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How does oceanic crust contribute to the cycle of plate tectonics?

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Earth's lithosphere and upper mantle — oceanic crust A cross section of Earth's outer layers, from the crust through the lower mantle.

Oceanic crust is a fundamental component of the plate tectonic cycle, acting as both the product of crustal creation and the primary vehicle for crustal destruction. This continuous process maintains the Earth's constant volume.1

Creation at Divergent Margins

The cycle begins at oceanic ridges, where seafloor spreading occurs. As tectonic plates diverge, magma wells up from the mantle to form new oceanic crust. This new crust is hot and buoyant, creating elevated topography that helps push the plates apart.23

Evolution and Destruction

As the oceanic crust moves away from the spreading center, it cools and undergoes thermal contraction, becoming denser and sinking deeper into the ocean. Eventually, this older, denser crust reaches a subduction zone. Here, it descends into the mantle, where it is consumed. This process balances the creation of new crust at ridges.3451

Because oceanic crust is continuously recycled into the mantle, it is significantly younger—generally less than 200 million years old—compared to the much older continental crust.1