Geology is Everywhere! Visit Rocktown in the Crockford-Pigeon Mountain WMA , explore Turtleback Rock Formations and discover an EarthCache.
Overview
This is an EarthCache and has no physical container. The goal is to learn why these rock surfaces develop “shell-like” polygon patterns, then visit the site, make observations, and answer the questions below. If you have any questions, please reach out to me.
Rocktown is located within the Crockford-Pigeon Mountain Wildlife Management Area (WMA), and a valid Georgia Outdoor Recreation Pass (GORP) or hunting/fishing license is typically required for legal entry on this property. If you are just visiting for geocaching (and don’t already have a valid GORP, hunting, or fishing license), purchase of a single-day Georgia fishing license may be the least costly way to go (currently $5.00 for Georgia residents and $10.00 for non-residents). Visit their web site or download their app and get the necessary license prior to driving up here (little or no cell service is available up on the mountain).
Make sure you use the parking coordinates for driving here and then be prepared for a 1-mile (fairly flat) hike to Rocktown and back. It’s easy to get turned around while visiting, so making sure you have clear coordinates will help you avoid problems.
IMPORTANT: Obey all WMA rules and posted closures. This WMA property has seasonal closures/restrictions during hunting season, including being closed prior to 10 am during turkey season. Verify the access status of this property on your planned visit date. georgiawildlife.com or call (706) 295-6041.
Make sure you either print off the cache description or download offline data so that you have what you need when you arrive at GZ.
Logging Requirements
- Observation: Find a clear "turtleback rock" pattern. What is the most common number of sides you observe in the individual "scutes" (polygons). Are the scutes mostly uniform in size and shape, or do they vary?
- Size: Walk around as much of the rock formation as you can. Estimate it's dimensions visible (height, length and width), ignoring any part of the rock formation buried underground.
- Process: Look at the surrounding boulders. Do you see fractures ("joints" or crack networks that could guide weathering? Briefly describe what you see (for example: straight cracks, intersecting cracks, blocky patterns, or curved cracks) and how they compare to the polygon boundaries in the turtleback surface.
- Photo: Post a photo of yourself or a personal item with the rock formation clearly in the background.
- Naming (Optional and just for fun): Suggest a name for this turtleback rock formation?
Location
Rocktown lies within the Crockford-Pigeon Mountain Wildlife Management Area (WMA) in Walker County. Rocktown’s diverse geological features exist because durable, jointed sandstone has been exposed for millions of years to groundwater movement, chemical reactions, and erosion, allowing multiple weathering processes to operate and overlap on the same rock surfaces. The unique rock formations here also make it popular with Rock Climbers, so don’t be surprised to see people climbing around you.
What is Turtleback Rock?
Among Rocktown’s most eye‑catching features are the “turtleback” surfaces—broad sandstone slabs etched into a mosaic of raised ridges and shallow, rounded polygon plates that look like the scutes (segments) on a turtle’s shell. These patterns develop where the sandstone’s natural fractures and subtle differences in cement and grain strength guide weathering, so some zones resist erosion while neighboring areas wear down, gradually bringing the turtleback texture into relief.
How Turtleback Rock Forms
The "turtleback rocks" found at Rocktown are primarily composed of Pennsylvanian-age sandstone. The distinctive patterns that resemble a turtle's carapace (its shell) are formed through a combination of geological processes:
- Spheroidal Weathering: This occurs when chemical weathering penetrates along joints or fractures in the rock. Over time, the corners and edges of rock blocks weather faster than the flat faces, rounding them into shell-like shapes. Spheroidal weathering is often more visible on block edges and corners around the area.
- Polygonal Jointing: Sandstone commonly contains natural fractures ("joints") created as the rock formed and later responded to burial, uplift, and unloading. On broad, exposed surfaces, intersecting joints (and smaller surface cracks that develop along weak zones) can outline polygone shapes - often roughly hexagonal, but commonly mixed - similar to the scutes on a turtle's back. Weathering then exploits these boundaries, gradually sharpening the pattern as some areas wear down faster than others.
- Differential Weathering: Different parts of the rock contain varying amounts of mineral "cement" (like iron oxide or silica). Harder, more resistant mineral veins weather more slowly than the surrounding softer rock, sometimes leaving behind raised ridges that enhance the "shell" appearance.
At Rocktown, the “turtleback” look comes from natural cracks that break the sandstone into a patchwork, and weathering that slowly rounds and deepens the pattern over time. As you explore, compare a few different slabs—no two are exactly alike. Please help protect this special place by following WMA rules and leaving the rocks as you found them. Most of all, enjoy your visit to Rocktown!
SOURCES:
Roadside Geology of Georgia (pages 155-156) by Pamela Gore and William Witherspoon (2013) by Mountain Press Publishing
Crockford-Pigeon Mountain WMA | Department Of Natural Resources Division
Rocktown - Wikipedia
Geology of Mesa Verde National Park – nps.gov (includes mention of turtleback rock formations found there).
Columnar Jointing on Turtleback Mountain - Lakes Region Conservation Trust
I used AI to help me write part of this description of this cache. I also used it to generate the image. The information was then cross-referenced to other sources.
