The North-eastern Plateau
- It is an extension of the main peninsular plateau.
- Due to the force exerted by the north-eastward 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.
- Meghalaya plateau is further sub-divided into three: Named after the tribal groups inhabiting this region.
- The Garo Hills
- The Khasi Hills
- The Jaintia Hills
- An extension of this is also seen in the Karbi Anglong hills of Assam.
- 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.
- The Meghalaya plateau has highly eroded surface.
- Cherrapunji displays a bare rocky surface devoid of any permanent vegetation cover.
Some quick facts
- The northern boundary of the Peninsular Block may be taken as an irregular line running from Kachchh along the western flank of the Aravali Range near Delhi and then roughly parallel to the Yamuna and the Ganga as far as the Rajmahal Hills and the Ganga delta.
- The north-eastern parts are separated by the Malda fault in West Bengal from the Chotanagpur plateau.
- The Peninsula is formed essentially by a great complex of very ancient gneisses and granites,
- Since the Cambrian period, the Peninsula has been standing like a rigid block
- As apart of the Indo-Australian Plate, it has been subjected to various vertical movements and block faulting.
- The rift valleys of the Narmada, the Tapi and the Mahanadi and the Satpura block mountains are some examples of it.
- The river valleys here are shallow with low gradients
- Aravali hills, one of the oldest ranges in the world
- the Vindhya and the Satpuras are the important ranges.
- The rivers of the Narmada and Tapi flow through these ranges.
- These are west-flowing rivers that drain into the Arabian Sea.
- The Western Ghats are almost continuous,
- The Eastern Ghats are broken and uneven
- The plateau is rich in minerals like coal and iron-ore.
- The western coastal plains are very narrow
- The eastern Coastal plains are much broader
- There are a number of east flowing rivers. The rivers Mahanadi, Godavari, Krishna and Kaveri drain into the Bay of Bengal.
- These rivers have formed fertile deltas at their mouth.
The Peninsula mostly consists of relict and residual mountains like
- The Aravali hills
- The Nallamala hills
- The Javadi hills
- The Veliconda hills
- Palkonda range
- The Mahendragiri hills
3) INDO GANGETIC PLAINS
- The third geological division of India comprises the plains formed by the river Indus, the Ganga, and the Brahmaputra.
- It was a geo-synclinal depression which attained its maximum development
- During the third phase of the Himalayan mountain formation approximately about 64 million years ago.
- Since then, it has been gradually filled by the sediments brought by the Himalayan and Peninsular rivers.
- The average depth of alluvial deposits in these plains ranges from 1,000-2,000 m.
The Northern Plain
- Formed by the interplay of the three major river systems, namely– the Indus, the Ganga and the Brahmaputra
- Formed of alluvial soil
- It spreads over an area of 7 lakh sq. km.
- The plain being about 2400 Km long and 240 to 320 Km broad, is a densely populated physiographic division
- The velocity of the river decreases which results in the formation of riverine islands
- Majuli, in the Brahmaputra River, is the largest inhabited riverine island in the world.
- The rivers in their lower course split into numerous channels due to the deposition of silt
- These channels are known as distributaries
- The Northern Plain is broadly divided into three sections.
- The Western part of the Northern Plain is referred to as the Punjab Plains. Formed by the Indus and its tributaries, the larger part of this plain lies in Pakistan.
- The Indus and its tributaries–the Jhelum, the Chenab, the Ravi, the Beas and the Satluj originate in the Himalaya. This section of the plain is dominated by the doabs.
- ‘Doab’ is made up of two words- ‘do’ meaning two and ‘ab’ meaning water
- ‘Punjab’ is also made up of two words- ‘Punj’ meaning five and ‘ab’ meaning water.
- The Ganga plain extends between Ghaggar and Teesta rivers.
- It is spread over the states of North India, Haryana, Delhi, U.P., Bihar, partly Jharkhand and West Bengal to its East, particularly in Assam lies the Brahmaputra plain
From the north to the south these plains can be divided into three major zones –
- The rivers, after descending from the mountains deposit pebbles in a narrow belt of about 8 to 16 km in width lying parallel to the slopes of the Shiwaliks.
- As a result of this, the streams and rivers coming from the mountains deposit heavy materials of rocks and boulders.
- All the streams disappear in this bhabar belt.
- South of this belt, the streams and rivers re-emerge and create a wet, swampy and marshy region
- This was a thickly forested region full of wildlife
- The forests have been cleared to create agricultural land and to settle migrants from Pakistan after partition.
- The alluvial plains can be further divided into Khadar, Kankar and the Bhangar
- The largest part of the northern plain is formed of older alluvium. They lie above the floodplains of the rivers and present a terrace like a feature.
- The soil in this region contains calcareous deposits
- The newer, younger deposits of the floodplains
- They are renewed almost every year and so are fertile, thus, ideal for intensive agriculture.
4) The Indian Desert
- The Indian desert lies towards the western margins of the Aravali Hills.
- It is a land of undulating topography dotted with longitudinal dunes and barchans.
- Receives very low rainfall below 150 mm per year.
- Arid climate with low vegetating cover.
- This is also known as Marusthali.
- Due to extremely arid conditions, its surface features have been carved by physical weathering and wind actions.
- Some of the well pronounced desert lands features present here are mushroom rocks, shifting dunes and oasis (mostly in its southern part).
- Most of the rivers in this region are ephemeral.
- 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.
- Luni is the only large river in this region
- On the basis of the orientation, the desert can be divided into two parts
- The northern part is sloping towards Sindh and the south towards the Rann of Kachchh.
Barchans (crescent-shaped dunes)
Cover larger areas but longitudinal dunes become more prominent near the Indo-Pakistan boundary.