When people cut the cliff to the northeast of the parking lot, they revealed conditions at this location 300 million years ago during the Paleozoic era. Paleozoic means ancient life and it was during this time period when life became abundant on earth. The start of the Paleozoic era was called the Cambrian Explosion because of the sudden explosion of many different kinds of life forms, including fish, amphibians and land plants. The Paleozoic era ended about 250 million years ago with the Permian Extinction, during which more than 80 percent of all life forms on earth disappeared.
Scientists believe in two principles that are useful in understanding the rocks in this cliff face. The first principle is the principle of original horizontality which states the sedimentary strata are horizontal when original placed. The second principle is the principle of superposition which states that in grouping of sedimentary rocks the oldest rocks will be at the bottom of the pile unless they have been disturbed.
Looking at the cliff to the north of the parking lot, you can see obviously different layers of rocks. These various layers of differing rocks were created 300 million years ago when a vast ocean covered this land all the way down to the Gulf of Mexico. The varying kinds of rocks indicate the various conditions of the water that used to cover the rocks. The rock layers visible here are sedimentary rocks, made by sediment being deposited and then cemented together
At the very bottom of the cliff is a layer of talus, which are rock fragments at the foot of a cliff
Just above the talus is a shallow layer of Silver Lake shale that has Elmo coal in it. The coal is easy to see because it is black.
The layer above that is Rulo limestone that has marine fossils in it. Limestone was created during a time of shallow marine water and is made up of the skeletal parts of marine animals. You can probably recognize it because you have seen it used in many buildings and in blocks to create walls.
Above the Rulo limestone is Silver Lake Shale. Shale crumbles and weathers quickly.
Immediately above the Silver Lake shale is a transitional zone of shale with chert pieces. Chert is a finely-grained sedimentary rock made of silica and can contain fossils.
Next is another layer of Silver Lake shale.
The dark brown layer next is finely-grained siltstone. Siltstone has smaller pores and more clay than sandstone does.
The top layer is sandstone, part of an ancient shoreline. Sandstone was created when the land was an ancient sandy beach. It looks like it is made of sand.
To receive credit for finding this geocache, please email the CO the answers to the following questions.
1. Which layer do you think is the oldest layer?
2. Can you tell that the various layers are different from each other? If so, how can you tell?
3. How many layers of different distinct layers of rocks can you see? Don’t worry if you are not sure of this answer because it can be hard for an untrained eye to distinguish between layers.
4. Do you think that these layers are still in the order in which they were originally laid down? If so, why do you think so? If not, why not?
5. Optional: you can insert a photo of you at the site.
Thanks go to Washburn University geology professor, Tambra Eifert, Ph.D. for telling me and for sharing information about this location and to EarthCache Academy for their course called Geologic Time.
As Dr. Eifert says, “Geology rocks.”