Editing Polar motion (section)

==Causes==
The slow drift, about 20 m since 1900, is partly due to motions in the Earth's core and mantle, and partly to the redistribution of water mass as the [[Greenland ice sheet]] melts, and to [[isostatic rebound]], i.e. the slow rise of land that was formerly burdened with ice sheets or glaciers.<ref name=Lambeck/>{{rp|2}} The drift is roughly along the [[80th meridian west]]. Since about 2000, the pole has found a less extreme drift, which is roughly along the central meridian. This less dramatically westward drift of motion is attributed to the global scale mass transport between the oceans and the continents.<ref name=Adhikari/>{{rp|2}}

Major [[earthquakes]] cause abrupt polar motion by altering the volume distribution of the Earth's solid mass. These shifts are quite small in magnitude relative to the long-term core/mantle and isostatic rebound components of polar motion.<ref>{{cite news|first1=Kevin |last1=Voigt |title=Quake moved Japan coast 8 feet, shifted Earth's axis|url=http://www.cnn.com/2011/WORLD/asiapcf/03/12/japan.earthquake.tsunami.earth/index.html?iref=obinsite |date=April 20, 2011 |newspaper=CNN <!-- |access-date={{Date}} automatically using date of last page refresh makes no sense for a citation -->}}</ref>