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PLATE TECTONICS

A. INTRODUCTION

• Driving framework: forces trying to change surface characteristics
  
  • plate tectonics: part of the driving framework
    
    
• Resisting framework: forces resisting change; trying to keep surface characteristics the same
  
  
• earth's composition & structure = resisting framework

B. HISTORY

Continental Drift - Alfred Wegener, 1912   similarity of coastlines continuity of disparate mountain ranges fossil distributions Image credit: Kious & Tilling, USGS. This Dynamic Earth: the Story of Plate Tectonics; Historical perspective. http://pubs.usgs.gov/gip/dynamic/continents.html glacial deposits

Image credit: Kious & Tilling, USGS. This Dynamic Earth: the Story of Plate Tectonics; Historical perspective. http://pubs.usgs.gov/gip/dynamic/historical.html

New Evidence paleomagnetism     Image credit: Kious & Tilling, USGS. This Dynamic Earth: the Story of Plate Tectonics; Developing the theory. http://pubs.usgs.gov/publications/text/developing.html age of the ocean floor

Image Courtesy of: Windows to the Universe, University Corporation for Atmospheric Research (UCAR). http://www.windows.ucar.edu Image credit: Peter Sloss, NOAA National Geophysical Data Center, Marine Geology & Geophysics. http://www.ngdc.noaa.gov/mgg/image/crustalimages.html

Theory of Plate Tectonics

Image credit: Kious & Tilling, USGS. This Dynamic Earth: the Story of Plate Tectonics; Historical Perspective. http://pubs.usgs.gov/gip/dynamic/historical.html

C. PLATE BOUNDARIES

Geographic distribution of earthquakes
Image credit: NASA/Goddard Space Flight Center Scientific Visualization Studio http://svs.gsfc.nasa.gov/vis/a000000/a001200/a001290/

• shallow focus: 0-70 km
  
  
• intermediate focus: 70-300 km
  
  
• deep focus: 300-670 km

Geographic distribution of active volcanoes

Image credit: USGS Energy Resources Program http://energy.usgs.gov/other/geothermal/geothermal_learn.html

Transform Boundaries shallow focus earthquakes	Image credit: NASA/JPL/NIMA. NASA Visible Earth. San Andreas fault, Palmdale, California. http://visibleearth.nasa.gov/view_rec.php?id=352
Divergent Boundaries / Rift Zones Image credit: Kious & Tilling, USGS. This Dynamic Earth: the Story of Plate Tectonics; Understanding Plate Motions. http://pubs.usgs.gov/gip/dynamic/understanding.html volcanic activity shallow focus earthquakes block faulting (normal faults)	Image credit: Kious & Tilling, USGS. This Dynamic Earth: the Story of Plate Tectonics; Understanding Plate Motions. http://pubs.usgs.gov/gip/dynamic/understanding.html

Convergent Boundaries

• subduction zones
  

  

  • deep ocean trenches
    
    
  • volcanic arcs: continental arcs & island arcs
    
    
  • shallow, intermediate & deep focus earthquakes
    
    
  • folding & reverse faults

Image credit: Kious & Tilling, USGS. This Dynamic Earth: the Story of Plate Tectonics; Understanding Plate Motions. http://pubs.usgs.gov/gip/dynamic/understanding.html

Image credit: USGS Earthquake Hazards Program, World Seismicity Maps, Pacific Rim. http://earthquake.usgs.gov/regional/world/seismicity/pac_rim.php

• continental collisions

• earthquakes

Image credit: USGS Earthquake Hazards Program, World Seismicity Maps, Central Asia.
http://earthquake.usgs.gov/regional/world/seismicity/c_asia.php

D. MECHANISM DRIVING PLATE MOTION

• Slab pull
  
  
• Ridge push

E. SUMMARY

• continental drift evolved into the theory of plate tectonics
  
  
  • scientific theory: overarching framework of ideas that have been widely and repeatedly tested; not idle speculation
    
    
  • sea floor spreading & paleomagnetism
    
    
  • earthquakes & volcanic activity
    
    
• tectonic plate boundaries
  
  
  • divergent boundaries/rift zones
    
    
  • transform boundaries
    
    
  • convergent boundaries: subduction zones and continental collisions
    
    
• driving mechanism