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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.
They also possess a distinct curved form, a chain of active or recently extinct volcanoes, a deep-sea trench, and a large negative Bouguer anomaly on the convex side of the volcanic arc. The small positive gravity anomaly associated with volcanic arcs has been interpreted by many authors as due to the presence of dense volcanic rocks beneath ...
Daikoku Seamount (Japanese: 大黒海山) is a submarine volcano located in the Northern Mariana Islands, in the western Pacific Ocean. It is situated on the Mariana volcanic arc. The seamount rises over 2,500 m (8,202 ft) meters from the seafloor, with its summit about 323 m (1,060 ft) below sea level.
Second, the Aegean Sea opened behind the arc because the crust was thinned and weakened there. Third, magma broke through the thinned crust to form a second arc composed of a volcanic chain. And finally, the Aegean Sea plate broke away from Eurasia in the new fault zone to the north. The extension is still ongoing.
The island, with an area of 12.6 square kilometres (4.9 sq mi), [4] represents the upper third of the volcano. [5] Its population was about 500 as of 2016 [update] . [ 2 ] The volcano has erupted many times and is constantly active with minor eruptions, often visible from many points on the island and from the surrounding sea, giving rise to ...
Gaua's geology is fairly typical of an immature volcanic island arc. The oldest part of the island is the southwestern corner, which consists largely of primitive basalts and ankaramites. [1] Most of the island is covered by the Santa Maria Pyroclastic Series, a mafic ignimbrite unit that was produced by the eruption that formed the caldera. [2]
About 40 submarine and island volcanoes make up the Northern Marianas arc. [6] NW Eifuku and Eifuku are small volcanoes at the northwestern end of a volcano chain that also includes Daikoku; [1] NW Eifuku is the smallest of these. [7] Daikoku also features hydrothermal venting [8] and has been considered a twin cone with Eifuku. [9]
A back-arc region is the companion region behind the volcanic arc. Many forearcs have an accretionary wedge which may form a topographic ridge known as an outer arc ridge that parallels the volcanic arc. A forearc basin between the accretionary wedge and the volcanic arc can accumulate thick deposits of sediment, sometimes referred to as an ...