Plate tectonics theory states that the earth’s major geologic features are the result of giant shifting tectonic plates. It is the unifying theory that combines ideas about geoclines and mountain building, continental drift, and seafloor spreading into one explanation. The theory was developed in the 1960s and is still being refined today.
• Geoclinal sediments are pushed up to create mountain chains along continent edges where plate movement causes continents to collide.
• Carried with the plate, continents “drift” around the earth’s surface in a pattern of colliding, rifting apart, and colliding again.
• Seafloors that spread apart and subduct into the earth’s interior are part of the shifting plates. Spreading seafloors push and pull continents along with them.