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DRIVING FORCES FOR LITHOSPHERIC DEFORMATION |
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Trench suction
Trench suction has long be disregarded as a significant tectonic force. Recently, however, it has been suggested that trench suction and slab-pull forces are of comparable magnitude but are of opposite sign.
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Maximum tectonic driving force
Disregarding all the resistive forces, the sum of the slab-pull force and ridge push force falls within the range -1012 Nm-1 to -1013 Nm-1, with -1013 Nm-1 being a reasonable upper boundary value for the maximum tectonic driving forces that can be applied on a continental lithosphere.
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The role of gravity in lithospheric deformation.
Active Rifting (column on the left) is driven by the gravitational force produced by the thermal thinning of the lithospheric mantle. There is no tectonic force acting on the plate's boundaries, and no convection drag the base of the plate.
Convective thinning (middle column) describes the drag on the lower part of the lithospheric mantle into the convective mantle. This process profoundly impacts on the balance of force acting on the plate.
Back-arc extension (right column) is here explained as the result of an extensional gravitational forces produced by the drag then the removal of the lower part of the overriding plate into the asthernosphere. |
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