Highland Rim
Encyclopedia
The Highland Rim is a geographic term for the area in Tennessee
surrounding the Central Basin
. Nashville
is largely surrounded by higher terrain in all directions.
Geologicially, the Central Basin is actually opposite, being a dome
. The Highland Rim is a cuesta
surrounding the basin, and the border where the difference in elevation is sharply pronounced is an escarpment
. Nashville is located in the northwestern corner of the Basin.
of the larger Interior Low Plateaus province, which in turn is part of the larger Interior Plains
physiographic division. Most of the Highland Rim is located in U.S. EPA
Ecoregion
71, Interior Plateau, which is a part of the Eastern Temperate Forest,
The sections of the Rim are referred to the four cardinal directions, e.g., "Northern Highland Rim", etc. It should be recognized that the Rim is rather continuous and any division of it, including the ones made below, are somewhat arbitrary. The term "Highland" here is relative: it is certainly higher than the Basin it surrounds, but it nonetheless is seldom at an elevation above 1100 feet (335.3 m) above sea level, and never more than about 1400 feet (426.7 m) above sea level except where interrupted, primarily to the southeast, by outliers of the Cumberland Plateau. With the exception of a few broad stream bottoms, the land is characterized by ridges and valleys with a few fairly low hills. The entire region is well watered with many perennial streams, and occasional waterfalls which sometimes delineate the Rim from the Basin which it surrounds.
. Underlying bedrock of the region is chiefly Mississippian limestone
, chert
, shale
, and sandstone
with exposures of Devonian
, Silurian
, Ordovician
, and Cambrian
limestone, chert, and shale. In the northern part of the Western Highland Rim, karstification or sinkhole
s, readily occur in an area with a southern extension of the Pennyroyal plateau of Kentucky, where the karst
is best developed on the Mississippian St. Louis Limestone
and the Ste. Genevieve Limestone
. The area is a hilly area that is bisected by the Tennessee River
and the Cumberland River
valleys.
. Erosion has exposed carbonate bedrock of Late Paleozoic
age. These carbonate rocks contain variable amounts of chert, and are often interbedded with fine grained clastic rocks. As a result, these rocks are more resistant to erosion than the underlying, purer limestones of the Lower (Early) Paleozoic. The geology is diverse, and is
typically limestone at valley floors (around 500 feet (152.4 m) elevation) and sandstone on ridges (to
around 1000 feet). The constituent bedrock is composed primarily of Mississippian, St. Louis, and Warsaw limestone with Fort Payne chert
underlain by Chattanooga Shale that forms a large part of the escarpment. This area is mostly undulating plains, hills, and karst.
border, and the region of Kentucky adjacent to it called the Pennyroyal
is in fact largely a continuation of it under another name.
. Again, the landforms here are continuous with those in adjacent portions of Alabama, although perhaps the most spectacular landforms of any portion of the Rim are to be found here.
The stratigraphy of the Southern Highland Rim is primarily composed of flat-lying limestones, dolomite
s, and shales, and to a much lesser extent, of cherts, siltstone
s, mudstone
s, and very fine grained to conglomeratic
sandstones.
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
surrounding the Central Basin
Nashville Basin
The Nashville Basin, also known as the Central Basin, is a term often used to describe the area surrounding Nashville, Tennessee. The Central Basin was caused by an uplifting known as the Nashville Dome. The Nashville Dome is evidenced by the underlying rock strata that all dip downwards away from...
. Nashville
Nashville, Tennessee
Nashville is the capital of the U.S. state of Tennessee and the county seat of Davidson County. It is located on the Cumberland River in Davidson County, in the north-central part of the state. The city is a center for the health care, publishing, banking and transportation industries, and is home...
is largely surrounded by higher terrain in all directions.
Geologicially, the Central Basin is actually opposite, being a dome
Dome (geology)
In structural geology, a dome is a deformational feature consisting of symmetrically-dipping anticlines; their general outline on a geologic map is circular or oval...
. The Highland Rim is a cuesta
Cuesta
In structural geology and geomorphology, a cuesta is a ridge formed by gently tilted sedimentary rock strata in a homoclinal structure. Cuestas have a steep slope, where the rock layers are exposed on their edges, called an escarpment or, if more steep, a cliff...
surrounding the basin, and the border where the difference in elevation is sharply pronounced is an escarpment
Escarpment
An escarpment is a steep slope or long cliff that occurs from erosion or faulting and separates two relatively level areas of differing elevations.-Description and variants:...
. Nashville is located in the northwestern corner of the Basin.
Geology and physiography
The Highland Rim is a physiographic sectionPhysiographic regions of the world
The physiographic regions of the world are a means of defining the Earth's landforms into distinct regions based upon classic 1916 three-tiered approach defining divisions, provinces, and sections...
of the larger Interior Low Plateaus province, which in turn is part of the larger Interior Plains
Interior Plains
The Interior Plains is a vast physiographic region that spreads across the Laurentian craton of central North America.-Geography:The Interior Plains are an extensive physiographic division encompassing 8 distinct physiographic provinces, the Interior Low Plateaus, Great Plains, Central Lowland,...
physiographic division. Most of the Highland Rim is located in U.S. EPA
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
Ecoregion
Ecoregion
An ecoregion , sometimes called a bioregion, is an ecologically and geographically defined area that is smaller than an ecozone and larger than an ecosystem. Ecoregions cover relatively large areas of land or water, and contain characteristic, geographically distinct assemblages of natural...
71, Interior Plateau, which is a part of the Eastern Temperate Forest,
The sections of the Rim are referred to the four cardinal directions, e.g., "Northern Highland Rim", etc. It should be recognized that the Rim is rather continuous and any division of it, including the ones made below, are somewhat arbitrary. The term "Highland" here is relative: it is certainly higher than the Basin it surrounds, but it nonetheless is seldom at an elevation above 1100 feet (335.3 m) above sea level, and never more than about 1400 feet (426.7 m) above sea level except where interrupted, primarily to the southeast, by outliers of the Cumberland Plateau. With the exception of a few broad stream bottoms, the land is characterized by ridges and valleys with a few fairly low hills. The entire region is well watered with many perennial streams, and occasional waterfalls which sometimes delineate the Rim from the Basin which it surrounds.
Western Highland Rim
The Western Rim is similarly encountered only a few miles west of Nashville, and extends to the western valley of the Tennessee RiverTennessee River
The Tennessee River is the largest tributary of the Ohio River. It is approximately 652 miles long and is located in the southeastern United States in the Tennessee Valley. The river was once popularly known as the Cherokee River, among other names...
. Underlying bedrock of the region is chiefly Mississippian limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
, chert
Chert
Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color , but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements...
, shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
, and sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
with exposures of Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
, Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
, Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
, and Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
limestone, chert, and shale. In the northern part of the Western Highland Rim, karstification or sinkhole
Sinkhole
A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks or suffosion processes for example in sandstone...
s, readily occur in an area with a southern extension of the Pennyroyal plateau of Kentucky, where the karst
KARST
Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
is best developed on the Mississippian St. Louis Limestone
St. Louis Limestone
The St. Louis Limestone is a large geologic formation covering a wide area of the midwest of the United States. It is named after an exposure at St. Louis, Missouri. It consists of sedimentary limestone with scattered chert beds, including the heavily chertified Lost River Chert Bed in the Horse...
and the Ste. Genevieve Limestone
Ste. Genevieve Limestone
The Ste. Genevieve Limestone is a geologic formation named for Ste. Genevieve, Missouri where it is exposed and was first described. It is a thick-bedded limestone that overlies the St. Louis Limestone. Both are Mississippian in age and part of the Meramecian series.Members of the Ste...
. The area is a hilly area that is bisected by the Tennessee River
Tennessee River
The Tennessee River is the largest tributary of the Ohio River. It is approximately 652 miles long and is located in the southeastern United States in the Tennessee Valley. The river was once popularly known as the Cherokee River, among other names...
and the Cumberland River
Cumberland River
The Cumberland River is a waterway in the Southern United States. It is long. It starts in Harlan County in far southeastern Kentucky between Pine and Cumberland mountains, flows through southern Kentucky, crosses into northern Tennessee, and then curves back up into western Kentucky before...
valleys.
Eastern Highland Rim
The Eastern Rim rises approximately fifty miles east of Nashville, and is bordered to its east by even higher terrain, the Cumberland PlateauCumberland Plateau
The Cumberland Plateau is the southern part of the Appalachian Plateau. It includes much of eastern Kentucky and western West Virginia, part of Tennessee, and a small portion of northern Alabama and northwest Georgia . The terms "Allegheny Plateau" and the "Cumberland Plateau" both refer to the...
. Erosion has exposed carbonate bedrock of Late Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
age. These carbonate rocks contain variable amounts of chert, and are often interbedded with fine grained clastic rocks. As a result, these rocks are more resistant to erosion than the underlying, purer limestones of the Lower (Early) Paleozoic. The geology is diverse, and is
typically limestone at valley floors (around 500 feet (152.4 m) elevation) and sandstone on ridges (to
around 1000 feet). The constituent bedrock is composed primarily of Mississippian, St. Louis, and Warsaw limestone with Fort Payne chert
Fort Payne Formation
The Fort Payne Formation, or Fort Payne Chert, is a geologic formation found in the southeastern region of the United States. It is a Mississippian cherty limestone that overlies the Chattanooga Shale and underlies the St. Louis Limestone . To the north, it grades into the siltstone Borden Formation...
underlain by Chattanooga Shale that forms a large part of the escarpment. This area is mostly undulating plains, hills, and karst.
Northern Highland Rim
The Northern Highland Rim is encountered just a few miles north of Nashville proper and extends to the KentuckyKentucky
The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...
border, and the region of Kentucky adjacent to it called the Pennyroyal
Pennyroyal Plateau
The Pennyroyal Plateau, or, as it is more commonly called in Kentucky, the Pennyrile, is a large area of the state that features rolling hills, caves, and karst topography in general. It is also called the "Mississippi Plateau"....
is in fact largely a continuation of it under another name.
Southern Highland Rim
For the most part the Southern Rim is the farthest from Nashville, rising at some points just a few miles north of the border with AlabamaAlabama
Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...
. Again, the landforms here are continuous with those in adjacent portions of Alabama, although perhaps the most spectacular landforms of any portion of the Rim are to be found here.
The stratigraphy of the Southern Highland Rim is primarily composed of flat-lying limestones, dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
s, and shales, and to a much lesser extent, of cherts, siltstone
Siltstone
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...
s, mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
s, and very fine grained to conglomeratic
Conglomerate (geology)
A conglomerate is a rock consisting of individual clasts within a finer-grained matrix that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts...
sandstones.