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Plate Tectonics Paradigm

Learner Outcomes
By completing these activities, the learner will:

Exploration

Consider the locations of earthquakes and volcanoes around the world.

Map of sea floor ages - courtesy of NOAA
Scale of sea floor ages
(Click globes to enlarge.  Caution: the enlarged version of this image is very large)

Concept Introduction

  1. Determine the age of the sea floor off the eastern shore of the US.
  2. Determine the age of the sea floor off the coast of northwestern Africa.
  3. Acquire the distance between South Carolina coast and the northwestern African coast.
  4. Calculate the rate that the continents are moving apart. (express your answer in centimeters per year)
  5. View the movie of the computer model demonstrating mantle convection. This model has been generated using super-computers and earthquake data.
  6. How does this convection influence the spreading of the sea-floor?
  • Convergence and divergence of lithospheric plates account for many of the Earth's major geologic features. Using a "paint" or "drawing" software package, sketch and label each major plate.


    • Concept Application

    Modeling: Draw a diagram TO SCALE from the center of the earth to the surface (you may even want to include oceans and atmosphere). It is very important that you research the appropriate thickness of each of the Earth's subdivisions (crust, mantle, core, asthenosphere, etc.) and draw them as carefully as you can. The reason for this is because many of the diagrams you will see on the web and in textbooks have greatly exaggerated the thickness of various subdivisions for the sake of a clear diagram.

    Researching Part 1: Examine the graphic of Sea Floor Topography carefully, pay particular attention to the shapes of trenches and the offset patterns of mid-oceanic ridges. From your reading and examination of this image, describe in your own words the origins of spreading center patterns (i.e., the transform fault offsets)*, and the patterns of subduction zones (i.e., arcuate trenches and arcuate island arcs)*.

    Researching Part 2: Just as important as recognizing features that fit our current model is recognizing patterns that DO NOT seem to fit. What areas or features do you see on the Sea Floor Topography image that do not seem to fit current model of plate tectonics? Researching Part 3: The newest oceanic crust is found closest to mid-oceanic ridges*, while ocean crust that is found farther away from spreading centers* is older and has accumulated more water-saturated sediment. Examine the ocean floor map carefully, and write a report on the geological future (very long term!) of the Pacific and the Atlantic oceans. Include in your report some reasons why the Pacific Ocean has so many trenches, while the Atlantic has none, and why the Atlantic ocean is so symmetrical (with respect to age of crust and the mid-oceanic ridge), while the Pacific is so asymmetrical. Researching Part 4: Examine the graphic of sea floor topography from gravity readings*. Are all types of plate boundaries found in both the Atlantic and the Pacific Oceans? Researching Part 5: Examine the graphic of sea floor topography from gravity readings. Of the continents moving away from each other, which show the best fit between their margins (true geological margins, not just geographic margins), and which show the poorest fit. Researching Part 6: Examine the graphic of sea floor topography from gravity readings. Notice the great number of peninsulas, large islands (continental crust fragments), island arcs, and shallow seas in the western Pacific. Write an essay that discusses what will happen to these features as plate tectonics continues on into the future, and what are the implications to the future geology of the nearby continental land masses. Researching Part 7: Find the Hawaiian Island-Hawaiian ridge-Emperor Seamount structure on the Pacific plate topography image. Write an essay on what the configuration of this structure tells you about past and present movement of the Pacific plate. Researching Part 8: Locate the Andes Mountains on a tectonic map, and then examine several images of these mountains. Determine what kind of volcanoes are shown on these images, and how this type of volcanism relates to the tectonic setting of the Andes. Write an essay discussing your findings.
     


    Assessment