Final answer:
Basalt and granite are the major rocks forming the Earth's crust, with basalt found in the oceanic crust and granite in the continental crust. They have different compositions and densities.
Step-by-step explanation:
The major rocks forming the crust of the Earth are basalt and granite. Basalt is the primary rock found in the oceanic crust, while granite is predominant in the continental crust. Basalt is formed from the cooling of volcanic lava and is composed of elements like silicon, oxygen, iron, aluminum, and magnesium. Granite, on the other hand, is a different class of silicate rock made mostly of silicon and oxygen. Both types of crustal rocks have densities around 3 g/cm³.