Continents & Oceans: The Basic Map of the World

Every country, city and landmark sits somewhere on the basic frame of the world map: seven continents and five oceans, moving slowly on the surface of a planet that is about 71% water. This article is about Earth's physical geography: how the continents and oceans are arranged, how they got that way, why some places have mountains and earthquakes, and how latitude and longitude let you describe any place on Earth with two numbers. Countries and capitals, flags, and landmarks are covered in separate articles; here the focus is on the land and water themselves, with plenty of examples from Pakistan and South Asia.

1.What Makes a "Continent"?

A continent is one of Earth's very large landmasses. There is no single scientific rulebook for deciding what counts. The divisions we use mix geography, geology (plate tectonics) and historical convention. Different countries teach different models: seven continents (the model used in this article and in most Pakistani, Indian and international curricula), six (joining Europe and Asia as Eurasia, or North and South America as the Americas), and even five, as in the five rings of the Olympic symbol.

Land covers about 29% of the Earth's surface and the oceans about 71%.

2.The Seven Continents at a Glance

Population figures are approximate and change every year, but the order has stayed the same for decades: Asia far ahead, then Africa. Asia holds roughly 60% of the world's people.

Asia

The largest continent. It holds the world's highest point, Mount Everest (8,849 m, on the Nepal–China border), and one of its lowest land surfaces, the shore of the Dead Sea, about 430 m below sea level. Pakistan lies in the north-west of the continent, where the Karakoram, Himalaya and Hindu Kush ranges meet. It is home to five of the fourteen mountains on Earth over 8,000 m: K2 (8,611 m, the second highest in the world), Nanga Parbat, Gasherbrum I, Broad Peak and Gasherbrum II.

Africa

The second-largest continent, with 54 recognised countries, more than any other. It contains the Sahara, the world's largest hot desert (about 9.2 million km²), and the Nile, traditionally given as the longest river at about 6,650 km, although some measurements place the Amazon as longer.

North America

Includes Canada, the United States, Mexico, Central America and the Caribbean. It has the Great Lakes, the largest group of freshwater lakes by total area, and the Rocky Mountains.

South America

Home to the Amazon Rainforest, the largest tropical rainforest, and the Andes, the longest continental mountain range at about 7,000 km.

Antarctica

The coldest, windiest and driest continent. It has no permanent population, only research stations. Its ice holds about 70% of the world's fresh water, and the ice sheet is in places over 4 km thick. Despite all that ice, Antarctica is technically a desert, because very little snow falls on most of it.

Europe

Physically the western part of one great landmass with Asia, which together are called Eurasia. It is counted as a separate continent for historical and cultural reasons. The conventional boundary runs along the Ural Mountains, the Ural River and the Caucasus region.

Australia / Oceania

Australia is the only continent that is also a single country. "Oceania" is the wider region that includes New Zealand and thousands of Pacific islands, grouped as Melanesia, Micronesia and Polynesia.

3.Extremes of the Earth

4.The Five Oceans

An ocean is one of Earth's great bodies of salt water. All the oceans are connected into one world ocean; the divisions between them are drawn using continents, underwater ridges and agreed boundaries. For much of the 20th century, geography taught four oceans. In June 2021, National Geographic formally recognised the Southern Ocean around Antarctica as the fifth, matching what many oceanographers had been using for years.

• The Pacific covers about a third of the Earth's surface. If Mount Everest were placed in the Challenger Deep, its peak would still be about 2 km under water.
• The Atlantic separates the Americas from Europe and Africa and is the saltiest of the major oceans.
• The Indian Ocean is the warmest ocean overall. Pakistan's coast, about 1,000 km long, lies on the Arabian Sea, part of the Indian Ocean. The Indian Ocean's wind patterns, the monsoons, have shaped trade and life in South Asia for thousands of years (see our article on weather and climate).
• The Southern Ocean encircles Antarctica and carries the great Antarctic Circumpolar Current.
• The Arctic is the smallest and shallowest and is partly covered by sea ice, which has been shrinking.

A sea is a smaller part of an ocean, usually partly enclosed by land, such as the Arabian Sea or the Mediterranean Sea. Some "seas" are really lakes: the Caspian Sea and the Dead Sea are enclosed bodies of water with no outlet to the ocean.

What lies beneath the surface

Ocean water is about 3.5% salt on average. Sunlight reaches only the top 200 m, where nearly all marine plants grow. Below about 1,000 m there is no sunlight at all, yet life, including fish with their own lights, exists even in the deepest trenches.

5.How the Continents Formed

About 335 million years ago, most of Earth's land was joined in a single supercontinent called Pangaea. About 175 million years ago it began to split apart. The cause is plate tectonics: Earth's rigid outer shell is broken into huge slabs called plates, which move very slowly over the hotter, softer rock beneath, at roughly the speed your fingernails grow.

The idea was first proposed as "continental drift" in 1912 by the German scientist Alfred Wegener. He was widely dismissed because he could not explain how continents moved. The mechanism, plate tectonics, was confirmed in the 1960s, mostly through studies of the ocean floor.

Evidence for drift. The east coast of South America and the west coast of Africa fit together like puzzle pieces; the same fossils and rock types are found on both sides of the Atlantic; and the sea floor is youngest near the middle of the oceans and oldest near the edges.

6.Plate Boundaries, Mountains and Earthquakes

Most earthquakes and volcanoes occur where plates meet. There are three kinds of boundary.

• Divergent: plates move apart, and new crust forms. Example: the Mid-Atlantic Ridge.
• Convergent: plates move together. If one plate dives beneath another, it forms deep ocean trenches and volcanoes; if two continents collide, they push up great mountain ranges.
• Transform: plates slide past each other. Example: the San Andreas Fault in California.

The Pacific "Ring of Fire", a belt of trenches, volcanoes and earthquakes around the edges of the Pacific plate, contains most of the world's active volcanoes.

The Himalaya and Pakistan. About 50 million years ago the Indian plate, moving north, began to collide with the Eurasian plate, and the crumpling of the crust raised the Himalaya, Karakoram and Hindu Kush ranges. The collision is still going on, so these mountains are still rising slowly, by a few millimetres per year. It is also why Pakistan and northern India experience earthquakes. The 2005 Kashmir earthquake, of magnitude 7.6, on 8 October 2005, caused huge loss of life across northern Pakistan and Azad Kashmir, and remains one of the country's worst natural disasters.

7.Finding Places: Latitude, Longitude and Time

Latitude measures distance north or south of the equator (0°) in degrees, up to 90° at the poles. Longitude measures distance east or west of the prime meridian (0°), which passes through Greenwich in London, up to 180°. Together they give the exact position of any place on Earth.

• The Tropic of Cancer (about 23.4° N) and Tropic of Capricorn (about 23.4° S) mark the farthest points north and south where the Sun can be directly overhead. Karachi (about 25° N) lies just north of the Tropic of Cancer.
• The Arctic Circle (about 66.6° N) and Antarctic Circle (about 66.6° S) mark the limits of the polar regions.
• One degree of latitude is about 111 km on the ground.
• The Earth turns 360° in 24 hours, which is 15° of longitude per hour, and this is the basis of time zones. Pakistan Standard Time is 5 hours ahead of UTC.

8.Key Terms

9.Common Mistakes

• Thinking Europe is separated from Asia by water.
• Counting only four oceans.
• Treating the Dead Sea or the Caspian Sea as parts of an ocean. They are enclosed bodies of water with no outlet to the ocean.
• Thinking that all deserts are hot. Antarctica is the largest desert on Earth.
• Mixing up latitude (north-south) and longitude (east-west).
• Thinking the continents have always been where they are now.

10.Summary

• There are seven continents and five oceans; about 71% of Earth is water.
• Asia is the largest and most populous continent, and Pakistan holds five of Earth's fourteen peaks over 8,000 m.
• The Pacific is the largest ocean and holds the deepest point; the Southern Ocean was recognised as the fifth in 2021.
• Pangaea began to split about 175 million years ago, and plates are still moving at a few centimetres per year.
• The Himalaya formed where the Indian plate collided with the Eurasian plate, and the collision still causes earthquakes.
• Latitude and longitude describe any place on Earth, and 15° of longitude equals one hour of time.

11.Check Your Understanding

Try each question first, then tap it to reveal the answer.

For Teachers and Parents

Suggested activities: use a world map to trace the outlines of the continents and cut them out like puzzle pieces; mark Pakistan's mountains and coast on a map and find their latitude and longitude; make a model of the three plate boundaries with clay or paper. Discussion prompts: Why did most people reject Wegener's idea at first? Why does Pakistan have earthquakes? Figures for area, depth, height and population are approximate and are rounded; sources differ slightly, especially for the Southern Ocean and the length of rivers. This article is general education for students up to age 18.