’s major physiographic divisions i.e. the Great Plains and the northern part of the Central Highlands.

On the basis of the existing relief features, Rajasthan has been divided into the following physiographic divisions:

 1. Western Sandy Plains (a) Sandy Arid Plains (i) Marusthali (ii) Dune free Tract

(b) Semi-Arid Transitional Plains (Rajasthan Bagar) (i) Luni Basin (Godwar Tract) (ii) Plain of Interior Drainage (Sekhawati Tract)

2. Aravalli Range And Hilly Region (a) Aravalli Range and Bhorat Plateau (b) Northeastern Hilly Region

 3. Eastern Plains (a) Banas Basin (b) Chappan Plains

 4. Southeastern Rajasthan Pathar (Hadoti Plateau) (a) Vindhyan Scarpland (b) Deccan Lava Plateau

1. Western plains :

The western Plain covers a large part of Rajasthan in the west and the northwest of the Aravalli axis. Its northern boundary is marked by Punjab and the southwest by Gujarat and the western boundary is the international boundary between India and Pakistan. The eastern boundary of the western sandy plain is marked by the Aravalli range’s western sub-montane zone up to the northern point of Udaipur district. Beyond which the boundary is marked by the great Indian watershed and 50 cm isohyte. The surface of western Rajasthan is covered with vast stretches of sand occasionally interrupted by rocky protruding right up to the Pakistan border. The Northwestern division is sandy, poorly watered and sterile. The Rajasthan desert in the west has been subdivided into several natural regions because of the Aravalli hills and the rocky terrain of Barmer-Jaisalmer-Bikaner tract.

The Western Sandy Plains are subdivided into two units:

(a) Sandy Arid Plains (Marushthali)

 (b) Semi-Arid Transitional Plain (Rajajsthan Bagar) divided into (i) Luni Basin (Godwar Tract) (ii) Plain of Interior Drainage (Shekhawati Tract) and (iii) Ghaggar Plain

The line dividing the Sandy Arid Plains and the Semi-Arid Transitional Plain is climatic, i.e. 25 cm isohyte. The western-most belt which is ‘The Great Desert’ is covered by sand dunes, stretches from the Great Rann along the Pakistan border to Punjab. The degree and extent of sand dunes greatly influence the economic activity in this area. 63 per cent sand dune area of Rajasthan is concentrated in the desert districts of Barmer, Jaisalmer and Bikaner.

2. Aravalli range and hilly region :

The principal and most dominant mountain range of Rajasthan is the Aravalli range. The geological history of the Aravalli range can be traced back probably close of the dharwar times. This range runs diagonally across the State from northeast near Delhi and extends to southwest up to the Plains of Gujarat, for a distance of about 692 kilometers., the range runs from Khetri in the northeast to Khed Brahma in the southwest Within Rajasthan for a length of about 550 kilometers. It is composed of rocks belonging originally to the Delhi system, folded in a synclinorium occupying the site of the geosynclines which have been deeply eroded.

The whole of this Aravalli range and Hilly Region has been further subdivided into two smaller physiographic units:

(a) Aravalli range and Bhorat plateau  : This division constitutes east Sirohi, nearly the whole of Udaipur except a narrow belt in the east and whole of Durgarpur district. The highest section of the Aravalli range known as ‘Bhorat’ Plateau lies northwest of Udaipur between Kumbhalgarh - Gogunda and the average elevation of this plateau is 1,225 metres.

(b) North-eastern hilly tract :  Northern edge of Bhorat Plateau marks the boundary of north eastern hilly tract in the southwest. North of Kumbhalgarh, especially at the Alwar hills the elevation varies between 550 m to 670 m. Further north and northeast, the hills are broken and their elevation decreases in the final extension of hills south of Delhi to about 306 m above sea level. This level is about 60 m to 90 m above the surrounding plain.

3. Eastern plains  :

The area on the northeast, east and southeast of the Aravalli range is known as the Eastern Plain. The Vindhyan Plateau marks the south eastern limit of the Plain. 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

(i) Banas 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 south of this watershed is 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 73 cm. From the foot of the Aravalli range the plain slopes gradually towards northeast. River Banas and its tributaries drain the Mewar plain.

(ii) The chappan plains  : 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 ‘Begaar’ and includes the hilly tracts of Banswara and Dungarpur.

 4. Southeastern Rajasthan pathar (Hadoti plateau)  :

The eastern part along the Chambal River is covered by the Hadoti Plateau. The Great Boundary Fault of the Aravallis forms its northwest boundary which extends eastward across the Rajasthan border. River Chambal drains the large part of this area. The Plateau has been divided into two smaller units:

(a) Vindhyan scarp : The scarp lands formed by massive sandstones separated by shale have an average elevation between 350m to 580m. The scarps are facing towards the southeast between the Banas and the Chambal and extend towards the east over Bundelkhand. A scarp block occupies the areas of Dholpur and Karauli.

 (b) Deccan lava plateau  :

The Deccan Lava Plateau is also known as ‘pathar (stony) or ‘uparmal’ plateau. It is a wide stony upland, including Kota-Bundi plateau section. The Chambal along with its tributaries Kali Sindh and Parbati form a triangular alluvial basin of 210 m, 275 m at Kota.