The wide variety of species is attributed to the shape of the mountains and their geologic history. The diversity of the elevations in the park, spanning a range from 266.7 meters to 2,024.8 meters (875 to 6,643 feet), creates many different environments in which diverse species make their homes. The Great Smoky Mountains are also some of the oldest mountains in the world, having formed 200 to 300 million years ago, and are arranged from a northeast to southwest direction. During major climatic shifts such as the last ice age in the region 10,000 years ago, species migrated across these mountains because they were not affected by glaciation due to their southern location. The mountains also experience extensive precipitation, leading to abundant plant growth.
The Smokies have a complex and ancient geological history. Initially, the rocks that made up the area were sedimentary, composed primarily of clays, silts, sands, gravels and limited amounts of calcium carbonate. The oldest rocks are approximately 800 million years old in these deposited flat layers. Nearby highlands made of granite and gneiss were weathered, creating sediments that were washed down into lower areas. The age of the rocks in the highlands is estimated to be one billion years old. The weathered material formed the coast of the ancient North American continent during the breaking up of an ancient super-continent. The mountains that we see today were formed when the ancient North American continent collided with ancient Africa and Europe, and closed an early Atlantic Ocean; this reunited the landmasses. This collision, and subsequent uplifting and metamorphosing of the rocks, created the Appalachian Mountains, a mountain chain that spans from Canada to Georgia and was part of the super-continent Pangaea. The Smokies are in the southern portion of this mountain chain. Today, the Smokies are lower than they were due to erosion. Scientists estimate that some areas of the mountains are being worn down approximately two inches every thousand years.
There is some debate as to whether the Smokies are still experiencing uplifting forces, since they possess very distinct features (i.e. steep slopes, high relief, river-incised gorges, frequent mass-wasting occurrences) that seem to indicate that the landscape is changing. Some areas of the region have even experienced uplift of 150% since the Miocene epoch. One explanation for these features is variable erosion of rock layers that make up the mountains. A competing hypothesis explains that the region is still tectonically active due to forces in the Earth’s mantle causing uplift.
If you like hiking, the tall (and potentially growing) Smokies are a great place for you to visit. I spent a day hiking there this past November after a recent snowfall and took some amazing photos. Just be careful—the incredible ecosystems that the Smoky Mountains provide are also home to approximately 1,500 black bears. This is one of the few places in the eastern United States where black bears still live in the wild.
I took this photo while hiking the Great Smoky Mountains in November 2012. I hope you enjoy it!