GC55D3C Alabaster Caverns Earthcache (Earthcache) in Oklahoma, United States created by hzoi

This cache has been archived.

hzoi: It's with a heavy heart that we archive this one.

Since we started caching while on active duty, we have to pick up stakes and remove all of our physical caches every time Uncle Sam tells us we are getting a new place to geocache. So we've tried to develop earthcaches wherever we went in order to leave a little mark behind, even after we leave.

Despite our short time in Oklahoma, we managed to find quite a few places that we could develop an earthcache, and this was one of our favorites. Unfortunately, with the partial collapse of Alabaster Caverns a while back, things have changed here from our visit, and we've not been in the position to update the cache description.

So, we're letting this one go. Thanks to the intrepid 43 cachers who found this one, and thanks especially to the 6 who thought it was worth a favorite point.

GC55D3C ▼

A cache by hzoi Message this owner

Hidden : 5/22/2014

Difficulty:

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Size: Size: other (other)

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Geocache Description:

This earthcache will introduce you to Alabaster Caverns, the minerals that make up the cave, and how the cave formed. There is no physical cache container to find; to log this earthcache, you will need to email us the answers to the questions below. The questions are repeated in the unencrypted hint for your convenience.

This earthcache was placed with the permission of Alabaster Caverns State Park management. There is a fee to enter the cavern, please check the park site for current hours and fee schedules. Tickets are required to tour the cavern, and tours leave promptly on the hour. Be ready for a 3/4 mile walk with a total of 330 steps either up or down stairs and on paths that might be slick at times -- watch your step. This cache does not require you to enter any closed areas; please follow all park rules during your visit. Finally, you might want to bring a jacket even in summer; the cave temperature stays around 55 degrees year round.

THE PERMIAN AGE

The geology of Alabaster Caverns and most of Woodward County dates to the Permian Age, from about 300 million years ago to 250 million years ago. Early in the Permian Age, a shallow inland sea (or “epeiric sea”) extended from the Gulf of Mexico, covering what is now western Texas and Oklahoma and extending as far inland as eastern Kansas and southeastern Nebraska. As organisms died in the sea, their remains decomposed and formed sediment that covered the sea floor. This sediment eventually became shale rock. Some of the calcium sediments dissolved in the water. As the sea levels dropped, the calcium precipitated from the water and formed rock, first dolomite and then gypsum. These minerals were then covered by shale. Over time, sea levels fluctuated, resulting in layers of gypsum and shale.

The oldest exposed layer of rock in Woodward County is Flowerpot Shale, named after Flowerpot Mound in Kansas. Flowerpot Shale is red, easily eroded rock that contains some imbedded layers of gypsum. On top of the Flowerpot Shale are layers of rocks called the Blaine Formation, made up of layers of gypsum separated by thinner layers of shale. The bottom layer of the Blaine Formation is Medicine Lodge Gypsum, out of which Alabaster Caverns formed.

GYPSUM, ALABASTER, SELENITE, AND ANHYDRITE

Gypsum is an evaporative rock made of calcium sulfate (calcium, sulfur, and oxygen). Evaporite rocks, in contrast to carbonate rocks (such as limestone), are deposited by chemical precipitation (not biochemical). These rocks form when waters become highly saline (such as Great Salt Lake in Utah) and supersatured for these minerals. Normal ocean waters contain about 34,500 parts per million (ppm) Total Dissolved Solids (TDS). If the concentration reaches about 100,000 ppm TDS, then gypsum will begin to precipitate from the water. Oklahoma is the largest producer of gypsum in the United States, and it is primarily mined from the Blaine Formation. It’s used to make plaster and drywall.

Gypsum is normally white, but, because of impurities, it may be shades of gray, red, or green. It is so soft that you can scratch it scratched with your fingernail. On the Mohs scale of mineral hardness, which ranges from the softest, talc, at 1 and the hardest, diamond, at 10, gypsum rates only around 1.5 to 2. Three varieties of gypsum are: (1) alabaster, a fine-grained massive variety that may be white, pink, gray, or even black and can be polished and made into attractive objects of art; (2) selenite, which occurs as clear, colorless crystals; and (3) satin spar, the fibrous gypsum with a silky luster.

Anhydrite is a rock generally associated with gypsum. It cannot be scratched with the fingernail and is normally white to gray. The principal distinction between gypsum (hydrous calcium sulfate) and anhydrite (anhydrous calcium sulfate) is the absence of water in the chemical composition of the latter. The addition of water to the crystalline structure of anhydrite will change it to gypsum and cause an increase in volume. This expansion causes the altered rock to pull away from the surrounding material, forming mounds.

Alabaster Caverns is one of only three places in the world where you can find so-called “black alabaster.” The other two places are in Italy and China, and Alabaster Caverns is the largest source. This dark form of gypsum is actually anhydrite, which is the waterless version of gypsum. The lack of water inside of the crystal results in higher weight and different optical properties, especially the dark appearance. The rock is actually not black or dark, it is transparent, and as a result light falling on its surface is not reflected, but shines through the crystal. As a result it appears dark due to the lack of reflection.

FORMING THE CAVERNS

The area around the park is characterized by what is called “karst topography.” Karst regions are characterized by features that result from the solution of rock, such as sinkholes, solution valleys, natural bridges, and caves. The few streams that form in karst regions are short and intermittent and drain into sinkholes, moving underground.

Four conditions are essential for karst development: (1) a soluble rock, such as limestone, dolomite, rock salt, or gypsum, must be present at or near the surface; (2) the rock should be dense, highly jointed, and preferably thin-bedded; (3) there must be entrenched major valleys below uplands underlain by these rocks; and (4) the area must receive at least a moderate amount of rainfall.

The Blaine Formation, although it contains four gypsum layers, is not ideally suited for karst development; although the gypsum layers are water soluble, the layers of shale are not. However, the Cimarron River and its major tributaries have eroded their channels well below the level of the lowermost gypsum bed and thus provide the required drainage conditions. In Alabaster Caverns State Park, both Long Creek and Cedar Creek have eroded their channels into the Flowerpot Shale below the Blaine Formation, enabling numerous karst features to develop.

Alabaster Cavern and the other caves of the area did not begin to take form until Late Pleistocene time (about 1 million years ago), by which time the Cimarron River had eroded its bed to a level below the base of the Blaine Formation. While the Cimarron was eroding its channel, sinkholes were developing and much drainage was being diverted to the subsurface. As the water moved downward, it was diverted laterally through openings in the rock. The water dissolved the gypsum rock, creating a channel. At one point, the stream was a river, capable of filling the entire cavern, but today the water levels are much lower. Through dissolution and erosion of the gypsum rock, the caverns formed. Even today, the caverns continue to grow; an underground stream can be seen at several points in the cave.

The domes in the ceiling of the cave formed when swirling water eddied and carved them out, back when the cave was younger and the water levels were higher. You can see bands on the sides of the domes marking different water levels. Some of the domes appear to have peeling surfaces. This is a great example of anhydrite expanding as it absorbs water molecules and becomes gypsum. If the caverns were not here, the rock might have expanded upard into a mound, but because the cave has been hollowed out, the rock can expand downward.

As you tour the cave, you are not going to see many stalagmites or stalactites. These features, while common in limestone caves, are much less common in gypsum caves, and any you see are likely to be quite small. Bonus question not required for logging: why do you think that is?

LOGGING THIS EARTHCACHE

To log this earthcache, email us or send us a message (visit link) and copy and paste these questions, along with your answers. Please do not post the answers in your log, even if encrypted. There's no need to wait for confirmation from us before you log, but we will email you back if you include your email address in the message. Group answers are fine; just let us know who was with you.

For #3, rough estimates are fine, this isn't a math test.

1. The name of this earthcache: Alabaster Caverns Earthcache

2. From the signs outside the visitors center: How many stages of development are there in the life of a cave? Currently, which stage is Alabaster Caverns?

3. In the collapse section: The tour should stop at Selenite Boulder. Describe the boulder. What did the tour guide show you here?

4. Throughout the tour: Name at least two named features in the cave that were shaped by the flow of water through the cave.

5. (optional) Why do you think that the stalagmites and stalactites in gypsum caves are so few and so small?

Pictures of your visit are always welcome.

SOURCES

Arthur Myers et al., "Oklahoma Geological Survey Guide Book XV: Alabaster Cavern and Woodward County," Oklahoma Geological Survey. 7th printing, 1994. (visit link)
Show Caves of the United States, “Alabaster Caverns.” (visit link)

Richard Hotchkiss, “Alabaster,” student paper, Cochise College, Arizona, Spring 2010. (visit link)

Oklahoma Historical Society, Encyclopedia of Oklahoma History and Culture, “Alabaster Caverns State Park.” (visit link)

Additional Hints (Decrypt)

[To log this earthcache, use the "send message" link in our profile and copy and paste these questions, along with your answers. Please do not post the answers in your log, even if encrypted. There's no need to wait for confirmation from us before you log, but we will email you back if you include your email address in the message. For #3, rough estimates are fine, this isn't a math test. 1. The name of this earthcache: Alabaster Caverns Earthcache 2. From the signs outside the visitors center: How many stages of development are there in the life of a cave? Currently, which stage is Alabaster Caverns? 3. In the collapse section: The tour should stop at Selenite Boulder. Describe the boulder. What did the tour guide show you here? 4. Throughout the tour: Name at least two named features in the cave that were shaped by the flow of water through the cave. 5. (optional) Why do you think that the stalagmites and stalactites in gypsum caves are so few and so small? Pictures of your visit are always welcome.]

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)

This cache has been archived.

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Alabaster Caverns Earthcache EarthCache

This cache has been archived.

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