The document discusses plate tectonics and how it has shaped the Earth's surface over geologic time. It describes how the Earth's crust is made up of large plates that move over convection currents in the mantle. When plates diverge new crust forms as magma rises, and when they converge mountains can form through collision or subduction zones can create volcanoes. It then outlines the four eras of geologic time - Precambrian, Paleozoic, Mesozoic, and Cenozoic - and some of the key events and lifeforms that emerged during each era, which ultimately gave the Earth its current shape and features through mountain building and erosion.