For this Lab, you do NOT need to print the Figures. Print the question sheet and answer sheets only.
MAMMOTH CAVE, KENTUCKY
Mammoth Cave National Park is one of the finest examples of karst topography in the world. Mammoth Cave is the longest cave in the world (> 215 miles), over twice as long as the second largest in the former Soviet Union. This region has all of the requirements for karst: thick limestone units, pure limestone (>80% CaCO3), humid climate, and well-jointed limestone. Water passing through this limestone dissolves the limestone and carries it in solution to the groundwater. This process has led to cavern formation beneath the surface and sinkholes and disappearing streams on the ground surface.
Figure One shows three distinct physiographic features of Mammoth Cave: the Pennyroyal Plateau, the Chester Upland, and the cliff that separates them, the Dripping Springs Escarpment. The cave is shown as black lines in the layers of limestone. Capping the limestone in places is a shaded layer, the Big Clifty sandstone. On the Pennyroyal Plateau, most of the sandstone has been eroded and remains only on isolated knobs. The general land surface of the Pennyroyal Plain is at a lower elevation today than the Chester Upland. This is because, as you can see in Figure One, the region is very slightly tilted toward the northwest. Toward the southeast, the rock layers occur at progressively higher elevations. The higher rocks are eroded by surface water more rapidly than those in lower elevations. Therefore, toward the southeast, the resistant Big Clifty sandstone is almost entirely removed. Without the resistant layer of sandstone, the limestone is rapidly dissolved, and now the surface of the Pennyroyal Plateau is several hundred feet below the Chester Upland. The Pennyroyal Plain is pockmarked with small sinkholes. Figure Two is a shaded relief diagram of the Mammoth Cave region. The small strip of lowland with numerous pits (sinkholes) at the bottom of the Figure is the Pennyroyal Plateau.
On the Chester Upland, the Big Clifty sandstone caprock is still relatively intact. Therefore caves can form beneath the surface, protected from erosion by the sandstone cap.
Look at the stereo pair of
Hart County, Kentucky.
1. Do you see streams in the
valleys in the photo? Explain.
2. What is the relationship
between sinkhole depth and elevation?
3.What is the overall pattern
of human land use in this area? What type of terrain has been cleared and
what areas have been left wooded?
4. The EPA has investigated
and repeatedly fined several companies in this area for dumping chemical
wastes into nearby sinkholes. Would you drink the water in Echo River,
a subterranean river that flows through Mammoth Cave? Why is ground water
pollution a particularly great hazard in karst areas?
5. In which parts of this photo
would the sandstone cap be present?
Glasgow North, Kentucky topographic
map
1. Why do some sinkholes have
water in them while others do not?
2. Describe the path of rainwater
from the ground surface to the water table in this region.
3. How did Prewitt's Knob form?
4. What is the relief of Prewitt's
Knob?
5. What is the depth of the
sinkhole in the upper left portion of the map (beneath the word "Louisville")?
6. Find a place where a stream
disappears into a sinkhole. Give the latitude and longitude of this location.
Topographic map of Mammoth
Cave National Park.
This map represents the same
area shown in the shaded relief diagram, Figure 2.
1. Find the Dripping Springs
escarpment and give its location.
2. How deep is the Green River
Valley at Nappers Rollover? Why is the Green River so deeply entrenched?
3. Find Woolsie Valley in the
center of the map. Describe the valley and what lies in it.
4. Describe the general trend
or direction of the deep depressions in this part of the map. What does
this pattern mean?
5. Describe the major differences
between sinkholes in the Pennyroyal Plain and those in the Chester Upland
(examples of sinkholes in the Chester Upland are Cedar Sink, Hunt's Sink,
and Double Cellars).
