Final answer:
Density increases as one gets closer to Earth's core due to the compression of mantle rock and the presence of heavy, compressed metallic elements in the core.
Step-by-step explanation:
As one gets closer to the core of the Earth, the density increases. This is because Earth's mantle rock can deform and flow, leading to greater compression caused by the weight of the overlying material. The mantle's density increases downward from about 3.5 g/cm³ to more than 5 g/cm³, and upon reaching the core, densities are even higher due to the presence of heavy elements like iron, nickel, and sulfur.
The core itself is divided into a liquid outer core and a solid inner core, both of which are subject to immense pressures that create densities much greater than those found in the mantle or crust. Earth's core, with a large amount of compressed metallic elements, has far greater densities approaching that of an atomic nucleus.