ANCIENT KENTUCKY LAKE EarthCache
Hidden : 12/21/2017
Difficulty:
1 out of 5
Terrain:
1 out of 5

Size: Size: other (other)

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Geocache Description:


This earthcache will bring you to a location that will provide information about some of Paducah's history with water.  The description below will describe an ancient lake that once covered the region.  This is not about the Mississippian Embayment.


IN ORDER TO LOG THIS FIND YOU MUST:   Click on my profile and e-mail the answers for the following questions to me. Do not post your answers when you log in your find. Logs which do not meet the requirements to claim the find will be deleted.

  1. Using your GPSr, what is the elevation above sea-level, in feet, at the base of the information on the wall. 
  2. Based on this reading and the information provided, what was the depth of the Pleistocene lake at your location?
  3. How far above the lake level was the 1937 flood?
  4. The Pleistocene lake was was estimated to cover an area of more than 13.5 BILLION(!) square feet.  What is the volume of water covered by the lake?  (Volume = Area x Depth)
  5. Optional, though greatly appreciated.  Take and log a picture of you (and your group) standing with the "Flood" Wall Mural at the waypoint.

Gravel ridges are found in the in the Ohio, Tennessee, and Clarks Rivers valley extending at least 40 miles from Metropolis, Illinois up the Ohio and Tennessee Rivers.  Elongated, round-crested ridges at an elveation of slightly more than 350 feet above sea-level mark the boundary of the old lake bed (figure 1).  These ridges are 200 to 500 feet wide and from a few hundred feet up to a mile long.  They rise 5 to 20 feet above an extensive lacustrine silt and clay deposits the represents the old lake bed.

Lake 1
Figure 1 - Location of Gravel Ridges in McCracken, Graves, and Marshall Counties, Ky

The ridges consist of poorly sorted gravel composed of chert pebbles and cobbles no larger than 3 inches, and small rounded quartz pebbles. Beach and Bay-mouth bar ridges similar to modern bars have also been identified (figure 2). Though modern bars are similar in in form, they differ in composition. The ancient bars are composed of sub-rounded chert gravel and not angular chert rubble. In many areas, deltaic deposition has occurred at the tributaries of the Ohio, Tennessee, and Clarks Rivers (figure 3). Another striking feature are gravel "islands" surrounded by lacustrine deposits like the township of Kaler, Ky.

Lake 2
Figure 2 - Modern gravel bar across small bay at
low water level of Kentucky Lake, east of Aurora, Ky

Lake 3
Figure 3 - Lacustrine deposits near Symsonia, Ky

Though gravel has been seen along the 350 foot margin in southern Illinois, the ridges have not been mapped.  The lake most likely exended 6 to 8 miles down river to Metropolis. Here the Ohio River have been diverted from its Cache River valley course and impounded by rapid alluviaton or faulting at the Metropolis Gap.

Absence of loess deposits on the gravel ridges indicate a farely young age, possible late Wisconsin Age, 10000 to 15000 years ago.  Terrace deposits in the vicinity of Paducah suggest Mankato age, 10000 to 11000 years ago.


Terminology:
  • Pleistocene Epoch - recent, within the last million years or within the time of man.
  • Lacustrine - relating to lakes.
  • Loess -  an unstratified, loamy deposits, generally very rich; soil delivered by wind.
  • Chert - rock resembling flint.
  • Alluvial - deposited by running water.

Source: Ancient Lake in Western Kentucky and Southern Illinois; Warren I. Finch, Wilds W. Olive, and Edward W. Wolfe, Paducah Ky and Menlo Park Califormia; Geological Survey Professional Paper, Volume 501 (1964)

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