Figure 10.260 illustrates that a block of pine floats higher than the same-sized block of oak because the pine is less dense. Continental rocks have an average density of about 2.7 grams per cubic centimeter, whereas oceanic crust is somewhat more dense(about 30 grams per cubic centimeter). Thus, continental crust is less dense and thicker than oceanic crust, which largely explains the elevation differences between the continents and the ocean basins.