Text Box: Interior Low Plateaus Introduction | Main Sections | Karst Features | Meteorite Impact Sites | Resources                                               The Interior Low Plateaus province covers central Tennessee and most of the western two-thirds of Kentucky; minor portions of the province extend into Alabama, Mississippi, Ohio, Indiana and Illinois.  Much of  its eastern border with the Appalachian Plateaus is the prominent  Pottsville Escarpment of relatively resistant sandstone.  (There is also a Pottsville Escarpment in the western portion of the province; it is not as prominent as the escarpment on the eastern border.)  The southern and southwestern boundaries coincide closely with, and in some places are on, the Tennessee River.  This portion of the border also is marked by the transition from the poorly indurated (hardened) rocks of the Atlantic-Gulf Coastal Plain province to the much harder rocks of the Interior Low Plateaus.  The northern border is less well demarcated by prominent physical features or transitional characteristics, and has been established mostly at the southern extent of Pleistocene continental glaciation here; in some sections the line is placed somewhat arbitrarily along the Ohio River, despite the fact that the ice extended slightly south of the river into Kentucky in a few places, and that the topography of this province extends slightly north of the river, although it is mantled there by glacial deposits.  The plateaus in this province, as the name appropriately states, are  relatively low, with most of the province between 500-1,100 feet in elevation.  There is a close relationship between geological structures and topography in the province: Except for the areas of intense folding and faulting in the Ridge and Valley province, there is probably no region in the eastern United States where structure and lithology are any better expressed in the topography than in the Interior Low Plateaus.  The sections and subsections are largely an expression of regional structural control.     The main structural feature in the province is the Cincinnati Arch.  The axis of this gentle anticline lies approximately parallel to, and about 75 miles west of the eastern border of the province.  The Cincinnati Arch is so named because its passes through the city of Cincinnati, Ohio (but it also goes through Frankfort, Kentucky and slightly east of Nashville, Tennessee).  It extends the entire length of the province, stretching 600 miles from northwestern Alabama toward the northeast through Tennessee and Kentucky.  It splits near Cincinnati, with one arm, the Findlay Arch (the northern portion of which is called the Algonquin Arch), continuing into the Central Lowlands province in a northeastward direction toward the western end of Lake Erie; another arm, the Kankakee Arch, extends northwestward toward Wisconsin.  The slopes of the Cincinnati Arch are gentle–only 10 vertical feet per horizontal mile in many areas, and rarely exceed 25-30 feet of rise per mile.  The general slope of the eastern half of the province that lies east of the axis of the Cincinnati Arch is down toward the Appalachian Plateaus; west of the axis the regional slope is down toward the Central Lowlands and Basin of the Mississippi River.  Because of the relatively gentle slopes of the arch, cuestas, rather than hogbacks, have developed on the limbs of the arch.  The edges of these have formed escarpments that are locally prominent, some more than 400 feet high.  These escarpments include: 1) the Pottsville Escarpments in the eastern and western portions of the province; 2) the Highland Rim Escarpment around the Nashville Basin; 3) Muldraugh’s Hill and associated escarpments and the Knobs nearly encircling the Bluegrass section in Kentucky; and 4) Dripping Springs Escarpment in southwestern Kentucky, and its northward continuation into Indiana known as the Chester Escarpment.  inundate The cause of broad upwarping that produced the Cincinnati Arch is not unquestionably known.  Peridotite dikes and sills around the flanks of the arch suggest that deep intrusive igneous activity may have been a factor, but this interpretation is open to question.  The region was probably a basin at one time and uplift was apparently initiated about 470 million years ago during the Ordovician, and rocks of this age occur on the crest of the arch.  Warping was relatively slow and  the arch was not a distinctive geomorphic entity until the Silurian, which began about 438 million years ago.  Periods of uplift and subsidence followed the initial uplift, with the area sometimes inundated by inland seas.     Interior Low Plateaus Introduction | Main Sections | Karst Features | Meteorite Impact Sites | Resources