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When the lower plate subducts at a shallow angle underneath a continent (something called "flat-slab subduction"), the subducting plate may have enough traction on the bottom of the continental plate to cause the upper plate to contract by folding, faulting, crustal thickening, and mountain building.
The continental crust on the downgoing plate is deeply subducted as part of the downgoing plate during collision, defined as buoyant crust entering a subduction zone. An unknown proportion of subducted continental crust returns to the surface as ultra-high pressure (UHP) metamorphic terranes, which contain metamorphic coesite and/or diamond plus or minus unusual silicon-rich garnets and/or ...
The oceanic Nazca plate subducts beneath the continental South American plate at the Peru–Chile Trench. Just north of the Nazca plate, the oceanic Cocos plate subducts under the Caribbean plate and forms the Middle America Trench. Oceanic crust of the South American plate subducts under the Caribbean plate in the Lesser Antilles subduction zone.
When two oceanic plates migrate towards each other, one subducts below the other. Generally, the oceanic plate with higher density subducts beneath and the other one overrides the down-going slab. [1] The process continues until a buoyant continental margin sitting on the top of the subducting plate is introduced into the down-going slab.
Subduction zones are areas where one lithospheric plate slides beneath another at a convergent boundary due to lithospheric density differences. These plates dip at an average of 45° but can vary. Subduction zones are often marked by an abundance of earthquakes, the result of internal deformation of the plate, convergence with the opposing ...
The subduction of bathymetric highs such as aseismic ridges, oceanic plateaus, and seamounts has been posited as the primary driver of flat slab subduction. [3] The Andean flat slab subduction zones, the Peruvian slab and the Pampean (Chilean) flat slab, are spatially correlated with the subduction of bathymetric highs, the Nazca Ridge and the Juan Fernandéz Ridge, respectively.
The denser oceanic crust of one plate subducts below the less dense continental crust of another plate. Convergent active margins are the most common type of active margin. Transform active margins are more rare, and occur when an oceanic plate and a continental plate are moving parallel to each other in opposite directions.
Associated with the slab suction force is the idea of trench roll-back. As a slab of oceanic crust subducts into the mantle, the hinge of the plate (the point where the plate begins to subduct) tends to regress away from the trench. This occurs because there is effectively no force to hold the hinge in one location. [5]