Lecture20_TectonicsII - EAS 1600 Introduction to...

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EAS 1600 Introduction to Environmental Sciences ____________________________ Class 22 - Plate Tectonics: Part 2 A more detailed look at plate tectonic-processes _____________________________ In our last lecture we reviewed the historical development of the theory of plate tectonics and introduced some basic aspects of the phenomena. In this lecture we take a more detailed look at the specific types of plate-to-plate interactions that occur – these are what ultimately determine the nature and stability of the planetary surface upon which we live. By the way: Want a really great resource on plate tectonics? check out this website: http://pubs.usgs.gov/publications/text/dynamic.html#anchor19978839 Types of Plate Motion As illustrated on next page, the interaction of plates depends upon their relative motion: ¾ divergent ¾ convergent ¾ transform and the types of crust is at the edge of each plate: ¾ continental ¾ oceanic. ¾ Why? Recall our discussion about oceanic and continental crust. ¾ Do you remember the differences? Why should these make a difference? Types of Plate Motion Divergent Plate Boundaries Lithospheric plates which move away from each other. Example: the mid-Atlantic Ridge As the plates move away new crustal material is produced.
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Common feature of divergent plate boundaries in the ocean: ¾ smokers; deep sea hot springs “Smoker” at the Galapagos rift Smokers provide unique environments for microbes that are able to flourish at high temperatures. It is thought that they may have been the cite of the initial evolution of living organisms. BUT: ¾ Not all divergent plate boundaries are ocean-ocean boundaries ¾ Consider Iceland . .. Note: the Mid-Atlantic Ridge passes through Iceland? Aerial view of the area around Thingvellir, Iceland, showing a fissure zone (in shadow) that is the on-land exposure of the Mid-Atlantic Ridge. Right of the fissure, the North American Plate is pulling westward away from the Eurasian Plate (left of the fissure). Large building (near top) marks the site of Lögberg, Iceland's first parliament, founded in the year A.D. 930. (Photograph by Oddur Sigurdsson, National Energy Authority, Iceland.) Photo and caption obtained from USGS Interesting puzzles for later: How did ridge get there? How/why do ridges form in the first place? Convergent Plate Boundaries The surface area of the earth is finite. If new crustal material is being created at divergent boundaries, there must be convergent boundaries where crustal material is consumed. The consumption of crustal material occurs as a result of ¾ Subduction along a convergent boundary . ..
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Subduction The existence of subduction zones was hinted at well-before the theory of plate tectonics had taken shape. .. ¾
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This note was uploaded on 04/18/2008 for the course EAS 1600 taught by Professor Jimstjohn during the Spring '08 term at Georgia Institute of Technology.

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Lecture20_TectonicsII - EAS 1600 Introduction to...

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