1. Crust: This is the outermost layer, thin and brittle, composed of igneous, sedimentary, and metamorphic rocks. It is divided into oceanic crust (thinner, denser) and continental crust (thicker, less dense).
2. Mantle: This is the thickest layer, made up of mostly solid rock, but with a partially molten layer called the asthenosphere. It is where the convection currents that drive plate tectonics originate.
3. Core: The innermost layer, composed primarily of iron and nickel. It is divided into the outer core (liquid) and the inner core (solid, due to immense pressure).
Let me know if you'd like more detail about any of these layers!
