Jointed Bedrock
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Falls of the Ohio circa 1600
In the depiction above you can see how the original falls looked in it's natural state. The river controlled it's own pace. It was wide and very shallow with many limestone outcrops dotting the area. However, this natural 'rapids' would created a serious impediment to future navigation for commercial vessels. In the 1960's an 8,627' concrete fixed weir dam with tainter gates was built to control water depth for navigation.
In many parts of the upper south flats, few fossils are visible. These areas have large fractures called joints that cut across the limestone, dividing the bedrock into a checkerboard pattern. The joints are natural cracks in the rock formed by stresses deep beneath the Falls and not initially and erosional process.
You can see that many of the sharp-edged ledges along the southern part of the Falls occur along these joints.
The joints are natural areas of water seepage throughout the year. The river water slowly dissolves the limestone along the joints, causing them to widen. As the joints grow, they intersect other joints, and blocks of limestone may break apart.
These broken pieces of bedrock are then broken further or carried away during floods. In this way, the Ohio River is slowly eroding the fossil beds at the Falls of the Ohio.
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The posted coordinates will bring you to the jointed bedrock seen in the image above. To earn credit for this earthcache and to demonstrate the educational value of your visit, please send answers to the following questions:
1. How long is the longest joint seen here?
2. Can you tell where the layers of bedrock have been stripped away? How?
3. In your observation along the exposed bedrock, where do these blocks of bedrock go?
4. Which of the images in the six-block below represents the spot where you are standing?
Which of these match where you are standing?
Do not post answers in your log. And no pics here, please. As always, logs not followed by answers within 48 hours will be deleted. You can always log again when prepared.
DO NOT POST IMAGES OF THIS LOCATION PLEASE
This Earthcache listed with knowledge and understanding of local governing entities