High island

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Moorea, a high island of volcanic origin where the central island is still prominent. Moorea ISS006.jpg
Moorea, a high island of volcanic origin where the central island is still prominent.
Stromboli is one of the eight Aeolian Islands, a volcanic arc north of Sicily. DenglerSW-Stromboli-20040928-1230x800.jpg
Stromboli is one of the eight Aeolian Islands, a volcanic arc north of Sicily.

In geology (and sometimes in archaeology), a high island or volcanic island is an island of volcanic origin. The term can be used to distinguish such islands from low islands, which are formed from sedimentation or the uplifting of coral reefs [1] (which have often formed on sunken volcanos).

Contents

Definition and origin

There are a number of "high islands" which rise no more than a few feet above sea level, often classified as "islets or rocks", while some "low islands", such as Makatea, Nauru, Niue, Henderson and Banaba, as uplifted coral islands, rise several hundred feet above sea level.

The two types of islands are often found in proximity to each other, especially among the islands of the South Pacific Ocean, where low islands are found on the fringing reefs that surround most high islands. Volcanic islands normally arise above a hotspot.

Habitability

High islands above a certain size usually have fresh groundwater, while low islands often do not, so high islands are more likely to be habitable.

See also

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Madeira began to form more than 100 million years ago in the Early Cretaceous, although most of the island has formed in the last 66 million years of the Cenozoic, particularly in the Miocene and Pliocene. The island is an example of hotspot volcanism, with mainly mafic volcanic and igneous rocks, together with smaller deposits of limestone, lignite and other sediments that record its long-running uplift.

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References

  1. Murphy, Raymond E. (July 1949). ""High" and "Low" Islands in the Eastern Carolines". Geographical Review . American Geographical Society. 39 (3): 425–439. doi:10.2307/210643. JSTOR   210643.