The Crust, Mantle, Outer Core, and Inner Core are the layers of the Earth. The Crust affects the land by how smooth or rough the land is. The Mantle is the thickest layer, making up about 2/3 of Earth's mass. The Outer Core is melted metal. The Inner Core is made of metal and makes up about 1/3 of the Earth. It affects the Earth's surface by forming earthquakes and volcanoes.