Final answer:
Continental lithosphere does not subduct because it is too buoyant. Oceanic plates are thin and dense enough to be subducted, but the thick and less dense continental plates are too buoyant to be forced beneath another plate. This is due to the composition and thickness of continental lithosphere.
Step-by-step explanation:
Continental lithosphere does not subduct because it is too buoyant.
Subduction occurs when one tectonic plate is forced beneath another. While oceanic plates are thin and dense enough to be subducted, the thick and less dense continental plates are too buoyant to be forced beneath another plate. This is due to the composition and thickness of continental lithosphere, which is predominantly made up of granite and has a lower density compared to the mafic rocks of the oceanic crust.
As a result, continental lithosphere rises higher on the mantle and forms continents, while oceanic lithosphere sinks into the mantle and forms basins, which later fill with water to create the planet's oceans.