Key Points

The physical features of India are broadly grouped into six major physiographic divisions: The Himalayan Mountains, The Northern Plains, The Peninsular Plateau, The Indian Desert, The Coastal Plains, and The Islands.

Geologically, the Peninsular Plateau is one of the most ancient and stable landmasses on Earth. In contrast, the Himalayas and the Northern Plains are the most recent and geologically unstable landforms.

The Himalayas consist of three parallel ranges in their longitudinal extent. From north to south, they are the Great or Inner Himalayas (Himadri), the Lesser Himalaya (Himachal), and the Outer Himalayas (Shiwaliks).

The northern-most range, known as the Himadri, is the most continuous range with the loftiest peaks, having an average height of 6,000 metres. Its core is composed of granite and it is perennially snow-bound.

The range south of the Himadri is the Himachal or Lesser Himalaya. It is composed of highly compressed rocks with altitudes varying between 3,700 and 4,500 metres. This range is famous for its hill stations and valleys like Kashmir and Kullu.

The outer-most range of the Himalayas is called the Shiwaliks. They have an altitude varying between 900 and 1100 metres and are composed of unconsolidated sediments brought down by rivers. The valleys between the Lesser Himalaya and Shiwaliks are called Duns.

The Himalayas are also divided from west to east based on river valleys. These divisions include the Punjab Himalaya (between Indus and Satluj), Kumaon Himalayas (between Satluj and Kali), Nepal Himalayas (between Kali and Teesta), and Assam Himalayas (between Teesta and Dihang).

The Northern Plains are formed by the interplay of three major river systems: the Indus, the Ganga, and the Brahmaputra. They are composed of fertile alluvial soil deposited over millions of years, making them agriculturally very productive.

Based on relief variations, the Northern Plains are divided into four regions. From north to south, these are the Bhabar (pebble belt), the Terai (wet and marshy), the Bhangar (older alluvium), and the Khadar (newer alluvium).

Bhangar is the largest part of the northern plain, formed of older alluvium, and lies above the floodplains. Khadar is the newer, younger deposit of the floodplains which is renewed almost every year and is very fertile.

The Peninsular Plateau is a tableland composed of old crystalline, igneous, and metamorphic rocks. It has two broad divisions: the Central Highlands, lying north of the Narmada river, and the Deccan Plateau, a triangular landmass south of the Narmada.

The Western and Eastern Ghats mark the western and eastern edges of the Deccan Plateau. The Western Ghats are continuous, higher (average 900-1600 metres), and cause orographic rain, while the Eastern Ghats are discontinuous and lower (average 600 metres).

The Indian Desert, also known as the Thar Desert, lies on the western margins of the Aravali Hills. It is a sandy plain with an arid climate, low vegetation, and receives very low rainfall (below 150 mm per year).

India has narrow coastal strips along the Arabian Sea (Western Coast) and the Bay of Bengal (Eastern Coast). The Western coast includes the Konkan, Kannad, and Malabar coasts, while the Eastern coast includes the Northern Circar and Coromandel Coast.

India has two main groups of islands. The Lakshadweep Islands in the Arabian Sea are composed of small coral islands. The Andaman and Nicobar Islands in the Bay of Bengal are an elevated portion of submarine mountains and are larger in size.