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Interior Plateau

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Map Legend & Subregion List

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NameColor on MapEPA Code*
Crawford-Mammoth Cave Uplands71a
Mitchell Plain71b
Knobs-Norman Upland71c
Outer Bluegrass71d
Western Pennyroyal Karst Plain71e
Western Highland Rim71f
Eastern Highland Rim71g
Outer Nashville Basin71h
Inner Nashville Basin71i
Little Mountain71j
Hills of the Bluegrass71k
Inner Bluegrass71l
Northern Shawnee Hills71m
Southern Shawnee Hills71n

* This code refers to the US EPA's Level 4 ecoregion codes for the continental U.S., see here.

About the Interior Plateau

The Interior Plateau is a diverse and somewhat oddly-shapped region situated northwest of the southernmost end of the Appalachians. It makes up a large portion of western Kentucky and western Tennessee and has smaller pieces in south-central Indiana, northern Alabama, and southern Illinois, and a tiny piece in southwestern Ohio. It is geologically distinct both from the Appalachians, and from regions to the west and southwest.

The topography here consists of extensive plains interrupted by diverse local features including dissected uplands, knobs, deeply cut valleys along larger streams, and large karst areas. Overall this area is much flatter than the Appalachians to the southeast, but less flat than areas to the northwest and southwest. Owing to the diverse features, both high-gradient and slower-moving streams can be found here. Underlying rocks include limestone, sandstone, siltstone, calcareous shale and other shale. The greater presence of limestone leads to greater alkalinity and buffering capacity in steams, and tends to create fertile soils that are well-suited to agriculture.

The region has a humid subtropical climate with continental influences. There are well-defined seasons. Precipitation is roughly equally distributed year-round but shows a weak seasonality, usually being highest in May and lowest in late summer to early fall. The interior, continental location leads to variable weather from year to year as well as the possibility of severe weather including heat or cold waves, drought, heavy rainfall, and tornadoes.

This area was originally covered with Oak-Hickory Forest, with small amounts of bluestem prairie. It is also home to numerous Limestone glades, a unique ecological community that is most common in this region, where eastern redcedar (Juniperus virginiana) is a dominant plant.

Much of the forests in this region have been cleared for agriculture. There is also significant urbanization in this region, which contains the metro areas of several medium-sized cities: Louisville and Lexington, KY, Nashville, TN, and part of the Cincinnati, OH metro area. All of these cities have experienced significant, sprawling suburban development.

This region is bordered to the east and south by the Appalachians: in the southern portion by the Southwestern Appalachians, and in the north by the Western Allegheny Plateau. The southernmost portion is bordered to the west by the Southeastern Plains. Just north of that there is a small border to the west with the Mississippi Valley Loess Plains. Much of this region is bordered to the north and west, in an irregular, snaking border, by the Interior River Valleys and Hills. The large northeasternmost portion of this region is bordered to the north by the Eastern Corn Belt Plains.

References

1. Wiken, E., Griffith, G. "North American Terrestrial Ecoregions - Level III", Commission for Environmental Cooperation, (2011) Web.