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Contents of 13.3 How does isostasy relate to active geologic processes?

• Isostatic adjustment to changes in crustal weight and thickness causes vertical motion of the crust
• Compressive stress that shortens the crust also thickens it, causing isostatic uplift. Tensional stress thins crust, causing isostatic subsidence of sedimentary basins.
• Isostasy causes crust beneath mountains to rise slowly even though the overall elevation decreases, because the weight of crust decreases as the mountain is eroded. Eroded sediments add mass to basins, causing them to subside.
• Flexural isostasy is a more accurate model than the Pratt and Airy models, which call for rapid crustal motion and vertical blocks of weak crust separated by faults.
• Slow flexural isostatic adjustment to changing weight is well-documented in eastern North America in response to glacial unloading.
• Isostatic adjustment of the crust causes movement along old faults, which accounts for many earthquakes that occur far from plate boundaries.

13.3 How does isostasy relate to active geologic processes?