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Contents of 12.8 What forces cause plate motions and plumes?

12.8 What forces cause plate motions and plumes?

• Upwelling: plumes, superplumes, divergent zones
• The exact relationship between plate tectonics and convective upwelling is not yet resolved.
• Upwelling appears to be more diffuse than the discrete zones of downwelling.
• Mantle convection should include core-mantle depth upwelling, as the downwelling seems to reach these depths.
• Seismic tomography indicates that large seismically slow zones exist near the core-mantle boundary.