Examination and evaluation of real-time oceanographic data on the internet
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and OCEAN BASINS |
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ATMOSPHERE DYNAMICS |
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Global Plate Motion (contd.):
- Aim: to determine and compare rates of plate motions.
- Website: a global map of GPS measurements of plate motion is presented at:
- Content: the GPS (Global Positioning System) determines plate motion by measuring changes in the position of a specific site on the Earth's surface relative to a satellite.
- Both VLBI ansd GPS techniques rely on assessment of changes in locations on Earth relative to a fixed point in space. For VLBI it is the position of the satellite and for GPS it is the position of the station on Earth. Also, the GPS data set is derived from many more sites than VLBI. A list of these sites is given at:
- More details about the International GPS Service are available at:
Procedures for GPS Data Set:
- In the global GPS map measurements of plate motions are shown as black arrows originating from each site, shown as a red circle.
- The arrows represent vectors indicative of the magnitude and direction of plate motion.
- The length of the arrow is proportional to the rate of plate motion.
- An arrow for scale (equivalent to 5cm/yr) is given in the Southern Indian Ocean. (Note that the scale is different from that for VLBI)
- The direction of the arrow represents the direction of plate motion
- The alternating black and white bars on the sides of the map represent latitude and longitude at 40° and 20° intervals, respectively.
- Southern latitudes are designated by negative numbers.
- Longitude is presented as °E from the prime meridian (i.e. not designated separately in terms of °E or °W).
Introduction to Questions on GPS Plate Motions:
- This is the second of four series of questions for this exercise, which are presented in separate tables.
- Reminder: you should submit your answers via oncourse.
| Spreading Rates and Plate Motions | pt | |
| Plate Motions using data from the Global Positional System | ||
| Compilation of data from GPS measurements
enables comparisons of the rates of plate motions in different regions of
the world. You should examine and interpret the directions of plate motion
documented in the GPS global map. http://sideshow.jpl.nasa.gov/mbh/series.html |
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| 7. | For individual plates (e.g. Africa, N. America, S. America), do the directions of motion for different locations on that plate appear to be uniform? Give two examples. HINT | 2 |
| 8. | Describe the type of motion shown by the North American plate? HINT |
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| 9. | How does the variability in the directions of motion for an individual plate provide clues about its internal stresses? (Bonus) HINT | 3* |
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Department of Geological Sciences,
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Phone: (812) 855-5582 Last updated: 22 September 2002
Comments: simon@indiana.edu
Copyright 2002, The Trustees of Indiana University