Lithosphere deformation by continental ice sheets

• Published in: Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1981
• Subjects: Ice Sheet
• Online Access: http://dx.doi.org/10.1098/rspa.1981.0165; https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.1981.0165

In treating problems of mantle deformation, a common assumption of convenience is that deformation is viscous or viscoelastic. An important consequence of this assumption is the unproven prediction that the lithosphere is depressed far beyond the margins of steady-state continental ice sheets at the time of their maximum extent. Depression beyond the margins of shrinking ice sheets is proven by the formation of proglacial lakes along melting margins of retreating late Wisconsin-Weichselian ice sheets. No such lakes existed during the maximum extent of these ice sheets. An investigation of viscoplastic deformation in anisotropic polycrystalline rocks leads to the conclusion that transient creep in the lithosphere is predominantly time-dependent viscous flow, but that slow steady-state creep in the lithosphere is time-independent viscoplastic flow and begins at a viscoplastic yield stress. These results predict lithosphere depression beyond the margin of a growing or shrinking ice sheet, but not beyond the margin of a steady-state ice sheet at its maximum extent.