By Lily Holmes
The first layer of the earth is the crust, that's the surface, like the crust on a piece of bread. The second layer is the mantle. Did you know the earth's mantle is 1,800 miles deep? The third layer is the outer core, like the core of an apple. Last the inner core, most scientist believe the inner core is a solid ball mostly out of iron and nickel.
How Mountains Form
When Earth's Plates Collide
When two plates collide a mountain forms, that's called ''Constructive''. When two plates come together one plate goes under the other. That's when a mountain is formed. That's called ''Subduction''.