<P> Oceanic crust is primarily composed of mafic rocks , or sima , which is rich in iron and magnesium . It is thinner than continental crust , or ( er it is denser , having a mean density of about 2.9 grams per cubic centimeter as opposed to continental crust which has a density of about 2.7 grams per cubic centimeter . </P>
<P> Oceanic crust is primarily composed of mafic rocks , or sima , which is rich in iron and magnesium . It is thinner than continental crust , or ( er it is denser , having a mean density of about 2.9 grams per cubic centimeter as opposed to continental crust which has a density of about 2.7 grams per cubic centimeter . </P>
earth 's crust under oceanic is composed of this rock type
earth 's crust under oceanic is composed of this rock type
mafic rocks , or sima
mafic rocks , or sima