The center of the earth is thought to contain a core of solid iron with a radius of about 850 miles. Surrounding this central core is an outer core of liquid iron, about 1,200 miles thick.
And surrounding this outer core is the earth’s mantle, which is about 1,800 miles thick. The crust of the earth, which surrounds the mantle, ranges from only 4 to 45 miles thick.
So, from the surface of the earth to its outer core the distance is roughly 1,825 miles; from the surface to the inner core, it’s 3,025 miles; and from the surface to the very center, about 3,900 miles.