Earth has seven main pieces of land, called continents. The seven continents are Asia, Africa, North America, South America, Antarctica, Europe, and Australia/Oceania. They are listed here in order of size. Asia is the biggest. Australia/Oceania is the smallest.

Usually, nearby islands are also part of a continent. For example, Japan is part of Asia. Greenland and all the islands in the Caribbean Sea are usually considered part of North America. Only a very few islands are not part of any continent.

Europe and Asia are not really separate pieces of land. They are both part of a single, huge piece of land called Eurasia. Still, they are usually thought of as two separate continents because their societies developed separately.

Three Main Layers Make Up Earth

Earth is made up of three main layers. The core is in the center. The mantle wraps around the core. The outer crust is like Earth's skin.

The crust and the top part of the mantle form a hard, stiff shell. This shell covers Earth. It is broken up into huge parts called tectonic plates. These plates slide around on the mantle. For hundreds of millions of years, they have been slowly sliding around the surface of Earth. They are still sliding today. Scientists believe their constant sliding formed the continents.

The continents first began to form nearly four billion years ago. At that time, a huge ocean covered Earth. Then pieces of land began to appear. They built up along the edges of tectonic plates. They were made of rock that rose up when plates crashed into each other.

Some of this rock formed into small islands. When plates carrying these islands crashed into each other, the separate islands sometimes joined together. Over time, these islands grew larger and larger. They became the first continents.

When There Was a Single, Huge Continent

The early continents were scattered chunks of land. These chunks slowly moved toward each other. In time, they formed into a single, huge continent. Scientists call this supercontinent Pangaea.

About 200 million years ago, Pangaea began to break apart. The separate pieces then slowly moved away from each other. They were the beginnings of the continents we know today.

One giant piece that split off from Pangaea later became Europe, Asia, and North America. Antarctica and Australia also broke away. At the time, they were still joined together. The small piece of land that would become India broke away too. For millions of years it moved north as a large island. It finally ran into Asia. Slowly, the different landmasses moved to their present places.

The positions of the continents are always changing. North America and Europe are moving away from each other. They drift apart by about 2.5 centimeters (one inch) a year. The continents are also continuing to break apart. In time, part of California will likely separate from North America. It will become an island.

The Crashing of Tectonic Plates Produced Mountains

The surface of the continents has changed many times. Great mountains have risen. Then, they have been worn away. Ocean waters have flooded huge areas and then slowly dried up. Huge ice sheets have come and gone. They shaped the land as they advanced and then melted away.

Mountains continue to form on every continent. They often form through the crashing together of two tectonic plates. The force of the crash creates raised wrinkles in the crust. These "wrinkles" are what we call mountains.

North America

North America is the third-largest continent. It stretches from the Aleutian Islands in the northwest to the Isthmus of Panama in the south.

The western part of the continent is full of young mountains. The Rockies are one example. They are North America's largest mountain chain. The East Coast has older mountain chains.

North America has a bigger range of climates than any other continent. Its Arctic regions are very cold. Other parts of the continent are very warm. For example, there are tropical jungles in the southern part of North America. The most southern part of North America is called Central America.

Some people think the United States and Canada are the only countries in North America. This is wrong. Mexico, Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama are all in North America too. Greenland is also geographically part of North America, even though Denmark partly controls it.

South America

South America is the fourth-largest continent. It stretches from the Caribbean Sea to the Antarctic Circle.

The Andes is the longest mountain range on any continent. It runs the whole length of South America.

The Amazon River flows through northern South America. It is the largest river in the world. The Amazon runs through the world's largest tropical rain forest. This rain forest is home to thousands of kinds of plants and animals. Many are found nowhere else in the world.

There are 12 countries in South America.

Europe

Europe is the sixth-largest continent. It is only slightly larger than Canada. Yet, its population is more than twice that of South America. Europe has more than 40 countries.

The Ural Mountains separate Europe from Asia. Two nations are in both continents. These are Russia and Kazakhstan.

Europe's most famous mountain chain is the Alps. It stretches across eight countries.

Africa

Africa is the second-largest continent. It is more than three times bigger than the United States. From north to south, Africa stretches about 8,000 kilometers (5,000 miles).

The Sahara covers much of North Africa. It is the world's largest hot desert. The world's longest river, the Nile, is also in Africa. It flows more than 6,560 kilometers (4,100 miles).

The middle of Africa is full of flat, grassy plains. This region is home to many well-known kinds of animals. Among them are lions, giraffes, and elephants.

Africa also has large mountains. One example is Mount Kilimanjaro, in the country of Tanzania. Its peak is covered by snow all year long.

Africa is slowly splitting in two. In time, land containing four African countries will break off from the rest of the continent. Those countries are Eritrea, Ethiopia, Djibouti, and Somalia.

Africa is home to 56 countries.

Asia

Asia is the largest continent. It stretches from the eastern Mediterranean Sea to the western Pacific Ocean. Six-tenths of Earth's population lives in Asia. More than a third of the world's people live in China and India alone.

Asia has many different climate regions. The Siberian Arctic is very cold. Indonesia is tropical. China's Gobi Desert is dry year-round.

Asia has more mountains than any other continent. More than 50 of the tallest mountains in the world are in Asia. Mount Everest is the highest point on Earth. It is more than 8,700 meters (29,000 feet) high. Mount Everest is in both Nepal and China.

There are more than 40 countries in Asia.

Australia/Oceania

Thousands of islands sit in the Pacific Ocean. Many of them are part of a region called Oceania.

Oceania includes the continent of Australia. It also includes a microcontinent called Zealandia, which includes the country of New Zealand. Much of Zealandia is formed by rocks that are underwater, with only New Zealand poking through the ocean surface.

The other large land area in Oceania is the island of New Guinea. It contains the country of Papua New Guinea.

Oceania also includes three areas made up of only islands. These areas are Melanesia, Micronesia, and Polynesia. Hawai'i is in Polynesia.

Australia/Oceania is the smallest continent, and also the flattest. Australia/Oceania has the second-smallest population of any continent. Fewer than 40 million people live there. Most live in coastal cities.

Australia/Oceania is full of unusual animals. Among them are the kangaroo, the koala, the platypus, and the Tasmanian devil.

Antarctica

Antarctica is the iciest place on Earth. It is larger than Europe or Australia, but has no full-time population. The only people there are visiting scientists.

Antarctica is unbelievably cold. Temperatures drop to lower than 73 degrees Celsius (100 degrees Farenheit) below zero. The continent is almost completely covered with ice. This ice covering can be up to 3.2 kilometers (two miles) deep.

Antarctica does not have any countries.