• India is a vast stretch plain of lands, rugged terrain with valleys and mountains, deserts, plateaus & islands.
• There are different types of rocks such as Hard Rock (Marble) and soft rock (soapstone).
• Variation in colour of soil is because soil is formed from different types of rocks.
• India is a large landmass formed during different geological periods which has influenced it’s relief and modified and created it through weathering, erosion & deposition in its present form.
Theory of Plate Tectonics
• This theory suggests that crust (upper part) of earth has been formed out of seven major and some minor plates.
• Stresses within plates and Continental rocks build up during movement of plates, leading to folding, faulting & volcanic eruptions.
Movement of Plates
Three types of plate boundary
Divergent Convergent Transform
1. Convergent boundary: Plates move towards each other.
2. Divergent boundary: Plates move away from each other.
3. Transform boundary: Plates moving horizontally, coming together, they may either collide and crumble, or one may go under other.
• These types of movements influenced evolution of present landform feature of India.
• Gondwana land – South part of Pangea
• Angara land – North part of pangea
• India-Peninsula part (oldest landmass), Australia, South Africa and Antarctica are parts of Gondwana.
Formation of India
• The conventional current splited crust into a number of pieces, thus leading to drifting of Indo-Australian plate towards north. The northward drift resulted in collision of plate with Eurasian plate, and Due to this collision, formation of sedimentary rocks took place which were accumulated in geosyncline called Tethys sea.
• The Himalayan upliftment out of Tethys sea and subsidence of northern flank of Peninsular Plateau resulted in formation of a large basin which got filled with deposition of sediments by rivers flowing from mountains in north.
Physical Variation of Indian Landmass
• Geologically, Plateau is one of oldest landmasses on Earth’s surface, Supposed to be one of most stable blocks composing of igneous and metamorphic rocks with gently rising hills and wide valleys.
• The Himalayas and northern plains are most recent landforms and they forms an unstable zone, these represents a very youthful topography with high peak, deep valleys and fast flowing rivers.
• Northern Plains are formed of alluvial deposits
Major Physiographic Divisions
• The Himalayan mountains
• The Northern plains
• The Peninsular Plateau
• The Indian desert
• The Coastal plains
• The Islands
The Himalayan Mountains
• Young and Fold Mountains stretched over northern borders of India.
• Runs from West to east direction, from Indus river to Brahmaputra.
• These represents Loftiest and rugged mountain barriers of world.
• Their width decreases as we move from Kashmir ( West) 400 km to Arunachal Pradesh (East) 150 km with altitudinal variations which are greater in eastern half than western half. Himalaya consists of three parallel ranges: Greater or inner Himalayas or Himadri -northern most region.
• Average height of 6000 meters
• Most continuous range with loftiest peak.
• Composed of granite at its core part, perennially snow bound with number of glaciers. Himachal or lesser Himalaya- south of Himadari
• Rugged Mountain system mainly composed of highly compressed and altered rocks.
• Altitude varies between 3700 to 4500 meters with average width of 50 km.
• Consists of many ranges such as Pir Panjal is longest and most important range. The Dhaula Dhar and Mahabharat ranges.
• Famous valleys: Kashmir, Kangra & Kullu.
• Well known for hill stations. Shivalik or Outermost Range
• It extend with a width of 10-50 km with an altitude varying between 900 and 1100 m.
• Composed of unconsolidated sediments brought down by rivers from north.
• Covered with thick gravel and alluvium.
• The longitudinal valley lying between lesser Himalaya and Shiwaliks are called Duns.
• Some famous Duns are Dehra Dun, Kotli Dun & Patli Dun.
Division Demarcated by River Valleys
• Region lying between The Indus and The Sutlej is traditionally called Punjab Himalayas and are regionally called Kashmir and Himachal Himalaya.
• Regions lying between The Satluj and The Kali river are called Kumaon Himalayas.
• Region between Kali and Teesta river is called Nepal Himalayas.
• Region between Teesta and Dihang is called Assam Himalayas.
• The Brahmaputra marks eastern most boundary of Himalayas.
Purvanchal or Eastern Hills and Mountains
• Beyond Dihang gorge,The Himalayas bend sharply to South and spread along eastern boundary of India, called Purvanchal Hills.
• Runs in Northeast State composed of sandstone which are sedimentary rock.
• The Patkai hills, The Naga hills, Manipur Hills and Mizo hills.
The Northern Plain
• The Indus, Ganga & Brahmaputra and their tributaries forms northern plain.
• Formed of alluvial soil at foothills of Himalayas.
• Spread over an area of 7 lakh sq. km
• Densely populated area rich in soil cover with an adequate water supply and favorable climate.
• Agriculturally it is a very important part of India.
• Riverine Island: Rivers coming from Northern Mountains are involved in depositional work, while in low course, gentle slopes as velocity of river decreases, that results in formation of riverine island.
• Distributaries: In lower course, rivers split into number of channels due to deposition of silts, these channels are called distributaries.
The Peninsular Plateau
• Tableland Plateau, composed of old crystalline, Igneous & metamorphic rocks, formed due to breaking and drifting of Gondwana land.
• Have broad and shallow valleys and round hills.
Consist of two Broad Division
• Central highlands: lying to north of Narmada river covering major part of Malwa plateau while Vindhaya range lies in South and Aravallis in northwest.
• It further merges with Sandy and Rocky Desert.
• Central Highlands is wider in West but narrower in east, called Bundelkhand and Baghelkhand while Chotanagpur plateau marks further extension, drained by Damodar river.
• Deccan plateau: It is a triangular landmass which lie to South of Narmada river.
• The Satpura range makes it boundary with Mahadeo hills in north, kaimur hills and Maikal range forms its eastern boundaries.
• Higher in westward, while slopes gently eastwards.
• The Northeast Region displaces this plateau locally known as Meghalaya, Karbi- Anglong plateau and North Cachar hills separated by a fault from chotanagpur plateau.
• The Garo, khasi, & Jaintia hills ranging from West to East in this region.
The Western Ghats and Eastern Ghats
• Marks western and eastern edges of Deccan Plateau.
• The Western ghats are higher than eastern ghats, while western ghats are continuous and eastern Ghats, are discontinuous and irregular and dissected by rivers draining into Bay of Bengal.
• The Western Ghats cause orographic rain and its height increases from north to South with highest peak Anaimudi and Doddabetta while Mahendragiri is highest peak in eastern ghats.
• The Shevroy hills and Javedi hills are located to southeast of Eastern ghats.
• Black soil called Deccan trap is found here with highly eroded and broken hills in western and northwestern margins. The Aravalli Hills extend from Gujarat to Delhi.
The Indian Desert
• Undulating Sandy Plain, covered with sand dunes, lie towards western margin of Aravalli Hills.
• Receives very low rainfall below 150 millimeters per year.
• Arid climate with low vegetation cover, streams appear during rainy season.
• Luni is one of largest rivers in this region.
• Crescent shaped dunes.
• Covers large areas but longitudinal dunes become more prominent near Indo- Pakistan boundary.
The Coastal Plains
• Stretch of peninsular plateau of narrow coastal strips running along Arabian sea in West and Bay of Bengal in East.
• Western coast looks like a sandwich between western ghats and Arabian sea.
• It consists of three sections.
• Northern part of coast called Konkan (Mumbai – Goa).
• Central stretch is called Kannad plain.
• Southern stretch is called Malabar Coast.
• The plains of Bay of Bengal are wide and level and they are termed as Northern Circar in north and Coromandel Coast in southern part.
• Lake Chilka is largest salt water lake in lake in India and it forms an important feature along eastern coast while rivers Mahanadi, Godavari, Kaveri, & Krishna forms a delta.
• India has two group of islands.
• Lakshadweep Island group lying close to Malabar coast of Kerala in Arabian Sea, Composed of small islands with great variety of flora and fauna.
• The Andaman and Nicobar Islands extending from north to South in Bay of Bengal, elevated portion of submerged mountains with great variety of flora and fauna.
• These islands are close to equator and experience an Equatorial climate and have thick forest cover.
• Barren Island is island where India’s only active volcano is found lies in Andaman and Nicobar Island.