Cherokee Park Big Rock EarthCache

	Cherokee Park Big Rock

The area surrounding Cherokee Park’s Big Rock has long been referred to as the Highlands.  The reason for this name is a result of the underling rock structure of this part of Louisville.  The limestone rock layers slope up toward the east from downtown Louisville at about 20 feet or more per mile.  The Louisville and Jeffersonville limestones are about 130 feet higher at Hogan’s Fountain in Cherokee Park than they are at the Falls of the Ohio.  This along with the fact that the limestone bedrock has been eroded down in the valley by the Ohio River and torrents of meltwater from Quanternary period glaciers helps explain why the Highlands sit well above downtown Louisville.
Long before Big Rock came to be, this area of the Highlands was entrenched by Beargrass creek to form the cliffs and valley we see today.
Although the primary water drainage in this area is on the surface, there is a substantial amount of subsurface drainage activity including springs found along the creek and surrounding area.  Louisville limestone is not the best for cave development, but it does allow for some karst activity on a smaller scale.

	Geologic Map of Cherokee Park

To get to Big Rock you will need to follow the lower trail near the creek.  No rock climbing is required on this trail.  The trail however is uneven, can get muddy, is narrow in spots, and the exposed tree roots can present a slipping hazard. Parking is available near the Big Rock Pavilion at N38 13.961 W085 40.936.

Big Rock Pavilion – N38 13.952 W085 40.980
This historic pavilion was built as part of the park improvements envisioned by Fredric Olmsted the designer of Cherokee park.  The shelter was built on Alluvium.  This material from the Quaternary geologic period is composed mainly of a mixture of silt, clay, sand, and gravel.  This glacial outwash material is typical of low lying areas near creek beds in Louisville.  The Big Rock trail starts at the edge of the woods just downstream from this pavilion.

Beargrass Creek – N38 13.967 W085 41.006
This is the Middle Fork of the Beargrass Creek watershed which is the largest in Jefferson County draining over 60 square miles.  The Middle Fork joins the South Fork and then the Muddy fork before dumping into the Ohio River near Towhead Island.  Notice that the creek in this area flows across a solid bed of Louisville limestone.  The elevation here is about 450 feet above sea level.

Occluded Spring – N38 13.960 W085 41.023
The first spring you encounter at the beginning of the trail is located just 5 feet off the trail.  This is an occluded Karst spring.  This type spring really does not issue from an opening but appears to be seeping right out of the ground.

Small Cave Spring – N38 13.959 W085 41.29 Just 30 feet up the trail is a small Cave Spring.  Water here flows out of a bedding plane in the Louisville limestone.  A bedding plane is the contact area between two depositional layers of sedimentary rock.  This usually appears as a horizontal joint or crack.  Water tends to take the easiest route and as it seeps down through the ground and it will find and utilize these bedding planes.  Over time water flowing through the crack continues to enlarge it and eventually a cave is formed.  The cave to the right of the spring actually extends back for more than 20 feet but is only about 2 feet high or less for most of that distance.  Shortly past the spring the trail splits and you will need to take the lower trial.

Small Spring & Cliffs –  N38 13.973 W085 41.054 This is a small ephemeral fracture type spring that flows out of a 3 inch bedding joint about 8 feet above the trail.  It mainly flows following rain but will continue to dribble water for even longer periods during the wetter time of the year. If you look carefully to the left of this spring you might spot some fossil fragments in the limestone.  Unfortunately there is not an abundance of fossil material exposed in this limestone.  This spot also marks the beginning of a 150 foot long Louisville Limestone cliff. There are a total of 4 weeping springs located along this stretch of cliff line. Small Spring  –  N38 13.980 W085 41.060 This is another small ephemeral spring that flows out of a 3 inch bedding joint about 8 feet above the trail.  Notice the Algae and tufa deposit along the wall below the spring.  Tufa is deposited calcium carbonate that had been previously dissolved in the spring water as it passed down through soil above the limestone.  When the spring water hits the fresh air the carbon dioxide levels in the water drop allowing the calcium carbonate to precipitate out forming this coating on the rock.

Big Rock – N38 13.994 W085 41.069 This big giant came to rest in the creek after it broke away and fell from the nearby Louisville limestone cliff many years ago.  No one knows for sure when or how this happened.  Who knows maybe it’s fall could have been helped along by frost wedging or earthquake activity.  What is known is that Big Rock has long been a popular destination for sightseers, picnickers, and swimmers. Through out the decades Big Rock has provided a good platform to jump from into the 6 foot deep water below. Unfortunately because of potential pollution during certain times, swimming is now discouraged but wading is still a popular activity in the creek.  The creek in the immediate area of Big Rock contains a small exposure of Waldron shale which underlies the Louisville Limestone.

At this point you can retrace you steps back on the trial or continue on the trail until you reach the road.  The trail past big rock becomes noticeable rougher and it is not required that you go any further than Big Rock to complete this Earthcache. 

Optional Features Beyond Big Rock

Rock Bridge – N38 14.014 W085 41.079
Here lies another large rock giant although much smaller than Big Rock.  This one also broke away from the cliff but only about 6 feet away.  The interesting thing about this big boy is that it is now being used as a bridge for the trail.  While your standing on the bridge facing the creek look to your right next to the bank.  There is yet another interesting large Louisville Limestone boulder that is standing on its end like a small monolith.  If you later look at this rock from across the creek it resembles a slice of pizza.

Continue on the trail until you reach the road.  At this point you have two choices.

1.     You can take a left and return to the parking lot on the road that goes above the top of the cliff.  If you decide to return this way look up in the yards of the homes above the road and you may see an outcropping of Jeffersonville limestone at about the 520 foot level.

2.     Or you can cross the bridge and return to the parking lot up the other side of Beargrass Creek.  If you decide to return this way, look for the small cave openings up on the cliff above the creek, and the remains of Wards Mill near the creek.

Old Spring Watering Trough - N38 14.064 W85 41.083
This was one of several old spring fed watering troughs that were located though out Cherokee Park.  These came in handy in the early years of the park for visitors in horse and buggies to provide water for their horses.

Wards Mill – N38 14.045 W085 41.077 Within the old iron fence is the stone ruins of Ward’s mill.  Prior to 1869 David L. Ward built a small stone dam across Beargrass creek and then built a stone mill and distillery nearby.  Nearby farmers would bring their grain to this mill to be ground.  A photo from 1895 shows the mill’s walls standing but partially destroyed.  Near the mill ruins are two mill stones made of a conglomerate material that are set up to show how materials like dried corn were crushed into cornmeal. Millstones that were actually used in mills were called Burrstones.  They were usually made of fine grain sandstone or silicified (impregnated with silica) limestone.

The dirt path next to Wards Mill ruins will take you back upstream along the creek past Big Rock to the Beargrass Creek Bridge. Cross this bridge to return to the Big Rock Pavilion parking lot.

To get credit for this Earthcache post a picture of yourself at Big Rock and send an email to Mooseky@gmail.com with the answers to the following questions

Questions:
1.  How far does the water drop from the Cave Spring down into Beargrass Creek.
2.  What is the Calcium Carbonate that’s deposited below the springs called?
3.  How many springs do you pass by before you get to Big Rock?
4.  What is the approximate height of the cliff on the way to Big Rock?
5.  What Kind of rock is Big Rock?  (What is it composed of?)
6.  Just How BIG is Big Rock?  (Estimate the Length, Width and Height)

Please use caution when in the area, these rocks can be slippery.  Climbing on the rocks is discouraged and can be dangerous.  Remember our parks are sanctuaries.  No removal of natural resources – such as rocks, plants and flowers is allowed.

References:
Geologic Map of The Louisville East Quadrangle, Jefferson County Kentucky by Roy C. Kepferle – 1974.

Why Are The Highlands High? by Barbara Conkin – 2003.
Cherokee Triangle: A History Of The Heart Of The Highlands by Samuel W. Thomas – 2003.

The Encyclopedia of Louisville by John E. Kleber – 2000.