If you were to slice through it, you would see the Earth is divided into distinct layers. On top is the relatively thin crust where we live. Beneath that is the 2,900 km thick mantle layer. Then, enclosed within the mantle is the innermost metallic core of our planet. If you were to slice through it, you would see the Earth is divided into distinct layers. On top is the relatively thin crust where we live. Beneath that is the 2,900 km thick mantle layer. Then, enclosed within the mantle is the innermost metallic core of our planet. Earth Sciences Phys.org – latest science and technology news stories