Final answer:
The oceanic crust is the type of crust that is thinner and predominantly made of basalt, which is notably different from the thicker continental crust composed mostly of granite.
Step-by-step explanation:
The type of crust that is thinner and usually made mostly of basalt is the oceanic crust. The oceanic crust covers 55% of Earth's surface and lies mostly submerged under the oceans. It is typically about 6 kilometers thick and is composed of volcanic rocks called basalt.
Basalt is produced by the cooling of volcanic lava and consists primarily of the elements silicon, oxygen, iron, aluminum, and magnesium. In contrast, the continental crust is composed predominantly of a different volcanic class of silicates called granite and is much thicker, ranging from 20 to 70 kilometers.