Lithospheric flexure and uplifted atolls

Abstract

Contrary to the expectation that islands should monotonicalIy sink as the aging sea floor thermally contracts, some atolls that were formerly at sea level are now elevated as much as 70 m. A eustatic sea level high cannot explain the magnitude of the larger uplifts or the simultaneous occurrence of elevated and sea level atolls. The observation that recently active volcanoes are found near these raised atolls suggests that they have been tectonically uplifted by the loading effect of the volcanoes. By modeling the oceanic lithosphere as an elastic plate overlying a fluid asthenosphere we can both explain the varying amounts of elevation and bracket the effective flexural rigidity of the oceanic lithosphere between 1.7 and 2.5 ×10 22 N m.