The outside layer of our planet is an active place. Earth's crust is always growing and changing. But do you know how Earth's crust forms? And what happens when its plates shift suddenly? Find out more about the moves that make mountains and ocean ridges in this interesting book! As part of the Searchlight Books collection, this series sheds light on Earth Science topics for readers who really dig it! Useful diagrams, eye-catching photos, and caption call-outs will help you find the answers you crave. Book jacket.