Geography of India (Part - 1) UPSC Notes | EduRev

Physical Geography
 Size and Location.

• India with an area of 32,87,782 sq. km., is the seventh largest country after Russia, Canada, China, USA, Brazil and Australia in that order and the second most populous (next to China) country in the world.
• It extends between 8°4' and 37°6' north latitudes and 68°7' and 97°25' east longitudes, lying north of the equator and thus belongs to Northern Hemisphere.
• The Tropic of Cancer (23°30' N) divides the country into almost two equal halves. While the southern half coinciding with peninsular India lies in the tropical zone, the northern half, somewhat continental in nature, belongs to the subtropical zone. Situated to the east of the Prime Meridian, India also belongs to the Eastern Hemisphere.
• The north-south extension of India covers about 30°of latitude or measures about 3,214 km and the east-west extension covers almost 30° of longitude or measures about 2,933 km which is one-twelfth of the Earth’s circumference at the Equator. 
• India has a land frontier of 15,200 km and a coastline of about 6,100 km.
• India takes its standard time from the meridian of 82°30' E, which is 5 1/2 hours ahead of Greenwich Mean Time (0° longitude). 
• Pakistan time is 5 hours ahead of GMT and Bangladesh time is 6 hours ahead of GMT.  
• The Indian subcontinent is a peninsula, more or less triangular in shape, which justs southward from the mainland of Asia. 
• The lofty mountain ranges of the Himalayas in the north form the base of the triangle while the apex runs far out into the Indian Ocean in the south. 
• It deserves to be called a subcontinent—meaning a large, relatively self-contained land mass forming a subdivision of a continent—both because of its large area and its large population.
• India occupies the southern part of the Asian continent, which is not only the largest but also the most populous continent of the world. 
• Such a location has its own geopolitical and economic advantages. In ancient times its location helped in establishing cultural and other contacts with the Arab world in the west and the south-east Asia and the Far East in the east.

Significance of Location.

• The country is isolated in a remarkable way from the rest of Asia, making it a distinct geographical unit. 
• Barring the plateau of Baluchistan (which forms part of Pakistan), the two great ranges of Sulaiman and Kirthar cut it off from the west. 
• Along the north, the great mountain wall formed by the Hindukush, Karakoram and the Himalayas, which is difficult to cross, cuts it off from the east of the continent. 
• Similarly, the southward offshoots of the Eastern Himalayas separate it from Russia. 
• The mountain barriers thus secure the country from rest of Asia. In the west, the Indian Ocean in the south and the Bay of Bengal in the east. 
• These again perform the security function besides providing a very good infrastructural component for development of not only a transport system but also a defence system.

• The tropical monsoon climate of India, which ensures a fair supply of moisture and forms the basis of farming in India, is also a result of its location in the southern part of Asia.
• India’s strategic location at the head of Indian Ocean from where the entire Asia could be controlled had encouraged the British to make it the base of British empire in the east. 
• India is favourably situated on the world’s highway to trade and commerce both to east and west. 
• The oceanic routes serving East and South-east Asia and Australia in the east and the countries of West Asia and Africa in the west pass through both the routes—the Cape of Good Hope and Suez Canal. Since the opening of Suez Canal (1867) India’s distance from Europe has been reduced by 7000 Km.
• It thus bridges the space between the highly industrialised nation of the west and the semi-arid, and south-western Asia and the most fertile and populated regions in the south-east and far-east countries.
• The lack of islands in the Indian Ocean and the absence of any other country having such a large coastline this ocean as ours, with natural resources and population comparable to that of India, makes India even today, by far the most significant amongst the countries bordering the Indian Ocean.

Fold Mountains

• The bending of rock starts due to compressional forces acting tangentially or horizontally towards a common point or plane from opposite directions is known as folding.
• In a simple series of folds, anticlines (upfolds) may be distinguished from synclines (downfolds)
• The central line of either fold is known as axis, while the two sides are known as the limbs.
• If one side of the fold is steeper than the other, it is said to be asymmetrical.
• A drag fold is a minor fold, formed either subsidiary to a main fold, or along the side of a fault, where the vertical displacement has made flexures and puckers in the rocks on either side.
• The rest of a fold is usually structurally weak, and igneous material or masses of salt may be forced through the cracks and fissures; these intrusions are known as diapirs and the fold as diapiric or piercement folds.
• In some fold systems, the main anticlines and synclines appear to have numerous minor folds superimposed upon them. These are called anticlinorium and synclinorium.
• If the folding movements are very intense, the asymmetrical anticline is pushed right over, and it becomes overfold.
• If it is pushed still further, it becomes a recumbent fold.
• In extreme cases, fracture may occur in the crust, so that the upper part of the recumbent fold slides forward over the lower part along a thrust plane, forming an overthrust fold.
• The over-riding portion of the thrust fold is called Nappe.
• The Klippe is a surviving portion of a nappe almost-destroyed by denudation.

Fault Mountains
Faulting: Faulting owes its origin to tension i.e. when forces act horizontally in opposite directions away from a given plane or a point.

• In a normal fault, usually the result of tension, the inclination of the fault plane and the direction of downthrow are either both to the left or both to the right.
• In a reverse fault, resulting from compressional forces, the beds on one side of the fault plane are thrust over the other.
• A tear or lateral fault is one in which rocks are displaced horizontally along a line of fracture.
• The amount of vertical displacement, if any, on a fault is referred to as the throw of the fault.
• The amount of lateral displacement is known as heave.
• The angle of inclination of the fault plane from the vertical is the hade.
• The rock face on the upper side of the fault is the hanging wall, on the lower the foot-wall.
• An escarpment is caused by faulting.
• The land between the two parallel faults, either rises forming block mountains or horsts, or subsides into a depression termed as a rift valley or graben.

Dome Mountains

• Igneous intrusions, sometimes make room for themselves by lifting up the overlying layers of the country rocks. 
• Thus a dome-shaped structure is formed which are sometimes large enough to be described as dome mountains i.e. laccolith. Example—Henery Mountain in Utah (USA).

Rocks

• These rocks have been formed inside the earth, under great pressure and heat. They do not occur in layers and most of them are crystalline.
• Some rocks like granite, have cooled slowly and contain large crystals: others like basalt have cooled quickly and contain small crystals. 
• Some rocks contain a high percentage of silica and are called acid rocks. Granite is a good example.
• Rocks like basalt contain a high percentage of iron, or aluminium or Magnesium oxides and are called basic rocks.
• Igneous rocks do not contain fossils. Igneous rocks are parents of all other rocks and also known as Primary rocks. Basalt is fine-grained and granite is coarse grained.
• There are two main groups of Igneous:
  • Volcanic: Also called extrusive igneous rocks. Magma erupting and solidifying after escape of gases as lava on reaching the earth surface. Basalt is the typical example of extrusive type, other examples—Gabbro, Lava-obsedian etc. 
  • Plutonic: Also called intrusive igneous rocks. This is formed by solidification of magma at moderate depths beneath the earth’s surface. Most common examples: granite, dolerite etc.

Igneous Rock Bodies

• Batholiths: Batholiths are the largest intrusive igneous rock bodies. Batholiths are great granite masses forming the cores of world’s mountain systems.
• Stocks: The batholiths covering small areas are called stocks, having somewhat rounded form and some general characteristics.
• Laccoliths: These are huge masses of igneous rocks that have been formed between horizontal or slightly tilted layers of sedimentary rock near the earth’s surface. These are dome shaped and appear like a mushroom or a loaf of bread. It may be regarded as inscarried volcano.
• Lapolith: When batholiths are deposited into a concave form it is called lapolith.
• Phacolith:  When magma is deposited in a wave like form.
• Dykes: These are near vertical formations. They come into existence when liquid material passes through cracks in the country rocks gets hardened into a rock.
• Sills: The magma trying to reach the surface squares between two rocks layers and solidifies into a thin sheet in horizontal position parallel to the layers of already existing rocks.

Sedimentary Rocks

• Sedimentary rocks constitute 75% of the earth’s surface but only 5% of the earth’s crust. All sedimentary rocks are non-crystaline. They contain fossils.

Mechanically formed sedimentary rocks:

• Wind-deposited sedimentary rocks—Loess
• Glacier-deposited sedimentary rocks—Moraines, sands and gravels and boulder clay or sill.
• River-deposited—clays, alluviums etc.
• By compaction—sandstone (from sand).
• By cementation—Shale (from clay) Conglomerate and Breccia.

Organically formed sedimentary rocks:

• By animals—chalk, coral and limestone.
• By Plants—Coal, peat, lignite

Chemically formed sedimentary rocks:

• Rock-salt, borax, gypsum, nitrates, potash.

Metamorphic Rocks

• When the original character of rocks—their colour, hardness, texture and mineral composition is partly or wholly changed. 
• It gives rise to metamorphic rocks, under favourable conditions of heat and pressure.
• The formation of metamorphic rocks under the stress of pressure is known as dynamic metamorphism.
• In this case granite is converted in genesis; clay and shale are transformed into schist.
• The change of form or recrystallisation of minerals of sedimentary and igneous rocks under the influence of high temperature prevailing within the earth’s crust is known as thermal or contact metamorphism.
• Examples: Sandstone changes into quartzite; Clay and shale into slate; Coal turns into authracite and graphite; Limestone into marble slate may further change into phyllite (at 150°C to 200°C)
• Quartzite rock is one of the most resistant to weathering, forming mountains and ridges. It is used in glass-making.