Minerals in the Mesas EarthCache
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The coordinates for this cache will bring you to an informational pull-off along the road where you will have a great view of a beautiful mesa vividly displaying many layers. Mesas include a variety of minerals in the different strata. This earthcache will help you learn about two of these minerals and the layers in which they occur.
Dakota Formation's Clay and Coal
While the rock formations in this region often presented formidable travel obstacles for early settlers, they also supplied many useful natural resources. Locally, a rock layer known as the Dakota Formation (the bottommost layer of which is just visible atop the colorful Entrada sandstone cliffs before you) yielded two important resources - bentonite clay and coal.
Bentonite Clay
In the mid-1900s, bentonite clay was mined about a mile east of here. Bentonite clay can absorb many times its volume in water, a quality that has led to its use in many applications. In the late 1950s, a Henrieville mine yielded thousands of tons of bentonite from these hills. Much of the bentonite was trucked to the Glen Canyon Dam site, where it was used to build a coffer dam that diverted the river so the main dam could be built.
Coal
Created from the remains of lush, coastal swamps that covered this region more than 80 million years ago, thin coal seams in the upper Bryce Valley sustained a handful of small mining operations during the 1900s. In the early 1900s, a small coal mine opened about two miles from here, where local residents could buy hand-dug coal for their stoves. During the 1940s, the Shakespear Mine near Tropic used dynamite to blast the coal seams, and miners hauled out the coal with horse-drawn trailers.
Logging Requirements
Earthcaches are placed in order to give people an educational experience. For this earthcache, you must complete the following in an e-mail to me (not to be included as part of your log).
1. Bentonite clay and coal come from what geologic period and what geologic era?
2. Given the layer/formation from which bentonite clay and coal come, what are the two layers/formations in this mesa above (newer than) that layer/formation, and what are the two layers/formations in this mesa below (older than) that layer/formation.
3. According to the informational sign, what uses do bentonite clay and coal have?
4. (Note: optional, but it sure helps to verify your smiley if your answers to the above are not 'quite right') Post (with your log) a picture of yourself and your GPSr (or just your GPSr) with the mesa in the background. Please do not include the informational sign in your picture.
Thanks for visiting this earthcache, and I hope that you now enjoy and understand this unique area even more!
Additional Hints
(Decrypt)
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