Final answer:
Continental crust is older than oceanic crust because the latter is recycled through mantle convection, where oceanic plates are formed and then subducted back into the mantle.
Step-by-step explanation:
The reason why continental rocks are much older than oceanic crust is because oceanic crust is continually recycled through the process of convection in the earth's mantle. This process involves the upward flow of warmer material and the sinking of cooler material. New oceanic crust forms at divergent plate boundaries, like those found in the Atlantic Ocean, and then it moves toward subduction zones where one plate dives beneath another, often marked by deep ocean trenches. When these plates are forced down into the upper mantle, the oceanic crust eventually melts, becoming part of the convection cycle. This recycling process makes the oceanic crust relatively young compared to the thicker, less dense continental crust which does not subduct and therefore, tends to be much older.