Question

Why do continental and oceanic crust differ in age

Answer 1

Because of Tectonic proceses. Divergent plate boundaries continually renew oceanic plates while subduction zones of convergent boundaries continually recycle them. As a result, the oldest oceanic rocks are less than 200 million years old.

Answer 2

Continental Crust is pretty much permanently above the surface, while oceanic crust is subducted back into the earth more often, so it is recycled more, making it younger.