The Northern Plains
- Formed by the alluvial deposits brought by the rivers - the Indus, the Ganga and the Brahmaputra.
- extend approximately 3,200 km from the east to the west.
- average width of these plains varies between 150-300 km.
- maximum depth of alluvium deposits varies between 1,000-2,000m.
- From the north to the south, these can be divided into three major zones: the Bhabar, the Tarai and the alluvial plains.
- The alluvial plains can be further divided into the Khadar and the Bhangar.
- Bhabar is a narrow belt ranging between 8-10 km parallel to the Shiwalik foothills at the break-up of the slope.
- As a result of this, the streams and rivers coming from the mountains deposit heavy materials of rocks and boulders, and at times, disappear in this zone.
- South of the Bhabar is the Tarai belt, with an approximate width of 1020 km where most of the streams and rivers re-emerge without having any properly demarcated channel, thereby, creating marshy and swampy conditions known as the Tarai.
- This has a luxurious growth of natural vegetation and houses a varied wild life.
- The south of Tarai is a belt consisting of old and new alluvial deposits known as the Bhangar and Khadar respectively.
- These plains have characteristic features of mature stage of fluvial erosional and depositional landforms such as sand bars, meanders, ox- bow lakes and braided channels.
- The Brahmaputra plains are known for their riverine islands and sand bars.
- Most of these areas are subjected to periodic floods and shifting river courses forming braided streams.
- The mouths of these mighty rivers also form some of the largest deltas of the world, for example, the famous Sunderbans delta.
- These river valley plains have a fertile alluvial soil cover which supports a variety of crops like wheat, rice, sugarcane and jute, and hence, supports a large population.
The Peninsular Plateau
- Rising from the height of 150 m above the river plains up to an elevation of 600900m is the irregular triangle known as the Peninsular plateau.
- Delhi ridge in the northwest, (extension of Aravalis), the Rajmahal hills in the east, Gir range in the west and the Cardamom hills in the south constitute the outer extent of the Peninsular plateau.
- However, an extension of this is also seen in the northeast, in the form of Shillong and Karbi-Anglong plateau.
- The Peninsular India is made up of a series of patland plateaus such as the Hazaribagh plateau, the Palamu plateau, the Ranchi plateau, the Malwa plateau, the Coimbatore plateau and the Karnataka plateau, etc.
- This is one of the oldest and the most stable landmass of India.
- The general elevation of the plateau is from the west to the east, which is also proved by the pattern of the flow of rivers.
- Some ofthe important physiographic features of this region are tors, block mountains, rift valleys, spurs, bare rocky structures, series of hummocky hills and wall-like quartzite dykes offering natural sites for water storage.
- The western and northwestern part of the plateau has an emphatic presence of black soil.
- This Peninsular plateau has undergone recurrent phases of upliftment and submergence accompanied by crustal faulting and fractures. (The Bhima fault needs special mention, because of its recurrent seismic activities).
- These spatial variations have brought in elements ofdiversity in the reliefof the Peninsular plateau.
- The northwestern part of the plateau has a complex relief of ravines and gorges.
- The ravines of Chambal, Bhind and Morena are some of the well-known examples. On the basis of the prominent relief features, the Peninsular plateau can be divided into three broad groups:
- The Deccan Plateau Rajeshra
- The Central Highlands
- The Northeastern Plateau.
The Deccan Plateau
- This is bordered by the Western Ghats in the west, Eastern Ghats in the east and the Satpura, Maikal range and Mahadeo hills in the north. Western Ghats are locally known by different names such as Sahyadri in Maharashtra, Nilgiri hills in Karnataka and Tamil Nadu and Anaimalai hills and Cardamom hills in Kerala.
- Western Ghats are comparatively higher in elevation and more continuous than the Eastern Ghats.
- Their average elevation is about 1,500 m with the height increasing from north to south. ‘Anaimudi’ (2,695 m), the highest peak of Peninsular plateau is located on the Anaimalai hills of the Western Ghats followed by Dodabetta (2,637 m) on the Nilgiri hills.
- Most of the Peninsular rivers have their origin in the Western Ghats.
- Eastern Ghats comprising the discontinuous and low hills are highly eroded by the rivers such as the Mahanadi, the Godavari, the Krishna, the Kaveri, etc.
- Some of the important ranges include the Javadi hills, the Palconda range, the Nallamala hills, the Mahendragiri hills, etc.
- The Eastern and the W estern Ghats meet each other at the Nilgiri hills.
The Central Highlands
- They are bounded to the west by the Aravali range.
- The Satpura range is formed by a series of scarped plateaus on the south, generally at an elevation varying between 600-900 m above the mean sea level.
- This forms the northernmost boundary of the Deccan plateau. It is a classic example of the relict mountains which are highly denuded and form discontinuous ranges.
- The extension of the Peninsular plateau can be seen as far as Jaisalmer in the West, where it has been covered by the longitudinal sand ridges and crescent-shaped sand dunes called barchans.
- This region has undergone metamorphic processes in its geological history, which can be corroborated by the presence of metamorphic rocks such as marble, slate, gneiss, etc.
The Northeastern Plateau
- In fact it is an extension of the main Peninsular plateau.
- It is believed that due to the force exerted by the northeastward movement of the Indian plate at the time of the Himalayan origin, a huge fault was created between the Rajmahal hills and the Meghalaya plateau.
- Later, this depression got filled up by the deposition activity of the numerous rivers. Today, the Meghalaya and Karbi Anglong plateau stand detached from the main Peninsular Block.
- The Meghalaya plateau is further sub-divided into three: (i) The Garo Hills; (ii) The Khasi Hills; (iii) The Jaintia Hills, named after the tribal groups inhabiting this region.
- An extension of this is also seen in the Karbi Anglong hills of Assam. Similar to the Chotanagpur plateau, the Meghalaya plateau is also rich in mineral resources like coal, iron ore, sillimanite, limestone and uranium.
- This area receives maximum rainfall from the south west monsoon. As a result, the Meghalaya plateau has a highly eroded surface.
- Cherrapunji displays a bare rocky surface devoid of any permanent vegetation cover.
The Indian Desert
- To the northwest of the Aravali hills lies the Great Indian desert.
- It is a land of undulating topography dotted with longitudinal dunes and barchans.
- This region receives low rainfall below 150 mm per year; hence, it has arid climate with low vegetation cover.
- It is because of these characteristic features that this is also known as Marusthali.
- The Luni river flowing in the southern part of the desert is of some significance.
- Low precipitation and high evaporation makes it a water deficit region.
- There are some streams which disappear after flowing for some distance and present a typical case of inland drainage by joining a lake or playa.
- The lakes and the playas have brackish water which is the main source of obtaining salt.
The Coastal Plains
- On the basis of the location and active geomorphological processes, it can be broadly divided into two: (i) the western coastal plains; (ii) the eastern coastal plains.
The western coastal plains
- are an example of submerged coastal plain.
- It is believed that the city of Dwaraka which was once a part of the Indian mainland situated along the west coast is submerged under water.
- Because of this submergence it is a narrow belt and provides natural conditions for the development of ports and harbours. Kandla, Mazagaon, JLN port Navha Sheva, Marmagao, Mangalore, Cochin, etc. are some of the important natural ports located along the west coast.
- western coast may be divided into following divisions -1- the Kachchh and Kathiawar coast in Gujarat, 2- Konkan coast in Maharashtra, 3- Goan coast and Malabar coast in Karnataka and Kerala respectively.
- The rivers flowing through this coastal plain do not form any delta.
- The Malabar coast has got certain distinguishing features in the form of ‘Kayals’ (backwaters), which are used for fishing, inland navigation and also due to its special attraction for tourists. Every year the famous Nehru Trophy Vallamkali (boat race) is held in Punnamada Kayal in Kerala.
The eastern coastal plain
- is broader and is an example of an emergent coast.
- There are well- developed deltas here, formed by the rivers flowing eastward in to the Bay of Bengal.
- These include the deltas of the Mahanadi, the Godavari, the Krishna and the Kaveri.
- Because of its emergent nature, it has less number of ports and harbours. (The continental shelf extends up to 500 km into the sea, which makes it difficult for the development of good ports and harbours.
- There are two major island groups in India — one in the Bay of Bengal and the other in the Arabian Sea.
The Bay of Bengal island groups consist of about 572 islands/islets.
- These are situated roughly between 6°N-14°N and 92°E -94°E.
- The two principal groups of islets include the Ritchie’s archipelago and the Labrynth island. The entire group of island is divided into two broad categories — the Andaman in the north and the Nicobar in the south.
- They are separated by a water body which is called the Ten degree channelhese islands are an elevatedportion of submarine mountains.
- However, some smaller islands are volcanic in origin. Barren island, the only active volcano in India is also situated in the Nicobar islands.
- The coastal line has some coral deposits, and beautiful beaches. These islands receive convectional rainfall and have an equatorial type of vegetation.
The islands of the Arabian sea
- include Lakshadweep and Minicoy.
- These are scattered between 8°N-12°N and 71°E -74°E longitude.
- These islands are located at a distance of280 km-480 km off the Kerala coast is built of coral deposits.
- There are approximately 36 islands of which 11 are inhabited.
- Minicoy is the largest island with an area of 453 sq. km.
- The entire group of islands is broadly divided by the Eleventh degree channel, north of which is the Amini Island and to the south of the Canannore Island.
- The Islands of this archipelago have storm beaches consisting of unconsolidated pebbles, shingles, cobbles and boulders on the eastern seaboar.