Structure And Physiography (India)
The Peninsular Block
The Peninsular Block is the oldest and most stable landmass of India. It is a part of the ancient supercontinent of Gondwanaland. It is composed of igneous and metamorphic rocks, including ancient gneisses and granites. It is largely a plateau, with a gently sloping terrain.
Key Characteristics:
- Age: It is one of the oldest landmasses on Earth.
- Composition: Primarily made up of crystalline, igneous, and metamorphic rocks.
- Topography: Generally a plateau with a triangular shape, broad at the north and tapering towards the south. It is relatively stable, with minimal seismic activity compared to the Himalayas.
- Drainage: Most peninsular rivers (like Godavari, Krishna, Kaveri) originate in the Western Ghats and flow eastwards into the Bay of Bengal, forming deltas. Some rivers, like Narmada and Tapi, flow westwards into the Arabian Sea through rift valleys.
- Features: Includes plateaus (like Deccan, Chota Nagpur), hills (like Aravalli, Vindhya, Satpura, Eastern Ghats, Western Ghats), and rift valleys.
Formation: The block was formed due to the breaking and drifting of the Gondwanaland landmass. This process led to the formation of the Indian peninsula, which then drifted northwards to collide with the Eurasian plate.
The Himalayas And Other Peninsular Mountains
India's physiography is dominated by two major geological units of different origins: the Himalayan mountains in the north and the Peninsular plateau in the south.
The Himalayas:
- Formation: Formed by the collision of the Indian plate with the Eurasian plate about 50 million years ago. This ongoing process is responsible for the upliftment of the Himalayas and the continued seismic activity in the region.
- Structure: A young, fold mountain system with a rugged topography and high peaks. They form an arc across the northern boundary of India.
- Extent: Stretch from Jammu and Kashmir in the northwest to Arunachal Pradesh in the northeast.
- Features: Includes the Greater Himalayas (Himadri), Lesser Himalayas (Himachal), and the Outer Himalayas (Shiwalik). They are dissected by valleys and river gorges.
- Significance: Act as a climatic barrier, source of rivers, and possess rich forest and wildlife resources.
Peninsular Mountains:
- Nature: These are older, eroded, and block mountains. They are part of the stable Peninsular Block.
- Examples:
- Aravalli Range: One of the oldest fold mountains in the world, located in Rajasthan and Gujarat.
- Vindhya Range: Forms the northern boundary of the Peninsular Plateau.
- Satpura Range: South of the Vindhyas, parallel to it.
- Western Ghats: Run parallel to the Arabian Sea coast, forming a western boundary of the plateau. They are a series of ranges, including the Sahyadri, Nilgiris, Anaimalai, and Cardamom hills.
- Eastern Ghats: Run parallel to the Bay of Bengal coast, discontinuous and eroded.
- Significance: They influence regional climates (e.g., Western Ghats receive orographic rainfall on their western side) and are rich in mineral resources.
Indo-Ganga-Brahmaputra Plain
This is one of the world's largest and most fertile alluvial plains, formed by the deposition of sediments by the Indus, Ganga, and Brahmaputra rivers and their tributaries. It stretches across northern India, Pakistan, and Bangladesh.
Formation:
- Formed by the deposition of alluvium brought down by the Indus, Ganga, and Brahmaputra rivers and their tributaries.
- It was formed as a successor to a large depression known as the 'Indo-Ganga Trough' or 'Depression' which was formed due to the sag in the western part of the Peninsular Plateau and the northern flank of the Peninsular Block.
- This trough was gradually filled with sediment deposited by the rivers flowing from the northern mountains and the Peninsular Block.
Characteristics:
- Extent: Stretches from the western part of Rajasthan, through Punjab, Haryana, Delhi, Uttar Pradesh, Bihar, Jharkhand, West Bengal, and Bangladesh.
- Fertility: Extremely fertile due to the rich alluvial soil, making it the "granary of India" and supporting intensive agriculture.
- Topography: Largely flat and featureless, with gentle slopes.
- Drainage Features: Characterized by riverine features such as meanders, ox-bow lakes, floodplains, and deltas.
- Density of Population: It is one of the most densely populated regions in the world due to its fertile land and availability of water.
Sub-divisions: The plain can be broadly divided into:
- Babar: A narrow belt at the foothills of the Shiwaliks.
- Bhangar: Older alluvial deposits, forming a terrace above the floodplains.
- Khadar: Newer alluvial deposits, found in the floodplains of rivers.
- Terai: A marshy, re-emergent belt south of the Babar, with dense forests and wildlife.
The Northern And North-eastern Mountains
This region comprises the lofty Himalayan mountain range and its extensions into the northeastern parts of India. It forms the northern and northeastern boundary of India and is characterized by rugged terrain, high peaks, deep valleys, and dense forests.
Kashmir Or Northwestern Himalayas
Location: Located in the northernmost part of India, encompassing Jammu and Kashmir, Ladakh, and parts of Himachal Pradesh.
Features:
- Great Himalayas: High peaks like K2 (Godwin-Austen), Nanga Parbat.
- Valleys: Famous for fertile valleys like Kashmir Valley and Ladakh Plateau.
- Glaciers: Home to major glaciers like the Baltoro and Siachen.
- Passes: Important passes like Khardung La, Pir Panjal Pass, Burzil Pass.
- Lakes: Dal Lake, Wular Lake.
- Vegetation: Coniferous forests and alpine meadows.
- Wildlife: Kashmir stag (Hangul), snow leopard, yak.
The Himachal And Uttarakhand Himalayas
Location: Lies south of the Kashmir Himalayas, covering Himachal Pradesh and Uttarakhand.
Features:
- Parallel Ranges: Consists of the Greater Himalayas (Himadri), the Lesser Himalayas (Himachal), and the Outer Himalayas (Shiwalik).
- Himachal Range: Includes important ranges like Pir Panjal, Dhaula Dhar, and Nag Tibba.
- Valleys: Kullu, Kangra, Chamba valleys.
- Hill Stations: Shimla, Mussoorie, Nainital.
- Rivers: Source of important rivers like Jhelum, Ravi, Beas, Sutlej, Yamuna, and Ganga.
- Vegetation: Coniferous forests, oak, rhododendron; alpine meadows at higher altitudes.
The Darjiling And Sikkim Himalayas
Location: Located between the Nepal Himalayas in the west and Bhutan and Arunachal Himalayas in the east.
Features:
- High Peaks: Kangchenjunga (world's third highest peak) is located here.
- Valleys: Steep, narrow valleys.
- Rivers: Teesta River flows through this region.
- Vegetation: Rich temperate forests, rhododendrons, orchids.
- Climate: Temperate and humid.
The Arunachal Himalayas
Location: Situated east of Bhutan, extending into Arunachal Pradesh.
Features:
- Mountain Ranges: Densely forested mountain ranges, often unnamed.
- Rivers: Brahmaputra enters India through a gorge in this region.
- Passes: Important passes like Bum La, Sela Pass.
- Vegetation: Dense forests, ranging from tropical to alpine depending on altitude.
- Wildlife: Diverse wildlife, including Takin, musk deer.
The Eastern Hills And Mountains
Location: These are the extensions of the Himalayas forming the northeastern boundary of India, running along the eastern border.
Features:
- Patkai Bum, Naga Hills, Manipur Hills, Mizo Hills (Lushai Hills): These hills are generally covered with dense forests, interspersed with grasslands.
- Formation: They are more of an extension of the Himalayas in a southward direction.
- Drainage: Rivers like Barak flow through this region.
- Vegetation: Dense forests, fertile valleys suitable for cultivation (jhum cultivation).
- Wildlife: Rich biodiversity, including various species of monkeys, deer, and birds.
The Northern Plain
The Northern Plain is one of the most important physiographic divisions of India, formed by the interplay of three major river systems: the Indus, the Ganga, and the Brahmaputra, along with their tributaries. It is the most productive and densely populated region of India.
Formation: Deposited by the alluvium brought by the rivers, it was formed in the large depression between the Peninsular Plateau and the Himalayas.
Extent: Covers an area of about 7 lakh sq km. It stretches from Rajasthan in the west to Arunachal Pradesh in the east.
Characteristics:
- Fertile Alluvial Soil: Rich in fertile alluvial soil, making it ideal for agriculture and supporting a large population.
- Flat Topography: Largely flat with a gentle slope towards the east, facilitating easy irrigation.
- River Systems: Divided into three sections based on the rivers:
- Indus Plain: Formed by the Indus and its tributaries, primarily in the western part of the Northern Plain (now largely in Pakistan).
- Ganga Plain: Extends from the Ghaggar river to the Teesta river. It covers parts of Haryana, Delhi, Uttar Pradesh, Bihar, Jharkhand, and West Bengal.
- Brahmaputra Plain: Lies in the eastern part of the Northern Plain, mainly in Assam.
- Sub-divisions based on Relief Features:
- Babar: A narrow belt (8-10 km wide) at the foothills of the Shiwaliks, where rivers deposit pebbles and coarse sand. Most streams disappear in this belt.
- Terai: A marshy and wet belt south of the Babar, where streams reappear. It is characterized by dense forests and diverse wildlife.
- Bhangar: The older alluvial plains, forming terraces above the floodplains. Contains calcareous deposits known as Kankar.
- Khadar: The newer alluvial plains, found in the floodplains of rivers, which are re-deposited annually. They are the most fertile areas.
- Density of Population: High population density due to fertile land and availability of water.
The Peninsular Plateau
The Peninsular Plateau is an ancient, triangular landmass composed of crystalline, igneous, and metamorphic rocks. It is one of the oldest and most stable landmasses in the world.
Key Characteristics:
- Composition: Made up of ancient crystalline, igneous, and metamorphic rocks like gneisses and granites.
- Topography: Generally a plateau with a broad, elevated base and a relatively flat or gently undulating top.
- Formation: Formed from the breaking and drifting of the Gondwanaland continent.
- Boundaries:
- North: Aravalli hills, Vindhya range, Satpura range.
- East: Bay of Bengal.
- West: Arabian Sea.
- South: Indian Ocean.
- Notable Features: Ranges like Aravalli, Vindhya, Satpura, Sahyadri (Western Ghats), Eastern Ghats, and hills like Nilgiris, Anaimalai, Palni Hills.
- Drainage: Most of the peninsular rivers originate from the Western Ghats and flow into the Bay of Bengal, forming deltas. The Narmada and Tapi are exceptions, flowing west into the Arabian Sea.
Major Divisions of the Peninsular Plateau:
The Deccan Plateau
Location: South of the Narmada river, forming the larger part of the Peninsular Plateau.
Boundaries:
- North: Satpura and Vindhya ranges.
- East: Eastern Ghats.
- West: Western Ghats.
- South: Nilgiri hills.
Topography: Gently sloping from west to east. The western part is higher than the eastern part.
Notable Features:
- Western Ghats: Higher and more continuous than the Eastern Ghats, with average elevation around 1,000-1,600 metres. Peaks include Anaimudi (highest peak in Peninsular India) and Doddabetta.
- Eastern Ghats: Discontinuous and eroded ranges running parallel to the Bay of Bengal.
- Black Soil Region: Famous for its black soils, ideal for cotton cultivation.
- Rivers: Godavari, Krishna, Kaveri, Mahanadi originate here.
The Central Highlands
Location: North of the Narmada river, forming the northern part of the Peninsular Plateau.
Boundaries:
- North: Aravalli Range.
- West: Gujarati coast.
- East: Chota Nagpur Plateau.
- South: Vindhya Range.
Composition: Composed of the Malwa Plateau and the Chota Nagpur Plateau.
Malwa Plateau:
- Location: South of the Aravalli Range, in Madhya Pradesh and Rajasthan.
- Soil: Covered with black soil.
- Rivers: Rivers like Chambal, Betwa, and Son originate here.
Chota Nagpur Plateau:
- Location: In Jharkhand, West Bengal, and Chhattisgarh.
- Features: Rich in mineral resources like coal, iron ore, mica, and copper.
- Rivers: Damodar river flows through a rift valley here.
The Northeastern Plateau
Location: Essentially an extension of the Peninsular Plateau, separated by the Malda fault, which lies between the Rajmahal hills and Meghalaya hills.
Components: Comprises the Meghalaya Plateau and the Karbi-Anglong Plateau.
Meghalaya Plateau:
- Features: Divided into Garo, Khasi, Jaintia, and Mikir hills.
- Rainfall: Receives one of the highest rainfall in the world (Mawsynram and Cherrapunji).
- Soil: Rich in mineral resources.
The Indian Desert
The Indian Desert, also known as the Thar Desert, is an arid region located in the northwestern part of India, primarily in Rajasthan.
Location: Westernmost part of the Northern Plains, west of the Aravalli Range.
Characteristics:
- Climate: Arid and semi-arid climate with very low rainfall (less than 25 cm annually). High temperatures during summer and cold nights in winter.
- Topography: Characterized by undulating topography with sand dunes (called 'dunar' or 'barchans'), rocky plateaus, and gravel plains.
- Vegetation: Sparse vegetation adapted to arid conditions (xerophytic).
- Trees: Thorny bushes like Babul, Kikar, and scattered trees like Neem and Khejri.
- Grasses: Dry grasses.
- Wildlife: Adapted to scarcity of water, including camels, desert foxes, snakes, lizards, and bustards.
- Drainage: Rivers like the Luni are seasonal and disappear in the sand. Inland drainage streams flow into larger sand bodies.
- Economic Activity: Primarily pastoralism and limited agriculture where irrigation is available (e.g., Indira Gandhi Canal).
The Coastal Plains
India has a long coastline extending to about 7,500 km. The coastal plains are the narrow strips of land along the eastern and western coasts of the peninsula.
West Coastal Plains:
- Location: Situated between the Western Ghats and the Arabian Sea.
- Extent: Stretches from Gujarat in the north to Kerala in the south.
- Characteristics: Narrower in the north and widens towards the south.
- Divisions:
- Gujarat Coast: Plains are wide and are sites of important ports like Kandla.
- Konkan Coast: Between Daman and Goa.
- Kannad Plain: Between Goa and Mangalore.
- Malabar Coast: South of Kannad Plain, characterized by backwaters and lagoons.
- Features: Sandy beaches, deltas, estuaries, and natural harbours.
- Climate: Humid climate with high rainfall.
East Coastal Plains:
- Location: Situated between the Eastern Ghats and the Bay of Bengal.
- Extent: Stretches from West Bengal in the north to Tamil Nadu in the south.
- Characteristics: Broader and more plains-like than the west coast.
- Divisions:
- Utkal Plain: Located in Odisha, known for the Chilika lake.
- Andhra Coast: Plains are fertile and known for the deltas of Godavari and Krishna rivers.
- Coromandel Coast: In Tamil Nadu, also characterized by fertile plains and deltas of Kaveri river.
- Features: Extensive deltas formed by major peninsular rivers, lagoons, and sandy beaches.
- Climate: Characterized by tropical wet climate, prone to cyclones.
The Islands
India has two major groups of islands: the Andaman and Nicobar Islands in the Bay of Bengal and the Lakshadweep Islands in the Arabian Sea.
1. Andaman and Nicobar Islands:
- Location: Situated in the Bay of Bengal, in the southeastern part of India.
- Formation: Believed to be elevated parts of submerged mountain ranges.
- Characteristics:
- Number: Comprises about 572 islands.
- Structure: Divided into the Andaman group in the north and the Nicobar group in the south, separated by the Ten Degree Channel.
- Topography: Hilly and densely forested.
- Climate: Equatorial climate with high temperatures and heavy rainfall throughout the year.
- Vegetation: Dense evergreen forests.
- Wildlife: Rich in biodiversity, including unique species like the Nicobari pigeon and Andaman teal.
- Main Islands: North Andaman, Middle Andaman, South Andaman, Little Andaman, Great Nicobar. Port Blair is the capital.
2. Lakshadweep Islands:
- Location: Situated in the Arabian Sea, southwest of the mainland.
- Formation: Composed of small coral islands.
- Characteristics:
- Number: Comprises about 36 islands, of which only 11 are inhabited.
- Structure: Grouped into Amindivi Islands (north) and Minicoy Island (south), separated by the 11 Degree Channel.
- Topography: Mostly flat, sandy islands with coral reefs.
- Climate: Equatorial climate with high temperatures and humidity.
- Vegetation: Limited vegetation, mainly coconut palms.
- Wildlife: Rich marine life, important for fisheries.
- Capital: Kavaratti.
Significance of Islands:
- Strategic Importance: Important for India's maritime security and defence.
- Biodiversity Hotspots: Home to unique and diverse ecosystems and species.
- Tourism: Potential for tourism development.