The Highland Rim is a
physiographic section 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 Highland Rim are referred to the four cardinal directions, e.g., "Northern Highland Rim", etc. The Highland 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 above sea level and never more than about 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. There are occasional waterfalls which sometimes delineate the Highland Rim from the Central Basin which it surrounds.
Western Highland Rim The Western Highland Rim is encountered a few miles west of Nashville and extends to the western valley of the
Tennessee River. The area is hilly, ranging from about 400 to 1000 feet in elevation, and is bisected by the
Tennessee River and the
Cumberland River valleys. 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,
sinkholes 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. Some farming is done in the flatter
interfluves, and in stream and river valleys. The constituent bedrock is composed primarily of
Mississippian aged
St. Louis, and
Warsaw limestones with
Fort Payne chert underlain by
Chattanooga Shale that forms a large part of the escarpment. This area is flatter than the Western Rim, characterizable as
tablelands of moderate relief combined with irregular
plains.
Northern Highland Rim The Northern Highland Rim is encountered a few miles north of Nashville and extends to the
Kentucky border, and the region of Kentucky adjacent to it called the
Pennyroyal is largely a continuation of it under another name as is the
Indiana Uplands, located to the north of the
Ohio River.
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
Alabama. The landforms 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 there. The stratigraphy of the Southern Highland Rim is primarily composed of flat-lying limestones,
dolomites, and shales, and to a much lesser extent, of cherts,
siltstones,
mudstones, and very fine grained to
conglomeratic sandstones. ==References==