The average density of earth continental crust is
about 2600 kg/m3 or 2.7 gm/ cc.
The average density of oceanic crust is about 2900
kg/m3 or 2.9 g/cc.
Continental crust stands higher (most is
sea level) than oceanic crust because continental
crust is buoyant relative to oceanic crust and
‘floats” higher on the earth's mantle of density
The word “float” needs to be understood on a
geologic timescale of tens of millions of years
because it is only on THAT timescale that the
earth at depth behaves like a VERY VERY viscous
fluid, but a fluid nonetheless.