* Crust: The crust is composed mostly of lighter elements like silicon, oxygen, aluminum, and iron. This makes it the least dense layer, with an average density of 2.7 g/cm³ (continental crust) and 3.0 g/cm³ (oceanic crust).
* Mantle: The mantle is made up of denser materials like iron, magnesium, and calcium. Its density ranges from 3.3 g/cm³ near the crust to 5.5 g/cm³ deeper down.
* Outer Core: The outer core is primarily composed of liquid iron and nickel. It has a density of 9.9 g/cm³.
* Inner Core: The inner core is solid, composed mainly of iron and nickel. It's the densest layer, with a density of 12.8 g/cm³.
Here's a simple analogy: Imagine a bowl of water with different objects floating in it. The lightest objects (like a cork) would represent the crust, while heavier objects (like pebbles or rocks) would represent the mantle, outer core, and inner core.
The lower density of the crust allows it to "float" on top of the denser mantle. This is similar to how a wooden block floats on water. The difference in density between the crust and the mantle is a key reason for plate tectonics, as the less dense crustal plates move on top of the flowing mantle.
