Welcome to Shelby Park and Bottoms. It is one of the oldest parks
Nashville. In old East Nashville, John Shelby was a physician and
businessman. Also, he was the founder of Shelby Medical School in
Nashville. Dr. John Shelby once owned the land that is now Shelby
Park. Around the turn of the 20th century, a real estate company
purchased the land which the company considered prime for
residential development. To create interest in that section, it was
decided to build an amusement park named for the early 19th century
physician Dr. John Shelby. The park had a roller coaster, offered
band concerts, dances and picnics, boat rides, balloon ascensions,
and horseback riding and there was a time when a free movie was
shown on Friday nights. Unfortunately, the development firm went
bankrupt in 1903. The Nashville Park Commission took and immediate
interest in the site. Shelby Park opened as a public facility for
citizens in 1912.
Within the park is a cave spring.
It is helpful to refer to the geologic time scale as we look at
geologic history of this area of Tennessee. The geologic time scale
was developed by scientists during the 18th century and provides a
general outline for the organization of the Earth’s geologic
and biologic history. The geologic time scale is divided into four
eons. Each eon is then divided into eras with the exception of the
Precambrian. Eras reflect the occurrence of major changes in the
history of the Earth such as patterns of dominance and extinction
of organisms. Each era is then subdivided into periods and then
into epochs that represent smaller sections of time.
A majority of Tennessee’s documented geologic history
began during the Paleozoic Era. Some of the oldest surface rocks in
Tennessee can be dated to this era and are located in eastern
Tennessee. The Paleozoic Era is further divided into the Cambrian,
Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian and
Permian Periods. During the Cambrian Period, Tennessee was still
covered by a shallow sea and a great amount of limy precipitate
hardened to form layers of limestone and dolomite. Internal forces
pushed the hardened layers up into two major domes known as the
Ozark and Nashville Domes that were connected by the Pascola
Arch.
The Nashville Dome of Middle Tennessee is composed of
sedimentary rock from the Ordovician Period. Limestone, sandstone,
shale, coal, conglomerate and chert are the most common sedimentary
rocks found in Tennessee. During this period, Tennessee was still a
warm marine environment, which allowed for continued deposition of
large amounts of limestone and some dolostone, which produced rock
layers thousands of feet thick. The formation of limestone versus
dolostone during this time was determined by seawater composition
and changes in the deposition environment. Many areas of rock
contained up to 95% calcium carbonate as well as phosphates, clay,
iron and silica. Towards the end of the Ordovician Period, land
emerged from the water as a result of the mountain building
processes in eastern Tennessee, exposing the thick carbonate layers
to a massive amount of erosion. The marine invertebrates were
responsible for the production of the thick limestone layers during
this period.
At the end of the Permian Period, after the Allegheny Orogeny,
the majority of Tennessee was never again covered with water, with
the exception of the Mississippi Embayment in West Tennessee. The
Mesozoic Era in Tennessee was an extremely active time of erosion,
which extensively changed features of the landscape.
Mountain-building processes from the Allegheny Orogeny caused land
in East Tennessee to continue to rise, which pushed the seas
westward and formed a coastal plain. Large drainage networks became
established and aided in the erosional and deposition processes of
the state during the Triassic and the Jurassic. By the Jurassic
Period, erosion had affected the Nashville Dome and by the
Cretaceous Period, Mississippian limestone was worn away creating a
karst landscape.
The Quaternary Period is divided into the Pleistocene and the
Holocene or Recent Epochs. The Pleistocene is often called the
“Ice Age” due to as many as four major advancements of
ice sheets that moved across North America during this time.
Tennessee was never directly affected by the encroachment of the
ice sheets; however the alternating extreme periods of cold
temperatures affected the climate, landscapes and life in the
state.
As the sea level changed with the advancement then retreat of
glaciers, patterns of erosion and deposition in rivers and streams
also changed. Tennessee’s extensive cave system and karst
landscape are products of the Quaternary Period with at least 2000
caves formed from the erosion and weathering of the carbonate-based
limestone and dolostone. Many large caves have been developed for
the tourist industry in areas of Sullivan, Blount, Grainger,
Hamilton and Warren Counties.
This location is an example of a karst spring emerging from the
side of a hill exiting through a cave. Though only the entrace to
this cave is big enough to explore, the water you see flowing out
of the right side comes from a well-developed karst conduit system.
Much of the water a karst spring receives is drainage from all the
sinkholes and sinking streams within its groundwater basin,
equivalent to a watershed on the surface.
Once beneath the surface, the groundwater is unevenly
distributed through the karst bedrock. There is plenty of soluble,
carbonate limestone bedrock and enough rain each year to allow for
dissolution of the limestone. Rain as it falls reacts with
carbondioxide to form some carbonic acid, which acidifies the
rainwater. This rainwater filters through cracks and dissolves the
limestoneas it passes carving conduits in the surrounding
limestone. These carrying water from each point where water sinks
joining together underground to form successively larger passages
with ever-increasing flow, which eventually discharges at a
spring.
The amount of water that flows from springs depends on many
factors, including the size of the caverns within the rocks, the
size of the spring basin, and the amount of rainfall. Human
activities also can influence the volume of water that discharges
from a spring. It’s likely that the nearby parking lots and
concrete have diverted much of the water that has been available to
feed this spring in the past.
Cave Springs can be classified by how much water is being
discharged. If a spring flows only after a hard rain is called an
ephemeral spring, but if it flows year-round it is classified as a
perennial spring. This cave spring is an perennial spring.
The largest springs are called "first-magnitude," defined as
springs that discharge water at a rate of at least 2800 L/s. The
scale for spring flow is as follows:
| Magnitude |
Flow (ft³/s, gal/min, pint/min) |
Flow (L/s) |
| 1st Magnitude |
> 100 ft³/s |
2800 L/s |
| 2nd Magnitude |
10 to 100 ft³/s |
280 to 2800 L/s |
| 3rd Magnitude |
1 to 10 ft³/s |
28 to 280 L/s |
| 4th Magnitude |
100 US gal/min to 1 ft³/s (448 US gal/min) |
6.3 to 28 L/s |
| 5th Magnitude |
10 to 100 gal/min |
0.63 to 6.3 L/s |
| 6th Magnitude |
1 to 10 gal/min |
63 to 630 mL/s |
| 7th Magnitude |
1 pint to 1 gal/min |
8 to 63 mL/s |
| 8th Magnitude |
Less than 1 pint/min |
8 mL/s |
| 0 Magnitude |
no flow (sites of past/historic flow) |
To log this cache:
E-mail the answers to the following questions. Do not post these
in your log. Logs without answers within a reasonable amount of
time will be deleted.
1. Estimate the amount of water flowing from the cave at the
time of your visit using the above chart and tell me what magnitude
it was.
2. What was growing at the base of the cave entrance and
what does it tell you about whether or not water is consistently
present.
3. What did you notice above (west) of the cave entrance
that might have an affect on the amount of water flowing now, that
wasn’t present before this area was urbanized?
4. Upload a picture of yourself or group with the cave in
the background with your log. (Optional but preferred)
Thank you for taking the time to explore this area. If you’re
a local resident you may want to consider getting involved with the
local organization that is dedicated to restoring the park and this
site to it’s former grandeur. E-mail me for the
details.
References: United States Geological Survey - Major
Divisions of Geologic Time Scale; Tandsley, Gia The Geologic
History of Tennessee: Tennessee State Museum, January 5, 2007;
Luther, Edward T. Our restless earth – the geologic regions
of Tennessee. Knoxville: University of Tennessee Press, 1977.;
Miller, Robert A. The geologic history of Tennessee, Bulletin 74.
Nashville: Tennessee Division of Geology 1974.; Moore, Harry L. A
geologic trip across Tennessee by Interstate 40. Knoxville:
University of Tennessee Press, 1994.
Websites: Geo World
http://www.geoworld.org/Tennessee/Prehistory; Geology.com
http://geology.com/time/geologic-time-scale.doc; Nashville Geology
Page
http://www.nashvillefossils.com/resources/pages/chattshale.html;
Paleontology Portal http://www.paleoportal.org
index.php?globalnav=time_space§ionnav=state&name=Tennessee;
Statefossils.com http://www.statefossils.com/tn/tn.html; Tennessee
Department of Environment and Conservation
http://state.tn.us/environment/tdg/cop/; Tennessee Division of
Geology - Gray Fossil Site
http://www.state.tn.us/environment/tdg/gray/; Tennessee
Encyclopedia Online,
http://tennesseeencyclopedia.net/imagegallery.php?EntryID=C141; The
Tennessee Conservationist - Gray Fossil Site
http://www.tn.gov/environment/tn_consv/archive/fossil.htm;