Aravallis

• The Aravallis of Northwestern India, one of the oldest fold mountains of the world, now form residual mountains with an elevation of 300m. to 900m. They stretch for a distance of 800 km. from Himmatnagar in Gujarat to Delhi, spanning Haryana, Rajasthan, Gujarat, and Delhi, the 692 kilometre (km).
• The mountains are divided into two, main ranges – the Sambhar Sirohi Range and the Sambhar Khetri Range in Rajasthan, where their extension is about 560 km.
• The hidden limb of the Aravallis that extends from Delhi to Haridwar creates a divide between the drainage of rivers of the Ganga and the Indus
• These are fold mountains of which rocks are formed primarily of folded crust, when two convergent plates move towards each other by the process called orogenic movement.
• The Aravallis date back to millions of years when a pre-Indian sub-continent collided with the mainland Eurasian Plate. Carbon dating has shown that copper and other metals mined in the ranges date back to at least 5th century BC.
• The Aravallis act as a barrier between the fertile plains in the east and the sandy desert in the west. Historically, it is said that the Aravalli range checked the spread of the Thar desert towards the Indo-Gangetic plains, serving as a catchment of rivers and plains.

Marwar

• Marwar is a sandy plain lying northwest of the Aravalli Range, which runs southwest-northeast through Rajasthan state. The Aravallis wring much of the moisture from the southwest monsoon, which provides most of India''s rainfall. Annual rainfall is low, ranging from 10-40cms. Temperatures range from 48 to 50 degrees Celsius in the summer, to below freezing point in winter. The Northwestern thorn scrub forests lie next to the Aravalli Range, while the rest of the region lies in the Thar Desert.
• The Luni River is the principal feature of the Marwar plains. It originates in the sacred Pushkar Lake of Ajmer District, and the main river flows through Marwar in a south-westerly direction until it finally disappears into the seasonal wetland of the Rann of Kutch in Gujarat. It is fed by numerous tributaries that flow from the Aravallis. Irrigation from the river and from wells near the river, support crops of wheat and barley.
• The sandy tracts of Thar Desert in western Marwar are characterized by a harsh physical geography and a fragile ecology. High wind velocity, shifting sand dunes and very deep and saline water sources pose a challenge to sustained human habitation in the Thar. The area is also prone to devastating droughts. The Thar Desert is one of the most inhospitable landscapes on earth. Apart from the huge distances between hamlets and settlements here, the landscape is constantly shifting with the sand, as wind and sandstorms re-arrange the landscape at will. This added to the lack of water in such an arid region, means that the villagers of the area often find themselves migrating on foot across hundreds of miles towards neighboring states in search of water.

Mewar

• The northern part of Mewar is a gently sloping plain, drained by the Bedach & Banas River and its tributaries, which empty northwest into the Chambal River, a tributary of the Yamuna River. The southern part of the region is hilly, and marks the divide between the Banas and its tributaries and the headwaters of the Sabarmati and Mahi rivers and their tributaries, which drain south into the Gulf of Cambay through Gujarat state. The Aravalli Range forms the northwestern boundary of the region, composed mostly of sedimentary rocks, like marble and Kota Stone, which has traditionally been an important construction material.
• The region is part of the Kathiawar-Gir dry deciduous forests'' ecoregion. Protected areas include the Jaisamand Wildlife Sanctuary, the Kumbhalgarh Wildlife Sanctuary, the Bassi Wildlife Sanctuary and the Sitamata Game Sanctuary.
• Mewar has a tropical climate. Rainfall averages 660 mm/year, and is generally higher in the southwest and lower in the northeast of the region. Over 90% of the rain typically falls in the period June to September every year, during the southwest monsoon.