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You're Just Tafoni!

A cache by josephaw Send Message to Owner Message this owner
Hidden : 04/08/2016
Difficulty:
2 out of 5
Terrain:
2 out of 5

Size: Size: other (other)

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Geocache Description:

At this spot looking north you will find some rather rare and somewhat mysterious geologic formations called Tafoni. Tafoni (plural of tafone) are ellipsoidal, pan- to bowl-shaped, natural rock cavities. To learn more about these geologic curiosities, read on below.


 


Note: This is an Earthcache. Put simply, that means it is not a traditional cache, but its purpose is to help educate those who find it about some geologic aspect of the area they find themselves in. To log this cache, you will NOT be looking for a typical geocache container (in fact, there IS no container to find). Rather, to prove you were here and learned something you'll need to find the answers to the given questions (found at the end of this description), which you will then email me, the owner (this is the same process for ALL Earthcaches).

So go ahead and log your experience while here, submit photos, etc., but email your answers to me (not in your visit log) to get credit for "finding" this cache. If it seems too complicated, don't sweat it too much (as long as I can see that you made an honest effort to answer all of the questions, that is fine). Remember that the purpose of this is to learn something, and most importantly, to have fun! Also, feel free to email me with any questions you may have, I'd be happy to help.

Note: This cache was placed with the help of Ray Kelsey, Outdoor Recreation Planner at the Salt Lake BLM Field Office, and I'd like to thank him for his assistance. Please be respectful of the area, and make sure to only drive on existing roads. Do not litter, and help pick up garbage if you see it. Thank you.


Also, thanks ought to go out to Dick Nielson, whose other Tafoni Earthcache inspired this one and one other of mine!

Tafoni

Even the origins of the word tafoni are mysterious, but it certainly has Mediterranean origins. The word tafoni may stem from the Greek word taphos meaning tomb or sepulcher, or from a Corsican / Sicilian word, taf(f)oni, meaning windows, or from tafonare (Italian) meaning to perforate.

Regardless of the name's history, tafoni continue to captivate both scientists and casual observers alike. These cavernous weathering features include tiny pits (even microscopic at times), softball-sized cavities, and even truck-sized caves. Sometimes smaller tafoni develop inside larger ones, and these smaller ones found inside other ones are called nested tafoni. Tafoni typically develop on inclined or vertical surfaces and occur in groups. These exquisite and fascinating cavernous weathering landforms are present on the surfaces of many different kinds of rocks located in a multitude of geographic regions around the world (and even found on Mars!). Since the late 1800s, more than 100 research articles have been published in numerous languages on this geomorphic topic. Tafoni development and evolution is puzzling and continues to arouse curiosity even today.

Above Right: Tafoni, much like you'll see at this site.

Weathering

Weathering defines the set of physical, chemical, and/or biological processes which decay and break rock down into smaller pieces. Weathering processes can act independently and in concert as well as at different scales of observation. Erosion is the transport of the weathered debris, often by wind and water, away from the cavity interior. Particularly in arid regions where wettings are infrequent, soil and weathering products often remain nearby. 

So how are these particular unique features created? What causes them to occur? There are many theories, but I'll give you a few to consider, and then you can decide how you think these particular ones are/were formed (and no, they aren't giant pieces of petrified Swiss cheese, though the resemblance IS striking).

Salt

One possible explanation is a process called salt weathering, a type of physical weathering. Basically, the salt can arrive in a number of ways to the rock that is undergoing tafonization. It can be in the nearby soil, and rain or wind can deposit it on the surface of the rock/tafoni. As this area was once the lakebed of the ancient Lake Bonneville, an inland sea, there is likely to be lots of salt around (i.e. the nearby Salt Flats, the Great Salt Lake, etc.). Or, it could be from nearby salty water, then carried aloft in fog or by wind. Sometimes the salt may originate in the rock itself.

However it gets there, once there it will eventually crystallize. If the rock already has some porosity, the salt will often fill the tiny and even microscopic holes near the surface of the rock, and as the salt accumulates, the arrival of water will help catalyze the formation of salt crystals (which grow and expand), thus causes stress to the rock around the salt, thereby flaking off grains and pieces. 

Above: "Frost action" diagram (note that this is process is nearly identical to salt weathering).

Water

Another explanation is simply the presence of water. When water arrives, whether in rainfall, floods, etc., it is absorbed by the rock. The presence of water can cause physical weathering through mineral swelling (especially if there is clay in the rock), which can weaken and break apart the rock particles, especially along the surface. Also, the water can be absorbed and then later freeze, which often happens in desert environments at night, as the temperatures drop dramatically. The formation of ice crystals (much like salt crystals) puts pressure and stress on the surrounding rock, which leads to flaking and breakup of the rock (this process is called frost action).

Water can also cause chemical weathering. Water can bring all sorts of different minerals along with it, which can chemically react with the stone and minerals therein. These processes can also weaken the rock, and lead to weathering, flaking, etc.

Biological

Biological weathering is another possibility. Creatures such as snails, plants, fungus, etc. often secrete different chemicals and acids into the environment around them, which can weaken the rock. Other forces, such as water, wind, etc. can then more easily weaken and weather and erode the rock. The nearby lichen is a possible candidate, as are other organisms that may grow along the surface.

Right: Lichen on a rock as can be found throughout Utah.

Other Factors

Frankly there are many possible candidates that could cause and develop these unique formations. One is cementation, which occurs when water laden with cementing agents like silica oxide, iron oxide (rust), and calcite coats the surface of a rock, thus causing weathering effects to be temporarily limited. Tafoni may then form when this hardened outer layer is breached revealing a core depleted in cement and especially susceptible to weathering, a process known as core softening.

Other factors including porosity, permeability, conductivity, feldspar concentration, bedding, jointing, fracturing, grain size, and grain sorting may also augment tafoni development. For example, if the rock is already porous, then any particles that fall or break off inside that cavity would be subject to wind, which would blow them around, further weathering away the inside of the cavity.

Conclusion

So how did these particular tafoni form? That is up for debate, but based on what you find at the site, you should be able to make an educated guess. I hope you enjoyed visiting this beautiful area, and enjoyed learning something about these interesting geologic curiosities. Thanks for visiting!

Modified and added to by the author from the following source: http://www.tafoni.com/

In conclusion, remember: to log this cache, use the following info, your surroundings and head to answer the following questions. Email me the appropriate answers (don't post them in your log, or per Earthcache guidelines your post will have to be deleted), and most of all, have fun!

  1. Find a nearby example of a tafone. Describe its size, the surrounding rock's composition, etc.
  2. How do you think these particular tafoni were formed, given the rock they are in, the surrounding environment, etc.?
  3. What is a nested tafone? Do you see any? If so, describe.
  4. (Optional) Find a tafone / some tafoni that you like, and post a picture (with yourself, if you like).

I have earned GSA's highest level:

Additional Hints (Decrypt)

Qb lbhe irel orfg, naq unir sha. Rznvy zr jvgu nal dhrfgvbaf.

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)



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