The article "Insights into Present-Day Crustal Motion in the Central Mediterranean Area from GPS Surveys" (M. Anzidei, P. Baldi, et al., Geophysical Journal International, 2001:98-100) reports that the components of velocity of the earth's crust in Zimmerwald, Switzerland, are 22.10 ± 0.34 mm/year in a northerly direction and 14.3 ± 0.32 mm/year in an easterly direction.
a. Estimate the velocity of the earth's crust, and find the uncertainty in the estimate.
b. Using your answer to part (a), estimate the number of years it will take for the crust to move 100 mm, and find the uncertainty in the estimate.