qSome lithospheric plates are composed primarily of oceanic crustal material, whereas
others are composed primarily of continental materials.
qThe continents stand, on average, about 4.5 km above the floor of the ocean
basins.
qContinental crust is relatively light (density 2.7 g/cm3), whereas oceanic crust is
relatively heavy (density close to 3.2 g/cm3).