Abstract

Isostatic depression of the earth's crust beneath an ice cap and postglacial crustal rebound are well documented by observation and are consistent with theory. In the central regions of an ice cap, where adequate time for complete compensation might be expected, crustal deflection will be directly related to ice cap thickness. Deflection beneath the ice will produce crustal tilting in the vicinity of the ice margin. The angle of tilt, when applied to an equation for the elastic crustal deformation of an unfaulted crust, may determine the amount of uplift, a forebulge, at the ice margin. The order of magnitude of tilting can be obtained from the relative uplift of shorelines of glacial lakes and from sub-ice Greenland profiles. Approximate tilts of 0.3 to 0.7 percent are estimated for North America and Greenland, which would produce ice marginal uplift of approximately 80 to 185 meters. Areas where evidence for contemporary and past uplifts may be found are suggested, but such features would be difficult to identify.

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