Plate Tectonics

Plates move at rates of about an inch (a few centimeters) per year. Scientists first estimated the rate of plate movement based on radiometric dating of ocean crust. By determining the age of a crustal sample, and knowing its distance from the MOR at which it formed, they estimate the rate of new ocean floor production and plate movement. Today, satellites capable of measurement of plate motion provide a more direct method. Results from these two methods agree fairly closely. The fastest plates move more than 4 in (10 cm) per year. The rate of motion of the North American plate averages 1.2 in (3 cm) per year.