Description and Logging Requirements
PLEASE NOTE: You MUST park at the Columbus Museum parking lot and then go to the sidewalk to make the observations and answer the questions. DO NOT attempt to observe and note the answers while driving your car on Wynnton Road. DO NOT park your car anywhere around The Wynn House and attempt to make the observations from on top of the hill.
There is absolutely NO reason to cross Wynnton Road. Observing the area and obtaining the answers can be safely done from the sidewalk on the Museum side of the road.
Read the description below, visit the location, answer the following questions and send them to me by e-mail:
1. In your own words, what causes a slope to creep?
2. How does water contribute to creep? Do you currently see any evidence of water at this location?
3. As indicated in the lesson, creep is imperceptible and can only be detected over time. Please describe at least two types of evidence that shows creep is acting on this slope.
4. Name at least two different mitigation techniques being used at this location. Do they seem to be working? What do you think could be done to further mitigate the creep here?
5. With your "found it" log, include a photo of you or your group with the creep in the background. 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.
Geological Creep
From a geological standpoint, the movement of mass material is categorized in several different ways, one of which is speed. Is the material moving fast or slow? For this EarthCache, you will observe material that is moving slowly. Very slowly. So slowly in fact that it can sometimes take decades, or longer, to detect the movement.
Movement like this is called “creep.”
So, what is creep? It is defined as the imperceptibly slow, steady, downward movement of slope-forming soil or rock.
What Causes Creep?
In a word…gravity. The higher something is, the lower it wants to bring it. A number of factors come into play to determine if a hillside will progress downward through creep though.
Chief among them is slope and friction. As slope increases, friction decreases between the sliding material. Decreasing friction allows for material to move more freely.
The amount of water in the soil is also important. Water may help the hillside stay put and give it cohesion, but if there is too much of it or after a large amount of precipitation the tiny spaces between the grains can become saturated and cause the ground to slide along an entire plane. When this happens, the water is decreasing the friction between particles.
Finally, there is sediment expansion. This occurs when individual particles are lifted at right angles to the slope. Sediments can expand when they freeze, get wet or are heated up in the sun. When the sediments shrink, the particles fall straight back down. Creep takes a long time because each particle might only move a millimeter to a few centimeters at a time.
Creep Evidence
Finding the evidence for creep is actually very easy to spot, once you know what to look for. Along a hillside, look for things that are partially buried in the ground and are tilting, bent or broken. These can include: fence or telephone posts, older gravestones, walls, roads and even buildings.
Tree trunks that are curved at the base and then straighten out are another sure sign. This is because the top of the soil layer moves faster than the soil beneath, causing the young trees to bend downslope. As the roots stabilize the soil, creep is greatly diminished, and the trees can then grow straight.
Mitigating Creep
Can you stop creep? Perhaps not entirely, but it can be mitigated. Vegetation is one of the best ways to increase slope stability. When a hillside contains many trees, ferns, and shrubs their roots create an interlocking network that can strengthen the unconsolidated material and act as an anchor. In addition, all that vegetation can also help absorb the excess water in the soil.
If absorbing the water is not an option, diverting it away from the loose material and soil can be exceptionally helpful. Drainage ditches or culverts help move the water away, reducing the overall erosion caused by runoff.
In some locations, creating terraces is an effective method. The steps divert water and prevent it from carrying soil down the hillside.
Another method is to create retaining walls at the base of the slope to help buttress all the material. Over time though, through gravity and the pressure of all the material bearing down on it, retaining walls can crack and potentially fail.
Free parking for this EarthCache has been made available by The Columbus Museum during normal opening hours. They are closed on Monday and are open between 10am – 5pm Tuesday thru Saturday (10am – 8pm Thursday) and 1pm – 5pm on Sundays. The museum staff have been kind enough to allow us to use their parking lot. In return, please repect their request and only park here when they are open.
Sources
https://pubs.usgs.gov/fs/2004/3072/fs-2004-3072.html
https://www.ntnu.edu/creep
http://www.onegeology.org/extra/kids/earthprocesses/creep.html
https://en.wikipedia.org/wiki/Downhill_creep
https://homeguides.sfgate.com/stop-earth-creep-hillside-96871.html