Journey to the centre of the Earth. Physical processes -The Earth and beyond - The Earth's layers Learning Points The Earth is made up of four layers. The crust is divided into plates. The mantle is the thickest layer. The inner core is solid iron and nickel. The outer core is molten iron and nickel. A Twig Curriculum Film. Delivering key learning points. Get straight to the facts in just three minutes – directly linked to core learning, Twig's curriculum films will fit neatly into your lesson plans.