(i) A long geological process has resulted in the formation of the present physical structure of India. India is mainly composed of three geological units:
a. The Himalayan Mountains b. The Northern Plains
c. The Peninsular Plateaus
(ii) After the splitting of the huge single landmass or supercontinent, the Indo- Australian plate drifted northwards, which resulted in the collision of the plate
with the much larger Eurasian Plate. Due to this collision, the sedimentary rocks which were formed at the bottom of the sea of Tethys, were folded to form the Himalayan mountain system. The movement of the Indo-Australian plate also led to stresses in the crust, leading to folding, faulting and volcanic activity, resulting in the formation of the Andaman and Nicobar Islands along with the Himalayas.
iii. In due course of time, the depression between uplifted young Himalayas and old peninsular plateau were gradually filled with sediment deposits by the rivers flowing from the Himalayas in the north and peninsular plateau in the south. Extensive alluvial deposits led to the formation of northern plains of India.
iv. The Peninsular Plateau is mainly covered by igneous and metamorphic rocks with smoothly rising hills and broad valleys. India has all major physical features of the earth i.e. mountains, plains, deserts, plateaus and islands. Besides geological formation, number of processes such as weathering, erosion and deposition have created and modified the relief to its present form.
