Out last topic is one that you have studied in your past geology courses: plate tectonics. The literature on this history is large. If you want to read more, I would suggest LeGrand (1988), Stewart (1990), Oreskes (1999, 2003), and (if you have the energy) the comprehensive work of Frenkel (2012). Keep in mind that our interest is in the timeline of development and how the various aspects of geophysics and geology came together in a relatively short time.

Harris sections 32

This section briefly presents how this was generalized to include the geometry of plate motions, seismology, and the integration with tectonics – all within a remarkably short time period (1966-1970). As with sea-floor spreading, you may probably read some of these papers in various geology classes – you have certainly seen some of the key diagrams in textbooks!

Allegre (1988) p. 91-122 

Once again, Allegre provides a more detailed narrative with some illustrations that will help you visualize the geometries. I will not belabor the obvious since most of this should be familiar. You will want to focus on p. 93-113 for the general story, and p. 116-17 on the proposal to characterize the history of ocean basins in terms of “Wilson cycles”.

Questions to think about

• What was needed to expand sea-floor spreading into plate tectonics?
• Please make a listing of the critical contributions during this transition.
• Three areas come into there own during this transition (1966-1970): the idea of “plates”, seismology, and the return of geologic/tectonic information.  Thinking about this:
  • What kind of information was used?
  • What were the key steps?
• How did plate tectonics (derived from the marine realm) get integrated with traditional (continent-based) tectonics?
• How similar and different is plate tectonics to continental drift?
• Important question for geohistorians: why was plate tectonics acceptable while drift was not?

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