Geoid Heights and Flexure of the Lithosphere at Seamounts

摘要

The sea suface height has now been mapped to an accuracy of better than + or - 1 m by using radar altimeters on board orbiting satellites. The major influence on the mean sea surface height is the marine geoid which is an equipotential surface. We have carried out preliminary studies of how oceanic volcanoes, which rise above the ocean floor as isolated seamounts and oceanic islands or linear ridges, contribute to the marine geoid. Simple one- and two- dimensional models have been constructed in which it is assumed that the oceanic lithosphere responds to volcanic loads as a thin elastic plate overlying a weak fluid substratum. Previous studies based on graviity and bathymetry data and uplift/subsidence patterns show that the effective flexural rigidly of oceanic lithosphere and the equivalent elastic thickness T sub e increase with the age of the lithosphere at the time of loading. This models predict that isolated seamounts emplaced on relatively young lithosphere on or near a mid-ocean ridge crest will be associated with relatively low amplitude geoid anomalities (about 0.4-0.5 m/km of height), while seamounts formed on relatively low over the Mid- Pacific Mountains and Line Islands, which formed on or near a mid-ocean ridge crest, and relatively high over the Magellan Seamounts and Wake Guyots, which formed off ridge.