India is the seventh largest and second most populous country in the world which lies at the head of Indian Ocean. It covers an area of 3,287,782 sq. kms. And lies entirely in northern hemisphere. It extends between 811 4? 28? N. latitude to 37° 17? 53? N. latitude i.e. from Cape Comorin in the south to Kashmir in the north. Its longitudinal extension is in between 68° 7? 33? E. to 97° 24? 47? E. i.e. Saurashtra in the west to Arunachal Pradesh in the east. The Tropic of Cancer passes through the centre.
The country is of vast size and measures about 3,214 kms. from north to south and about 2,933 kms. From east to west. The northern portion of India is very broad and the southern portion is very narrow as it tapers off into the Indian Ocean. The coast line is 6,100 kms. Long, most of which is smooth with few large harbors. India has land frontiers in the north-west, north and north-east. It is about 15,200 kms. in length.
To the south,’ south-east and south-west. India has water frontier. This water frontier is provided by the Indian Ocean which washes three sides of India.
India contains three well-defined geological regions i.e., the peninsular region, the extra-peninsular region and the Indo-Genetic plain region.
(1) Peninsular region:
This region includes the Shilling plateau of Assam in the north-east and Kutch Kathiawar in the west. It occupies nearly 70 per cent of the total land area. It is the oldest shield consists of gneiss and schist rocks of the Achaean and Proterozoic ages. This region is a stable land- mass of great rigidity.
(2) Extra peninsular region:
This region includesss the Himalayas, Kashmir, Himachal Pradesh, Nagaland, Arunachal Pradesh, Assam, Tripura, Manipur and Andaman and Nicobar Islands. It occupies nearly 15 per cent of the land area. Major part of this region consists of sedimentary rocks though parts of the sub-Himalayas contain ancient meta- morphic and intrusive igneous rocks. This region is a weak and flexible region which has been folded, faulted and over-thrust.
(3) Indo-Gangetic plain region:
This region includes the States of Uttar Pradesh, Bihar, West Bengal, Orissa, southern Madhya Pradesh, northern and eastern Rajasthan and the contiguous coastal plains. This region is composed of a great thickness of alluvium derived especially from the Himalayan and the peninsular rivers.