The "Boils" is a locally famous phenomenon, resulting from the emergence of a strong underwater spring. The force of the spring current makes the water above appear to "boil". The water is far from hot, however. It's actually a steady 58F-ish year-round. The Boils is one of the highest discharge springs in the entire State of Tennessee.
Let's discuss that.
First of all, Wikipedia describes a "spring" as "a natural exit point at which groundwater emerges out of the aquifer and flows onto the top of the Earth's crust to become surface water." (ref: Wikipedia). Most of us are familiar with springs. Often, their steady and reliable output is directed via a pipe where anyone can freely fill a water jug with fresh, clean water. Spring water usually tests very clean and healthy due to the filtering effect of the minerals in the rock it has been forced through. However, caution should be used any time you drink from an unknown source. This is particularly true for the Boils, which is not well filtered - more on that later.
The underground air temperature (and thus also the water temperature) doesn't vary much. If you venture deep into a cave on a hot, sunny day, it will feel pleasantly cool. Enter that same cave in the winter, and it will feel warm. Underground water temperature is "generally equal to the mean air temperature above the land surface." (ref: National Ground Water Association)
The "Boils" is an unusual spring form, since it emerges from the ground underwater. Even in times of dry weather, I have never known the Boils to dry out. The source of the water that emerges from the Boils was dye-traced in 2015 to three large drains, or "swallets", on Spring Creek in nearby Overton County. The dye tracing proved that portions of Spring Creek drained and ran underground for up to 7 miles, taking 14 hours. The rapidity of transfer from input to output showed that very little - if any - filtering of the water is taking place underground. The water from the Boils is most definitely not safe to drink.
How is this possible? Simply put, the Boils and Spring Creek are two components of the same Karst basin. Karst can be defined as "a topography formed from the dissolution of soluble carbonate rocks such as limestone, dolomite, and gypsum. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground" (ref: Wikipedia). In this case, this dissolution has formed a maze of tunnel-like conduits from three swallets on Spring Creek to emerge at the Boils.
Once above ground, water from the Boils flows a very short distance (about 800 feet) before it confluences with the Roaring River. Tourists wading and fishing in the Roaring River in the summer will feel a distinct difference in the water temperature when they reach that confluence. It's quite chilly!
Logging requirements:
This EarthCache is intended to be interesting and educational. I would love for you to visit the Boils yourself to see the effect on the water's surface. As a result, I require you to message me with the following info. Don't include it in your log, or your log will be deleted. Logs without supporting verification will be deleted after a day or two:
1. How do you think the solubility of the rock in this area contributed to the formation of the Karst system?
2. Estimate how deep the pool is at the spring. Do you think that this might vary, or does the spring output the same amount all the time?
3. REQUIRED: add your own photo of the Boils to your log. Optional: Include yourself in the photo.
References:
Wikipedia: https://en.wikipedia.org/wiki/Spring_(hydrology)
Wikipedia: https://en.wikipedia.org/wiki/Karst
National Ground Water Association: https://www.ngwa.org/what-is-groundwater/About-groundwater/groundwater-temperature's-measurement-and-significance
TTU dye tracing study: https://www.flickr.com/photos/chucksutherland/24590643596