The Eastern Ghats are a discontinuous range of mountains, which have been eroded and cut through by the four major rivers of southern India, the Godavari, Mahanadi, Krishna, and Kaveri. These mountain ranges extend from West Bengal in the north, through Orissa and Andhra Pradesh to Tamil Nadu in the south. They run parallel to the Bay of Bengal and are not as tall as the Western Ghats, though some of its peaks are over 1000 m in height.

The Eastern and Western Ghats meet at the Nilgiri knot in Tamil Nadu. The Anai Mudi in the Cardamom Hills at 2,695 m (8,841 feet) in Kerala is the highest peak in the Western Ghats. The Nilgiris are considered to be a part of the Western Ghats.

Indo-Gangetic plain

The Indo-Gangetic plains are large floodplains of the Indus and the Ganga-Brahmaputra river systems. They run parallel to the Himalaya mountains, from Jammu and Kashmir in the west to Assam in the east, draining the states of Punjab, Haryana, eastern Rajasthan, Uttar Pradesh, Bihar, Jharkhand and West Bengal. The plains encompass an area of 700,000 km² (270,000 mile²) and vary in width through their length by several hundred kilometres. Major rivers that form a part of this system are the Ganga (Ganges) and Indus River along with their tributaries; Beas, Yamuna, Gomti, Ravi, Chambal, Sutlej and Chenab.

The Indo-Gangetic belt is the world’s most extensive expanse of uninterrupted alluvium formed by the deposition of silt by the numerous rivers. The plains are flat and mostly treeless, making it conducive for irrigation through canals. The area is also rich in ground water sources.

The plains are one of the world’s most intensely farmed area in the world. Crops grown on the Indo-Gangetic Plain are primarily rice and wheat, grown in rotation. Other crops include maize, sugarcane and cotton. Also known as the Great Plains, the Indo-Gangetic plains rank among the world’s most densely populated areas.

Thar Desert

The Thar Desert (also known as the Great Indian Desert) is a hot desert that forms a significant portion of western India. Spread over four states in India - Punjab, Haryana, Rajasthan, and Gujarat it covers an area of 208,110 km² (80,350 mile²). The desert continues into Pakistan as the Cholistan Desert. Most of the Thar Desert is situated in Rajasthan, covering 61 percent of its geographic area. Most of the desert is rocky, with a small part of the extreme west of the desert being sandy.

The origin of the Thar Desert is uncertain. Some geologists consider it to be 4,000 to 10,000 years old, whereas others state that aridity began in this region much earlier. The area is characterised by extreme temperatures of above 45 °C (113 °F) in summer to below freezing in winters. Rainfall is precarious and erratic, ranging from below 120 mm (4.72 in) in the extreme west to 375 mm (14.75 in) eastward.

The lack of rainfall is mainly due to the unique position of the desert with respect to the Aravalli range. The desert lies in the rain shadow area of the Bay of Bengal arm of the southwest monsoon. The parallel nature of the range to the Arabian Sea arm also means that the desert does not receive much rainfall.

The desert can be divided into two regions, the great Desert and the little desert. The great Desert extends northwards from the edge of the Rann of Kutch region of Gujarat. The little desert extends from the River Luni between the towns of Jodhpur and Jaisalmer, up to the northern areas. The soils of the arid region are generally sandy to sandy-loam in texture. The consistency and depth vary according to the topographical features. The low-lying loams are heavier and may have a hard pan of clay, calcium carbonate or gypsum. Due to the low population density, the effect of the population on the environment is relatively less compared to the rest of India.