Islands

The world's ten largest islands (drawn to scale)

Islands	Ocean
Greenland New Guinea Borneo Madagascar Baffin Island Sumatra Honshu Great Britain Victoria Ellesmere	Arctic Pacific Pacific Indian Arctic Indian Pacific Atlantic Arctic Arctic

Some islands were originally parts of continents. These islands were separated from the mainland as a result of a rise in sea level. For example, Great Britain was connected to the mainland of Europe about 11,000 years ago. As the climate got warmer, ice melted and the sea level rose. As a result, water covered the land that had connected Great Britain to the mainland.

Other islands rise from the ocean. Some are volcanoes, such as the islands of Hawaii and the islands of Japan. Some volcanic islands are millions of years old, but new islands are forming all the time. For example, Iceland was formed millions of year ago by a volcano. In 1963, a volcano started to form a new island called Surtsey near Iceland.

Islands differ greatly in size. Greenland is the largest island in the world. The difference between an island and a continent is based on size. Because Australia is three times the size of Greenland, geographers classify Australia as a continent.