GEOS 112L:
Determining the Speed of Plate Motion

This exercise is based on data from the Quantitative Environmental Learning Project (QUELP)

Plate tectonic theory assumes that hotspots are stationary plumes of molten material that melt their way from the lower mantle all the way to the surface of the earth.  When plates move over an active hotspot the result is a chain of active and extinct volcanoes like the Hawaii-Emperor seamount chain. The figure below shows a three dimensional view of a hotspot and the resulting chain of volcanoes.

(from: http://oceanexplorer.noaa.gov/explorations/03mountains/background/geology/media/chain.html)

If hotspot plumes do remain stationary (there is some debate whether this is really true) we can use the position and age of old hotspot volcanoes to calculate the rate of plate motion.  The Excel file below lists the age and distance (from Hawaii - the present position of the hotspot) of several seamounts in the Hawaii-Emperor seamount chain.

Hawaii-Emperor seamount data

Questions:

Briefly answer the following questions.  Make sure you type your answers.

  • How common are seamount chains? Use your textbook to find out how many (major) seamount chains there are.
  • Are there any seamount chains close to home? If so, what are they called?
  • Open up the file in Excel and make sure you understand what it contains. Using the map below, locate some of the seamounts. Which way does the Pacific Plate move today, has this direction of movement been constant over the past?
  • How can you calculate the speed of the Pacific plate using the provided data?
    One way to determine the rate of plate movement is to generate a graph of seamount distance as a function of time and construct a best fit line through the data. The slope of that line is an estimate for the rate of plate movement.
  • Did the speed and direction of plate movement change over time?
  • What happens to these seamounts at the end of the chain (opposite from Hawaii)?

 

(from: http://seattlecentral.org/qelp/sets/073/073.html)

Note, there are several ways to answer these questions. Some people prefer plain old numbers, some graph the data, each is fine, but your answers have to be based on your data and well reasoned.
Finally, you might want to check out this webpage.

back to GEOS 112 homeworks