Oak Hill Falls at Grahn EarthCache

This EarthCache is located near Olive Hill, Ky. in the community of Grahn. The falls and the rock shelter can be viewed from the pull off making this a terrain of 1.0. If you walk to the falls it would be a 1.5

Oak Hill Falls at Grahn

The Waterfall

This waterfall is a two step system with the water falling first onto a ledge and then plunging downward again into a pool. This occurs most spectacularly after a heavy rain, but will continue for several days afterward. It is unique in that most of these areas require a moderate to significant hike to reach a similar area, especially one with this height.

A water fall is where a body of water such as a stream or river that flows over erosion resistant rock with a sudden break in elevation. Often there are rock layers underneath the harder rock that breaks away due to gravity or are eroded away by “splashback”, water splashing from the pool and striking the bedrock behind the falls. This forms a rock shelter behind the waterfall as seen at these coordinates. Over time the rock at the top will erode away and the waterfall will “retreat”, or move farther upstream. Notice at the top this process is evident as we can see a crescent shape with the water flowing near the middle. This crescent has been eroded away, mostly in the middle due to the greatest amount of water erosion at this location.

The diagram below shows this process which is still going on at this site, note the undercutting (1) and the waterfall retreat (4).

Types of waterfalls:

Block:Water descends vertically from a wide stream or river.

Cascade:Water descends a series of rock steps.

Cataract:A large, powerful waterfall.

Fan:Water spreads horizontally as it descends while remaining in contact with bedrock.

Horsetail: Descending water maintains some contact with bedrock.

Plunge:Water descends vertically, losing contact with the bedrock surface.

Punchbowl: Water descends in a constricted form and then spreads out in a wider pool.

Tiered: Water drops in a series of distinct steps or falls.

Multi-step:A series of waterfalls one after another of roughly the same size each with its own sunken plunge pool.

The Rockhouse and What it is Made Of

The rock that is seen at this location is sedimentary. It has been eroded away from rocks millions of years ago and turned into sediments. These tiny sand-grain sized or smaller particles were washed into the shallow waters of ancient seas and settled to the bottom. Over vast amounts of time these layers of sediments were compacted and cemented together to form the rock we see today. As the land raised (see below for more information on this event) due to the collision of two crustal plates, the shallow seas receded and the process of erosion started all over again.

Contained within the rock that makes up the outcrop you can also see quartz pebbles and gravel, sometimes called “Jack Gravel”. The shape of the pebbles tells us that they were eroded from larger rocks and have been worn smooth by water. As these rocks were in an ancient stream or river bed, flowing water, moving sand and other sediments over the heavier pebbles has removed the sharp edges and left them as we see them today. During times of flooding, the faster moving water would have moved these quartz rocks downstream and ground them against heavier, non-moving rocks further eroding away the pebbles and in turn, eroding away the larger rock as well.

It has been suggested that the quartz itself was transported to this area by ancient rivers that flowed from what is now Canada into Kentucky. According to researchers Stephen Greb from the Kentucky Geological Survey, and Allen Archer from Kansas State University, the river drained nearly as much land in North America as the Amazon does today in South America. The river that was responsible for this transport of materials is of course no longer in existence.

Typically rockhouses are formed when harder material, (such as the higher, overhanging) rock layers seen here are overlaying softer, more easily eroded materials (such as the location of the rock house itself). Over the millions of years since the ancient seas receded erosion has drastically changed the land forming the hills and valleys we see today. Since the arrival of the Native Americans somewhere around 13,000 years ago, rockhouses have provided shelter for those who inhabited the area. Evidence of daily life can be found in many such places across the state. Flint tools, bone fragments, and pottery shards, as well as carbon build up on the rock walls from ancient fires can still be found at some locations.

Qualifications for credit:

To get credit for the EarthCache, email the answers to the following questions and then post a picture of you holding your GPSr with the rock shelter and waterfall in the background (this can be taken from the road if necessary) when you log your find. Posts with no pictures or without emailing the answers will be deleted. If no picture is possible, for instance you dropped your camera in the water or the batteries died, let us know first and we will work something out.

Questions:

1. What is the estimated overall height of the falls where the water flows or would flow?

2. What type of rock is found at this location, igneous, metamorphic, or sedimentary?

3. What type of waterfall is this?

4. Where do some geologists believe the quartz gravels originated?

Credits and Ammosuperman EarthCaches:

Special thanks to Fred, Carolyn, and Harold Collins (I) for showing us this area and for their insight and history of the Grahn region.

Special thanks to Mr. Greg Shuck from the Louisville Firebrick Co. who owns the land and has given permission for EarthCachers to visit this unique site.

This EarthCache was created by a team of two Platinum EarthCache Masters, Ammosuperman EarthCaches are a collaborative effort. We have used resources such as the Internet and magazine articles as well as personal experience in visiting the sites, as research tools in its construction. Our goal is to learn more about our planet and to pass along what we have learned to others having similar interests. We hope you enjoy the experience.

The Appalachian orogeny was a time of mountain building as the supercontinent Gondwana (Europe and Africa) collided with North America approximately 325 million years ago. This collision produced an upwelling of the land creating the Appalachian mountain range that may have been higher than the present day Himalayas. At the point of contact the sedimentary rock was converted to metamorphic rock by pressure from the collision. We can see in southern and eastern Kentucky the synclines and anticlines associated with “folding” of the rock layers. The Pine Mountain area in the southeast of Kentucky is a massive over-thrust fault as a result of the collision.