A Changing Landscape
Basically every landscape on the Earth’s surface has, in one manner or another, been shaped by the power of water. Water can be one of the Earth's most powerful landscapers, drastically changing the terrain in the blink of an eye, or it can be very subtle, taking hundreds, thousands, even millions of years to alter the landscape. At this location you will see a landscape altered by the effects of moving water as it flows over three separate and distinct rock layers (strata).
Limestone Formation
During the Silurian period (approximately 440 million years ago) the Earth entered into a long period of global warming. This stabilization of the earth's climate caused melting of large glacial formations worldwide. It was during this time that a shallow, warm, salt-water sea developed and covered the central portion of the North American continent, which at that time was located near the equator. This warming gave to ideal conditions for marine life to thrive and evolve. Brachiopods, crinoids, stromatoporoids, trilobites, conodonts, corals and many other creatures inhabited this vast inland sea. Over the ages, the sea bottom became covered with the skeletal remains (Calcium Carbonate) of these ancient marine creatures and sediment from the virtually lifeless landmasses. This sediment, under pressure, heat and time, eventually solidified and altered into a “porous” stratum called Limestone. This process of solidification is called Lithification. Limestone is ordinarily white but impurities make it appear cream, gray, yellow, beige, blue or even black. On the Mohs scale of hardness, Limestone/Calcite is a 3. Limestone makes up about 10% of the total volume of all sedimentary rocks found worldwide.
Dolomite Formation
After Lithification of the above mentioned Calcium Carbonate has completed, the process of Diagenesis occurs. Diagenesis is the chemical, physical or biological change of sediment “after” its initial deposition. When Magnesium-rich water comes into contact with Limestone, Calcium Magnesium Carbonate replaces the Calcite Calcium Carbonate within the rock, creating a harder, less porous Stratum called Dolomite. On the Mohs scale of hardness, Dolomite/Calcium Magnesium Carbonate is a 3.5/4. Being harder than Limestone, it is used as ornamental stone, as a concrete aggregate and as a source of magnesium oxide, a refractory material. Dolomite is generally white, gray or pink in color.
Shale Formation
Approximately 500 million years ago, particles from the erosion of the Appalachian Mountains were transported westward by winds and water currents and deposited in a shallow intercontinental sea. The process of Lithification altered these erosional deposits (Clasts) into a blue-gray colored strata called Shale. These soft Shale layers are easily eroded once they become exposed to the environment. Since Shale is a Clastic sedimentary rock and not a mineral, it is not listed on the Mohs scale of hardness. Shale (if it were to be listed) would probably be between a 2 and a 3 in hardness, depending on quality and other factors. Shale is the most common type of sedimentary rock found worldwide.
Erosion
Running water, such as the creek at this location, erodes land formations in 3 different processes. The first process is called dissolution. Dissolution is the dissolving of particles within the rock itself. Sedimentary rocks, cemented together with calcite, are extremely vulnerable to this process. The second is called scouring. Scouring is the process of uplift and transport of loose rock particles and depositing them downstream. The third process is abrasion. Abrasion occurs when rock particles, transported downstream, collide with other rock formations, chipping and wearing away at the formation itself. These 3 processes can occur individually or in tandem.
The coordinates listed will bring you to a small loop parking area. To the backside of the parking area is a dirt path. Follow this path to the railroad tracks, turn right and cross the small bridge. Just past the bridge there will be a trail leading off to your left and another trail to your right. You will have to take both of these trails to collect the information for completion of this EarthCache.
Email your answers to the questions using the link in my profile only. If your answers are not recieved by me, your log will be deleted. Photos are accepted and appreciated as long as the answers to the questions are not revealed. You do not have to wait for confirmation from me before logging this cache as completed.
At location #1.
What type of rock are you standing on?
A. Limestone
B. Shale
At location #2.
Look across the creek at the cliff facing you. What rock type is just above water level? (the lowest).
A. Limestone
B. Shale
From water level to the top of the lower rock Strata, what is the overall height?
Which of the layers is eroding much faster than the others?
What is the MAJOR cause of erosion found at this location? (Subjective)
A. Dissolution
B. Scouring
C. Abrasion
At location #3.
What type of rock is visible here?
A. Shale
B. Limestone
C. Both
What do you believe is the MAJOR cause of erosion found here? (Subjective)
A. Dissolution
B. Scouring
C. Abrasion
The Geocache Notification Form has been submitted to Doug Hartman, Brown County Facility and Park Management Department of the Wisconsin DNR. Geocaches placed on Wisconsin Department of Natural Resource