Geography of Tennessee
The U.S. state of Tennessee is geographically diverse, with varying terrains and several distinct physiographic regions. Its landforms range from the Blue Ridge Mountains in the eastern part of the state to flat and fertile plains along the Mississippi River. The state is geographically, legally, culturally, and economically divided into three Grand Divisions: East Tennessee, Middle Tennessee, and West Tennessee.
Overview
Tennessee is in the Southeastern United States. Most of the state is considered part of the Upland South, and the eastern third is part of Appalachia. Tennessee covers roughly, of which, or 2.2%, is water. It is the 16th smallest state in terms of land area. The state is about long from east to west and wide from north to south. Tennessee is geographically, culturally, economically, and legally divided into three Grand Divisions: East Tennessee, Middle Tennessee, and West Tennessee. As culturally and historically distinct regions, the Grand Divisions are sometimes called "The Three Tennessees". Tennessee borders eight other states: Kentucky and Virginia to the north, North Carolina to the east, Georgia, Alabama, and Mississippi on the south, and Arkansas and Missouri on the west. It is tied with Missouri as the state bordering the most other states. It is trisected by the Tennessee River, and its geographical center is in Murfreesboro, the state's sixth-largest city. The boundary between Eastern and Central Time passes across the Cumberland Plateau through the state.Borders
Tennessee's eastern boundary roughly follows the highest crests of the Blue Ridge Mountains, and the Mississippi River forms its western boundary. Due to flooding of the Mississippi River that has changed its path, the state's western boundary deviates from the river in some places. Neither the northern nor the southern border of Tennessee follows a geographic feature. The northern border was originally defined as the parallel 36°30′ north and the Royal Colonial Boundary of 1665, but due to faulty surveys, the border begins north of this line in the east, and to the west, gradually veers north with multiple minute shifts. Once at the Tennessee River in the western part of the state, the border shifts south onto the actual 36°30′ parallel. An 1818 survey erroneously placed the state's southern border south of the 35th parallel; Georgia legislators continue to dispute this placement, as it prevents Georgia from accessing the Tennessee River.Topography
Marked by a diversity of landforms and topographies, Tennessee features six principal physiographic provinces, from east to west, which are part of three larger regions: the Blue Ridge Mountains, the Ridge-and-Valley Appalachians, and the Cumberland Plateau, part of the Appalachian Mountains; the Highland Rim and Nashville Basin, part of the Interior Low Plateaus of the Interior Plains; and the East Gulf Coastal Plain, part of the Atlantic Plains. Minor regions include the southern tip of the Cumberland Mountains, the Western Tennessee Valley, and the Mississippi Alluvial Plain. The state's highest point is Kuwohi, at above sea level. Kuwohi is the highest point on the Appalachian Trail and the third-highest peak in the United States east of the Mississippi River. The state's lowest point,, is on the Mississippi River at the Mississippi state line in Memphis. Tennessee is home to the most caves in the United States, with more than 10,000 documented.Blue Ridge Mountains
The western Blue Ridge Mountains lie within Tennessee's eastern edge. This range is characterized by towering mountains and jumbled terrains, and is divided into several subranges, namely the Great Smoky Mountains, the Bald Mountains, the Unicoi Mountains, the Unaka Mountains, and the Iron Mountains. The average elevation of the Blue Ridge Mountains in Tennessee is above sea level. The state's border with North Carolina roughly follows the highest peaks of this range, including Kuwohi, the state's highest point. The Blue Ridge area was never more than sparsely populated, and today most of it is protected by the Cherokee National Forest, the Great Smoky Mountains National Park, and several federal wilderness areas and state parks.Ridge-and-Valley Appalachians
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 of Tennessee consists of numerous linear parallel ridges and 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. Most of this province is coterminous with the Great Appalachian Valley, where the valleys become broader and the ridges lower. In this region are numerous towns and three of the state's urban areas: Knoxville and Chattanooga, the state's third and fourth-largest cities, respectively; and the Tri-Cities: Bristol, Johnson City, and Kingsport. Numerous tributaries join to form the Tennessee River in the Ridge and Valley Region.Cumberland Plateau and Cumberland Mountains
The Cumberland Plateau rises to the west of the Tennessee Valley. This landform is part of the larger Appalachian Plateau, and is mostly covered by flat-topped tablelands. The elevation of the Cumberland Plateau ranges from about above sea level, with an average elevation of approximately. The eastern part of the plateau is, on average, higher than the western part, and most of the water on the Plateau drains to the west into the Cumberland River. The plateau's eastern edge is relatively distinct, but the western escarpment is irregular, with several long, crooked stream valleys separated by rocky cliffs that run into the interior of the plateau and contain 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 largely undeviating Sequatchie Valley. The boundary between East and Middle Tennessee straddles the top of the Cumberland Plateau, as does the boundary between Eastern and Central Time.Highland Rim and Nashville Basin
West of the Cumberland Plateau is the Highland Rim, an elevated plain that surrounds the Nashville Basin. 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 divided into the Eastern and Western Highland Rim. The Eastern Highland Rim is characterized by relatively level plains dotted by rolling hills, and averages about above sea level. The Western Highland Rim and western parts of the Nashville Basin are covered by a mix of uneven rounded knobs with steep ravines and meandering streams in between. Elevations in the Western Highland Rim range from approximately along the eastern edge to at the western escarpment.Much of the Nashville basin is relatively level, and supports rich, fertile farmland and a great diversity of natural wildlife. It averages about above sea level, although elevations vary greatly, with some hills reaching higher than the Eastern Highland Rim. Porous limestone bedrock underlies the Nashville Basin and much of the Eastern Highland Rim very close to the surface. These areas form karst, containing many caves, sinkholes, depressions, and underground streams. Nashville is in the northwestern corner of the Basin, and most of its suburbs radiate outward to the south, southeast, and east, owing to its geography. Clarksville, the state's fifth largest city, sits in the northwestern Highland Rim.
To the west of the Highland Rim is a narrow region known as the Western Tennessee Valley, which consists of about in width of hilly land that runs along the banks of the Tennessee River. The Tennessee River forms the boundary between Middle and West Tennessee here. Most geographers do not include this region as a major physiographic province of Tennessee. Some maps place the portion of this region west of the Tennessee River as part of the Gulf Coastal Plain; however this is inaccurate, as it is not part of the drainage basin of the Mississippi River.
Gulf Coastal Plain and Mississippi embayment
West of the Tennessee River is the Gulf Coastal Plain, a broad area that begins at the Gulf of Mexico and extends northward into southern Illinois, gradually losing elevation westward. In Tennessee, this plain consists of two distinct sections. From the east, the plain begins with low rolling hills and wide stream valleys, known as the West Tennessee Highlands, or Uplands, and gradually levels out to the west. The flat western part of the plain contains extremely fertile soils, and is one of the most productive cotton producing regions in the country. These parts also contain thick and fertile loess, and end at steep bluffs overlooking the Mississippi embayment. This is the westernmost physiographic division of Tennessee, and is part of the larger Mississippi Alluvial Plain. This flat strip, commonly known as the Mississippi Bottoms, ranges from wide, and has an elevation of less than. It consists of lowlands, floodplains, and swamplands, and is sometimes considered part of the Mississippi Delta region. Memphis is in the southwestern corner of the Gulf Coastal Plain, and is West Tennessee's most populous city. All of West Tennessee is part of the Jackson Purchase historical region, and it is the least populated of the state's Grand Divisions.Geology
Geological formations in Tennessee largely correspond with the state's topographic features, and, in general, decrease in age from east to west. Most of the Blue Ridge Mountains in the east were formed during the Precambrian era, and contain the state's oldest rocks, igneous strata that is more than 1 billion years old. Most of the southern Blue Ridge Mountains are composed of Precambrian granite and sedimentary rocks, and Cambrian strata that have been altered by metamorphism. Most of the formations in East and Middle Tennessee consist of strata deposited during the Paleozoic era. Shale and carbonate rocks that formed during the Ordovician period are found in the Nashville Basin, Ridge-and-Valley region, and the Sequatchie Valley. The inner part of the Nashville Basin is a geological dome that was uplifted between 300 and 400 million years ago during the Carboniferous and Devonian periods. Devonian and Silurian strata are found in the Western Tennessee Valley and in small patches in the Western Highland Rim. The Highland Rim formed during the Mississippian era, and is underlain by soluble limestone bedrock that has formed karst, with patches of chert, shale, and sandstone. The Cumberland Plateau was formed during the Pennsylvanian period about 300 million years ago, and consists predominantly of sandstone, silt, and shale, with an abundance of coal. The eastern part of the Gulf Coastal Plain is composed of Mesozoic Cretaceous; most of the plain to the west was deposited during the Cenozoic Tertiary era. The youngest geological formations in Tennessee are sands and silts deposited during the current Quaternary period, and are located within the Mississippi Alluvial Plain and the valleys of rivers that drain into the Mississippi River.File:Reelfoot Lake.jpg|thumb|right|Reelfoot Lake in northwestern Tennessee was formed by the 1811–1812 New Madrid earthquakes
Devonian and Silurian strata are found in the Western Tennessee Valley and in small patches in the Western Highland Rim, formed 360 to 420 million years ago. The Highland Rim formed during the Mississippian era about 350 million years ago, and is underlain by soluble limestone bedrock that has formed karst, with patches of chert, shale, and sandstone. and the Cumberland Plateau was formed during the Pennsylvanian period about 300 million years ago. It consists predominantly of sandstone, silt, and shale, with an abundance of coal. The eastern part of the Gulf Coastal Plain is composed of Mesozoic Cretaceous strata that appeared between 66 and 145 million years ago; most of the plain to the west was deposited during the Cenozoic Tertiary era between 2.6 and 66 million years ago. The youngest geological formations in Tennessee are sands and silts deposited during the current Quaternary period in the last 2.6 million years, and are located within the Mississippi Alluvial Plain and the valleys of rivers that drain into the Mississippi River.
Tennessee is considered seismically active and contains two major seismic zones, although destructive earthquakes rarely occur in the state. The Eastern Tennessee seismic zone spans the entirety of East Tennessee from northwestern Alabama to southwestern Virginia. The region is considered one of the most seismically active zones in the Southeastern United States, and frequently produces low-magnitude earthquakes. The New Madrid seismic zone is located in the northwestern part of the state. This seismic zone produced a series of devastating earthquakes between December 1811 and February 1812 that formed Reelfoot Lake near Tiptonville.