Oceanography (2+1)

The Crust

Crust is the uppermost and thinnest segment of the earth. Thickness varies from 5 to 50 kilometers. It is enriched with basaltic content in the oceanic crust and granitic in the continental crust. The crust of the earth rests on the Moho and is 6 to 50 kilometers thick. The crust is thicker under continents and diminishes progressively under ocean basins. It may be 50 kilometers under mountainous regions of continents and may be lesser than 5 kilometers under ocean. The crust is divided into two principal layers: the lower layer, sima, which carries heavy concentrations of silica and magnesium, whereas the upper layer, sial, has heavy concentration of silica and aluminium.