I think the correct answer is crust. I am really sorry if I am wrong.
Actually, California is one of the most geologically complex area in the world. Which contribute to its vast amount of water reserve.
This make California a desirable environment for a lot of plants and animals which makes California as one of the best wildlife reserves in the world
hope this helps
Because modern civilization had accomplish that
Tropical climates and rainforests are found near the equator