elevations in eastern North America. The state's border with North Carolina roughly follows the highest peaks of this range, including Clingmans Dome. Most of the Blue Ridge area is protected by the Cherokee National Forest, the Great Smoky Mountains National Park, and several federal wilderness areas and state parks. The Appalachian Trail roughly follows the North Carolina state line before shifting westward into Tennessee. Stretching west from the Blue Ridge Mountains for about are the Ridge-and-Valley Appalachians, also known as the Tennessee Valley or Great Valley of East Tennessee. This area consists of linear parallel ridges separated by valleys that trend northeast to southwest, the general direction of the entire Appalachian range. Most of these ridges are low, but some of the higher ones are commonly called mountains. Numerous tributaries join to form the Tennessee River in the Ridge and Valley region. The Cumberland Plateau rises to the west of the Tennessee Valley, with an average elevation of . This landform is part of the larger Appalachian Plateau and consists mostly of flat-topped tablelands. The plateau's eastern edge is relatively distinct, but the western escarpment is irregular, containing several long, crooked stream valleys separated by rocky cliffs with numerous waterfalls. The Cumberland Mountains, with peaks above , comprise the northeastern part of the Appalachian Plateau in Tennessee, and the southeastern part of the Cumberland Plateau is divided by the Sequatchie Valley. The Cumberland Trail traverses the eastern escarpment of the Cumberland Plateau and Cumberland Mountains. West of the Cumberland Plateau is the Highland Rim, an elevated plain that surrounds the Nashville Basin, a geological dome. Both of these physiographic provinces are part of the Interior Low Plateaus of the larger Interior Plains. The Highland Rim is Tennessee's largest geographic region, and is often split into eastern and western halves. The Eastern Highland Rim is characterized by relatively level plains dotted by rolling hills, and the Western Highland Rim and western Nashville Basin are covered with uneven rounded knobs with steep ravines separated by meandering streams. The Nashville Basin has rich, fertile farmland, and porous limestone bedrock very close to the surface underlies both the Nashville Basin and Eastern Highland Rim. This results in karst that forms numerous caves, sinkholes, depressions, and underground streams. West of the Highland Rim is the Western Tennessee Valley, which consists of about in width of hilly land along the banks of the Tennessee River. West