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A schematic cross-section of an island arc from trench to back-arc basin. Below are some of the generalized features present in most island arcs. Fore-arc: This region comprises the trench, the accretionary prism, and the fore-arc basin. A bump from the trench in the oceanward side of the system is present (Barbados in the Lesser Antilles is an ...
They are found on the oceanward side of island arcs and Andean-type orogens. [3] Globally, there are over 50 major ocean trenches covering an area of 1.9 million km 2 or about 0.5% of the oceans. [4] Trenches are geomorphologically distinct from troughs.
The Tonga–Kermadec Ridge is an oceanic ridge in the south-west Pacific Ocean underlying the Tonga–Kermadec island arc.It is a result of the most linear, fastest converging, and seismically active subduction boundary on Earth, the Kermadec–Tonga subduction zone, and consequently has the highest density of submarine volcanoes.
A number of microplates exist between the two major plates and host various back-arc structures of which the largest are the volcanic Tonga–Kermadec Ridge, the actively spreading Lau Basin and the Havre Trough. At the southern end there is a transition to the transform faults of the South Island of New Zealand.
The Tonga Trench-Arc system is an extension-dominated, non-accretionary convergent margin. The Pacific plate is being subducted westward in the trench. The convergence rate has been estimated to 15 cm/year (5.9 in/year) but GPS measurements in the northern trench indicate a convergence rate of 24 cm/year (9.4 in/year) there. [ 10 ]
The Aleutian island arc formed ~50-55 ma as a result of Kula Plate subduction under the North American Plate before the Pacific plate arrived. [3] There are three stratigraphic units of the Aleutian island arc: volcanic rocks from ~55-33 ma, marine sedimentary rocks from ~23-33 ma, and sedimentary and igneous rocks from ~5 ma-present. [3]
The Aleutian Trench (or Aleutian Trough) [1] is an oceanic trench along a convergent plate boundary which runs along the southern coastline of Alaska and the Aleutian islands. The trench extends for 3,400 kilometres (2,100 mi) from a triple junction in the west with the Ulakhan Fault and the northern end of the Kuril–Kamchatka Trench , to a ...
Oceanic lithosphere moves into trenches at a global rate of about a tenth of a square meter per second. Trenches are generally parallel to a volcanic island arc, and about 200 km from a volcanic arc. Oceanic trenches typically extend 3 to 4 km (1.9 to 2.5 mi) below the level of the surrounding oceanic floor.