Twin Falls EarthCache
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Twin Falls EarthCache
Located near the junction of Caney Fork and Collins rivers you will find the wonderful waterfall pictured below.
Known as Twin Falls these waterfalls are, (as far as I know) unique in the United States and maybe the world, in of the fact that prior to 1916 they did not exist, they are man made. But not in a way you might first suppose.
The Story of Twin Falls.
Our story actually begins millions of years ago during the Paleozoic age when the rocks forming the western edge of the Cumberland Plateau were deposited in layers. These Layers eventually became the base of a raised area of land in middle Tennessee that became known as the Eastern Highland Rim.
The Eastern Highland Rim of the state of Tennessee contains some of the best examples of Karst topography to be found anywhere in the world.
Karst topography is a landscape that consists of caves and sinks formed by the dissolving of rock layers by water. Such rock layers are usually carbonate type rocks such as limestone or dolomite. Many karst regions consist of surface features such as sinkholes dolines and caves. In some areas surface features may be completely absent where the soluble rock is confined by another type of rock strata. Most karst regions also include numerous caves, but large caves themselves are not required to define an area as karst topography. However this area that lies between Nashville and Knoxville consists of carbonate rock dating to the Late Paleozoic age and lying over purer limestone of the Early Paleozoic age. As a result of this combination thousands of caves have formed in this area. Twin Falls is a result of this specific combination of geological layers combined with a unique route taken by the meandering of the Collins river over eons of time have given rise to one of the most unusual waterfalls to be found anywhere in the world.
In 1901, Nashville entrepreneur Arthur Dyer formed the Great Falls Power Company and purchased land on either side of the Caney Fork River gorge near Rock Island Tennessee with plans to build a dam. After several years of failed attempts at securing financing for the project he sold the land to the Tennessee Power Company in 1912. With outside financing construction on the dam began immediately but was soon stopped cold by the floods of 1913. Despite the set backs construction resumed two years later, and in 1916 the Great Falls Dam finally closed its gates and Great Falls Lake Begin to form.
The Location of the dam (Indicated by the Red Arrow Below) Resulted in the effective damming of not only the Caney Fork River, (Indicated by the black dotted line below), but also the Collins River, (Indicated by the red dotted line below) This unique location gave rise to at least two remarkable features that exist no where else in the world.
The appearance of Twin Falls
The primary subject of this Earthcache is Twin Falls, this is their story.
From the very beginning of construction Great falls Dam was plagued with leakage caused by the significant Karst topography common in the area. Consequently much grouting was required to seal and make the dam viable. Once Great Falls Dam was complete and the level of the newly created Great Falls Lake begin to rise, previously unknown caves became apparent when the Collins River to the south begun to leak through the meander neck, (blue arrow above,) between the then quickly rising Great Falls Lake and the now much lower Caney Fork gorge. These caves were never sealed and because of this highly unusual set of circumstances we have this wonderful the cascade now known as Twin Falls.
Even stranger is the fact that no one source for the falls has ever been identified. The water that forms Twin Falls is believed to seep through numerous small channels and cracks in the rocks along the north shore of Collins River before joining together in a underground cavern that exits in the cliffs below the Great Falls generating station.
Great Falls power generation.
The second distinguishing feature of the area is the placement of the power house and the route used for the water that passes through the TVA operated generators. While most hydro plants around the world are built adjacent to dams and many are actually integral to the construction of the dam itself, the Great Falls hydro plant is the exception. As you can see from aerial photo below, the Great Falls hydro plant (indicated by the green arrow) is built more than ¾ mile below the dam itself, and the intake towers (indicated by the black arrows) are actually in the Collins River several hundred feet to the south, and the water tunnels (indicated by the blue dotted lines) pass directly under the public road.
Taken together the unique geographic features of the area chosen for the Great Falls Dam combine to make Rock Island State Park an interesting as well as educational area to visit while out caching.
One more interesting aspect of the area is the name Great Falls itself. Most people today assume that name refers to the twin water falls described above, it does not. They are named and referenced here correctly as Twin Falls, the name Great Falls actually refers to a cascade waterfall in the gorge of the Caney Fork River, about half way between the Great Falls Dam and the Great Falls power house, indicated by the red arrows in the photo below.
In order to log this cache you must;
Take a photo of yourself standing at the given coordinates with your GPS and Twin Falls in the background, and post to your log.
And then perform any two of the four following tasks.
1 Count the number of steps in the stairway in front of you when you reach the parking area and e-mail the answer.
2 Calculate, or estimate to the best of your ability, how long you think the tunnels are passing through the rock from the intake towers in the Collins River to the south and the power house in the Caney Fork gorge are, and e-mail the answer.
3 Using your GPS walk along the trail across from the falls and measure the width of the falls, and e-mail your answer.
4 Take a GPS altitude reading at the trail opposite the falls then drive to the public road on top of the meander neck above the falls and take a second altitude reading and e-mail me the difference.
Any log not complying with the assigned tasks is subject to deletion.
Additional Hints
(No hints available.)