Unformatted text preview: imilar to high and low
pressure systems in the atmosphere.
This convection based view is somewhat different that the
plate forces we just discussed…. Does basal traction have
any meaning? Are plates “passive” or “active”?
OCE 661 In the earth, symmetrical convection does not exist. 85-90% of
the Earth’s heat comes from radiogenic heating, not from
contact with the molten Iron outer core (Turcotte and Schubert,
How does this change the picture? The dominance of internal heating means that the convection
becomes asymetrical. The bottom boundary layer only has
to transfer heat from the core, while the upper boundary layer
has to transfer heat from radiogenic heating, plus the heat
from the core, to remain in balance.
This means that the cold downwellings dominate the system,
and the upwellings are relatively weak and diffuse (Davies
and Richards, 1992).
and OCE 661 What about all our other assumptions, like constant viscosity?
Also incorrect. Mantle viscosity is highly temperature
dependent. Whether motio...
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- Winter '14
- Plate Tectonics, Atlantic Ocean, Mantle, Alfred Wegener, Richards