How do oceanic crust and continental crust differ in density and age?

• A. Oceanic crust is denser and younger than continental crust
• B. Oceanic crust is denser and older than continental crust
• C. Continental crust is denser and younger than oceanic crust
• D. Continental crust is darker and thinner than oceanic crust

Answer: (A)

The key idea here is that oceanic and continental crust differ in density and age because of their rock types and how they form and recycle at plate boundaries. Oceanic crust is mainly basalt, which is a dense, dark mafic rock, giving it a higher density. Continental crust, on the other hand, is largely granitic and less dense, so it sits higher on the mantle. Because oceanic crust forms at mid-ocean ridges and is constantly produced and then recycled back into the mantle at subduction zones, it is relatively young overall. Continental crust builds up over long times and contains much older rock, with portions billions of years old, and it tends to persist rather than be recycled as quickly. So oceanic crust is denser and younger than continental crust, which is why that statement best describes the difference.