Other Plate Tectonics Info:
Plate Tectonics Intro
Plate Tectonics Basics
Other Implications

More links to web sites that contain information about Plate Tectonics can be accessed through the Links Page of this web site.  The figures shown here were taken and/or modified from the USGS Plate Tectonics web pages.

Plate  Tectonics, History of the Theory:
For a cool website that shows what the surface of the earth has looked like in the geologic past, as well as a lot of other plate tectonic information, click here.
Early Suggestions about a changing Earth
 
Abraham Ortelius (1528-1598) - suggested in 1596 that the Americas were "torn away from Europe and Africa . . . by earthquakes and floods" and went on to say: "The vestiges of the rupture reveal themselves, if someone brings forward a map of the world and considers carefully the coasts of the three [continents]."
Francis Bacon (1561-1620) - suggested Western Hemisphere once joined with Eurasia.

In 1858, geographer Antonio Snider-Pellegrini made these two maps showing his version of how the American and African continents may once have fit together, then later separated. Left: The formerly joined continents before (avant) their separation. Right: The continents after (aprés) the separation. (Reproductions of the original maps courtesy of University of California, Berkeley.) (from USGS website - click on images to go to it)
 Eduard Suess - 1885-1909 - noted correspondence of geologic formations in S. Hemisphere landmasses, suggested once formed a single continent he called GONDWANALAND -
What was Wegener's evidence?
Wegener's Evidence:
  • (Figure is from USGS website)
  • Glossopteris Flora
  • Mesosaurus
  • Cynognathus
  • Lystrosaurus
    		•
                                                      Present day distribution of coral reefs The problem: Mechanism:
    Result: belief in Stable Earth

    What alternatives to Wegener's data were suggested?
    Other ideas explaining Wegener's data:

    What then led up to Plate Tectonic Theory?
    WWII
    Ways used to combat submarines: Harry Hess (1962) used echo-soundings to map the seafloor, and based on this suggested that molten rock (magma) oozes up from the Earth's interior along the mid-oceanic ridges, creating new seafloor that spreads away from the active ridge crest and, eventually, sinks into the deep oceanic trenches. (from a USGS website) new data:
    Paleomagnetism = study of Earth's magnetic field as recorded in rocks

    •  
    Fred Vine (l), Drummond Matthews (r)
    		 Result: Marine Magnetic Anomalies (MMA) - used by Fred Vine and Drummond Matthews (King's College, Cambridge) to infer Seafloor Spreading in 1963, based on MMA obtained during the 1950s and 60s.  (click on figure above to see USGS discussion of MMA's)


    Changes in magnetic polarity: take about 10,000 years to occur, and last (in either polarity) for (on average) 1/4 to 1 million years in either the Reversed or Normal direction.

    The MMA's are produced by sequential changes in the the earth's magnetic field, as seafloor spreading occurs:


    (from USGS Website - click on image to go to that site)

    Result (map view):

    Comparing the pattern of Marine Magnetic Anomalies to the pattern in the Geomagnetic Polarity Time Scale has allowed us to determine the age of the ocean floor over virtually the entire Earth:
    (Click on this image
    to see the entire Earth)

    This has also allowed us to map out probable spreading patterns over time:

    		 From this website:

    http://www.searchanddiscovery.net/documents/97019/index.htm
    Earthquake information:
    Hugo Benioff, 1954 - the Benioff Zone
     
  • These data from earthquakes and paleomagnetism allowed the discovery of what eventually became the Theory of Plate Tectonics in the middle 1960's.

    Other Plate Tectonics Info:
    Plate Tectonics Intro
    Plate Tectonics Basics
    Other Implications

    More links to web sites that contain information about Plate Tectonics can be accessed through the Links Page of this web site.  The figures shown here were taken and/or modified from the USGS Plate Tectonics web pages.