Sunken Cave EarthCache
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Welcome to Cave Spring!
Cave Spring is an existing attraction along the Natchez Trace Parkway in northeast Mississippi. It is a feature that is a combination of a cave and sink hole. Originally, it existed as a cave in the form of a large room/corridor just under the surface. At one point, the roof of the room weakened and collapsed. The result is what you see today, which are two openings to caves that border the sink hole feature in the middle.
Parking is located within one hundred feet of the feature. A cement walkway is provided that leads people to several observation stands for optimal viewing. It is wheelchair accessible all along the upper observation area. There are steps down to the walkway that runs alongside the cave openings. However, it is not necessary to descend to the lower walkway to complete this earthcache.
There are no access fees or access restrictions. All you have to do is get there. The site is located less than one mile west of the Mississippi/Alabama border. It is about a 45 mile northeasterly drive from Tupelo, Mississippi (take US-45 north, and then Natchez Trace Parkway north). It is about a 35 mile southwesterly drive from Muscle Shoals, Alabama (take US-72 west, and then Natchez Trace Parkway south).
When visiting this location, do not leave the walkway. Under no circumstances should you attempt to enter the cave openings. The caves are dangerous. They contain deep pools into which you could fall. Also, the water is not safe to drink.
How Caves Are Formed:
Caves are formed in many ways. By far, the most common way is by the dissolution of sedimentary rock by acidic water. That is the process that formed the caves here at Cave Spring. There are other forces that can create caves. Following are the descriptions of several.
Rainwater - By far, most of the caves in the world were formed by a process supported by rainwater. The rainwater seeps into the soil until it reaches the water table, which is where the soil, rock, or other material is saturated with water. The water, which has become acidic (possibly from various sources), eats away at the rock at the bottom of the water table, eventually forming channels. The larger a channel becomes, the more water it holds and the faster this dissolution process progresses. Typically, a cave forms over a period of several million years. Later, the water table can drop leaving the void of the cave, and the expansion of the cave channels stops.
Waves - Over time, waves crashing against the base of a cliff can form a sea cave. A sea cave forms along a vertical zone of weakness in the rock, perhaps a crack or an area of softer rock. The erosive power of the waves wear away the rock, creating an opening that can deepen and expand with an overhang where the cliff rises above the waves. Sea caves are typically found in sedimentary rock such as sandstone and limestone. They are less commonly formed in hard rock such as granite.
Lava - Lava, which is molten rock on the surface of the earth, can create long intricate cave systems. When lava flows, it typically flows down a slope in a shape that resembles a long skinny tongue. The "tongue" is a channel of flowing lava, with the hotter, faster-flowing lava in the center of the channel and the cooling lava closer to the edges of the channel. The cooling lava on the edges solidifies, forming walls and eventually a "crust" over the top of the lava flow. When the eruption stops, the remaining lava flows out of the voids and a tube-like cave remains. Additional lava flows can occur over the top of the cave, burying the cave deeper and deeper.
Bacteria - There are bacteria that thrive on oil deposits deep within the earth. These bacteria, which are named extremophiles because they thrive in extreme conditions, expel a gas that combines with oxygen to create sulfuric acid. This highly corrosive acid eats away at limestone, leaving behind gypsum, and creating the large voids of caves. This bacterial process can feed upon itself, with some of the bacteria eating the byproducts and other minerals, accelerate the formation of caves.
Manmade - The word "cave" implies a feature created by natural forces, therefore there really is no such thing as a manmade cave. We have other words to describe the holes that humans have created in the earth. Humans have dug holes for many reasons, including shelter, passage, mining, disposal, battle, escape, etc.
The cave feature at Cave Spring is obviously not a sea cave. There is not a lot of volcanic activity going on around here either. It certainly is not manmade. I suppose it is possible that those wacky bacteria could have done it, but that just isn't the case here.
This cave feature was formed by rainwater becoming groundwater, getting all acidy, and dissolving the rock. It was formed by the same process that has formed most of the caves in the world.
Historically, the Native Americans that lived in this area used Cave Spring as a source for water, rock, and shelter. Today however, as stated before, the water is not safe to drink.
WHAT YOU MUST DO TO COMPLETE THIS EARTHCACHE:
Now, on to the tasks that you must complete. Items you should bring with you include a camera and a pen and paper.
The tasks you must complete are listed below.
Requirement #1 - Photo In Front Of A Cave Opening: You must post a photo of yourself with one of the cave openings appearing in the background of the image. I don't care about your GPSr being in the image. Please be careful to ensure that neither of the informational signs appear in the photo. You must post your photo with your find log.
Requirement #2 - Answer Questions About The Sink Hole: At the site, you will encounter a large sign and a small sign. Closer to the caves, you will find the small sign that describes the process of the formation of the sink hole between the two cave openings. From this small sign, answer the following questions in your email to me:
1) What is the basic type of rock in this area?
2) What two substances combine to form an acid that eventually dissolves that rock?
3) Do you think that the leaf litter and surface material that becomes trapped in the fissures contributes to the dissolution process, and if so, in what way? (this is an open question for which you need to provide your own answer/theory - i.e., you have to use your brain and think about it 
.)
Requirement #3 - Answer Question About The Cave: From the large sign, answer the following question in your email to me:
1) Based on the ground surface and the type of rock involved, this cave was a result of what?
Logs not accompanied by email within a reasonable amount of time will be deleted per earthcache rules. I don't like doing that. So please be careful to get done what you need to get done.
Remember Your Three Simple Requirements:
Photo,
Email answers about sink hole, and
Email answer about cave.
Have fun!
Special Information: The Natchez Trace Parkway is a 444-mile drive through exceptional scenery and 10,000 years of North American history. Used by American Indians, "Kaintucks", settlers, and future presidents, the Old Trace played an important role in American history. Today, visitors can enjoy not only a scenic drive but also hiking, bicycling, horseback riding, and camping. For more information, visit the Natchez Trace Parkway website at www.nps.gov/natr, or Facebook, or call 1-800-305-7417.
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