From continental drift to plate tectonics
In 1912 Alfred Wegener argued the continents once formed a single landmass, Pangaea, citing matching coastlines and fossils across the Atlantic, but he couldn't explain what moved them. In the 1960s, ocean surveys found symmetrical magnetic stripes on either side of mid-ocean ridges, proving seafloor spreading, and the pieces came together as plate tectonics. Plates move a few centimeters a year—about as fast as fingernails grow.
Plate boundaries
Plates pull apart at divergent boundaries (the Mid-Atlantic Ridge, Iceland), collide at convergent boundaries (subduction zones and collision zones like the Himalayas), and slide past each other at transform boundaries (California's San Andreas Fault). Earthquakes and volcanoes cluster along the Pacific's Ring of Fire. Over geologic time, plate motion also shapes the atmosphere and climate, including the greenhouse effect.
FAQ
- What drives the plates?
- Mantle convection plus, most importantly, the pull of sinking slabs at subduction zones.
- Will the continents merge again?
- Scientists predict a new supercontinent in a few hundred million years.
Sources reviewed: 2026-10-26
References
- Wegener, A. (1915). Die Entstehung der Kontinente und Ozeane. Vieweg.
- Vine, F. J., & Matthews, D. H. (1963). Magnetic anomalies over oceanic ridges. Nature, 199, 947–949.
- U.S. Geological Survey. This Dynamic Earth: The Story of Plate Tectonics.