Things to Know before you arrive:
1. Oak Mountain State Park charges a $3 daily usage fee. The park opens at 7 AM.
2. The website for the Park is http://www.alapark.com/oakmountain/.
3. In Oak Mountain State Park, there are @50 miles of hiking trails and caches of all types and difficulty levels. Numerous challenge caches which are specifically designed for Oak Mountain can also be a consideration. Plan ahead!
4. Alabama State Parks and especially Oak Mountain State Park are strong supporters of geocaching. Respect all rules so other geocachers can enjoy this Park.
Shale We Talk
The Birmingham Area
The mountains east and northeast of Birmingham are the southern foothills of the Appalachian Mountains. The mountains in this area are known for limestone, sandstone, iron ore, and other sedimentary rocks. Birmingham was built on the presence of these minerals.
How shale is formed
Shale is a sedimentary rock formed over a long process of silt drifting or gathering on the bottom of water locations. Shale is made of the smaller and lighter silt; therefore, it is slower to settle and is found in areas of “quite water”. Examples of these "quiet" water would include lagoons, secluded bays, and other similar water areas. The actual sedimentary rock is formed by the presence of years of deposit being compressed and heated until the silt becomes rock. This shale at the Earth Cache is part of the Parkwood Formation.
The Parkwood Formation & Oak Mountain
Oak Mountain has a large amount of shale lying in the hills around you. On the far western side of the park, the Floyd Shale Formation can be found. At these coordinates you are in the Parkwood Formation. This formation was formed between 350-310 million years ago during the Pennsylvanian-Mississippian eras. It is made of primarily shale and some sandstone. Shale is very susceptible to erosion – leaving such areas of easily accesible exposed shale - a great treasure.
The nature of Shale
Shale breaks along lines of weakness in the rock. Fissility is the name given to this property. Since shale is acceptable to erosion while sandstone tends to withstand weathering, one gets to see large boulders of sandstone around Oak Mountain. This is not true of shale.
FTF: KItKat
To Receive credit for Shale we Talk:
- Email me your answers by my profile email link – PLEASE: do not log your answers. I ask you to provide answers in a timely manner after you log. Thanks!
- Any pictures pertaining to this Earth Cache are greatly appreciated – but never required. I do ask that your pics not give away any logging requirements.
- Find the destination coordinates on the red trail.
- Is the shale layered & broken or a large block of stone – in your own words explain your observation? Is it similar to other rocks in the park or other locations you are familiar with?
- What is Fissility?
- What type of rock is shale and how is it formed?
- Near the destination coordinates – find a piece of shale. You need not dig or even break off a piece. Pick it up and in your own words describe it – thickness, color, weight, etc. Please do not take the shale – replace it on the ground.
- Look up the hill from the Earth Cache – there is a clump of moss on your right. Walk downhill on the path using the moss as the starting point, and tell me in feet, yards, paces, etc. how far down the red trail you can find exposed shale.
Once again photos are always enjoyed but never required!
References
http://en.wikipedia.org/wiki/Fissility_(geology)
http://trekbirmingham.com/articles/the-geology-of-double-oak-mountain/
http://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=ALPAMpw%3B2
http://en.wikipedia.org/wiki/Shale