The continental crust has a density of roughly 2.7 g/cm^3. The oceanic crust has a density of 2.9 g/cm^3. Even though the difference in density may not appear significant, the fact that the continental crust is less dense than the oceanic crust leads to the continental crust rising above the oceanic crust when the two plates meet in subduction zones. The heavier oceanic crust is subducted (pushed below) the less dense continental crust.
