To compare the densities of the Earth's crust, mantle, and core:
- The Earth's crust is the least dense layer, with an average density of about 2.2 to 2.9 g/cm³. Continental crust is less dense than oceanic crust, due to its felsic (silica and aluminum rich) composition versus the denser mafic (iron and magnesium rich) oceanic crust.
- The mantle has a higher density than the crust, averaging from about 3.3 to 5.7 g/cm³. The upper mantle is less dense (~3.3 to 3.9 g/cm³) than the lower mantle (up to about 5.7 g/cm³). The mantle is composed mostly of silicate minerals rich in iron and magnesium.
- The core is the densest layer: the outer core has a density around 9.9 to 12.2 g/cm³, and the inner core is even denser, about 12.6 to 13.1 g/cm³. The core is primarily iron and nickel.
In summary, density increases progressively from the crust, through the mantle, and is highest in the core. This gradient reflects the composition and pressure conditions of each layer. The crust is lightest and least dense, the mantle is denser intermediate, and the core is densest.