The rates at which geologic processes occur range from imperceptibly slow to exceptionally fast.

At the slow end of the spectrum, mountain ranges rise, basins subside, and tectonic plates move over time periods that span many millions of years. Recent research using repeated GPS (global positioning satellite) measurements of crustal deformation has shown, for example, that the Los Angeles basin is being shortened at a rate that is on the order of a few millimeters per year as the result of movement along faults throughout the basin. Likewise, the rate at which the earth's crust rebounds after the retreat of continental glaciers is generally on the order of a few millimeters per year and decreases with time. Measurements of offset strata cut by faults, combined with radiometric age dating, also suggest that crustal deformation rates are on the order of...