Rock City
Welcome!
This state forest received its name, “Rock City State Forest” due to the massive boulders the size of houses which are naturally arranged so that they resemble a city with “streets” running between them. This unique “city” is formed by many factors including a massive resistant conglomerate bed, erosion of the weak shale base and soil creep.
Required Logging Task
To log this EarthCache, complete the following task:
- Describe the approximate height, width and length of the "building" you are standing on.
Earth Science Lesson
What is a Conglomerate?
The conglomerate bed actually has its own geological designation known as Devonian Salamanca conglomerate. A conglomerate is a rock consisting of individual stones that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts. Both conglomerates and breccias are characterized by clasts larger than sand.
Why are the Conglomerates moving?
With nothing to prevent this bed of rock from sliding downslope, the conglomerate has been carried slowly downhill by soil creep which has been going on for thousands of years. This downhill slide has caused the conglomerate bed to break into huge blocks to form the “buildings” and “roads” of the “city”. As these blocks lean against each other they form caves, tunnels and passageways.
References
Geological Society of America (GSA) - EarthCache Guidelines