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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).
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.
Tenerife is a volcanic island that has built up from the ocean floor during the last 20 million years. [79] [80] Underwater fissural eruptions produced pillow lava, which are produced by the rapid cooling of the magma when it comes in contact with water, obtaining their peculiar shape. This pillow-lava accumulated, constructing the base of the ...
A volcano needs a reservoir of molten magma (e.g. a magma chamber), a conduit to allow magma to rise through the crust, and a vent to allow the magma to escape above the surface as lava. The erupted volcanic material (lava and tephra) that is deposited around the vent is known as a volcanic edifice, typically a volcanic cone or mountain. [2] [22]
Rarotonga is a kidney-shaped volcanic island, 32 km (20 mi) in circumference, and 11.2 km (7.0 mi) wide on its longest (east-west) axis. [3] The island is the summit of an extinct Pliocene or Pleistocene volcano, which rises 5,000 metres (16,000 feet) from the seafloor. [4]
A volcanic arc is part of an arc-trench complex, which is the part of a subduction zone that is visible at the Earth's surface. A subduction zone is where a tectonic plate composed of relatively thin, dense oceanic lithosphere sinks into the Earth's mantle beneath a less dense overriding plate.
island arc A chain of volcanic islands or mountains formed by plate tectonics as an oceanic tectonic plate subducts under another tectonic plate and produces magma. isomorphic Two crystals that have similar shapes and sizes, usually through the angles. isotope different forms of an element each having different atomic mass (mass number).
The hotspot highway intersects in the area of the Cook Islands. The tracks shown in this map are no longer fully accurate due to further definition. The Rarotonga track has indifferent evidence. There are fifteen Cook Islands, all being related to extinct volcanoes that have erupted in the volcanic hotspot highway of the south-central Pacific ...