Revision: Physiography and Drainage Geography SSC (English Medium) 10th Standard Maharashtra State Board

The total area drained by a river and its tributaries is known as a drainage basin.

A drainage system is an integrated system of tributaries and a trunk stream which collects and drains surface water into the sea, lake or some other body of water.

• The Himalayas are young fold mountains and one of the major mountain systems in Asia.
• They extend from the Pamir Knot in Tajikistan to eastern India (Jammu & Kashmir to Arunachal Pradesh).
• The Himalayas consist of parallel mountain ranges: the Siwaliks (youngest), the Lesser Himalayas, the Greater Himalayas (Himadri), and the Trans-Himalayas (oldest).
• The ranges are arranged south to north by age — youngest in the south, oldest in the north.
• The Himalayas are divided into Western (Kashmir), Central (Kumaun), and Eastern (Assam) Himalayas.

• The North Indian Plains lie between the Himalayas and the Peninsular Plateau, from Rajasthan to Assam.
• They were formed by alluvial deposits from the Indus, Ganga, and Brahmaputra rivers.
• These plains are flat, low-lying, and suitable for farming and settlements.
• They cover one-fifth of India’s area but support nearly half of the population.
• The plains are divided into Rajasthan, Punjab–Haryana, the Ganga Plains, and the Brahmaputra Plains.
• The Punjab–Haryana and Ganga Plains are fertile, irrigated, and densely populated.
• The Brahmaputra Plains are marshy and include Majuli Island; the Sunderbans Delta is the world’s largest.

• The Indian Peninsula lies south of the North Indian Plains and tapers toward the Indian Ocean.
• It is the oldest and largest physiographic division of India, mostly made of stable tableland.
• It is bounded by the Aravalli Range in the northwest and the Western and Eastern Ghats on the sides.
• The region includes many hill ranges and plateaus, such as the Vindhyas, Satpuda, and Aravalis.
• The Deccan Plateau is triangular and lies between the Western and Eastern Ghats, covering Maharashtra, Telangana, and Karnataka.
• The plateau is divided into Central Plateaus, Eastern Plateaus, Deccan Plateau, Kathiawar–Kutch region, and North-Eastern Plateau.
• This region is rich in minerals, has old rivers, and supports forests, farming, and mining.

• India has a coastline of approximately 7,500 km, extending along the eastern (Bay of Bengal) and western (Arabian Sea) sides of the Peninsula, meeting at Cape Comorin.
• The Western Coastal Plains are narrow, rocky, and indented, with short rivers forming estuaries; major ports include Mumbai and Kochi.
• The Eastern Coastal Plains are broad and flat, formed by deposition from major rivers like the Mahanadi, Godavari, Krishna, and Kaveri, leading to fertile deltas.
• Subdivisions: East coast – Northern Circars and Coromandel Coast; West coast – Gujarat, Konkan, Kanara, Malabar.
• The coastal plains are important for ports, minerals (like salt and monazite), and fisheries.

• India has two major island groups: the Lakshadweep Islands in the Arabian Sea and the Andaman & Nicobar Islands in the Bay of Bengal.
• The Lakshadweep Islands are mostly coral atoll islands, small, flat, and low in height, and lie off the Kerala coast.
• The Andaman & Nicobar Islands consist of many islands (about 265–300), mostly forested and hilly, and are separated by the Ten Degree Channel.
• Barren Island in the Andaman group has India’s only active volcano, and Indira Point in Great Nicobar is India’s southernmost point.
• These island groups are important for strategic location, biodiversity, and are surrounded by coral reefs and rich marine life.

• The Brazilian Highlands cover southern Brazil and are also called the Brazilian Shield or Plateau.
• The Guyana Highlands extend into northern Brazil, mainly in Roraima, Pará, and Amapá.
• Pico de Neblina (3014 m) is Brazil’s highest peak, on the Brazil–Venezuela border.
• The highlands mostly lie between 500–1000 m, with higher parts in the east and south.
• Rivers such as the Amazon's tributaries, Uruguay, Paraguay, and Paraná originate here, forming rapids and waterfalls.

• The Great Escarpment occupies a small area but is a distinct physiographic region due to its steep slope.
• It marks the eastern edge of the Brazilian Highlands.
• The escarpment has an average height of about 790 m, though the height decreases in some areas.
• It is very steep from São Paulo to Porto Alegre, forming a sharp slope.
• The escarpment blocks Southeast Trade Winds, creating a rain-shadow region called the Drought Quadrilateral in the northeast.

• Brazil has a coastline of about 7400 km, divided into the northern coast and the eastern coast.
• The northern coast (Amapa to Rio Grande do Norte) is part of the North Atlantic coast and is low-lying due to many river mouths, including the Amazon.
• Marajo Island, located between the mouths of the Amazon and Tocantins Rivers, is a major coastal island.
• The eastern coast is drained by many small rivers, with the Sao Francisco River being the only major one entering the Atlantic Ocean here.
• The Brazilian coast features beaches, sand dunes, and is partly protected by coral reefs and atoll islands.

• Brazil has two main plain regions: the Amazon Basin (north) and the Paraguay–Paraná source region (southwest).
• The Amazon plains are the largest, sloping eastward between two highlands.
• These plains are widest in the west and narrowest (240 km) where the highlands come close.
• The Amazon plains are forested, flooded, and hard to access.
• The Pantanal is a large wetland in the southwest, with swamps and marshes, partly in Argentina.

• Brazil has both coastal islands and marine islands apart from its mainland.
• Coastal islands are formed mainly by deposition near the shore.
• Marine islands lie over 300 km from the mainland in the Atlantic Ocean.
• These marine islands are usually rocky and are the tops of submerged mountains.
• Some islands in the South Atlantic Ocean are coral islands and are known as atolls.

• Brazil has three major river systems: the Amazon, the Paraguay–Parana, and the Sao Francisco.
• The Amazon River is the largest, starting in the Andes, has a very wide mouth (150 km), and is highly navigable.
• The Paraguay and Paraná Rivers flow from southwestern Brazil to Argentina and form part of the Plata Basin.
• The São Francisco River flows north and then east to the Atlantic and is navigable in its lower course.
• Brazil also has many short coastal rivers that are important for coastal settlements.

• Indian rivers are divided into Himalayan (perennial) and Peninsular (seasonal) rivers.
• The Indus and Ganga systems drain the north; the Ganga forms a large delta with the Brahmaputra.
• Brahmaputra is called Tsang Po in Tibet, Dihang in India, and joins the Ganga in Bangladesh.
• Peninsular rivers flow east to the Bay of Bengal or west to the Arabian Sea; the Western Ghats form the water divide.
• West-flowing rivers include Narmada, Tapi, Mahi, Sabarmati, and Luni.
• East-flowing rivers include the Mahanadi, Godavari, Krishna, and Kaveri.
• Godavari is India’s second largest river system; Krishna and Kaveri are important for irrigation.