Home > Causes > Plate Tectonics > Plate Tectonics Theory

Plate Tectonics Theory

Alfred Wegener (1880-1930)
Source: Univesity of California, Berkeley

In the 20th century, a German meteorologist by the name of Alfred Wegener proposed the Continental Drift Theory which states that the surface of the Earth actually consisted of plates which were in constant slow motion.

By the 1950s, the theory was later improved to become the Theory of Plate Tectonics which is widely accepted today. According to this theory, the Earth's surface is broken into eight major plates and several other smaller ones.

The way the Earth's surface is broken up has been likened to that of a cracked egg shell. The edges of these plates are known as the plate boundaries, and are areas with intense geologic activity, e.g. earthquakes, volcanic activities and folding of the crust. These plates are continuously in motion, forming sites of convergence, divergence and sliding.

Plate tectonics is a combination of two earlier ideas, namely the Continental Drift Theory by Alfred Wegener (above) and sea-floor spreading. It states that the earth was actually made up of a huge continent many hundreds of millions of years ago, called Pangaea, which broke up into smaller continents to form the continents of today.

Sea floor spreading is the creation of new oceanic crust at divergent plate boundaries where two plates move apart from each other, allowing magma from the mantle to well up and cool, forming new sea floor.

Tectonic plates of the Earth
Source: United States Geological Survey


  • Retrieved February 1, 2005, from http://pubs.usgs.gov/publications/text/historical.htm
  • Elastic Rebound. Pacific Earthquake Engineering Research Center. Retrieved March 5, 2005, from http://peer.berkeley.edu/~jrodgers/EQDef/eqdef2.htm
  • 2004 Indian Ocean earthquake. Wikipedia. Retrieved February 20, 2005, from http://en.wikipedia.org/wiki/2004_Indian_Ocean_Earthquake
  • Tsunami. Wikipedia. Retrieved February 20, 2005 from http://en.wikipedia.org/wiki/Tsunami
  • The Earth: A Living Planet Retrieved April 10, 2005, from http://www.seed.slb.com/en/scictr/watch/living_planet/beneath.htm
  • Marianne Chong. Aspects of Physical Geography (2001).
  • Plate Tectonics. Wikipedia . Retrieved April 10, 2005, from http://en.wikipedia.org/wiki/Plate_tectonics

Content Outline