The document summarizes plate tectonics theory. It explains that originally all continents were joined together in a supercontinent called Pangaea, which has since broken apart and drifted to their current locations. The Earth's crust is made up of plates that move relative to each other at boundaries where they converge, diverge or move past each other laterally. These plate interactions cause geological events like mountain building, volcanic activity, and the formation of ocean basins and trenches.