Welcome to GLG101C Introduction to Geology
Fall 2004
Professor James Tyburczy
Department of Geological Sciences  

 
Chapter 2 Plate Tectonics

Chapter 2 PLATE TECTONICS: The Unifying Theory

Plate Tectonics - The Earth's surface is broken up into a small number of major plates that move about on the surface. Major geological activity (volcanism, earthquakes, mountain building) occurs at the boundaries between these plates. This concept combines the ideas of Continental Drift and Sea Floor Spreading

Evidence for Continental Drift - some of these ideas and observations had been around since late 1800's

Observations of the sea floor leading to idea of Sea Floor Spreading

Combine continental drift idea with seafloor spreading idea (mechanism) to give modern Plate Tectonics - Earth's surface is covered by a small number of plates, most geologic activity occurs at plate boundaries. New material (new lithosphere) is created at the mid-ocean ridges and

Lithospheric plates

Divergent plate boundaries

Transform plate boundaries - Transform faults

Convergent plate boundaries

Determining Past Plate Locations and Motions

  • Transform faults that offset mid-ocean ridge indicate the directions of plate motion
  • Age of ocean floor (isochrons) gives speed of plate motion in the geologic past
  • We can measure present day motions in 'near real time' using the Global Positioning Satellite (GPS) system
  • Plate Configurations

  • During the late Paleozoic (280 million years ago) plates were joined together to form a super continent - Pangaea.
  • Through geologic and geomagnetic reconstructions, we can reconstruct plate motions and continental configurations back almost 800 million years (early supercontinent called 'Rodinia')
  • Tests, Successes of Plate Tectonic Model

    Mechanism of Plate Tectonics

    Forces acting on the plates

    Mantle plumes (hot spots, intraplate volcanoes, such as Hawaii) may come from very deep in the mantle (maybe as deep as the core-mantle boundary). The tracks of hot spots tell us the relative motions of the plates.


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    ©2004, James A. Tyburczy, Department of Geological Sciences, Arizona State University
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    Last update 8/27/2004