» This article's about the composition of the Earth's crust. For other uses, see Sial (disambiguation). In geology, the sial's the upper layer of the Earth's crust made of rocks rich in silicates and aluminium minerals. It's sometimes equated with the continental crust because it's absent in the wide oceanic basins, but "sial"'s a geochemical term rather than a plate tectonic term. When the sial comes to the surface it's typically granitic, so sometimes this layer's called the 'granitic layer'… (More on Sial)