Antarctica Chapter Notes | Geography Class 7 ICSE PDF Download

Introduction

Location

• Located entirely in the Southern Hemisphere, surrounding the South Pole.
• Lies within the Antarctic Circle.
• Surrounded by the southern parts of the Pacific, Atlantic, and Indian Oceans, forming the Southern Ocean.
• Covered by ice sheets spanning 14 million square kilometers in summer.
• East Antarctica faces the Atlantic and Indian Oceans.
• West Antarctica, smaller in size, lies south of South America.
• West Antarctica includes the Antarctic Peninsula and Ross and Ronne Ice Shelves.

Status of Antarctica

• Antarctica has no native population or government.
• Seven countries:  (Argentina, Australia, Chile, France, New Zealand, Norway, UK) claim parts of it.
• Claims are not recognized internationally due to the Antarctic Treaty.
• The Antarctic Treaty, signed in 1961 by 12 nations, now includes 45 nations.
• The treaty ensures Antarctica is used only for peaceful purposes.

Climate

• Antarctica has a very cold and dry climate.
• Average annual temperature is around -50°C.
• Interior regions can drop below -60°C in winter and -20°C in summer.
• Precipitation falls as snow, about 200 mm annually in coastal areas.
• Mountainous regions and East Antarctica receive less than 50 mm of snow yearly.
• Strong winds can reach speeds of up to 200 miles per hour.
• Katabatic winds, flowing down mountains, contribute to low precipitation.
• The Dry Valleys, an extremely dry area, have had no rain for about 2 million years.
• The Onyx River, Antarctica’s longest river, is about 40 km long.
• Both Arctic and Antarctic are cold due to low-angle sunlight and long periods of darkness.
• The South Pole is colder than the North Pole despite equal sunlight.

Why Is It So Cold and Dry?

• Low-angle sunlight spreads energy over a large area.
• 24 hours of darkness in winter means no sunlight for months.
• High albedo reflects most sunlight back into space.
• High altitude reduces temperature by about 1°C per 100 m increase.
• Cold air holds less water vapor, reducing precipitation.
• Antarctica’s large landmass limits the moderating effect of oceans to its edges.

Division of Antarctica

East Antarctica

• Also called Greater Antarctica, it covers two-thirds of the continent.
• It is the oldest part of Antarctica.
• Has an ice plateau rising 3,000 meters above sea level.
• Strong winds create sastrugi, wavelike grooves in the snow.

West Antarctica

• Also known as Lesser Antarctica, it is smaller and less stable geologically.
• Covered by a thin ice sheet and includes mountainous islands.
• Contains the Antarctic Peninsula, closest to South America.
• Includes islands like the South Shetland Islands.
• It is the warmest part of Antarctica, popular for cruise ship visits.

Ice, Sea, and Lakes

• Antarctic and Greenland ice sheets hold over 99% of Earth’s freshwater ice.
• The Antarctic Ice Sheet covers nearly 14 million square kilometers.
• Contains 30 million cubic kilometers of ice.
• Ice sheet grows from 3 million square kilometers in summer to 19 million in winter.
• Growth is largely due to ice shelves.
• Major ice shelves include: Ross, Amery, Larsen, and Ronne.
• Surrounding seas include:  Ross, Amundsen, Bellingshausen, and Weddell Seas.
• Antarctica has over 160 sub-glacial lakes, with Lake Vostok being the largest.
• Lake Vostok lies 4 km below the ice sheet, sealed for up to 35 million years.

Mountain Ranges

Transantarctic Mountains

• Stretch 3,500 km across Antarctica, separating East and West Antarctica.
• Contain rocks similar to those in Tasmania, indicating a historical connection.
• High peaks rise above the ice sheets, some over 4,300 meters.
• Near sea level, they include the Dry Valleys, the largest ice-free areas.
• Dry Valleys act as a dam, holding back East Antarctica’s ice.

Vinson Massif

• Located in the Sentinel Range of the Ellsworth Mountains in West Antarctica.
• Highest peak in Antarctica at 4,892 meters.
• Named after Carl Vinson, a supporter of Antarctic research.
• Not difficult to climb but isolated with extreme weather.
• Average summer temperature is -29°C.

Mount Erebus

• An active volcano on Ross Island in the Ross Sea, West Antarctica.
• Formed by eruptions through the 700-meter-thick Ross Ice Shelf.
• About one million years old and highly active.
• Rises to 3,794 meters with a permanent lava lake in its caldera.
• The caldera formed when the summit collapsed, filled by later eruptions.
• Eruptions are usually small, but ash is found across Antarctica from larger eruptions.

Life in Antarctica

• Antarctica is a cold desert with moving ice and high elevation.
• No permanent human settlements exist.
• Research stations are set up by various countries for scientific studies.
• India has three research stations: Dakshin Gangotri (supply base), Maitri, and Bharati.
• Antarctic Treaty of 1961 protects Antarctica as a wilderness.
• The treaty prevents military use and radioactive waste disposal.
• Antarctica is called a Human Void Zone due to no permanent human presence.
• Hardy plants like pearlwort, mosses, and lichen grow along the coast and Antarctic Peninsula.
• Abundant sea life includes zooplankton, seals, whales, and seabirds like petrels.
• Penguins are the main inhabitants, evolved 40-50 million years ago.
• Penguins have oily feathers for waterproofing and fat for insulation.
• Their solid bones aid diving but prevent flying, suitable for a predator-free environment.
• Penguin wings act like flippers for swimming.
• World Penguin Day is observed on April 25.

Point to Remember

• Antarctica is a cold continent surrounded by the Southern Ocean.
• Divided into East and West Antarctica by the Transantarctic Mountains.
• It is a cold desert with minimal moisture despite ice and snow.
• No permanent human settlements, only research stations for scientists.
• Vinson Massif in the Sentinel Range is the highest mountain.