13. pieces of earth's crust move on top of the a. ocean b. mantle c. outer core d. inner core 14. the fact that ice floats on top of water is like the fact that a. the mantle causes earthquakes and volcanoes b. the mantle is colder than the crust c. the less dense crust sits on top of the mantle d. the crust is melting 15. a map of global earthquakes and volcanoes tells you a. where the edges of the continents are b. where the earth is the hottest c. nothing, it looks random d. where the plate boundaries are open