8. World Geography Part 4 | RAS RPSC Prelims Preparation - Notes, Study Material & Tests - RPSC RAS (Rajasthan) PDF Download

The Northern Plains

• Formed by the alluvial deposits of rivers – Indus, Ganga and Brahmaputra.
• Length: 3200 KM; Width: 150-300 KM

Three main zones:

1. Bhabar
2. Tarai
3. Alluvial Plains (Khadar and Bangar)

Bhabar

• Narrow belt. 8-10 KM wide.
• Paralllel to Shivalik at the break-up of the slope. Hence, streams and rivers deposit heavy rocks (and at times disappear) in this zone.

Tarai

• South of Bhabar. 10-20 KM wide.
• Rivers re-emerge and create marshy and swampy conditions known as Tarai.

Alluvial Belt

• South of Tarai.
• Features of mature stage of fluvial erosional and depositional landforms such as sand bars, meanders, ox-bow lakes and braided channels. Riverine islands in Brahmaputra.
• Brahmaputra takes a turn an almost 90 degree turn at Dhubri (Assam) before entering Bangladesh.

Peninsular Plateau

• Bounded by the Delhi ridge, Rajmahal Hills, Gir range and Cardamom hills.
• Made up of a series of patland plateaus: Hazaribagh, Palamu, Ranchi, Malwa, Coimbatore, Karnataka etc.
• One of the oldest and most stable landmass of India.
• Physiographic Features: Tors, block mountains, rift valleys, spurs, bare rocky structures, hummocky hills and quartzite dykes offering natural sites for water storage.
• Black soil in western and northwestern parts.
• Bhima fault in this region has frequent seismic activity (Lathur earthquake)
• NW part also has ravines and gorges: Chambal, Bhind and Morena.

Three broad regions:

1. Deccan Plateau
2. Central Highlands
3. Northwestern Plateau

Deccan Plateau

• Bordered by Eastern Ghats, Satpura, Maikal range and Mahadeo hills
• Important ranges: WG: Sahyadri, Nilgiri, Anaimalai and Caradamom hills; EG: Javadi hills, Palconda range, Nallamala Hills, Mahendragiri hills
• EG and WG meet at Nilgiri hills.
• Highest peak: Anaimudi (2695 m) on Anaimalai hills; Dodabetta (2637 m) on Nilgiri hills.
• Rivers: Mahanadi, Godavari, Krishna, Kaveri etc.

Central Highlands

• Bounded by the Aravali and Satpura range.
• Relic mountains, highly denuded and form discontinuous ranges.
• Near Jaisalmer it is covered by the longitudinal sand ridges and crescent-shaped sand dunes called barchans.
• Elevation: 700-1000 m
• Banas, a tributary of Chambal, originates in the Aravalli. Other tributaries of Yamuna originate from the Vindhyan and Kaimur ranges.
• Minerals in Chotanagpur plateau.

Northeastern Plateau

• Extension of the main Peninsular plateau.
• Meghalaya and Karbi Anglong plateau.
• Megahalaya plateau: Garo hills, Khasi hills and Jaintia hills (named after the tribals inhabiting the region)
• Rich in minerals like coal, iron, sillimanite, limestone and uranium.
• Receives maximum rainfall from SW monsoon.  Hence, Meghalaya plateau has a highly eroded surface. Cherrapuni and Myswarnam.

Indian Desert

• Aka MarusthalI
• Northwest of the Aravali hills
• Dotted with longitudinal dunes and barchans.
• Low rainfall: >150 mm per year                           Low vegetation cover
• Evidence that this area was under the sea during the Mesozoic era.
• Features: mushroom rocks, shifting dunes and oasis.
• Rivers are ephemeral: Luni.                      Brackish lakes. Inland drainage.

Coastal Plains

Two divisions:

1. Western coastal plains
2. Eastern Coastal Plains

Western Coastal Plains

• Submerged coastal plain. Hence, a narrow belt. Narrow in middle and broader towards north and south.
• Ports: Provides natural conditions for the development of ports and harbours due to submergence. Kandla, Mazagaon (Mumbai), JLN port Navha Sheva, Maramagao, Mangalore, Cochin etc.
• Mumbai has the world’s largest natural harbour.
• May be divided into: Kachchh and Kathiawar coast in Gujarat, Konkan coast, Goan coast and Malabar coast.
• Rivers don’t form delta.
• Kayals (Backwaters): Found in the Malabar coast. Used for fishing and inland navigation. Every year Nehru Trophy Vallamkali (boat race) is held in Punnamada Kayal in Kerala.

Eastern Coastal Plains

• Broader
• Emergent coast. Hence, less number of ports and harbours. Chennai, Vizag, Paradwip, Haldia.
• Delta formation

The Islands

Two major Divisions: 

1. Andaman and Nicobar
2. Lakshwadeep & Minicoy

Andaman and Nicobar

• Two major island groups: Ritchie’s archipelago and the Labrynth island.
• The group is divided into: Andaman in the North and Nicobar in the South.
• Andaman and Nicobar separated by the Ten Degree channel.
• Barren Island
• Peaks: Saddle Peak (N.Andaman – 738 m), Mt. Diavolo (Middle Andaman – 515 m), Mt. Koyob (S Andaman – 460 m) and Mt. Thuiller (Great Nicobar – 642 m)
• Coral deposits found
• Convectional rainfalls and equatorial type of vegetation.

Lakshadweep and Minicoy

• Entire group built of coral deposits.
• Total of 36 islands of which 11 are inhabited.
• Smallest UT
• Minicoy is the largest island
• Separated by the 9 Degree Channel, north of which is the Amini Island and to the south Canannore island.
• These islands have storm beaches consisting of unconsolidated pebbles, shingles, cobbles and boulders.

Drainage System

• Drainage: Flow of water through well-defined channels. Network of such channels is called a drainage system .
• Drainage basin: An area drained by a river and its tributaries.
• Watershed: Boundary line separating one drainage basin from other.
• River basins are larger watersheds.
• Drainage pattern of an area depends on the geological time period, nature and structure of rocks, topography, rocks, slope, amount of water and periodicity of flow.

Important drainage patterns:

1. Dendritic: Resembling the branches of a tree. Eg. Northern Plain rivers
2. Radial: Originate from a hill and flow in all directions. Eg. Rivers in Amarkantak
3. Trellis: Primary tributaries parallel to each other and secondary tributaries join them at right angles.
4. Centripetal: Rivers discharge waters from all directions in a lake or depression

A river drains the water collected from a specific area, which is called its catchment area.

Nearly 77 pc of drainage is towards the Bay of Bengal while about 23 pc is towards the Arabian Sea.

The Himalayan Drainage System

Mainly includes the Ganga, Indus and Brahmaputra river basins.

Over the plains, rivers of this system change the course often. River Kosi is also known as the ‘sorrow of Bihar’ due to flooding by its frequent change of course by deposition of sediments.

Evolution

Geologists believe that a mighty river called Shivalik or Indo-Brahma traversed the entire length of the Himalayas some 5-24 million years ago. Over time this got dismembered into the present three major river systems.

The Indus System

Indus river originates from a glacier near Bokhar Chu in Tibet in the Kailash Mountain range. Known as Singi Khamban (Lion’s mouth) in Tibet. It forms a spectacular gorge near Gilgit in J&K. Enters Pakistan near Chillar in the Dardistan region. Flows only through the Leh distt of J&K.

Smaller tributaries: Shyok, Gilgit, Zaskar, Nubra, Hunza, Shigar, Gasting, Dras. On right bank: Kabul river, Khurram, Tochi, Gomal, Viboa and hte Sangar.

Major tributaries: Satluj, Beas, Ravi, Chenab, Jhelum

The Ganga System

It is the largest river system in India.

Ganga rises in the Gangotri glacier near Gaumukh in the Uttarkashi district. Here it is known as the Bhagirathi. At Devprayag, Bhagirathi meets Alaknanda and is known as Ganga hereafter.

Panchprayag

• Ganga enters the plains at Haridwar.
• Left Bank tributaries (LBT): Ramganga, Gomati, Ghaghara, Gandak, Kosi and Mahananda.
• Right Bank tributaries (RBT): Son
• Discharges into Bay of Bengal near Sagar island.

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