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:
- Aim: to determine and compare rates of seafloor spreading.
- Websites: global and regional data sets of VLBI (Very Long Baseline Interferometry) are examined at the following URL's:
- Global: http://lupus.gsfc.nasa.gov/plots/maps/jpg/World_Wide_Totals.jpg
- Europe: http://bowie.gsfc.nasa.gov/926/eurotect.html
- North America: http://bowie.gsfc.nasa.gov/926/noamtect.html
- Content: relative rates of plate motion from VLBI are obtained from satellite measurements that record minute variations in the positions of stations on Earth.
- The principles behind VLBI measurements are described at:
Procedures for VLBI Data Sets:
- In the global map of VLBI measurements plate motions are shown as light blue arrows.
- 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 ten mm/yr) is given in the Southeast Pacific.
- 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 45° intervals.
- The equator is close to Indonesia on the left hand margin.
- The prime meridian lies above the "r" of the word "version" in the legend.
- In the regional maps of VLBI measurements of plate motions focus on the red arrows.
- Again, these 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.
- A scale (equivalent to 50mm/yr) is given in the lower left of each map.
- The ellipses around the arrow head represent data uncertainty.
- Latitude and longitude are given on the margins of each map.
Introduction to Questions on VLBI Plate Motions:
- This is the first 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 Motion | pt | |
| Plate Motions from Very Long Baseline Interferometry | ||
| Compilation of data from VLBI measurements
enables comparisons of the rates of plate motions in different regions of
the world. The first questions require that you examine the measures of plate
motion shown in the global map: http://lupus.gsfc.nasa.gov/plots/maps/jpg/World_Wide_Totals.jpg |
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| 1. | Which global site has the greatest velocity of plate motion (i.e. the longest arrow)? Either name the location or provide its approximate co-ordinates. | 1 |
| 2. | What is the azimuth (direction) of this longest arrow as an approximate compass bearing? (i.e. N = 0°, E = 90°, S = 180°, W = 270°) |
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| Compare the measurements of the direction and magnitude of plate motion for different sites in Europe: http://bowie.gsfc.nasa.gov/926/eurotect.html | ||
| 3. | Is the direction and magnitude of plate motion generally similar throughout Europe, or not? HINT | 1 |
| 4. | Describe where any prominent differences in the directions and magnitudes of plate motion for Europe are observed. Either name the location (country) or provide approximate co-ordinates (latitude and longitude). HINT | 2 |
| Compare the measurements of the direction and magnitude of plate motion for different sites in North America: http://bowie.gsfc.nasa.gov/926/noamtect.html | ||
| 5. | Is the direction and speed of plate motion generally similar throughout North America, or not? HINT |
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| 6. | Describe any significant differences observed in either the directions or magnitudes of plate motion for North America. Refer to specific sites in your answer, either by naming the location, or state, or by providing approximate co-ordinates (latitude and longiude). HINT | 2 |
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Department of Geological Sciences,
1001 E. Tenth Street, Bloomington, IN 47405-1403
Phone: (812) 855-5582 Last updated: 23 September 2002
Comments: simon@indiana.edu
Copyright 2002, The Trustees of Indiana University