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The surface expressions of subduction zones are arc-trench complexes. On the ocean side of the complex, where the subducting plate first approaches the subduction zone, there is often an outer trench high or outer trench swell. Here the plate shallows slightly before plunging downwards, as a consequence of the rigidity of the plate. [18]
Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches. Oceanic trenches are prominent, long, narrow topographic depressions of the ocean floor. They are typically 50 to 100 kilometers (30 to 60 mi) wide and 3 to 4 km (1.9 to 2.5 mi) below the level of the surrounding oceanic ...
The Cascadia subduction zone is where the oceanic Juan de Fuca, Gorda and Explorer Plates subduct under the continental North American plate. The oceanic Pacific plate subducts under the North American plate (composed of both continental and oceanic sections) forming the Aleutian Trench. The oceanic Pacific plate subducts beneath the ...
Arc magmas account for more than 20% of terrestrially produced magmas [2] and are produced by the dehydration of minerals within the subducting slab as it descends into the mantle and are accreted onto the base of the overriding continental plate. [3] Subduction zones host a unique variety of rock types formed by the high-pressure, low ...
The Kermadec–Tonga subduction zone is a convergent plate boundary that stretches from the North Island of New Zealand northward. The formation of the Kermadec and Tonga plates started about 4–5 million years ago. Today, the eastern boundary of the Tonga plate is one of the fastest subduction zones, with a rate up to 24 cm/year (9.4 in/year ...
The Mariana Trench is the deepest known submarine trench, and the deepest location in the Earth's crust itself. [38] It is a subduction zone where the Pacific Plate is being subducted under the Mariana Plate. [3] At the deepest point, the trench is nearly 11,000 m deep (almost 36,000 feet).
Most of the material in the accretionary wedge consists of marine sediments scraped off from the downgoing slab of oceanic crust, but in some cases the wedge includes the erosional products of volcanic island arcs formed on the overriding plate. An accretionary complex is a current (in modern use) or former accretionary wedge.
[11] [12] Marianas Trench is an example of a deep slab, thereby creating the deepest trench in the world established by a steep slab angle. [13] Slab breakoff occurs during a collision between oceanic and continental lithosphere, [14] allowing for a slab tear; an example of slab breakoff occurs within the Himalayan subduction zone. [4]