The part of the earth's crust which is made up of silica and alumina is the_____?

The part of the earth's crust which is made up of silica and alumina is called Sial. Sial is the upper layer of the Earth's crust, which is composed primarily of silicon and aluminum. The name "sial" is derived from the first two letters of silicon and aluminum. Sial is less dense than sima, which is the lower layer of the crust that is made up of silica and magnesium. The sial layer is typically thicker beneath continents than beneath oceanic crust, as it forms the underlying structure for the continents.