The dirt, soil and rocks on the Earth's surface are directly above the Earth’s crust. The crust forms the continents and ocean basins of the world, and the molten mantle lies below the crust. Beyond the mantle lies the Earth’s core, which has separate inner and outer segments.
The Earth’s crust is primarily composed of alumino-silicates and varies greatly in thickness. The thinnest portions of oceanic crust are only about 6 miles thick, while the thickest continental plates have portions that are more than 43 miles thick. The mantle is composed primarily of ferro-magnesium silicates. Approximately 1,800 miles thick, the mantle is much thicker than the crust and contains most of the planet’s heat. This heat causes convection currents, which drives the process of plate tectonics, as explained by Universe Today.
The outer layer of the Earth’s core is composed of nickel-iron alloys, while the inner core is thought to be composed almost entirely of iron. The outer core is about 1,400 miles thick, while the inner core is only 750 miles thick. According to Universe Today, the inner core is thought to spin at a different rate than the rest of the planet. This creates the Earth’s magnetic field, which protects the planet from the Sun’s harmful rays.