Kentucky's physiographic regions comprise the distribution of
prominent topographic features that border the regions, and the
general trend of major rivers. The names of some regions, such as
the Knobs and the Plateaus, are descriptive.
Other regions such as the Bluegrass, Jackson Purchase, and the
Western Coal Field are not named for their landforms but are
nevertheless well-recognized geographic areas with common
socioeconomic histories related to their natural resources. Each
region is characterized by distinctive landscapes produced by
erosion and deposition of different rock types.
The Knobs Region forms a long, narrow region shaped like an
irregular horseshoe with both ends touching the Ohio River. The
Knobs embraces the Bluegrass country on its inner side, the
Mountain area on the east, and the Pennyrile on the west. Its
landscape is one of rounded hills and ancient escarpments. The
Knobs is the smallest of the Kentucky landform regions, covering
2,300 square miles. In the valleys, the land is rich and good for
farming. The knobs are surrounded by farms, which are developed on
sediment called alluvium. The alluvium was deposited in floods from
the river. There are hundreds of isolated, steep sloping, often
cone-shaped hills throughout the narrow region. In physiographic
terms, the hills are monadnocks or erosional remnants. Many of the
knobs are still capped by erosionally-resistant limestones or
sandstones.The sharp slopes of the Knobs are mostly composed of
shales of the Mississippian-age Borden Formation, which are less
resistant to erosion than the overlying limestones and
sandstones.
The Knobs are erosional remnants or outliers of the back wasting
Pottsville Escarpment on the east and Muldraughs Hill on the south
and west of the Bluegrass Region. The region lies in a narrow belt
10 to 15 mi wide and marks the outer limit of the Bluegrass region.
Elsewhere, other knobs occur along the outer margins of the
Pottsville Escarpment between the Cumberland and Mississippian
Plateaus. Although solitary knobs rise above surrounding plains or
valley bottoms, most occupy narrow interfluves between broad
alluvial flood plains of the rivers and creeks dissecting a nearby
escarpment. Trails of knobs extend like fingers from the continuous
cliffs of the escarpment into the adjacent plains. As the distance
from a highland rim increases, knobs become lower, more rounded,
and farther apart. Individual knobs are characterized by
symmetrical concave-upward slopes which rise gently out of the
bottomlands or surrounding plains.
When escarpments are deeply incised by headward-eroding streams,
a drainage network develops. The escarpment marks the boundary
between two retreating regions. Outlying erosional remnants mark
former limits of the scarps. The outliers erode to form "knobs."
Belts of knobs are common at the base of all the major scarps, but
they are most extensive and best known around the outer margin of
the Bluegrass.
Most runoff from Kentucky drains into the Ohio River, which
forms the northern boundary of the ommonwealth; some passes
directly into the Mississippi River, which forms the westernmost
border. The great valleys of the Mississippi and Ohio and the lower
reaches of their tributaries contain terraces underlain by thick
deposits of alluvium and glaciofluvial sediments. Knob terrains
generally develop where resistant caprocks overlie easily eroded
shale and siltstone. As drainage systems work their way headward
into a highland rim, streams cut once-continuous spurs and ridges
of the caprock, creating incipient knobs. Mass wasting sculpts the
hills into their characteristic symmetrical shapes.
The existence of ancient rivers along the Pottsville Escarpment
is evident and promoted the erosion of the plateau. The paleo
erosion is marked in the strata that was formed when eastern
Kentucky was part of a shallow sea. Sandstones created were then
part of volatile processes of the earth and were uplifted. Here in
eastern Kentucky where the narrow outcrop belt of Knobs occurs
along the Pottsville Escarpment on the western edge of the
Appalachian basin, an unconformity in the rock strata is marked by
paleochannels as much as 200 ft deep on underlying Mississippian
limestone.
The Knobs Physiographic Province is characterized by a rugged
landscape with poor soils and thus poor resources. Differential
erosion of overlying more competent Mississippian rocks and the
underlying weaker Devonian rocks resulted in the formation of the
Knobs region, which rings the outer Bluegrass. Abrupt changes in
slope occur at these border areas because the rocks on either side
of the region erode at different rates. The individual knobs are
made of a basal Devonian shale and caprock of Mississippian
sandstone or limestone. The base of the Knobs commonly contain
Devonian black shale. The Knobs region occurs along the outcrop
belt of the Devonian-Mississippian contact. The knobs are usually
associated with the outcrop belt of Silurian and Devonian rocks
which commonly crop out nearby. The view they afford is picturesque
and worth paying a visit for.
To view the Knobs off in the distance, travel down the
Industrial Parkway (KY 67) to the coordinates provided. Take a
picture of the Knobs to post with your log. Then email the answers
to the questions below.
1. What heading are the Knobs located at from the coordinates
provided?
a. East b. West c. North d. South
2. Look due north across a small valley here between hilltops of
the ridge line. Estimate the distance across the adjacent valley
slope to the tree line. The break in the ridge line permits viewing
of the Knobs from the coordinates.
a. 500’ b. 600’ c. 700’
3. Take an elevation reading at the coordinates provided.
4. Travel to Waymark 38 30.778 and 082 48.169 to the rock
outcrop within sight of the pull off area. Notice the fault that
has formed here from folding and uplifting of the plateau on the
north and east side of the Parkway here. Take a picture of the
fault.
5. Within the Pennsylvanian limestone you will notice a coal
seam that runs the entire length of the rock exposure. Estimate the
height of the exposure that remains consistent throughout the
exposure.
a. Less than 1’ thick b. Greater than 1’ thick
The Knobs Region is the area where the mountains begin to rise
as small hills. The vegetation in the area is very diverse
containing many interesting forest communities including maple, oak
and beech tulip poplar forests. The weathered shale soil is not
rich and is easily eroded, making it better adapted to forest
growth. Some of the thickest forest are in the Appalachian Area
along the Knobs region. Lumbering is on the modest scale, with an
average cut of millions of long board feet. It is truly a unique
area.
