The Earth is composed of four main layers from the innermost outwards: the core, mantle, crust, and lithosphere. The core is mostly iron and nickel with a temperature between 3000-5000°C. The mantle is between 1400-3000°C and composed of solid and molten rocks. The crust varies in thickness and composition depending on if it is continental or oceanic. The lithosphere is made up of tectonic plates that are constantly shifting. When plates diverge they form mid-ocean ridges, when they converge they can form subduction zones, volcanoes, and mountains, and when they move past each other they form transform boundaries often along fault lines.