What is the correct order (starting from the surface) of Earth's layers?

a. crust, outer core, inner core, mantle

b. mantle, outer core, inner core, crust

c. crust, mantle, outer core, inner core

d. outer core, inner core, crust, mantle

C. crust, mantle, outer core, inner core

Answer is C - crust, mantle, outer core, inner core.

Crust -

Crust is the outermost layer. The thickness of the crust is about 5 - 70 km.

Mantle -

Mantle is the second layer from the Earth's surface. Thickness is about 2890 km.

Mantle can be divided into two parts as upper mantle and lower mantle.

Outer core -

The thickness is about 2400 km. It is made from mostly iron and nickel.

Inner core -

The innermost part of the Earth is inner core. Mainly made from iron-nickel alloy. It is solid sphere which has a radius about 1220 km.