1. Crust: The outermost layer, thin and rocky, where we live. It's divided into oceanic crust (thinner, denser) and continental crust (thicker, less dense).
2. Mantle: The thickest layer, mostly solid rock but with a semi-molten layer called the asthenosphere. It's responsible for plate tectonics.
3. Outer Core: Liquid iron and nickel, generating Earth's magnetic field.
4. Inner Core: Solid iron and nickel, incredibly dense and hot, due to immense pressure.
