Brief immersion of southern Australia by change in relative plate speed

Abstract

Dynamic subsidence and uplift of plates are often explained by the vertical motion of density anomalies in the mantle. Such models predict surface vertical motion rates of less than 100 m Myr−1 at long‐wavelengths with a timespan of tens of Myr. However, during periods of relative sea‐level stability, some of the phases of vertical motion on stable portions of plates have occurred at rates greater than 100 m Myr−1 during episodes that may last only a few Myr. Here, we show that vertical surface motions, with rates greater than 100 m Myr−1 and durations less than a few Myr, can be explained by changes in basal shear stress caused by variation in horizontal motion of a viscous plate relative to the asthenosphere. We apply our physical model to the short‐lived mid‐Eocene immersion of the southern margin of Australia.