Shape of the Earth
Changes in the shape of the Earth occur for many reasons: tides, tectonic activity, changes in the loading on the surface of the Earth (one example being from the seasonal transport of water), and many others. Presently, these changes are measured by satellite observations, very long base line interferometry or other geodetic techniques. Beyond the modern estimates, changes in the Earth's oblateness (i.e flatness) thousands or even millions of years ago have been estimated from periodicities within the geological record. Current estimates have the oblateness of the Earth remaining essentially constant over the past 25 Ma. However, with Jerry Mitrovica, Alex Forte, Petar Glisovic and Peter Huybers we demonstrated that this is interpretation of the history of the long-wavelength shape of the planet is inconsistent with our present understanding of the rheology of the Earth's mantle.