<P> Oceanic crust is the uppermost layer of the oceanic portion of a tectonic plate . It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates . The crust overlies the solidified and uppermost layer of the mantle . The crust and the solid mantle layer together constitute oceanic lithosphere . </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 sial, generally less than 10 kilometers thick; however it is denser, having a mean density of about 3.0 grams per cubic centimeter as opposed to continental crust which has a density of about 2.7 grams per cubic centimeter . </P>

Where would you expect to find new oceanic crust being created