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A model of the subducting Farallon slab under North America. In geology, the slab is a significant constituent of subduction zones. [1] Subduction slabs drive plate tectonics by pulling along the lithosphere to which they attach in a process known as slab pull and by inducing currents in the mantle via slab suction. [2]
The failure of a flat slab is associated with ignimbritic volcanism and the reverse migration of arc volcanism. [2] Multiple working hypotheses about the cause of flat slabs are subduction of thick, buoyant oceanic crust (15–20 km) [6] and trench rollback accompanying a rapidly overriding upper plate and enhanced trench suction. [7]
Cross section depicting the tectonic evolution of the Bangong-Nujiang suture zone. 1. Slab rollback of the oceanic crust between the Lhasa and Amdo terranes causes an Early Jurassic oceanic back-arc basin to form between the Amdo and Qiangtang terranes. 2. During the Early-Middle Jurassic, subduction of oceanic crust beneath the Amdo terrane ...
Slab rollback is not always a continuous process suggesting an episodic nature. [34] The episodic nature of the rollback is explained by a change in the density of the subducting plate, such as the arrival of buoyant lithosphere (a continent, arc, ridge, or plateau), a change in the subduction dynamics, or a change in the plate kinematics. The ...
Slab suction is weaker than slab pull, which is the strongest of the driving forces. When measuring the forces of these two mechanisms, slab pull in subducting plate boundaries for upper mantle slabs is 1.9 × 10^21 N. [ clarification needed ] In comparison slab suction in the upper and lower mantle totaled 1.6 × 10^21 N. [ 3 ]
The backward motion of the subduction zone relative to the motion of the plate which is being subducted is called trench rollback (also known as hinge rollback or hinge retreat). As the subduction zone and its associated trench pull backward, the overriding plate is stretched, thinning the crust and forming a back-arc basin.
The pulling effect of the slab as it goes down into the mantle causes a rollback motion of the trench, which also applies stress on the back-arc region of the upper plate. [2] However, this last process has less of an impact on deformation compared to upper plate motion. [2] Back-arcs can form on either oceanic crust or continental crust.
In plate tectonics, slab detachment or slab break-off may occur during continent-continent or arc-continent collisions. When the continental margin of the subducting plate reaches the oceanic trench of the subduction zone , the more buoyant continental crust will in normal circumstances experience only a limited amount of subduction into the ...