On my recent trip to Florida, our flight crossed Tennessee just west of Knoxville. From my east side window on that clear, sunny afternoon, I could easily see the broad swath of the Ridge and Valley Province in the distance. The rolling landscape of the Appalachian Plateau (known as the Cumberland Plateau in this region) lay beneath our path while the more rugged profile of the Smokies stretched across the southeastern horizon.
Nearing the Tennessee and Clinch River Valleys, I noticed a cluster of mountains northwest of Knoxville. Rising along the north edge of the Ridge and Valley swath, these peaks were clearly higher than the adjacent plateau and their topography was more typical of the Smoky Mountains to the south. Confused by what seemed to be an outlier of the Smokies on the north side of the Ridge and Valley, I began looking for an explanation over the following days. I soon learned that this rugged piece of terrain is known as the Crab Orchard Mountains and that it represents the southwestern end of the Cumberland Mountains.
The Cumberland Mountains stretch along the southeast edge of the Appalachian (Cumberland) Plateau; faulting and uplift along this margin, which coincides with the Kentucky-Virginia border and then penetrates central Tennessee, has produced the highest elevations of the Plateau and has given the terrain a rugged, mountainous character. The same is true along the eastern edge of the
Appalachian Plateau in Pennsylvania and West Virginia, where the "Allegheny Front" is typified by high, imposing terrain.
The Crab Orchards harbor fourteen peaks over 3000 feet, the highest landscape in the State outside of the Smoky Mountains. Like the adjacent Plateau, they are composed of Pennsylvanian sedimentary rock (in their case, a thick layer of reddish Crab Orchard Sandstone); by comparison, the core of the Smokies is composed of Precambrian igneous rock, which is at least 500 million years older. Though the age of their component rocks differ, the uplift of the Appalachian Plateau, Cumberland Mountains and Smoky Mountains occurred in concert, as North America collided with Africa, some 250 million years ago.
Nearing the Tennessee and Clinch River Valleys, I noticed a cluster of mountains northwest of Knoxville. Rising along the north edge of the Ridge and Valley swath, these peaks were clearly higher than the adjacent plateau and their topography was more typical of the Smoky Mountains to the south. Confused by what seemed to be an outlier of the Smokies on the north side of the Ridge and Valley, I began looking for an explanation over the following days. I soon learned that this rugged piece of terrain is known as the Crab Orchard Mountains and that it represents the southwestern end of the Cumberland Mountains.
The Cumberland Mountains stretch along the southeast edge of the Appalachian (Cumberland) Plateau; faulting and uplift along this margin, which coincides with the Kentucky-Virginia border and then penetrates central Tennessee, has produced the highest elevations of the Plateau and has given the terrain a rugged, mountainous character. The same is true along the eastern edge of the
Appalachian Plateau in Pennsylvania and West Virginia, where the "Allegheny Front" is typified by high, imposing terrain.
The Crab Orchards harbor fourteen peaks over 3000 feet, the highest landscape in the State outside of the Smoky Mountains. Like the adjacent Plateau, they are composed of Pennsylvanian sedimentary rock (in their case, a thick layer of reddish Crab Orchard Sandstone); by comparison, the core of the Smokies is composed of Precambrian igneous rock, which is at least 500 million years older. Though the age of their component rocks differ, the uplift of the Appalachian Plateau, Cumberland Mountains and Smoky Mountains occurred in concert, as North America collided with Africa, some 250 million years ago.
