of the asthenosphere. Areas with higher viscosity are subject to quick isostatic rebound while in regions of low viscosity crustal uplift occurs at a slower rate. Uplift is still occurring through isostatic rebound from the Last Glacial Maximum. Glacial isostatic rebound leads to sea level regression which can be measured using 14C dating to determine the age of sublittoral sediment in different regions along the seafloor. Notes Plate tectonics Vertical position