PLATE TECTONIC EVOLUTION DURING THE LAST 1.5 BILLION YEARS: THE MOVIE

This computer animation illustrates the plate tectonic development of the continents and ocean basins during the past 1.5 billion years. The GPlates program was used both to build the plate tectonic model and to produce the animation. The latitudinal orientation of the continents was derived largely from paleomagnetic data. Hot spot tracks and seafloor spreading isochrons were used to constrain the longitudinal positions of the continents back to ~200 million years. Plate tectonic reconstructions older than 200 million years are necessarily more speculative and were derived by combining diverse lines of evidence: the tectonic history of the continents (i.e, the timing of continent-continent collisions or the ages of rifting), the distribution of paleoclimatic indicators (i.e., bauxites, coals, tillites, and salt deposits), and in some cases the biogeographic affinities of fossil faunas and floras.

Though a diverse data set has been used to produce these reconstructions, this data, in itself, was not enough to do the job. So much time has passed, and so little direct evidence of past plate interactions remains, that guidance must also be sought from the “Rules of Plate Tectonics”. The rules of plate tectonics are largely intuitive. They state that the Earth’s tectonic plates do not move randomly, but rather evolve in a manner that is consistent with the forces that drive them. The principal forces are slab pull, ridge push, and trench roll-back. Understanding how these forces work provides important insights into how plate boundaries will evolve through time. Simply said, plates move only if they are pulled back into the mantle by a subducting slab or pushed laterally by a mature mid-ocean ridge system.

It is also important to note that plate tectonics is a “catastrophic” system. Though “slow and steady” is the general rule, a major plate tectonic reorganization takes place every 50 – 100 million years. These “plate tectonic catastrophes” most often occur when mid-ocean ridges are subducted or when major continents collide. Plate tectonic reorganizations have played an important role in shaping the rock record and providing the evolving context for climate change, the changing distribution of land and sea, and the evolution of distribution of life on Earth. The animation can be viewed at: https://www.youtube.com/watch?v=IlnwyAbczog