Carving the Mountains

While the Atlantic Ocean was still in its infancy, the Appalachians were already being attacked by erosion. At the time they formed, the Appalachians were much higher than they are now, more like the present-day Rocky Mountains. For the last 100 million years, erosion has carved away the mountains, leaving only their cores standing in the ridges of today.

Four times during the past 2 to 3 million years, great sheets of ice advanced steadily southward from the polar region. The glaciers did not extend as far south as the Southern Appalachians, but the resulting change in climate did. Animals and plants migrated southward. Species more common to northern climates, such as the saw-whet owl, established themselves in the Southern Appalachians and persist to this day at high elevations. Hunters who were ancestors to the Cherokees also migrated to the east and south during the most recent ice age.

Alum Creek

Effects of the ice ages also can be seen in the rocks. When water freezes in cracks or between rock layers, it gradually wedges the rocks apart. With repeated freezing and thawing in extremely cold climates, boulders accumulate on treeless slopes and at the bases of cliffs or ledges. In the Southern Appalachians, concentrations of boulders can be seen in the present-day forested mountainsides at many places. They are silent testimonies to the ice age.

Even though glaciers have retreated, the process of erosion continues. Mosses and lichens grow on rocks and begin the process of breaking them down. Plants grow in fractures, slowly widening them and enhancing the process of soil development. Rock layers slip along inclined surfaces, break off, and produce landslides. Wind and water continue the process of breaking down the rocks and returning them to the ocean. The sediments from the Southern Appalachians move toward the Atlantic Ocean and the Gulf of Mexico, where they are, once again, deposited on the ocean floor.

Whats next? The age old processes continue. Change is constant.