Q: Given a scientific passage and an answer, generate a question for the given answer.
Passage: You can't go to the mantle but small pieces of the mantle can come to you. Kimberlite forms deep in the mantle and is erupted violently into the crust. Kimberlite can contain diamonds. Most kimberlites reached the surface much earlier in Earth history. Answer: crust
A:
What is the upper most level of earth's layers called?