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A trench marks the position at which the flexed, subducting slab begins to descend beneath another lithospheric slab. Trenches are generally parallel to and about 200 km (120 mi) from a volcanic arc. Much of the fluid trapped in sediments of the subducting slab returns to the surface at the oceanic trench, producing mud volcanoes and cold seeps.
Subduction zones are marked by oceanic trenches. The descending end of the oceanic plate melts and creates pressure in the mantle, causing volcanoes to form. Back-arc basins can form from extension in the overriding plate, in response to the displacement of the subducting slab at some oceanic trenches. This paradoxically results in divergence ...
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 example). The fore-arc basin forms between the fore-arc ridge and the island arc; it is a region of undisturbed flat-bedded sedimentation.
Oceanic trenches are narrow topographic lows that mark convergent boundaries or subduction zones. Oceanic trenches average 50 to 100 km (31 to 62 mi) wide and can be several thousand kilometers long. Oceanic trenches form as a result of bending of the subducting slab.
Divergent boundaries (constructive boundaries or extensional boundaries). These are where two plates slide apart from each other. At zones of ocean-to-ocean rifting, divergent boundaries form by seafloor spreading, allowing for the formation of new ocean basin, e.g. the Mid-Atlantic Ridge and East Pacific Rise. As the ocean plate splits, the ...
Continental-continental divergent/constructive boundary Oceanic divergent boundary: mid-ocean ridge (cross-section/cut-away view). In plate tectonics, a divergent boundary or divergent plate boundary (also known as a constructive boundary or an extensional boundary) is a linear feature that exists between two tectonic plates that are moving away from each other.
Movements of tectonic plates and the formation of oceanic ridges and trenches. Convergent boundary: the plates collide, and eventually the denser one slides underneath the lighter one, a process known as subduction. This type of interaction can take place between an oceanic and an oceanic crust, creating a so-called oceanic trench.
Oceanic trenches are the deepest parts of the ocean floor. Beyond the trench is the forearc portion of the overriding plate. Depending on sedimentation rates, the forearc may include an accretionary wedge of sediments scraped off the subducting slab and accreted to the overriding plate. However, not all arc-trench complexes have an accretionary ...