Geoscience Reference
In-Depth Information
4.2 Regional Landscape
Geologic and environmental issues in Mammoth Cave National Park are affected
by areas far beyond the park boundary. The erosional dynamics between the Green
River and tributaries, rocks in the Chester Upland, karst valleys in the park, and the
Pennyroyal Plateau all influence the shape of the land, cave development, flora and
fauna communities, and human culture.
Erosion is the removal of rock and soil material that has been broken down or
dissolved over the years. Erosion by water, whether above or below ground, is the
primary agent that sculpts the landscape, and the variable rate of this erosion and the
type of rock dictates the shape of the land. This is the reason we have the distinc-
tive Chester Upland caprock sequence, karst valleys connected with the Pennyroyal
Plateau, and the Dripping Springs Escarpment, which separates these major phys-
iographic areas. The insoluble rocks, mainly sandstone, of the Chester Upland are
more resistant to erosion and are able to remain high above the soluble limestone
of the Pennyroyal Plateau. The Pennyroyal Plateau and its underlying limestone are
spectacularly pitted with countless depressions called sinkholes. In fact, this area
is commonly called the Sinkhole Plain. Sinkholes are formed when openings in
the limestone are widened by the dissolving action of water. The karst valleys in
between the resistant ridges of the Chester Upland once contained surface streams
that drained into the Green River. As the streams eroded through the caprock and
encountered the soluble limestone, the water was diverted underground, forming a
karst landscape (Fig.
4.2
).
A karst landscape is one that is underlain by soluble rocks (mainly limestone)
and contains features such as sinkholes, caves, springs, and disappearing streams.
Much of Kentucky's farmland, major cities, and recreational lands are underlain by
karst, where springs and water wells provide water to thousands of people. About
55% of Kentucky is underlain by limestones that could develop a karst landscape
given enough time, and about 38% of the state has at least some development of
karst features (Currens
2002
). The Pennyroyal Plateau is one of the largest regions
Fig. 4.2
Cross-section through the Mammoth Cave area showing the relationship of the cave to
the landscape and geology. Modified from Palmer, A.N. (1981; credit to Authur N. Palmer and
Cave Books for its use)
