1. Crust: This is the outermost and thinnest layer, made up of mostly igneous, sedimentary, and metamorphic rock. It's divided into oceanic crust (thinner and denser) and continental crust (thicker and less dense).

2. Mantle: The thickest layer, composed mostly of solid rock but capable of flowing very slowly over long periods. This layer is responsible for plate tectonics.

3. Outer Core: A liquid layer primarily composed of iron and nickel. It's responsible for generating the Earth's magnetic field.

4. Inner Core: The innermost layer, a solid sphere of iron and nickel, despite being extremely hot. The intense pressure from the layers above is the reason it remains solid.

Let me know if you want more detail about any of these layers!