Q.3.The ___________ forms develop on islands like ___________ because of their _____________ isolation.
Answers
There are countless islands in the ocean, lakes, and rivers around the world. They vary greatly in size, climate, and the kinds of organisms that inhabit them.
Many islands are quite small, covering less than half a hectare (one acre). These tiny islands are often called islets. Islands in rivers are sometimes called aits or eyots. Other islands are huge. Greenland, for example, covers an area of about 2,166,000 square kilometers (836,000 square miles).
Some islands, such as the Aleutian Islands in the U.S. state of Alaska, are cold and ice-covered all year. Others, such as Tahiti, lie in warm, tropical waters. Many islands, such as Easter Island in the South Pacific Ocean, are thousands of kilometers from the nearest mainland. Other islands, such as the Greek islands known as the Cyclades in the Aegean Sea, are found in closely spaced groups called archipelagoes.
Many islands are little more than barren rock with few plants or animals on them. Others are among the most crowded places on Earth. Tokyo, one of the world’s largest cities, is on the island of Honshu in Japan. On another island, Manhattan, rise the towering skyscrapers of the financial capital of the world, New York City.
For centuries, islands have been stopping places for ships. Because of isolation, many islands have also been home to some of the world’s most unusual and fascinating wildlife.
Island Formation
There are six major kinds of islands: continental (1), tidal (2), barrier (3), oceanic (4), coral (5), and artificial (6).
Continental islands (1) were once connected to a continent. They still sit on the continental shelf. Some formed as Earth’s shifting continents broke apart.
Scientists say that millions of years ago, there was only one large continent. This supercontinent was called Pangaea. Eventually, slow movements of the Earth’s crust broke apart Pangaea into several pieces that began to drift apart. When the breakup occurred, some large chunks of land split. These fragments of land became islands. Greenland and Madagascar are these type of continental islands.
Other continental islands formed because of changes in sea level. At the peak of the most recent glacial period, about 18,000 years ago, ice covered large parts of the Earth. Water was locked in glaciers, and the sea level was much lower than it is today. As glaciers began to melt, the sea level rose. The ocean flooded many low-lying areas, creating islands such as the British Isles, which were once part of mainland Europe.