| The elastic-plastic-viscous lithosphere | |||||||||
| Elastic thickness and brittle-ductile rheology | |||||||||
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| The concept of elastic thickness can be visualized by using graphs of yield strength envelopes.
• Ideal elastic plate. For both high curvature (high bending stress) and low curvature (low bending stress), the plate has the same elastic thickness, e.g. 30km. The elastic plate thickness of an ideal elastic plate is independent of the applied stress. • For a viscoelastic plate part of the bending stress are relaxed through time via viscous flow but the plate retains its elastic thickness. • The elastic thickness of a lithospheric plate with brittle/ductile rheology is thinner at bending stress than for lower bending stress. Both brittle failure and power-law flow contribute to the reduction of the elastic thickness of the plate. |
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| It is easier to break rocks by extension than by compression, as cracks open up in extension (weakening the rock) but close down in compression increasing the overall strength. | |||||||||
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