Aravalli range

Background and evolution

Scientists have also studied the Aravallis as a natural laboratory of early Earth history. Their rocks, which include ancient granites, quartzites and schists, record the assembly of the Indian landmass from older crustal blocks. Mining has long exploited this geology: zinc smelting at Zawar is among the oldest known in the world, dating back more than two thousand years.

The Aravallis were once lofty mountains raised by ancient collisions of crustal blocks in the Proterozoic era, long before the Himalayas formed. Over hundreds of millions of years, erosion has worn them down into a chain of low ridges and isolated hills, broken in many places by gaps. They form a major divide in north-western India: rivers such as the Luni and Sabarmati flow west and south from them, while the Banas and other streams drain east towards the Chambal and the Ganga system.

Because the range runs from south-west to north-east, parallel to the Arabian Sea branch of the monsoon, it does not block moist winds effectively, and this is one reason why western Rajasthan stays dry. At the same time, the range acts as a barrier slowing the spread of desert sand towards the eastern plains. This page focuses on the Aravallis as an ecological shield for north-west India and as a site of conflict between mining, real estate and conservation, rather than on general mountain types.