Cliff and talus communities are a system that includes cliff faces, ledges, cliff-top outcrops or cliff-edge, and the cliff base. Tennessee's cliffs are associated mostly with consolidated rock formations such as limestone, dolomite, shale, sandstone, and a variety of metamorphic types. In the Coastal Plain of West Tennessee there are also cliffs that are formed of unconsolidated materials such as gravel, clay, loess, and lignite. The face of some cliff types may be shear or vertical, they may be deeply recessed and cave-like (e.g. rockhouses), they may be very steeply sloping and with or without ledges. In areas with heavily dissected topography there may not be well-developed cliffs but prominent rock ledges or large rock outcrops and boulders may occur on otherwise forested slopes. Such forested communities with embedded ledge systems are treated under Forests, Woodlands, and Shrublands. At the top of many Tennessee cliffs at the cliff edge there may be open glade-like outcrops. These have been considered by others to be part of the overall cliff community. All cliff communities are subject to erosional forces. Water, wind, mass wasting, freeze-thaw processes are often the major forces responsible for maintaining cliff communities. These erosional processes result in much material that is deposited at the base of the cliff. This jumbled mass of material--called talus and resulting in the formation of a talus slope--is often unstable and loose and is itself often subject to slope creep. Talus communities that are non-forested are treated below on this page. These have few trees rooted among the talus and thus lack or are covered only by a sparse canopy. Forested talus slope communities are treated under the Forest, Woodlands, and Shrublands section. Non-forested talus communities are often covered by crustose lichens and some are covered by vines such as poison ivy (Toxicodenron radicans) or Virginia creeper (Parthenocissus quinquefolia) whereas others are covered by herbs such as Canada leafcup (Polymnia canadensis). On some of the steeper slopes of the Blue RIdge Mountains there are large accumulations of rock debris called blockfields. These are periglacial features that are not necessarily associated with upslope clifflines. On Mount LeConte, Great Smoky Mountains National Park, the Anakeesta slate formation that is associated with the steep upper slopes often is prone to landslides. These landslides support distinctive scree slope communities.
Below, the cliff, talus, blockfield, and scree slope communities of Tennessee are classified by ecoregion location and geology.