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Island Formation: Where do Islands come from?
By Islomaniac | June 26, 2007
If you are an islomaniac you must have wondered at one time or another where
Volcanic Island Formation
Geographers claim two major classifications of islands: oceanic islands and continental islands. Each of these two categories have sub-categories.
Oceanic
Oceanic islands are not attached to any continental mass. These islands are a result of either coral deposits or volcanic ejections.
Most oceanic islands originated from ancient volcanic activity. Volcanic islands form along the boundaries of tectonic plates. Evidence of this process can be seen in the “island arcs” of
Volcanic islands are also created by “hot spots”. From deep within the earth’s mantle, magma rises up and spews lava onto the sea floor. Over time, the lava builds up and emerges above sea level to form an island volcano. Eventually tectonic plates move the volcano away from the hot spot, essentially cutting off its supply of magma and thus forming an island. Chains of islands are formed as, over time volcano’s are formed and then carried away by the tectonic plates. Examples of this process include the islands of
Volcanic Island formation
Coral Islands
The second type of oceanic island is known as a coral island. These islands are formed by coral building sea organisms known as polyps. Polyps protect their bodies by building limestone walls around themselves. Over time, these colonies grow large enough to form reefs. These large reefs form the basis for islands. Reefs become islands when the sea level drops around the reef or the land beneath the reef rises. Over long periods of time Sand, dust and other materials accumulate on the exposed reef, eventually forming an island. Well-known coral islands are found in the Florida Keys,
Island formation in the Galapagos Islands
Continental islands form the second major classification of islands. Continental islands are bodies of land that are connected to a continent. These islands tend to sit in shallow waters, existing in 600 feet of water or less. There are a number of ways that these islands can come into existence. Most often continental islands are formed when sea levels rise causing low lying areas to fill with water, sectioning off portions of the land that sit higher. A perfect example of this is
Manhattan Island: A Continental Island
A subgroup of continental islands are known as microcontinental islands. Microcontinental islands are formed when a portion of the landmass separates from the continent; island nations such as
Islands, private or otherwise are a fascinating and unique natural resource. It is my hope that by explaining the immensely long time it takes for islands to form that we will begin to have a greater appreciation for how precious our islands are. As global warming, environmental disasters and pollution threaten our island resources it’s more important than ever for us to understand, appreciate and protect our islands.
Sources:
http://www.hawaii.edu/environment/ainakumuwai/html/ainakumuwaiislandformation.htm
http://www.privateislandsonline.com/how-islands-are-made.htm
My son David.
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