Our knowledge of the motion of Earth's major tectonic plates, which move at velocities of up to several centimeters per year, has come primarily from observations and dating of marine magnetic anomalies. As mid-ocean ridge magmas cooled, they locked in magnetic signatures that recorded the orientation of Earth's magnetic field and allowed the spreading and the geometry of ocean crust to be reconstructed. More recently, global positioning system (GPS) measurements, which have been made for about 20 years, have provided comparable resolution and perhaps a better indication of current plate motions.
Sella et al. provide a synthesis of GPS data from the past decade and compare it with the best estimates from magnetic anomalies. Overall, the agreement is good, although there are differences in the motions across the North American, South American, and Caribbean plate boundaries. The resolution of the GPS data is sufficient to show that the current plate motion for the Antarctic, North American, and Eurasian plates has been perturbed by the melting of the major ice sheets during the past 15,000 years. -- BH
J. Geophys. Res. 107, 10.1029/2000JB000033 (2002).
