McKenzie, D.

Two different free-air gravity datasets from the Apennines have been analysed in the frequency domain to investigate the mechanisms of support of topography. At short wavelength (λ<150 km) the best fit between the observed and the calculated admittance gives a value of the elastic thickness of 3.7 km. The observed behaviour of the admittance at larger wavelengths (λ>150 km) shows that such topography is not supported by elastic stresses in the lithosphere but is dynamically supported by mantle convection. The distribution of gravity anomalies and topography suggests that the mantle is rising beneath the main topographic bulge of the Apennines and that this flow is maintained by buoyancy forces, rather than being driven by movement of the subducted slab.