RBSE Class 11 Indian Geography Notes Chapter 4 India: Structure, Relief and Physiographic Regions

Go through these RBSE Class 11 Indian Geography Notes Chapter 4 India: Structure, Relief and Physiographic Regions contain important concepts so that students can score better marks in the exam.

Rajasthan Board RBSE Class 11 Indian Geography Notes Chapter 4 India: Structure, Relief and Physiographic Regions

Structure

  • The geological structure of India shows different rock forms because it was formed in different eras as well as epochs.
  • The relief and topography of a country depends on its geological structure.
  • Minerals, soil, vegetation and underground water resources of a country also depend on the geological structure.
  • The geological history of India can be divided into Archean era, Purana era, Dravid era and Aryan era.

Archean Era

  • The rocks of this era are divided into two parts: Archean system and Dharwar system.
  • Bengal gneiss, Bundelkhand gneiss and Nilgiri gneiss are included in Archean system, while Mysore-Dharwar, Bellari, Chota Nagpur plateau, Aravalli, Punjab and sub Himalayan rocks are included in the Dharwar system.

Purana Era

  • The rocks of this era are divided into the rocks of Cudappah system and the rocks of Vindhyan system.
  • The rocks of Cudappah system are found between Krishna and Pennar, Valley of Cudappah, Nallamalai, Venikonda, Valley of Godavari, Delhi and several places of Kashmir, while the rocks of Vindhyan system are found in Panna, Anantpur, Golkunda, Sasaram and Chittorgarh.

RBSE Class 11 Indian Geography Notes Chapter 4 India: Structure, Relief and Physiographic Regions

Dravid Era

  • The rocks of Gondwana system are found in this era which are mainly seen in Damodar Valley, Mahanadi Valley, Godavari Valley, Hills of Rajmahal and the regions of Kutch, Kathiawar and Spiti.

Aryan Era

  • The rocks of this era are of the Carboniferous period, in which coal, mineral oil, natural gas etc. are found at large scale.

Relief

  • Various high and low landforms found on the earth are called relief, which control the climate, natural vegetation and the lifestyle of living beings.
  • Different patterns of relief are found in India. 33.4 per cent of total area in India is less than 2 meters, 28.3 per cent is 2.5 meters, 18.6 per cent is 5-10 meters, 8.7 per cent is 10 – 20 meters and remaining 11 per cent is more than 20 meters in height.

Physiographic Regions

  • India has been divided into six physiographic regions-Northern mountainous region, Great Plains region, Thar Desert, Southern Plateau, Coastal Plains and Islands.

Northern Mountainous Region

  • The Northern mountainous region stretches from the north-west to the south-east direction. It looks like an arch and is spread in an area of 5 lakh square kilometres. Its length is 2400 km and breadth is 250 – 400 km.
  • This region is always covered with ice so it is also known as the home of ice glaciers. The peaks like Kanchenjunga, Nanga Parbat, Badrinath and Nanda Devi are found in this region.

RBSE Class 11 Indian Geography Notes Chapter 4 India: Structure, Relief and Physiographic Regions

Origin of Himalayas and Classification

  • The Himalaya is a newly-folded mountain and its origin is the result of collision of India with Asia along the convergent plate boundary.
  • It was formed by the development of folds in the layers of the sedimentary rocks. There was a shallow sea named Tethys, where the present Himalayan range is situated.
  • According to the scholars named Hogue, Chhal, Daana and Steers, ’’Geosynclines are relatively long, narrow and shallow water areas, which undergo continuous depression along with sedimentation.”
  • About 300 million years ago, earth did not have seven continents, but instead, one massive super continent called ‘Pangea’, which was surrounded by a single ocean called Panthalassa.
  • Its Northern part was known as Laurasia and the Southern part was known as Gondwana land.
  • The part of Eurasia was famous as Angaraland. The Tethys ocean ocean was situated between Gondwana land and Angaraland.
  • According to Kober, Angaraland and Gondwana land are the forelands which exerted pressure from the both sides, and the debris of Tethys land part folded in the form of Himalayas. Its central part is present in the form of Tibetan Plateau as a median mass.
  • Himalaya is divided into three parts: Greater Himalayas, Mid-Himalayas and the Sub-Himalayas.
  • The Greater Himalayas are called Himadri, whose all the peaks are covered with snow, during the entire year. The main peaks of it are Kanchenjunga (8598 m), Nanga Parbat (8126 m), Annapurna (8078 m), Nanda Devi (7818 m) etc.
  • The Smaller Himalayas are also known as mid or Himachal-Himalayas. The mountain ranges such as Dhauladhar, Pir Panjal, Nag Tibba, Mahabharata and Mussorie are found in this part of Himalayas.
  • The grasslands found in this part of the Himalayas are called ‘Marg’ in Kashmir, and Bugyal or Payar in Uttarakhand.
  • The Sub-Himalayas are also famous as Shivalik or outer Himalayas. It is the latest form of Himalayas which is spread from Potwar Basin to the Kosi River.
  • Plain areas found in the Shivalik ranges are called as “Dwar” in the east and “Doon” in the west.
  • On regional basis, the Himalaya is divided from west to east as Himachal Himalaya, Kumaon Himalaya, Nepal Himalaya and Assam Himalaya.
  • The Himalaya is also called the Parvatraj (king of the mountains) or Devbhumi (land of the gods). Its physical structure, location and expansion is very important for the country in various contexts.

Great Plains

  • The Great Plains region in Northern India was formed by the deposits brought by the three major rivers and their tributaries.
  • Alluvial soils was deposited at the foothills of the Himalayas for millions of years and they are now present in the form of the fertile Northern Plains.
  • These plains are spread 2400 km in length and their width is 150 km to 480 km.
  • This plain region is divided into Bhabar, Terai, Bangar and Khadar on geographical basis.
  • On regional basis, it is divided into the Plains of Punjab and Haryana, Plains of Ganges, Plains of Brahmaputra and Delta of Ganges and Brahmaputra.
  • As it is an even plain region, it is very important with the view-point of agriculture, population, transportation and communication and urbanization.

Thar Desert

  • This Indian desert part has been formed by the deposits of Tethys geosyclines and it is located in the western part of India.
  • This part is arid or semi-arid and hence is a desert.
  • This desert part has a height of 150 – 380 meters and its length and width is 640 km and 160 km respectively, in which “Talli” and “Rann” are found.
  • It has a lot of minerals, mineral oil and many types of rocks, so it is very important for India.

Deccan Plateau

  • It is a large plateau in southern India and has an area of 16 lakh square kilometres.
  • It is surrounded by water on its three sides in the south.
  • Its length is 1800 km maximum, width is about 1400 km maximum, and its average height is 600 m.

Origin of Deccan Plateau and its Classification

  • This plateau part was formed due to the Gondwana land getting disintegrated and shifting towards the north-east.
  • This plateau part is divided into Western Ghats, Eastern Ghats and the Southern Plateau.
  • Bhor-ghat, Tbal ghat and Palghat are the passes situated in the Western Ghats, while the Eastern Ghat region is mutilated. The Deccan plateau is a very ancient landmass.
  • It is a fixed land-mass which is very rich with the view-point of minerals. North-western part made of black soil is very important for agriculture and the region of laterite soil is very useful in context to plantation agriculture.

Coastal Plains

  • There are coastal plains at both the sides of Deccan Plateau, which are divided into Western and Eastern Coastal Plains.
  • The Western has again been divided into Saurashtra, Konkan and Malabar coasts and Western Coast into Circar and Coromandel coasts.
  • The coastal plains are important for agricultural purpose, tourism, trade and business.

RBSE Class 11 Indian Geography Notes Chapter 4 India: Structure, Relief and Physiographic Regions

Islands

  • There are two major islands groups in India. Andaman and Nicobar Archipelago in the Bay of Bengal and Lakshadweep Islands in the Arabian Sea.
  • Coastal islands have been divided into alluvial islands and rocky islands, and distant islands have been divided into mountainous islands and coral islands.
  • Islands are of special importance with the point of view of tourism and security.

India: Structure, Relief and Physiographic Regions Notes Important Terms

→ Archean Era: It is a geologic period 4,000 to 2500 million years ago, that followed the Hadean Eon and preceded the Proterozoic Eon.

→ Quaternary Era: It is the current and most recent of the three periods of the Cenozoic era in the geological time scale. It follows the Neogene period and spans 60 millions of years.

→ Deposits: An accumulation of sediments, minerals, ores, coal, etc.

→ Plateau: A plateau is a flat, elevated landform, that rises sharply above the surrounding area on at least one side.

→ Purana Era: The middle period of Archean Era and Quaternary Era is called the Purana era. It includes the rocks of Cudappah and Vindhyan system.

→ Peninsula: It is a piece of land that is almost entirely surrounded by water but is connected to the mainland on one side.

→ Bay: A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay.

→ Geosyncline: It is a long trough in the surface of the earth where sediments and
deposits get collected.

→ Pangea: A former “supercontinent” on the earth. It was a combination of all the present continents.

→ Laurasia: The northern part of Pangea, in which present Europe, Asia and Latin America were included.

→ Gondwana-land: The southern part of Pangea, in which South America, Africa, Sub-continental India, Australia and Antarctica were included.

→ Angaraland: The north part of Pangea in which Eurasia was situated, it was called the Angaraland.

→ Foreland: Kober named the two banks of geosyncline which exerted pressure to form Himalayas as foreland.

→ Median mass: A high intermontane area within a zone of folded mountains.

→ Ghat or Wharf: Two mountain ranges forming the eastern arid western edges respectively of the Deccan Plateau of Peninsular India.

→ Coniferous Forests: A type of forest characterized by trees with cone-shaped, needle leaves; they are often a source of soft wood, timber and pulp.

→ River Capture: It is the process where by a strong river diverts a parallel weak river and forms a larger stream.

→ Gorge: A gorge is a narrow valley with steep rocky walls located between hills or mountains.

→ Bad Lands: Bad lands are a type of dry terrain where softer sedimentary rocks and clay-rich soils have been extensively eroded by wind and water.

→ Bhabar: It is a narrow belt covered with pebbles lying along the foot of the Shivaliks from the foot of the Indus river to the Tista river.

→ Terai: The Bhabhar region formed of pebbles and rocks in the northern India, especially on the northern border of the states of Uttar Pradesh and Bihar in the north, and a narrow plain belt situated between the major plains in the south, whose surface is extremely moist and swampy.

→ Bangar: Bangar is the largest part of the northern plain and is composed of the oldest alluvial soil and it lies above the flood plains.

→ Khadar : Khadar areas are prone to flooding and sometimes include portions of former river beds that became available for agriculture where a river changed its course.

→ Bhur: Small dunes found in the arid parts of Bangar regions, i.e., high plains, are known as Bhur in local dialect.

→ Char: A high region which does not come under the area of influence of tidal water.

→ Lagoon: It is a shallow body of water separated from a larger body of water by barrier islands or reefs.

→ Plantation: It is a type of agriculture that involves growing of one crop on a large farm for profit.

→ Alluvial Islands: The island formed due to the deposition of alluvial soil are called alluvial islands.

→ Rocky Islands: The islands formed by rocks and pebbles.

→ Distant Island: The islands situated away from the sea shore.

→ Hilly Island: The island formed by submergence of the hills or mountains.

→ Coral Islands: It is a type of island formed from coral reefs and associated organic materials.

→ Metamorphic Rocks: Rock that was once a form of rock, but has changed to another, under the influence of heat, pressure or some other agent without passing through a liquid phase.

→ Deposit-mountains: Lower mountains formed from the activities of withering and erosion are called deposit mountains.

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