5 the above leads directly to global plate circuits

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Unformatted text preview: the same plate, the angular velocity vectors sum to zero. 5) The above leads directly to Global plate circuits such as 5) Minster and Jordan, 1978, and the NUVEL-1 model. OCE 661 Marine gravity anomalies from satellite altimetry Satellite radar altimetry has revolutionized our knowledge of the Satellite topography of oceanic basement, and helped greatly to construct better plate tectonic models through geologic time. Radar altimetry works by measuring the distance between the satellite and the sea surface by radar (below). These data are used to provide a geoid map. The geoid is an equipotential field. equipotential From these geoid anomalies we can derive anomalies in the gravity field. Gravity From anomalies are deviations of the gravity field of that caused by the best ellipsoid approximation of the Earth (i.e. the Earth’s shape can roughly be described by an ellipsoid, but not quite – there are many deviations. Short wavelength marine gravity anomalies are mostly caused by oceanic basement topography, such as fracture zones, seamounts, ridges and trenches (see figure below). as OCE 661 EXPLORING THE OCEAN BASINS WITH EXPLORING SATELLITE ALTIMETER DATA SATELLITE David T. Sandwell - Scripps Institution of Oceanography David [email protected] [email protected] and Walter H. F. Smith - Geosciences Laboratory, NOAA Walter [email protected] [email protected] According to the laws of physics, the surface of the ocean is an "equipotential surface" of the earth's gravity field. (Lets ignore waves, winds, tides and currents for the moment.) Basically this means that if one could place balls everywhere on the surface of the ocean, none of the balls would roll down hill because they are all on the same "level". To a first approximation, this equipotential surface of the earth is a sphere. However because the earth is rotating, the equipotential ocean surface is more nearly matched by an ellipsoid of revolution where the polar diameter is 43 km less than the equatorial diameter. While this ellipsoidal shape fits the earth remarkably well, th...
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This document was uploaded on 01/26/2014.

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