Introduction
- Physiography refers to the physical features of the Earth’s surface, like mountains, plains, and plateaus.
- Drainage refers to the river systems and how water flows through a region.
- This chapter compares the physiography and drainage of India and Brazil, focusing on their landforms and river systems.
Physiography of India
Major Physiographic Divisions
India is divided into five major physiographic regions:
1. The Himalayas
2. The North Indian Plains
3. The Peninsula
4. The Coastal Plains
5. The Island Groups
1. The Himalayas
Description: Young fold mountains, one of the highest in the world, stretching from Jammu and Kashmir to Arunachal Pradesh.
Ranges (from south to north):
- Siwaliks: Youngest and southernmost range.
- Lesser Himalayas: Middle range.
- Greater Himalayas (Himadri): Highest peaks, like Everest.
- Trans-Himalayan Ranges: Northernmost, older ranges.
Divisions:
- Western Himalayas (Kashmir Himalayas)
- Central Himalayas (Kumaun Himalayas)
- Eastern Himalayas (Assam Himalayas)
Key Fact: The Eastern Himalayas mark the deep plains of the Brahmaputra River.
2. The North Indian Plains
Location: Lies between the Himalayas (north) and the Peninsula (south), from Rajasthan/Punjab to Assam.
Features: Flat, low-lying, fertile area, ideal for agriculture.
Parts:
- Ganga Plains: East of Aravali ranges, slopes eastward, includes the Sunderbans (world’s largest delta formed by Ganga-Brahmaputra).
- Western Plains:
- Thar Desert (Marusthali): Covers most of Rajasthan, dry and sandy.
- Punjab Plains: Fertile, formed by deposition from the Sutlej River and its tributaries, slopes westward.
3. The Peninsula
Location: South of the North Indian Plains, tapering towards the Indian Ocean.
Features: Made of plateaus and hill ranges, including:
- Aravali Ranges: Oldest fold mountains in the north, act as a water divide between the Narmada and Ganga basins.
- Vindhya and Satpura Ranges: Central India, Vindhyas divide Ganga and Narmada basins.
- Western Ghats (Sahyadri): Along the western edge, height increases southwards, act as a water divide.
- Eastern Ghats: Along the eastern edge, includes peaks like Mahendragiri.
- Deccan Plateau: Covers states like Maharashtra, Karnataka, Andhra Pradesh, and Telangana.
- Plateaus: Malwa, Chhota Nagpur, and others lie between Aravalis and Chhota Nagpur Plateau.
Key Fact: The Nilgiri Hills are in the southern part of the Western Ghats.
4. The Coastal Plains
Extent: India has a 7,500 km coastline along the Arabian Sea (west) and Bay of Bengal (east).
Western Coast:
- Rocky, narrow, with spurs from Western Ghats reaching the coast.
- Rivers (short and swift) form estuaries, not deltas.
Eastern Coast:
- Wider, formed by sediment deposition from rivers.
- Rivers (slower) form deltas, like the Godavari and Kaveri deltas.
Key Difference: Western coast is rocky; eastern coast has deltas due to gentle slopes.
5. The Island Groups
Two Main Groups:
- Lakshadweep Islands (Arabian Sea): Small, coral (atoll) islands, not very high.
- Andaman and Nicobar Islands (Bay of Bengal): Volcanic islands (Andaman) and atolls (Nicobar).
Special Feature: Barren Island in Andaman has India’s only active volcano.
Physiography of Brazil
Major Physiographic Divisions
Brazil is divided into five physiographic regions:
1. The Highlands
2. The Great Escarpment
3. The Coastal Region
4. The Plains
5. The Island Groups
1. The Highlands
Description: Large plateaus and small mountains cover most of Brazil, called the Brazilian Highlands or Brazilian Shield.
Extent: Includes parts of Roraima, Para, and Amapa in the north; Guyana Highlands extend into Venezuela and French Guiana.
Highest Peak: Pico de Neblina (3,014 m), on the Brazil-Venezuela border.
Altitude:
- East and south: Over 1,000 m.
- Other parts: 500-1,000 m.
Slopes: Gradual towards the north, steeper towards the east.
Rivers: Tributaries of the Amazon form rapids and waterfalls in the north; southern rivers like Uruguay, Paraguay, and Parana flow into Argentina.
2. The Great Escarpment
Description: A steep slope on the eastern side of the Brazilian Highlands, with an altitude of about 790 m.
Significance: Acts as a barrier to Southeast Trade winds, creating a rain-shadow area called the Drought Quadrilateral in the northeast.
Location: Very steep from Sao Paulo to Porto Alegre.
3. The Coastal Region
Extent: Brazil has a 7,400 km coastline along the Atlantic Ocean, divided into:
- Northern Coast: From Amapa to Rio Grande do Norte, low-lying with river mouths (e.g., Amazon, Tocantins).
- Eastern Coast: Receives smaller rivers, like Sao Francisco.
Features: Beaches, sand dunes, coral reefs, and atoll islands; includes Praia do Cassino, the world’s longest sandy beach (over 200 km).
Key Island: Marajo Island, a large coastal island between the Amazon and Tocantins rivers.
4. The Plains
Two Main Plains:
Amazon Basin (North):
- Largest plain in Brazil, between Guyana and Brazilian Highlands.
- Slopes eastward, wide in the west (1,300 km), narrow in the center (240 km), widens near the Atlantic.
- Covered by tropical rainforests, often flooded and inaccessible.
Paraguay-Parana Plains (Southwest):
- Source region for Paraguay and Parana rivers, slopes south and southwest.
- Includes Pantanal, one of the world’s largest wetlands, with swamps and marshes.
Altitude: Mostly below 200 m.
5. The Island Groups
Types:
- Coastal Islands: Formed by deposition, near the mainland.
- Marine Islands: Over 300 km from the coast, rocky, tops of submerged mountains, some are coral atolls.
Location: Found in the South Atlantic Ocean.
Drainage of India
Classification of Rivers
India’s rivers are divided into:
- Himalayan Rivers: Perennial (flow year-round), fed by glaciers and monsoon rains.
- Peninsular Rivers: Seasonal, rain-fed, rarely flood.
Himalayan Rivers
Major Systems:
- Indus System: Includes Indus, Jhelum, Chenab, Ravi, and Satlej; flows through Jammu and Kashmir, Ladakh, and Pakistan; forms Punjab Plains.
- Ganga System: Ganga originates at Gangotri glacier, flows east; tributaries include Yamuna (from Yamunotri), Brahmaputra (called Tsang Po in Himalayas, Dihang when crossing Himalayas), Chambal, Ken, Betwa, and Damodar.
Key Feature: Ganga and Brahmaputra form the Sunderbans delta in West Bengal and Bangladesh.
Fun Fact: Himalayan rivers may be older than the Himalayas due to geological processes.
Peninsular Rivers
Divided By:
- Western Ghats: Major water divide.
- Vindhyas and Aravalis: Also act as water divides.
West-Flowing Rivers (to Arabian Sea):
- Short, swift, form estuaries (e.g., Narmada, Tapi, Mahi, Sabarmati, Luni).
- Narmada and Tapi flow through rift valleys; Luni flows into the Gulf of Kutch.
East-Flowing Rivers (to Bay of Bengal):
- Longer, form deltas (e.g., Mahanadi, Godavari, Krishna, Kaveri).
- Godavari: Second largest river basin in India.
- Kaveri: Used for irrigation since the 2nd century AD (Chola dam near Tiruchirapalli).
Special Feature: Kerala’s coastal rivers form Kayals (backwaters) near their mouths.
Drainage of Brazil
Major River Basins
Brazil has three major river basins:
1. Amazon Basin
2. Paraguay-Parana System
3. Sao Francisco Basin
4. Coastal Rivers
1. Amazon Basin
Headwaters: Eastern slopes of the Andes in Peru.
Features:
- Huge discharge (2 lakh m³/s), washes away sediments, so no typical delta forms.
- Mouth is 150 km wide, with islands in the Atlantic Ocean.
- Suitable for navigation throughout most of its course.
Location: Northern Brazil, between Guyana and Brazilian Highlands.
2. Paraguay-Parana System
Location: Southwestern Brazil, forms the catchment of the River Plata in Argentina.
Headwaters: Southern Brazilian Highlands.
Other River: Uruguay River also originates here.
3. Sao Francisco Basin
Location: Eastern part of the Brazilian Highlands, entirely within Brazil.
Flow: Flows north for 1,000 km over the plateau, then east to the Atlantic Ocean.
Navigation: Navigable for 250 km downstream.
4. Coastal Rivers
Description: Short rivers, significant due to dense coastal population.
Examples:
- North-Flowing: Paraniba, Itapecuru (meet North Atlantic Ocean).
- South-Flowing: Puraguaco (enters Atlantic near Salvador).
Comparison of India and Brazil
Physiography
India:
- Has high mountains (Himalayas), flat plains, and a large peninsula with plateaus and hills.
- Coastal plains vary: rocky west, deltaic east.
Brazil:
- Dominated by highlands and plateaus, no very high mountains.
- Limited plains (Amazon and Paraguay-Parana), narrow coastal region.
Drainage
India:
- Himalayan rivers are perennial; peninsular rivers are seasonal.
- Major rivers form large deltas (e.g., Ganga, Godavari).
Brazil:
- No glacier-fed rivers; all are rain-fed.
- Amazon has a wide mouth with islands, not a delta.
Altitude
- India: Highest altitudes (over 6,000 m) in the Himalayas (north).
- Brazil: Highest altitudes (500-1,000 m) in the Brazilian Highlands (east and south); Pico de Neblina is only 3,014 m.
Slopes
- India: Deccan Plateau slopes eastward.
- Brazil: Amazon basin slopes eastward.
Rain-Shadow Areas
- India: Thar Desert (west of Aravalis).
- Brazil: Drought Quadrilateral (northeast of Great Escarpment).
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