The document discusses continental drift and plate tectonics. It introduces Alfred Wegener's theory of continental drift from 1912, which proposed that the continents were once joined together in a supercontinent called Pangaea. Evidence that supported continental drift included matching coastline shapes, matching fossil and rock formations on separated continents, and mountain ranges formed perpendicular to the drift direction. Seafloor spreading provided further evidence as studies showed rocks were youngest at mid-ocean ridges and older further away, with matching magnetic patterns on either side. This led to the theory of tectonic plates, with ocean floors spreading at ridges and subducting at zones. Plate boundaries were classified as divergent, convergent, or transform.