Welcome to the Rock City Trail!
Welcome to Coopers Rock State Forest! One of the jewels in North Central West Virginia, Coopers Rock offers many scenic views throughout its footprint - and if you were wondering...nearly all of the rocks around you are sandstone. But did you know that the sand used to create this stone was moved here either by wind or water action? We know this because we find evidence of cross-bedding on nearly every outcrop of sandstone.
What is cross-bedding?
Cross-bedding is the layering within a sedimentary rock that is inclined relative to the original bedding plane. Normally, layered sedimentary rock should be flat. With cross-bedding, you'll find layers that are at a distinct angle compared do the rock underneath and perhaps above it. It's not the same as just titled layers because it forms during deposition, not after.
What causes cross-bedding?
Cross-bedding is caused by an agent of force, typically either wind or water, that moves sediment. How do we know which agent of force is in action here? One of the main ways to determine what caused a cross-bed is by its size. Wind-formed cross-beds are typically larger, on the scale of meters, while water-formed cross-beds are smaller, on the scale of centimeters.
How does a cross-bed form?
Cross-bedding is formed by the downstream movement of sediment. The movement flow causes the grains to move up the stoss slope (upstream) side of the bed and accumulate at the peak until it reaches a certain point, called the angle of repose. At this point, the crest of the material has grown too large and will be overcome by the flow, falling down the lee face (downstream) side, like a tiny avalanche. Over time, these repeated avalanches form the cross-beds and provide clues to the direction of flow.
Accessing the featured Crossbedding
To visit this EarthCache, use the posted parking coordinates and follow the Rock City Trail for about 0.37 miles until you arrive at the Rock City Shelter. From there, keep to the left to stay on the Rock City Trail. Shortly after, you should be walking in between two large rocks. On the right hand side, you should see a small path (look for a tree growing out of the rock). Follow this path until you arrive at the crossbedding example with a white dot painted above it!
LOGGING REQUIREMENTS
Please submit your answers within seven days of your online log.
0) What is the name and GC Code of the Earthcache you are submitting answers for?
1) In your own words, how are cross-beds formed?
2) How thick are the individual cross-bed sets at GZ (you dont need to provide a specific measurement)? Which agent of force do you think these were formed by, wind or water? Why?
3) Using your compass and observing the angle of the cross-bed, provide the direction you think the agent of force was travelling.
4) REQUIRED - Take a photo of yourself (or a personal item) with the cross-bedded rock in the background and attach this photo to your log.
This EarthCache has been placed with permission of WV State Parks. A special thanks to thekingofbattle for assisting with the development of this EarthCache!