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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]
Caroline plate – Minor oceanic tectonic plate north of New Guinea – 1,700,000 km 2 (660,000 sq mi) Cocos plate – Young oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America – 2,900,000 km 2 (1,100,000 sq mi) Indian plate – Minor plate that separated from Gondwana – 11,900,000 km 2 (4,600,000 sq mi)
In the second situation, the oceanic lithosphere always subducts because the continental lithosphere is less dense. The subduction process consumes older oceanic lithosphere, so oceanic crust is seldom more than 200 million years old. [20] The process of super-continent formation and destruction via repeated cycles of creation and destruction ...
Some lithospheric plates consist of both continental and oceanic lithosphere. In some instances, initial convergence with another plate will destroy oceanic lithosphere, leading to convergence of two continental plates. Neither continental plate will subduct. It is likely that the plate may break along the boundary of continental and oceanic crust.
The average density of the continental crust is about, 2.83 g/cm 3 (0.102 lb/cu in), [6] less dense than the ultramafic material that makes up the mantle, which has a density of around 3.3 g/cm 3 (0.12 lb/cu in). Continental crust is also less dense than oceanic crust, whose density is about 2.9 g/cm 3 (0.10 lb/cu in). At 25 to 70 km (16 to 43 ...
Specifically, oceanic lithosphere (lithosphere underneath the oceanic plates) and subcontinental lithosphere, is defined as a mechanical boundary layer that heats via conduction and the asthenosphere is a convecting adiabatic layer. In contrast to oceanic lithosphere, which experiences quicker rates of recycling, subcontinental lithosphere is ...
Continental rifting forms new ocean basins. Eventually the continental rift forms a mid-ocean ridge and the locus of extension moves away from the continent-ocean boundary. The transition between the continental and oceanic lithosphere that was originally formed by rifting is known as a passive margin.
Continental crust is a tertiary crust, formed at subduction zones through recycling of subducted secondary (oceanic) crust. [18] The average age of Earth's current continental crust has been estimated to be about 2.0 billion years. [21] Most crustal rocks formed before 2.5 billion years ago are located in cratons.