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Geologically, a volcanic island is an island of volcanic origin. The term high island can be used to distinguish such islands from low islands, which are formed from sedimentation or the uplifting of coral reefs (which have often formed on sunken volcanoes). [1]
The Canary Islands and the Hawaiian Islands are end members of a spectrum of intraplate volcanic oceanic islands that form in deep parts of the oceans, far from tectonic plate boundaries. [14] [15] These volcanic islands follow a sequence of several development stages.
There are generally three volcanic series from which the types of volcanic rock that occur in island arcs are formed: [15] [16] The tholeiitic series – basaltic andesites and andesites. The calc-alkaline series – andesites. The alkaline series – subgroups of alkaline basalts and the rare, very high potassium-bearing (i.e. shoshonitic) lavas.
The Samoa hotspot is marked 35 on map. Diagram showing how islands are formed by hotspots. The Samoa hotspot is a volcanic hotspot located in the south Pacific Ocean.The hotspot model describes a hot upwelling plume of magma through the Earth's crust as an explanation of how volcanic islands are formed.
Some islands are formed when coral reefs grow on volcanic islands that have submerged beneath the surface. [12] When these coral islands encircle a central lagoon, the island is known as an atoll. [13] The formation of reefs and islands related to those reefs is aided by the buildup of sediment in shallow patches of water.
The island is an example of hotspot volcanism, [1] with mainly mafic volcanic and igneous rocks, together with smaller deposits of limestone, lignite and other sediments that record its long-running uplift. Distribution of the islands of the archipelago (not including the Savage Islands)
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A volcanic arc (also known as a magmatic arc [1]: 6.2 ) is a belt of volcanoes formed above a subducting oceanic tectonic plate, [2] with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench , with the arc located further from the subducting plate than the trench.