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How do the Earth's continental and oceanic crust compare in density?
Question Date: 2018-02-02
Answer 1:

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 above sea level) than oceanic crust because continental crust is buoyant relative to oceanic crust and ‘floats” higher on the earth's mantle of density 3300 kg/m3.

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.

Answer 2:

The density of continental crust is usually about 2700 kg/m3 (2.7 g/cm3), and the density of oceanic crust is often 3000 kg/m3 (3.0 g/cm3).

Continental crust is lighter because it contains lighter minerals like quartz and feldspar.

Oceanic crust usually has heavier minerals like pyroxenes and amphiboles.

The continental crust stands higher than the oceanic crust (compare where we are to the average depth in the ocean!). Continental crust is higher partially because it's lighter.

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