This EarthCache at Providence Canyon does not require you to venture into the actual Canyon. GZ is at an overlook along the canyon rim. If you hike down, under no circumstances should you attempt to climb, carve your initials in or otherwise deface any of the canyon walls. Not only can you be cited for criminal trespass but, more importantly, this accelerates the erosion rate of the soils.
Please use caution on the trails and do not go beyond fences or overlooks. Erosion can cause the canyon walls to collapse without notice.
This is an EarthCache, so there is no container to find and no additional research is necessary. In order to log this EarthCache as found, you must read the information below, visit and observe the location, and then send me your answers regarding the location's geology.
1. In your own words, explain the principle of original horizontality. Do the formations you see here appear to meet that criteria or have other geological forces caused any tilting?
2. According to the principle of superposition, which of the two geological formations seen here is the oldest? Why?
3. Do you see any evidence of lateral continuity from these two formations?
4. What cross-cutting action has occurred here at Providence Canyon? In other words, what is the last geological event that occurred, and continues to occur, here in the Canyon?
5. With your "found it" log, include a photo of you or your group at your favorite place in the park. Optionally, you can take a photo of a personal item such as a geocoin or a piece of paper with your geocaching name.
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 will be deleted without notice. According to the guidelines, sending the answers is a requirement, not a request.
Relative Time
If you have ever been or seen a photo of the Grand Canyon, you are seeing geological events that were hundreds of million and even billions of years in the making. Igneous and metamorphic rocks first formed there billions of years ago and then layer upon layer of sedimentary rock were laid upon these basement rocks. At some locations, you can observe where the tilting of various layer occurred as well, due to lifting actions caused by plate tectonics. Then you also have the formation of the canyon itself, caused by the downcutting action of the Colorado River. All of these actions combine to create a truly beautiful spectacle.
Here at Providence Canyon, Georgia’s “Little Grand Canyon,” you see some of the same types of geological events that have taken place at the Grand Canyon. Here though, the sediments were “only” laid down between 59 – 74 million years old.
Looking at either location, some questions might come to you mind. Questions like: How did all these geological formations come to pass? In what order? Did other forces act on these sedimentary layers?
While it may all seem a bit mind-boggling to the uninitiated, for a geologist, they have been trained to look at the various formations and then “rewind the clock,” explaining the geological events and the sequence in which they occurred.
This approach is called relative dating. It is the science of determining the relative order of past events but without determining their absolute age. Determining the age of a geologic formation uses “absolute” or “calendar” dating techniques such as radiocarbon dating and is the topic for another EarthCache.
Principles for Determining Relative Age
There are four principles, some call them laws, that are used to determine the relationship of geologic events from one another:
1. Original Horizontality – All beds of sedimentary rock deposited in water under the influence of gravity initially formed horizontally or nearly horizontally. If the layers are currently not horizontal, then some geological process caused them to shift.
2. Superposition – In rock layers that have been undisturbed, the layers get younger from bottom to top. A new layer cannot be deposited beneath an existing layer.
3. Lateral Continuity – As rock layers form, each layer typically continues across a horizontal surface until another object or geologic feature stops it. Additionally, the layer will taper or thin at its edges.
4. Cross-Cutting Relationships – A disrupted pattern is older than the cause of the disruption. For example, when one type of rock cuts through another, the cutting rock is younger than the rock it cuts through. Also, streams and rivers carving into rocks or formations constitute a cross-cutting relationship.
Observing Relative Age Principles in Action at Providence Canyon
While Providence Canyon is not as large, or as old, as the Grand Canyon, you can still use the above principles to determine the relative order of one formation to another, if the formations have been disturbed by other geological processes and how these formations have been disrupted through natural means.
From the overlook at GZ, you’ll see the two main formations: the Clayton and the Providence. The Clayton Formation is reddish brown, indicating the presence of iron ore, while the Providence Formation is the white, having mixed with other minerals such as kaolin and mica. Yes, geologists have determined the “absolute” dates when these formations were laid down, but by using the Relative Age Principles, you can still determine the relative age of each formation, or the order in which they occurred. You can also determine if any other type of geologic process imposed itself on these formations. Which formation is older? Do they appear tilted to any significant degree, implying something tectonic has occurred since the formations were laid down or were they perhaps intruded by an igneous rock?
The story behind the canyon itself is fascinating, since it shows man-made influence on the local geology. The canyons formed because of poor farming practices starting in the 19th century. Instead of plowing around the contours of the hills, farmers plowed through them. Rainfall created an incising, downcutting action, continuing until it encountered a more water-resistant clay formation.
Providence Canyon State Park
Providence Canyon State Outdoor Recreation Area is a 1,003 acre state park located in Stewart County in Southwest Georgia. Providence Canyon is sometimes called Georgia’s, “Little Grand Canyon” and is considered to be one of the Seven Natural Wonders of Georgia.
Hours (subject to change):
Outdoor Recreation Area: 7am – 6pm
Visitor Center: September 15 – April 14, Wednesday – Sunday 8am – 6pm; April 15 – September 14, Wednesday – Sunday 8am – 9pm
Fees and Passes: $5 parking but annual passes are available
Sources
- Physical Geology, 9th Edition by Charles Plummer, David McGeary and Diane Carlson, 2003.
- Understanding Earth, 6th Edition by John Grotzinger and Tom Jordan, 2010.
- Geologic Guide 9: Geologic Guide to Providence Canyon State Park by Lisa G. Joyce, 1985. Department of Natural Resources, Environmental Protection Division
- Roadside Geology of Georgia by Pamela J.W. Gore and William Witherspoon, 2013.
- Grand Canyon National Park: https://www.nps.gov/grca/learn/nature/grca-geology.htm
- Providence Canyon State Park: http://gastateparks.org/ProvidenceCanyon