Answer:
SiAl are the rocks that are rich in silican and aluminium.
Step-by-step explanation:
SiAl is a geological term that refers to the composition of silica and aluminium on the upper layer of the earth's crust. The SiAl ( silica and aluminium) elements have less density than the other minerals of the earth's crust.
SiAl is around 25Km thick from the surface and thin near the ocean floor. The rocks of SiAl layer are known as felsic.