1. Crust: This is the outermost, thinnest layer, made up of solid rock.

2. Mantle: A thick layer of mostly solid rock, but with a partially molten layer called the asthenosphere.

3. Outer Core: A liquid layer of iron and nickel.

4. Inner Core: A solid ball of iron and nickel, despite the intense heat.

It's important to note that the boundaries between these layers are not sharp lines but rather transition zones. Some scientists also divide these layers further into sublayers, especially the mantle.

For example, the mantle can be subdivided into the:

* Lithosphere: This includes the crust and the uppermost part of the mantle, forming a rigid layer.

* Asthenosphere: The partially molten layer within the mantle, which allows for the movement of tectonic plates.

* Mesosphere: The lower mantle, which is more solid.

So, while there are four main layers, you can find more detailed divisions within them depending on the level of detail you're considering.