A brief history of the development of the Theory of Plate Tectonics

Geologists have known for more than 100 years that the continents move across the surface of the Earth. Sir Francis Bacon in about 1620 recognized that the coastline of North America could be nicely fit against the coastlines of Europe and northern Africa. In 1799, von Humboldt noted that the same symmetry existed between the coastline of South America and that of central and southern Africa and that there were extensions of mountain ranges of South America on the African continent. It seemed as though the continents, separated by the Atlantic Ocean, had once been joined. This hypothesis was clearly stated by A. Snider in 1858 in France. In the early 1900s, the hypothesis took on some geological popularity as F. Taylor, H.D. Baker and then Alfred Wegener described theories of “Continental Drift”. Geophysicists were slow to the accept the possibility because, as Lord Rayleigh argued, “Solid rock can’t move through solid rock!”. Some geophysicists held vainly to an alternate theory, the “Expanding Earth Hypothesis” which argued that Earth’s volume had increased over geological time and that the earlier surface was no longer large enough in area to cover the surface of the greater volume. The Atlantic Ocean was seen to be an ever-widening crack on the surface of a growing Earth. In 1963, J. Tuzo Wilson, a physicist at the University of Toronto, wrote a famous article entitled “Continental Drift” which was published in the April issue of Scientific American magazine. He argued a mechanism which quickly found acceptance among geophysicists who finally joined their geological colleagues in this view of the tectonic process on Earth.

Some links to sources on Plate Tectonics

Plate Tectonics: History of an Idea: http://www.ucmp.berkeley.edu/geology/techist.html

Motion of tectonic plates: http://denali.gsfc.nasa.gov/dtam/

History of plate motions: http://www.ucmp.berkeley.edu/geology/tectonics.html

A detailed tectonic map of the Pacific: http://www.gps.caltech.edu/~dla/images/oblique.jpg

A detailed tectonic map of North Polar: http://www.gps.caltech.edu/~dla/images/n_polar.jpg

A detailed tectonic map of South Polar: http://www.gps.caltech.edu/~dla/images/s_polar.jpg

Understanding plate motions: http://pubs.usgs.gov/publications/text/understanding.html

Some tectonic animations: http://tasaclips.com/animations.html

The Cascadia Subduction Zone: http://www.earthquakescanada.nrcan.gc.ca/historic-historique/events/17000126-eng.php & http://www.earthquakescanada.nrcan.gc.ca/pprs-pprp/re/ETS-eng.php

Ocean-floor magnetics: http://pubs.usgs.gov/gip/dynamic/magnetic.html

Magnetic anomaly data used in geological mapping http://research.utep.edu/Portals/73/PDF/ofr-02-0400.pdf See page 14.