The Kasota Prairie is a preserved tract of land that has a mixture of virgin prairie, former grazing areas, as well as a mix of hardwood trees. Named for it’s view, the word kasota from the Dakota language means "a cleared place." This piece of land is situated 70 feet above the Minnesota River Valley, offering breathtaking views no matter the season. This particular area was bought by Unimin with the plans to open a quarry to harvest the limestone beneath the earth. Concerns were raised about the nature of this area, and how unique it is both geologically and ecologically. Studies to the area revealed that the top soil can be as thin as 12 inches deep in areas!
Unimin set aside this 90-acre area after petitions called for an environmental impact study to be performed. It is now open to the public for recreation, and to allow people to explore this unique area.
The Minnesota River is only about 12,000 years old. It is situated within the former river bed of Glacial River Warren, which formed when Glacial Lake Agassiz was draining. During that time this terrace was flooded by Glacial River Warren as it carved its way through Minnesota. Once Glacial Lake Agassiz was drained, the Glacial River Warren disappeared around 9400 BC.
The Kasota Limestone is a product of the early Ordovician era, Prairie du Chien group. The rock formation is approximately 450 million years old. The density of this rock is dependent on its porosity, as well as its silicate content. Average densities of the Kasota Limestone put it at 157.75lbs/ft3. Being resistant to erosion at heavier densities, it is a popular building block. Due to the erosion resistant characteristics, the area here is littered with examples of the stone that peek out from the eroded soils.
When it comes to erosion present in this area, there are 4 main types; wind, water, ice, and physical. Wind erosion is caused by particles of sand and dirt being blown as if in a weak, slow, but steady sand blaster. Rain, rivers, and waves cause water erosion. Small creeks can carry a dump-truck worth of soil away over the course of a year. Multiply that my centuries and you have a lot of dirt missing! Water and ice erosion go hand in hand in this climate. As the water freezes in cracks, it expands and busts apart the rock formations. Lastly we have physical erosion. As we hike across this area, we slowly wear away the earth. Trails left where people have walked the same path will eventually wear down the top soil until it reaches the limestone. From there the exposed faces of the limestone will be worn flat, and edges of “steps” will be worn into a bowl like appearance from people taking the same steps time and time again.
Requirements to log a find on this cache:
Please message me either via email or messanger from my profile, the answers to question 1 and 2. Do not post these answers in your log, as any logs with spoilers will be deleted.
1. Looking around the area and gathering info from the cache page, what do you suspect resulted in the soil being so thin here?
2. At the posted coordinates you will find a “pedestal” of stone. Examine it and answer the following questions:
A) What forms of erosion do you think impact this stone the most? There is a great example on one side of the slab, find it and tell me what form of erosion this would be.
B) Measure the top slab being supported by the column of the "pedestal" and calculate the cubic feet of material. Using the information in the cache description, how much does it roughly weigh?
3. Please find an exposed outcropping of limestone different from the pedestal that you find interesting and take a photo with it. If you prefer to not have your face shown, your GPS or personal item is acceptable! Include this photo in your log and feel free to share why you found the outcropping interesting.