Here's a breakdown of Earth's layers and their densities:

* Crust: The thinnest, outermost layer. Density ranges from 2.7 to 3.0 g/cm³.

* Mantle: The thickest layer, composed mostly of silicate minerals. Density ranges from 3.3 to 5.7 g/cm³.

* Outer Core: A liquid layer composed mostly of iron and nickel. Density ranges from 9.9 to 12.2 g/cm³.

* Inner Core: A solid sphere of mostly iron and nickel. Density is incredibly high, around 13.0 g/cm³.

The immense pressure at Earth's center forces the iron and nickel of the inner core into a solid state despite its extremely high temperature. This pressure is the primary factor contributing to the inner core's exceptional density.