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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]
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.
Below is a list of new islands created since the beginning of the 20th century by volcanism, erosion, glacial retreat, or other mechanisms. One of the most famous new volcanic islands is the small island of Surtsey, located in the Atlantic Ocean south of Iceland. It first emerged from the ocean surface in 1963.
North America and Northwest Africa separated while the Atlantic Ocean grew between them. Although this volcanic activity formed the ocean floor on which the Canary Islands were later formed, this seafloor spreading type of volcanic activity was not involved in the formation of the islands. [11]
Mascarene Islands were formed in a series of undersea volcanic eruptions 8–10 Ma, as the African plate drifted over the Réunion hotspot. Yellowstone hotspot, Twin Fall volcanic field, Idaho; 8.6 to 10 Ma. [65] Yellowstone hotspot, Grey's Landing Supereruption, Idaho; 8.72 Ma, 2,800 cubic kilometers (672 cu mi) of Grey's Landing Ignimbrite. [66]
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)
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.
Some of the eruptive structures formed during volcanic activity (counterclockwise): a Plinian eruption column, Hawaiian pahoehoe flows, and a lava arc from a Strombolian eruption. A volcanic eruption occurs when material is expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists.
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