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The cool, rigid, outer layer of the earth, the lithosphere, is broken into massive plates along discrete boundaries. What are these plates, and what do the boundaries represent?

Narrated by Michael Hubenthal, IRIS Senior Education Specialist
Animation & graphics by Jenda Johnson, Earth Sciences Animated
Reviewed by: Robert Butler, Geophysicist, University of Portland, OR
and Wendy Bohon, IRIS Informal Education Specialist
Earthquake locations from IRIS Earthquake Browser (www.iris.edu/ieb)
Tectonic maps and cross sections modified from US Geological Survey images
Additional maps from Google Earth and GeoMapApp
Big Hunk analogy from Dr. Robert Butler
Animation of San Andreas Fault by Tanya Atwater
Photos from NOAA, USGS, NASA
Made possible by support from the National Science Foundation