These shifts should be apparent to any future scientist who chemically analyzes exposed layers of rock from our era. (theatlantic.com)
He concludes that an unusually dense layer of rock made up the root in this region. (discovermagazine.com)
When we look out at the earth, we see its rigid crust, a relatively thin layer of rock that makes up the continents and the ocean floor. (sciencedaily.com)