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New oceanic lithosphere is constantly being produced at mid-ocean ridges and is recycled back to the mantle at subduction zones. As a result, oceanic lithosphere is much younger than continental lithosphere: the oldest oceanic lithosphere is about 170 million years old, while parts of the continental lithosphere are billions of years old. [12] [13]
The melt rises as magma at the linear weakness between the separating plates, and emerges as lava, creating new oceanic crust and lithosphere upon cooling. The first discovered mid-ocean ridge was the Mid-Atlantic Ridge , which is a spreading center that bisects the North and South Atlantic basins; hence the origin of the name 'mid-ocean ridge'.
Age of oceanic lithosphere; youngest (light colour) is along spreading centers Seafloor spreading , or seafloor spread , is a process that occurs at mid-ocean ridges , where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.
Cratons are the oldest and most stable parts of the continental lithosphere, and shields are exposed parts of them. Terranes are fragments of crustal material formed on one tectonic plate and accreted to crust lying on another plate, which may or may not have originated as independent microplates: a terrane may not contain the full thickness of ...
Sea floor spreading is where new oceanic lithosphere is being created by upwelling of material, unlike rifting where it only involved the stretching of the crust. Convection currents in the sub-lithospheric mantle are the driving mechanisms that caused sea floor spreading to occur. New lithosphere is made when hot material beneath ocean ridges ...
Lithosphere underlying ocean crust has a thickness of around 100 km (62 mi), whereas lithosphere underlying continental crust generally has a thickness of 150–200 km (93–124 mi). [5] The lithosphere and overlying crust make up tectonic plates, which move over the asthenosphere. Below the asthenosphere, the mantle is again relatively rigid.
Geology is largely the study of the lithosphere, or Earth's surface, including the crust and rocks. It includes the physical characteristics and processes that occur in the lithosphere as well as how they are affected by geothermal energy. It incorporates aspects of chemistry, physics, and biology as elements of geology interact.
The rifting of the continents created new oceans and seafloor spreading, which produces warmer, less dense oceanic crust. Lower-density, hot oceanic crust will not lie as deep as older, cool oceanic lithosphere. In periods with relatively large areas of new lithosphere, the ocean floors come up, causing the sea level to rise.