LIMESTONE FORMATION
Limestone is typically formed from the remains of plant and animal remains (calcium carbonate) deposited on a sea floor. Limestone is a sedimentary rock and is laid down in layers; usually separated by bedding planes (horizontal layers of weakness). These bedding planes are caused by changes in the rates of deposits or by the content of the material being deposited. The rate of deposit and erosion at this site is significantly affected by the river water level.
SCOURING
Glacial movement scoured the earth as it advanced and receded throughout the ages. The weight of this ice passing over the Limestone caused small fractures which followed the existing bedding planes here at the Mississinewa River. It also caused fractures in other lines of weakness called joints. These lines tend to run at 90 degree angles to those of bedding planes. Slightly acidic water, from dissolved carbon dioxide and decaying vegetation, eroded these lines of weakness. As these fissures widened, soil from the top of the limestone platform would be washed down into these fissures and eventually carried downstream. Over time, "all" of the topsoil would vanish, uncovering the fractured Limestone bedrock. These fractured, sharp edged, Limestone blocks are called Clints and the deep vertical fissures (joints) around the Clints are called Grikes. The Clints and Grikes can be widen and shift as ice, vegetation, and varying levels of water flow influence their formation and development.
RUNNELS
Runnels are gutter-like channels eroded out of the surface of the Limestone and drain into Grikes. Runnels formed on steeply sloping Limestone are generally close together and parallel. Runnels that have formed on more gently sloped Limestone (as seen in this river) appear more branched (dendritic).
PITS and PANS
Pits and pans are solution features that are found on the tops of Clints. They are formed by water and acids dissolving into the limestone itself. Pits are generally deep and free draining, while Pans are generally shallow and retain water.
MOVEMENT
Thermal expansion (ice wedging), root wedging and other factors now have entry points in which to enter the Limestone and, working in tandem, force these blocks to spread and separate as vegetation grows and ice freezes and separates the large sections of limestone. When the gravitational force acting upon these blocks exceeds the resistance force, slope failure (mass wasting) occurs.
Please answer the following questions correctly in order to be able to claim the smiley for this earthcache. I expect the required logging information for this earthcache to be sent to me within three days or the "Found It" log will be in jeopardy of deletion. Thanks!
1. There are 3 distinct levels (almost like spaced out stair-steps) of bedding planes at this earthcache site. Some are on dry ground and one is in the river (most of the year). All have one or more of the features listed above depending on their state of development. Why are the multiple bedding planes at this earthcache site at varying levels and how might that change throughout the year and years to come?
2. All 3 bedding planes have one or more of the features listed above depending on their state of development. What features are contained in plane #1 (highest plane)? plane #2 (middle plane?
3. Please post a picture of yourself at the Limestone Bedding Planes, Clints and Grikes (not required).
