Free trade areas, customs unions, common markets, and economic unions
The layers will be denser as you move from the crust to the inner core.
The density are as the following:
crust (2.55 g/cm³)
upper mantle (3.9 g/cm³)
lower mantle (5 g/cm³)
outer core (11.05 g/cm³)
inner core (12.95 g/cm³)
Thus we can also see that the inner core is the densest layer.
Hope it helps!
