Island (Encyclopedia of Science)
An island is a relatively small area of land that is completely surrounded by water. It is impossible to give a total number to the islands that exist on the surface of the planet. As a result of erosion or rising sea level, some islands drown over time. The longest surviving islands usually last no more than 5 to 10 million years (Earth is 4.5 billion years old). Ongoing volcanic activity continues to create new islands and to add to existing ones. On November 14, 1963, a underwater volcanic explosion off the southern coast of Iceland created the island of Surtsey, which continues to gain land as the ongoing lava flows cool.
The eight largest islands on Earth are (in descending order): Greenland, New Guinea, Borneo, Madagascar, Baffin Island, Sumatra, Honshu (largest of the Japanese islands), and Great Britain. Islands can be divided into two types: continental or oceanic.
Continental islands are parts of the continental shelveshe submerged, gradually sloping ledges of continents. These islands are formed in one of two ways: rising ocean waters either cover coastal areas, leaving only the summits of coastal highlands above water, or cut off a peninsula or similar piece of land jutting out from the mainland. Continental islands lie in shallow water, usually less than 600 feet (180 meters) deep. Greenland and Newfoundland...
(The entire section is 913 words.)
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