Tahlequah Uplift EarthCache
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Located on the north side of the Tahlequah Bypass just past Park Hill Road. The uplift formation is on the shoulder of the highway just below Tahlequah Lumber Company. You can pull off the shoulder far enough to be out of the way of traffic.
The Ozark Plateau was formed about 500 to 570 million years ago. A plateau is an area of land that has been pushed upward by geologic forces (which I will explain shortly) and is higher than the surrounding land. When we discuss geologic events such as mountain building, we need to understand geologic time. It is a difficult concept to the human brain. It is very hard to imagine how long 500 ?
million years actually is. Let's do a little thought experiment. You invented a time machine. It looks like a treadmill. To go back in time, you must walk on this treadmill. The treadmill time machine was built so that about one year equals one inch of movement on the treadmill. The more steps you take, the further back in time you go. 10 years equals 10 inches, 50 years equals 50 inches and so on. If you wanted to see Oklahoma Statehood in 1907 you would walk 100 inches. Let’s say you wanted to go back to the year 1776 when America got its independence. That was 224 years ago. So you need to walk about 19 feet. If you walk one mile, you will go back 63,360 years. Get the idea? Hopefully, this thought experiment gets you thinking about geologic time. You need to understand geologic time to understand what you see when you look at the Ozarks,
Now back to the Ozarks. In terms of the age of mountain ranges they are very very old. The Rockies are only 70 million years old. Remember that the Ozark Plateau was formed between 500 and 570 million years ago. More than a billion years ago, an igneous (volcanic) layer of rocks "bubbled" up or uplifted forming the core of what is now the Ozark Mountains. The forces that uplifted these rocks came from deep within
the Earth. The exact causes of these forces is still unknown but scientists think it has to do with "blobs" of mantle (melted rock) rising up to the Earth's crust, pushing against it and causing the crust to bulge. If the blob breaks through, it becomes a volcano. This is how the Hawaiian Islands were formed.
During this time, way back in geologic history, the middle of what is now North America was covered in ancient shallow seas. The Ozark uplift was still not high enough to be covered by these seas. So deposits of mud piled up over this dome of hard volcanic rock. Think of it as layering a piece of cheese over chunky
meat on a sandwich. Up until about 500 million years ago, there were more periods of uplift and eventually the dome rose above the ancient seas. From then until now (a very long time), there were more "transgressions" or times when the sea covered areas of the Ozarks and more sea mud was deposited but mostly rain and wind have been eroding (wearing) down the Ozark mountains, reshaping the area into what we see today.
In order to log this cache you must answer the three questions and post a picture of yourself at the cache site. You will need to do some internet research to find two of the answers. One can only be answered at the uplift.
Questions-
1. In what period of geologic time did the Ozark Plateau form?
2. According to the display on your time machine how far would you have to walk to go back 500 million years? Please answer in miles.
3. Name one type of rock you see present at the site?
Thanks to Paul Schuster of the U.S. Geological Survey for helping with the information gathered here.
Additional Hints
(Decrypt)
Znxr fher lbh pbaireg lbhe ahzoref pbeerpgyl
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