On a sunny day the Tetons seem ageless and constant. Stand by a river during the spring run-off and listen to the clack as one stone tumbles over another. Hike a mountain trail in the summer and see the tops of sub-alpine fir broken by an avalanche the previous winter. Watch the clouds build along the crest as you race a thunderstorm down from Paintbrush Divide on a summer afternoon. Witness the re-growth of grasses, wildflowers, and sapling lodgepole pines following a fire. Soon you begin to realize that the park is constantly changing. Some of these forces are incredibly powerful and their impact is easily and readily observed. Some, however, work on a time-scale imperceptible to our understanding, but change the landscape in no less dramatic a fashion. Some changes are the result of natural processes and some are the result of human actions. It is certain, however, that change is a constant in the Teton Range.