Continents are very large pieces of land. Earth has seven continents. Asia is the biggest and Australia is the smallest. Listed in order of size they are: Asia, Africa, North America, South America, Antarctica, Europe and Australia/Oceania.
Islands near a continent are usually part of that continent. For example, Japan and the Philippines are part of Asia. Greenland and the islands in the Caribbean Sea are usually considered part of North America.
A very few islands don't follow this pattern. They are not part of any continent.
Europe and Asia are not really separate. They are both part of one giant piece of land. This land is called Eurasia. Still, Europe and Asia are thought of as separate continents because their peoples' cultures are so different.
Plates in Motion
Earth is covered with a layer of hard rock. This is broken into several huge parts called tectonic plates. These plates move around. They often crash into each other. Their crashing is what created the continents.
The continents started forming four billion years ago. At the time, Earth was almost completely covered by a huge ocean. Then, pieces of land began to appear. They were made of rock. This rock rose up when plates crashed together. It gathered at the edges of plates.
Some of this rock formed into small islands. When plates crashed together, an island on one plate might crash into an island on another plate. When this happened, islands joined together to become a single, larger island. Over time, such islands grew larger and larger. They became the first continents.
The Big Break-up
Over time, the early continents formed into one huge continent. This supercontinent is called Pangaea.
About 200 million years ago, Pangaea began to break apart. The separate pieces were the beginnings of today's continents. Slowly, they began to move away from each other.
One of the pieces that broke off was gigantic. Later, North America broke off from it. The rest became Europe and Asia.
Antarctica and Australia headed south. At the time, they were still joined together. The small piece of land that became India broke away too. It became an island. For millions of years it moved north. Finally, it ran into Asia. It then became part of Asia.
Slowly, the different continents moved to where they are now.
The continents are still moving. North America and Europe are moving away from each other. They travel 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.
Our Changing World
The surface of the continents has changed many times. Great mountains have risen. Then, they have been worn away. Ocean waters have flooded across plains. Then, they have slowly dried up. Huge ice sheets have come and gone. Along the way, they shaped the land.
Mountains are still forming. They often form when two tectonic plates crash together. Such crashes push bits of land up.
North America is the third-largest continent. It stretches from the Aleutian Islands to the Isthmus of Panama.
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 many kinds of weather. It has a bigger range of climates than any other continent. Its Arctic regions are very cold. Other parts are very warm.
Some people think the United States and Canada are the only countries in North America. This is wrong. Mexico is in North America. So are Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama. Greenland is also geographically part of North America, even though Denmark partly controls it.
South America is the fourth-largest continent. It stretches from the Caribbean Sea to the Antarctic Circle.
The Andes is the world's longest mountain range. 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 rainforest. This rainforest is home to thousands of kinds of plants and animals. Many are found nowhere else.
There are 12 countries in South America.
Europe is the sixth-largest continent. It is only slightly larger than Canada. Yet, it has more than twice as many people as South America.
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.
Europe has more than 40 countries.
Africa is the second-largest continent. It is more than three times bigger than the United States.
The Sahara Desert 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 full of wildlife. It is where lions, giraffes, and elephants are all found.
Africa also has large mountains. One is Mount Kilimanjaro, in the country of Tanzania. Its top is covered by snow all year long.
Africa is slowly splitting in two. In time, four African countries will break off from the rest of the continent. Those countries are Eritrea, Ethiopia, Djibouti, and Somalia.
Africa has 56 countries.
Asia is the largest continent. It stretches from the Mediterranean Sea to the Pacific Ocean. Six-tenths, or 60 percent, 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 climates. 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 world's tallest mountains 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 two countries. It is in both Nepal and China.
There are more than 40 countries in Asia.
Oceania is a region that includes the continent of Australia. There are two other larger lands here. One is the country of New Zealand, which is part of a microcontinent called Zealandia.
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. It is also the flattest.
Australia/Oceania has the second-smallest population of any continent. Altogether fewer that 40 million people live there. Most live in cities along the coasts.
Australia and Oceania is full of unusual animals. They include the kangaroo, the koala, and the platypus.
Antarctica is the iciest place on Earth. It is larger than Europe or Australia. Yet, it has no full-time population. The only people there are visiting scientists.
Antarctica is unbelievably cold. Temperatures can drop below minus 73 degrees Celsius (100 degrees Farenheit). The continent is covered with ice. This ice covering can be up to 3.2 kilometers (two miles) deep.
Antarctica does not have any countries.