■ INTERNAL STRUCTURE OF THE EARTH.
◇ The interior of the earth is made up of several concentric layers of which the crust, the mantle, the outer core and the inner core are significant because of their unique physical and chemical properties.
◇ The crust is a silicate solid, the mantle is a viscous molten rock, the outer core is a viscous liquid, and the inner core is a dense solid.
◇ Mechanically, the earth’s layers can be divided into lithosphere, asthenosphere, mesospheric mantle (part of the Earth’s mantle below the lithosphere and the asthenosphere), outer core, and inner core.
◇ Chemically, Earth can be divided into the crust, upper mantle, lower mantle, outer core, and inner core.