Flexi Says: Core, mantle, and crust are divisions based on composition: The crust is less than 1% of Earth by mass. The two types are oceanic crust and continental crust. The mantle is hot, dense, dark (ultramafic) rock. It represents about 68% of Earth's mass. The core is mostly iron metal. The core makes up about 31% of the Earth. Earth's metallic core has two layers: a solid inner layer and a liquid outer layer. By mechanical properties, the crust and upper mantle are divided into lithosphere and asthenosphere.
