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Plate tectonics (from Latin tectonicus, from Ancient Greek τεκτονικός (tektonikós) 'pertaining to building') [1] is the scientific theory that Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago.
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 slab affects the convection and evolution of the Earth's mantle due to the insertion of the hydrous oceanic lithosphere. [3]
On a global scale, surface expression of this convection is the tectonic plate motions and therefore has speeds of a few cm per year. [15] [16] [17] Speeds can be faster for small-scale convection occurring in low viscosity regions beneath the lithosphere, and slower in the lowermost mantle where viscosities are larger. A single shallow ...
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]
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 tectonics in 1970, but still results in net destruction when summed over major plate boundaries. [2]
Earth's tectonic evolution over time from a molten state at 4.5 Ga, [11] to a single-plate lithosphere, [24] to modern plate tectonics sometime between 3.2 Ga [25] and 1.0 Ga [26] Primordial heat energy comes from the potential energy released by collapsing a large amount of matter into a gravity well, and the kinetic energy of accreted matter.
Plate tectonics (from Latin tectonicus, from Ancient Greek τεκτονικός (tektonikós) 'pertaining to building') is the scientific theory that Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago.
For purposes of this list, a major plate is any plate with an area greater than 20 million km 2 (7.7 million sq mi) African plate – Tectonic plate underlying Africa – 61,300,000 km 2 (23,700,000 sq mi) Antarctic plate – Major tectonic plate containing Antarctica and the surrounding ocean floor – 60,900,000 km 2 (23,500,000 sq mi)