There is absolutely NO reason to cross over the fence. Observing the area and obtaining the answers can be safely done from the hiking trail.
Description and Logging Requirements
Read the description below, visit the location, answer the following questions and send them to me by e-mail BEFORE you log the cache:
1. In your own words, what is exfoliation?
2. What causes the change in pressure that creates the conditions for exfoliation?
3. As you walk along the trail, what evidence can you see proving that exfoliation is at work? Are there any sheet joints, “onion-type” slabs or other cracks noticeable?
4. While pressure change is the main catalyst for exfoliation, other types of mechanical weathering processes contribute as well. Based on the lesson and your observation, can you tell if any other processes are a contributing factor?
5. With your "found it" log, include a photo of you or your group.
If your answers are profoundly off, I’ll contact you. Otherwise, please log your find after you send an e-mail. In the e-mail, please indicate your geocaching name and include the names of other geocachers with you. Logs without accompanying answers sent or photos uploaded will be deleted without notice. According to the guidelines, sending the answers is a requirement, not a request.
Exfoliation
Exfoliation is the term used to describe the peeling away of sheets of rock millimeters to meters in thickness from a rock's surface due a range of physical and chemical processes during weathering and erosion. Much like humans exfoliate skin, the granitic pluton at Panola Mountain is “shedding” rock over time.
What causes exfoliation?
Homogeneous granitic plutons, such as Panola Mountain, are created in high-pressure environments and slowly solidify beneath the earth's crust. Hundreds of millions of years ago, the surface at this location would have been much higher, resulting in higher pressure where the pluton is created. Over time, weathering and erosion has brought the surface down to today’s level.
While the pluton was formed under high-pressure, when the pluton is exposed by weathering and erosion of the overlying rock, there is a decrease in the confining pressure on the it, causing the rock to expand. This expansion promotes cracking of the rock, which we call exfoliation.
While the reduction in pressure is the main cause of exfoliation, other factors can contribute as well. These include tectonic uplift, glacier retreat and mass wasting. Once the rock is exposed at the surface, chemical and other forms of mechanical weathering such as extreme temperatures, plant growth, frost action, or burrowing animals can speed up the exfoliation process.
Evidence of Exfoliation
Finding the evidence for exfoliation is actually very easy to spot, once you know what to look for. Cracks called sheet joints develop parallel to the outer surface of the rock as the outer part of the rock expands more than the inner part. The cracks may also cause rocks to break away from the overall pluton. This is known as "unloading" and opens additional areas of the rock to both mechanical and chemical weathering.
On slopes, gravity may cause the rock between such joints to break loose in concentric slabs from the underlying granite mass, similar to peeling layers from an onion.
Panola Mountain State Park
Panola Mountain is a 100-acre granite outcrop similar to Stone Mountain, but smaller and much more pristine. Park visitors will see the outcrop and its rare ecosystem just as Native Americans did centuries ago.
Hours (subject to change):
- Park: 7am – Sunset
- Visitor Center: 8am – 5pm
Fees and Passes: $5 parking with annual passes available.
Sources
Geologic Guide 2: Geologic Guide to Panola Mountain State Park – Rock Outcrop Trail by Robert L. Atkins and Martha M. Griffin, 1977. Department of Natural Resources, Environmental Protection Division
https://en.wikipedia.org/wiki/Exfoliating_granite
https://www.encyclopedia.com/earth-and-environment/minerals-mining-and-metallurgy/metallurgy-and-mining-terms-and-concepts/exfoliation
https://opentextbc.ca/geology/chapter/5-1-mechanical-weathering/
Physical Geology, 15th Edition by Charles Plummer, Diane Carlson and Lisa Hammersley. McGraw Hill Education.
Panola Mountain State Park: https://gastateparks.org/PanolaMountain