1. Crust: The thin, outermost layer of Earth, made of solid rock.
2. Mantle: The thickest layer, made of mostly solid rock but with a partially molten layer called the asthenosphere.
3. Moho Barrier: This isn't actually a distinct layer, but rather a boundary between the crust and the mantle. It's marked by a significant change in seismic wave velocity.
4. Core: The innermost layer, consisting of a liquid outer core and a solid inner core, primarily composed of iron and nickel.
