Thinking about the layers of our Earth. @APSscience @CampbellAPS By @CampbellAPS | November 30, 2017 Thinking about the layers of our Earth. @APSscience @CampbellAPS https://t.co/znWpmxR973 Posted in Daily News and tagged @CampbellAPS ← Thinking about the layers of our Earth. @APSscience @CampbellAPS Sliver of red peel=amount of plantable topsoil on Earth. 3rd gr. discusses soil &impact we have on our planet.… →