Inside, the Earth is similar to the other terrestrial planets. It has an outer, solid [[rock]] layer called the [[crust (geology)|crust]]. Everything that lives on Earth is on top of the crust. Below that is a layer of thick, [[semi-liquid]] rock called the [[mantle]]. Under that is a thin liquid layer called the outer [[planetary core|core]] and then the solid [[iron]] inner core.
The thickness of the crust changes. On land the average is between 30–50 kilometers thick. Under the [[ocean]]s in some places it is only 6 kilometers thick.<ref>{{cite web|url=http://www.agu.org/reference/gephys/15_tanimoto.pdf|title=Crustal Surface of the Earth|author=Toshiro Tanimoto|accessdate=2009-08-02|publisher=American Geophysical Union}}</ref> The inside of the Earth is very hot, the temperature of the outer core may be as high as {{convert|7000|°C|°F}}.<ref>{{cite web|url=http://chianti.geol.ucl.ac.uk/~dario/pubblicazioni/PTRSA2002.pdf|title=The ab initio simulation of the Earth’s core|date=2002-04-25|accessdate=2009-08-02|publisher=The Royal Society|author=D. Alfé|coauthors=M. J. Gillan, L. Vočadlo, J. Brodholt, G. D. Price|publisher=D. Alfé}}</ref>
