Advanced Plate Tectonics

Cold downwelling will be the same difference from

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Unformatted text preview: etrical convection, where heat from the bottom is equal to loss off the top, viscosity is constant, and both top and bottom boundaries are free-slip. Cold downwelling will be the same difference from average as the warm upwelling, And both top and bottom will have symmetrical Thermal Boundary Layers. These are the symmetrical transition zones that are unstable, and are in contact with either the heating or cooling source. Tectonic plates are the upper boundary layer. Much of the rest of the fluid is OCE 661 gravitationally stable. The upper boundary layer thickens and cools as it moves away The from the divergence zone and toward the downwelling zone, forming a horizontal boundary current. It flows as far as it can before cooling enough to sink, thus defining the size of a tectonics plate in the simplest sense. An aspect ratio of 1 is typical. Forces: Gravity drives the vertical currents, but the horizontal currents are driven by pressure gradients. High pressure forms as the plumes reach the surface, and flow toward low pressure in the more dense downwelling zones, s...
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