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Some volcanoes occur in the interiors of plates, and these have been variously attributed to internal plate deformation [15] and to mantle plumes. Tectonic plates may include continental crust or oceanic crust, or both. For example, the African plate includes the continent and parts of the floor of the Atlantic and Indian Oceans.
Where the plates meet, their relative motion determines the type of plate boundary (or fault): convergent, divergent, or transform. The relative movement of the plates typically ranges from zero to 10 cm annually. Faults tend to be geologically active, experiencing earthquakes, volcanic activity, mountain-building, and oceanic trench formation.
Extensional tectonics is associated with the stretching and thinning of the crust or the lithosphere.This type of tectonics is found at divergent plate boundaries, in continental rifts, during and after a period of continental collision caused by the lateral spreading of the thickened crust formed, at releasing bends in strike-slip faults, in back-arc basins, and on the continental end of ...
These smaller plates are often not shown on major plate maps, as the majority of them do not comprise significant land area. For purposes of this list, a minor plate is any plate with an area less than 20 million km 2 (7.7 million sq mi) but greater than 1 million km 2 (0.39 million sq mi).
Extension in the plate is a consequence of deformation at plate boundaries, thermal contraction, and isostatic adjustment. Extension originated at a spreading ridge around 80 Ma. The plate's stress field evolved over the next 30 million years, causing the region of extension and consequent volcanism to migrate south-southeast.
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 which was only incorporated in the theory of plate ...
The convergent boundary between the Eurasian plate and the Indian plate formed the Himalayas mountain range. The geodynamics of Central Asia is dominated by the interaction between the Eurasian plate and the Indian plate. In this area, many sub-plates or crust blocks have been recognized, which form the Central Asian and the East Asian transit ...
Some material may have accreted from volcanic island arcs which formed further out in the ocean and later collided with Gondwana as a result of plate tectonic movements. The igneous activity had started by 730 million years ago and continued until around 570 million years ago, [ 3 ] resulting in a region of volcanic islands within a shallow sea.