The mantle is the thickest of the four main layers of the Earth.

Here's a breakdown of the layers and their approximate thicknesses:

* Crust: 5-70 km (3-44 miles)

* Mantle: 2,890 km (1,796 miles)

* Outer Core: 2,200 km (1,367 miles)

* Inner Core: 1,220 km (758 miles)