American mountain range along North Carolina/Tennessee border
The Great Smoky Mountains (, "Equa Dutsusdu Dodalv") are a mountain range rising along the Tennessee–North Carolina border in the southeastern United States. They are a subrange of the Appalachian Mountains and form part of the Blue Ridge Physiographic Province. The range is sometimes called the Smoky Mountains, and the name is commonly shortened to the Smokies. The Smokies are best known as the home of the Great Smoky Mountains National Park, which protects most of the range. The park was established in 1934 and, with over 11 million visits per year, is the most visited national park in the United States.
The Smokies are part of an International Biosphere Reserve. The range is home to an estimated of old-growth forest, constituting the largest such stand east of the Mississippi River. The coves hardwood forests in the range's lower elevations are among the most diverse ecosystems in North America, and the Southern Appalachian spruce–fir forest that covers the upper elevations is the largest of its kind. The Smokies are home to the densest black bear population in the Eastern United States and the most diverse salamander population outside of the tropics.
Along with the biosphere reserve, the Great Smoky Mountains have been designated a UNESCO World Heritage Site. The U.S. National Park Service preserves and maintains 78 structures within the national park that were once part of the numerous small Appalachian communities scattered throughout the range's river valleys and coves. The park contains five historic districts and nine individual listings on the National Register of Historic Places.
The name "Smoky" comes from the natural fog that often hangs over the range and presents as large smoke plumes from a distance. This fog is caused by the vegetation emitting volatile organic compounds, chemicals that have a high vapor pressure and easily form vapors at normal temperature and pressure.
Geography.
The Great Smoky Mountains stretch from the Pigeon River in the northeast to the Little Tennessee River in the southeast. The northwestern half of the range gives way to a series of elongate ridges known as the "Foothills," the outermost of which include Chilhowee Mountain and English Mountain. The range is roughly bounded on the south by the Tuckasegee River and to the southeast by Soco Creek and Jonathan Creek. The Smokies comprise parts of Blount County, Sevier County, and Cocke County in Tennessee and Swain County and Haywood County in North Carolina.
The sources of several rivers are located in the Smokies, including the Little Pigeon River, the Oconaluftee River, and Little River. Streams in the Smokies are part of the Tennessee River watershed and are thus entirely west of the Eastern Continental Divide. The largest stream entirely within the park is Abrams Creek, which rises in Cades Cove and empties into the Chilhowee Lake impoundment of the Little Tennessee River near Chilhowee Dam.
Other major streams include Hazel Creek and Eagle Creek in the southwest, Raven Fork near Oconaluftee, Cosby Creek near Cosby, and Roaring Fork near Gatlinburg. The Little Tennessee River passes through five impediments along the range's southwestern boundary, namely Tellico Lake, Chilhowee Lake, Calderwood Lake, Cheoah Lake, and Fontana Lake.
Notable peaks.
The highest point in the Smokies is Kuwohi, the tallest mountain in Tennessee, which rises to an elevation of . It has the range's highest topographic prominence at . Mount Le Conte is the "tallest" (i.e., from immediate base to summit) mountain in the range, rising from its base in Gatlinburg to its summit.
Climate.
The Smokies rise prominently above the surrounding low terrain. For example, Mount Le Conte () rises more than a mile (1.6 km) above its base. Because of their prominence, the Smokies receive a heavy annual amount of precipitation. Annual precipitation amounts range from , and snowfall in the winter can be heavy, especially on the higher slopes. For comparison, the surrounding terrain has annual precipitation of around . Flash flooding often occurs after heavy rain.
In 2004, the remnants of Hurricane Frances caused major flooding, landslides, and high winds, which were soon followed by Hurricane Ivan, making the situation worse. Other post-hurricanes, including Hurricane Hugo in 1989, have caused similar damage in the Smokies.
As for temperatures, the average temperature difference between the mountains (Newfound Gap around MSL and the valleys (Park Headquarters around MSL in the Great Smoky Mountains National Park is between 10 and 13 °F (6 and 7 °C) with highs and between 3 and 6 °F (2 and 3 °C) with lows. The difference between high temperatures is similar to the moist adiabatic lapse rate (3.3 degrees Fahrenheit per 1,000 ft), while the smaller difference between low temperatures is the result of frequent temperature inversions developing in the morning, especially during autumn.
Strong damaging winds (, or sometimes greater) are observed a few times each year around the Smoky Mountains during the cool season (October through April), as a result of a phenomenon known as mountain waves. These mountain wave winds are strongest in a narrow area along the foothills and can create extensive areas of fallen trees and roof damage, especially around Cades Cove in the Great Smoky Mountains National Park and the Camp Creek community. Strong winds created by mountain waves were a contributing factor with the devastating Gatlinburg fire on November 28, 2016 during the 2016 Great Smoky Mountains wildfires. Damaging winds can also be generated by strong thunderstorms, with tornadoes and strong thunderstorm complexes (also known as mesoscale convective systems) occasionally affecting the Smoky Mountains.
The climate of Kuwohi is hemiboreal (Köppen "Dfb", Trewartha "Dcb"). As with much of the southern Blue Ridge, the area qualifies as part of the Appalachian Rainforest. On the other hand, Gatlinburg's climate is four-season subtropical ("Cfa") under Köppen (oceanic "Do" under Trewartha), typical of Tennessee.
Geology.
Most of the rocks in the Great Smoky Mountains consist of Late Precambrian rocks that are part of a formation known as the Ocoee Supergroup. The Ocoee Supergroup consists primarily of slightly metamorphosed sandstones, phyllites, schists, and slate. Early Precambrian rocks, which include the oldest rocks in the Smokies, comprise the dominant rock type in the Raven Fork Valley (in the Oconaluftee valley) and lower Tuckasegee River between Cherokee and Bryson City. They consist primarily of metamorphic gneiss, granite, and schist. Cambrian sedimentary rocks are found among the outer reaches of the Foothills to the northwest and in limestone coves such as Cades Cove.
The Precambrian gneiss and schists—the oldest rocks in the Smokies—formed over a billion years ago from the accumulation of marine sediments and igneous rock in a primordial ocean. In the Late Precambrian period, this ocean expanded, and the more recent Ocoee Supergroup rocks formed from accumulations of the eroding land mass onto the ocean's continental shelf.
By the end of the Paleozoic era, the ancient ocean had deposited a thick layer of marine sediments which left behind sedimentary rocks such as limestone. During the Ordovician period, the North American and African plates collided, destroying the ancient ocean and initiating the Alleghenian orogeny—the mountain-building epoch that created the Appalachian range. The Mesozoic era saw the rapid erosion of the softer sedimentary rocks from the new mountains, re-exposing the older Ocoee Supergroup formations.
Around 20,000 years ago, subarctic glaciers advanced southward across North America, and although they never reached the Smokies, the advancing glaciers led to colder mean annual temperatures and an increase in precipitation throughout the range. Trees were unable to survive at the higher elevations and were replaced by tundra vegetation. Spruce-fir forests occupied the valleys and slopes below approximately . The persistent freezing and thawing during this period created the large blockfields that are often found at the base of large mountain slopes.
Between 16,500 and 12,500 years ago, the glaciers to the north retreated and mean annual temperatures rose. The tundra vegetation disappeared, and the spruce-fir forests retreated to the highest elevations. Hardwood trees moved into the region from the coastal plains, replacing the spruce-fir forests in the lower elevations. The temperatures continued warming until around 6,000 years ago, when they began to gradually grow cooler.
Flora.
Heavy logging in the late 19th century and early 20th century devastated much of the forests of the Smokies, but the National Park Service estimates of old-growth forest remains, comprising the largest old-growth stand in the Eastern United States. Most of the forest is a mature second-growth hardwood forest. The range's 1,600 species of flowering plants include over 100 species of native trees and 100 species of native shrubs. The Smokies are also home to over 450 species of non-vascular plants and 2,000 species of fungi.
The forests of the Smokies are typically divided into three zones:
Appalachian balds—patches of land where trees are unexpectedly absent or sparse—are interspersed through the mid-to-upper elevations in the range. Balds include grassy balds, which are highland meadows covered primarily by thick grasses, and heath balds, which are dense thickets of rhododendron and mountain laurel typically occurring on narrow ridges. Mixed oak-pine forests are found on dry ridges, especially on the south-facing North Carolina side of the range. Stands dominated by the Eastern hemlock ("Tsuga canadensis") are occasionally found along streams and broad slopes above .
Cove hardwood forest.
Cove hardwood forests, which are native to southern Appalachia, are among the most diverse forest types in North America. The cove hardwood forests of the Smokies are mostly second-growth, although some are still old-growth. The Albright Grove along the Maddron Bald Trail (between Gatlinburg and Cosby) is an accessible old-growth forest with some of the oldest and tallest trees in the entire range.
Over 130 species of trees are found among the canopies of the cove hardwood forests in the Smokies. The dominant species include yellow birch ("Betula alleghaniensis"), basswood ("Tilia americana"), yellow buckeye ("Aesculus flava"), tulip tree ("Liriodendron tulipifera"; commonly called "tulip poplar"), silverbells ("Halesia carolina"), sugar maple ("Acer saccharum"), cucumber magnolia ("Magnolia acuminata"), shagbark hickory ("Carya ovata"), Carolina hemlock ("Tsuga caroliniana") and eastern hemlock ("Tsuga canadensis"). The American chestnut ("Castanea dentata"), which was arguably the most beloved tree of the range's pre-park inhabitants, was killed off by the introduced Chestnut blight in the 1920s.
The understories of the cove hardwood forest contain dozens of species of shrubs and vines. Dominant species in the Smokies include the Eastern redbud ("Cercis canadensis"), flowering dogwood ("Cornus florida"), Catawba rhododendron ("Rhododendron catawbiense"), mountain laurel ("Kalmia latifolia"), and smooth hydrangea ("Hydrangea arborescens").
Northern hardwood forest.
The mean annual temperatures in the higher elevations in the Smokies are cool enough to support forest types more commonly found in the northern United States. The northern hardwood forests constitute the highest broad-leaved forest in the eastern United States. About are old-growth.
In the Smokies, the northern hardwood canopies are dominated by yellow birch ("Betula alleghaniensis") and American beech ("Fagus grandifolia"). White basswood ("Tilia heterophylla"), mountain maple ("Acer spicatum") and striped maple ("Acer pensylvanicum"), and yellow buckeye ("Aesculus flava") are also present. The understory is home to diverse species such as coneflower, skunk goldenrod, Rugels ragwort, bloodroot, hydrangea, and several species of grasses and ferns.
A unique community is the beech gap, or beech orchard. Beech gaps consist of high mountain gaps that have been monopolized by beech trees. The beech trees are often twisted and contorted by the high winds that occur in these gaps. Why other tree types such as the red spruce fail to encroach into the beech gaps is unknown.
Spruce-fir forest.
The Southern Appalachian spruce–fir forest—also called the "boreal" or "Canadian" forest—is a relict of the ice ages, when mean annual temperatures in the Smokies were too cold to support a hardwood forest. While the rise in temperatures between 12,500 and 6,000 years ago allowed the hardwoods to return, the spruce-fir forest has managed to survive on the harsh mountain tops, typically above . About of the spruce-fir forest are old-growth.
The spruce-fir forest consists primarily of two conifer species—red spruce ("Picea rubens") and Fraser fir ("Abies fraseri"). The Fraser firs, which are native to southern Appalachia, once dominated elevations above in the Smokies. Most of these firs were killed, however, by an infestation of the balsam wooly adelgid, which arrived in the Smokies in the early 1960s. Thus, red spruce is now the dominant species in the range's spruce-fir forest. Large stands of dead Fraser firs remain atop Kuwohi and on the northwestern slopes of Old Black. While much of the red spruce stands were logged in the 1910s, the tree is still common throughout the range above . Some of the red spruces are believed to be