There are two types of lithosphere:
Oceanic lithosphere, which is associated with oceanic crust and exists in the ocean basins. Oceanic lithosphere is typically about 50–100 km thick
Continental lithosphere, which is associated with continental crust. Continental lithosphere has a range in thickness from about 40 km to perhaps 200 km, of which about 40 km is crust.
The lithosphere is divided into tectonic plates, which move gradually relative to one another.
Oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge. This thickening occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle, and causes the oceanic lithosphere to become increasingly dense with age. Oceanic lithosphere is less dense than asthenosphere for a few tens of millions of years, but after this becomes increasingly denser than asthenosphere.
When a continental plate comes together with an oceanic plate, at a subduction zones, the oceanic lithosphere always sinks beneath the continental.
New oceanic lithosphere is constantly being produced at mid-ocean ridges and is recycled back to the mantle at subduction zones.

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