Teacher Suggestions

1.  Explain equipotential surface.

See information in "Satellite Altimetry" in: http://www.ngdc.noaa.gov/mgg/announcements/text_predict.HTML
 

2.  Explain what a polar orbit is, what a satellite orbit is and how these differ from the shape of the earth’s orbit around the sun.

You will have to use other sources to answer this question.

These tiny bumps and dips in the geoid height can be measured using a very accurate radar mounted on a satellite (Figure). For example, the Geosat satellite was launched by the US Navy in 1985 to map the geoid height at a horizontal resolution of 10-15 km (6 - 10 mi) and a vertical resolution of 0.03 m (1 in).  Geosat was placed in a nearly polar orbit to obtain high latitude coverage (+- 72 deg latitude). The Geosat altimeter orbits the earth 14.3 times per day resulting in an ocean track speed of about 7 km per second (4 mi/sec). The earth rotates beneath the fixed plane of the satellite orbit, so over a period of 1.5 years, the satellite maps the topography of the surface of the earth with an ground track spacing of about 6 km (4 mi)
 

3.  Explain how the sea floor is measured with satellite data.

See information in "Satellite Altimetry" in: http://www.ngdc.noaa.gov/mgg/announcements/text_predict.HTML
 

4.  How are plate tectonics and gravity maps related?

These satellite altimeter data provide an important and definitive confirmation of the theory of plate tectonics. Indeed, almost everything apparent in the marine gravity field was created by the formation and motion of the plates. The Indian Ocean Triple junction (27 deg S latitude, 70 deg E longitude) is a textbook example of seafloor spreading. Spreading ridges are characterized by an orthogonal pattern of ridges and transform faults. The scar produced in the active transform valley is carried by seafloor spreading out onto older seafloor leaving evidence of the past plate motions. At this Indian Ocean site, three spreading ridges intersect forming a triple junction as described by plate tectonic theory. The theory predicts that the ridges would intersect at 120û angles if the three ridges were spreading at exactly the same rate. In this case, one can measure the intersection angles and infer the relative spreading rates of each ridge.

5.  Explain power dissipation in the asthenosphere and its relation to the age of the sea floor.

See information in: http://luna.geol.niu.edu/prs/drag.html