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Islands
Factfile |
 Islands |
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How Islands are formed |
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Islands are made in different ways. Some are the tops of undersea volcanoes and mountains. Surtsey Island off the coast of Iceland is one of Earth’s youngest islands and is the result of submarine (underwater) volcanic activity.
When volcanoes erupt under the sea, new islands may appear. In the case of Surtsey Island, first molten rock broke through Earth’s crust and as more lava was deposited on the seabed, a cone shape built up. As more lava was deposited, the cone shape built up until it broke through the water’s surface. This building process continued for about three years, in which time the island grew to a height of 170m and today, the island has an area of about 2.5m².
Some islands like the British Isles, were once part of large continents. Thousands of years ago, during the last Ice Age, Britain was connected to western Europe by dry land. The Stone Age hunters and animals, like the Mammoth, used this land as a bridge. As a result, they spread out all over the world. As the climate warmed, the sea levels rose, and by about 8,000 years ago, the lower parts of the land were flooded, cutting the islands off.
Other islands like New Zealand were formed because they became separated from large continents when movements in the Earth’s plates caused the land to break off and drift away. New Zealand was originally part of the eastern side of Australia. About 85 million years ago, movement in the Earth’s plates caused the islands to move east, separating them from Australia.
Plates are huge sections of the Earth’s crust that contain the continents. These plates move slowly, over hundreds of thousands of years. As the plates meet and their edges grind against each other, volcanoes erupt and earthquakes occur.
Sursey Island
Since the time New Zealand became islands, the country has taken a special geological history of its own because of frequent earthquakes, geothermally active areas and volcanoes which are the result of its modern position on the boundary of the Australian and Pacific Plates.
So what about Antarctica? While Antarctica is classed as a continent and not an island, it was once joined to South America, Africa, India and Australia to form a super-continent called Gondwana. About 180 million years ago, the continents started to separate and drift apart on different plates over the next 150 million years. Geologists are still uncertain exactly how the break up took place, but some suggest it was caused by abnormally hot upwellings of magma (molten rock) from deep below the Earth’s surface.
As Earth’s plates are still moving, in 100 million years, a map of the world will look quite different from today!
Milford Sound, New Zealand - Steve Canipe
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