Accretionary wedge

An accretionary wedge (from Latin: Accretio "increase " ) is a geological structure which forms the upper, about moving lithospheric plate under plate tectonic processes during subduction of oceanic crust at the front (English forearc ). It is caused by the accretion ( addition ) of sediments, partly of oceanic crust, and is characterized by strong deformation of the accreted material is decomposed by innumerable thrusts.

Formation

Along the plate boundary where the denser plate is subducted, forms on the basis of their buckling under the top plate a deep furrow, which is referred to as deep-sea channel. At the side of the upper, with extended plate out work in the field of deep-water channel by the collision of two tectonic plates are enormous mechanical pressure and friction forces. This lead to the marine sediments and partly layers of the oceanic crust sliced ​​off from the subducting plate and are attached in a wedge-shaped accumulation under the edge of the upper plate ( tectonic underplating ). By the end of this accumulation is often solve sediment masses and mud flows ( Olisthostrom ), landslides and turbidites shifts in the offshore deep-water channel, where these sediments are designated according to their consolidation as flysch.

Plate tectonic

Akkretionskeile are typically locate at destructive plate boundaries such as island arcs and plate boundaries from the Cordilleras or Andes type. They often occur in conjunction with other structures that are generated by the Subduktionsvorgang. The overall system has the following elements: outer bulge ( engl. outer swell or bulge ) - accretionary prism (English accretionary prism ) - Sheet - gutters - gap ( engl. arc- trench gap or forearc ) - island arc or continental margin arc - backarc area or marginal basin ( engl. back arc basin, marginal basin ).

Akkretionskeile of island arcs

Island arcs are structures that occur as a result of plate tectonics. They arise where two oceanic lithospheric plates move toward each other and it finally comes to subduction. This is one of the two lithospheric plates - mostly the older of the two, since they are already more grown cold in the rule and thus has a higher specific gravity - "pressed" under the other and forced to dive into the mantle.

The accretionary prism is the actual island arc in front as a kind of external threshold that has nothing to do with the Inselbogenvulkanismus. Depending on the accretion, ie growth rate, and sea depth of the accretionary wedge can rise to the sea surface over.

38394
de