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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 ...
Depth of oceanic trenches seems to be controlled by age of the oceanic lithosphere being subducted. [5] Sediment fill in oceanic trenches varies and generally depends on abundance of sediment input from surrounding areas. An oceanic trench, the Mariana Trench, is the deepest point of the ocean at a depth of approximately 11,000 m (36,089 ft).
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).
The oceanic trench and the associated outer trench swell mark where Pacific Plate begins its descent into the IBM Subduction Zone. The IBM trench is where the Pacific Plate lithosphere begins to sink. The IBM trench is devoid of any significant sediment fill; the ~400 m or so thickness of sediments is completely subducted with the downgoing plate.
At zones of ocean-to-ocean subduction a deep trench to forms in an arc shape. The upper mantle of the subducted plate then heats and magma rises to form curving chains of volcanic islands e.g. the Aleutian Islands, the Mariana Islands, the Japanese island arc.