Why is the Earth layered and how is each layer different?
The Earth having layer is a theory, there is no real reason for it to be layered, but each layer is believe to be different in composition, temperature and in state.
The inner core is solid and made up of iron and nickel with immense temperatures up to 5,500 degrees centigrade.
The outer core is a liquid layer, made up of iron and nickel, with temperature close to 5,500 degrees centigrade.
The mantle, is a semi-liquid semi-solid rock, known a magma, with a thickness of up to 2,900 km, it is cooler and harder nearer the crust, and hot and liquid like nearer the core, this semi-solid rock can have convection currents form in it, which is a factor of continental drift, caused by the radioactive processes that occur in the core that release heat which cause the currents.
The crust is the habitable layer of Earth which we live upon, which is between 0-60 km thick, which is split up into 'tectonic plates' of which all the continents sit upon, which these plates are split into continental and oceanic.