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Wonder Speleothems EarthCache

Hidden : 04/06/2009
Difficulty:
2 out of 5
Terrain:
3 out of 5

Size: Size:   not chosen (not chosen)

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Geocache Description:


Wonder Speleothems
         A speleothem, a word from the Greek that stands for "cave deposit", it’s an addition mineral deposit formed in a cave.
         Like all the most solution caves, Wonder Caves at Aracena was dissolved while they are below the water table. All the amazing variety of these features that we can appreciate at this place only started to be formed after the cave drained and exposed to air where the deposition of secondary mineral features or speleothems may begin.
         Please, take a good look to all you want, but don't touch them. These are fragile things formed over thousands of years and just one simple touch of your fingers can, and will, compromise the rest of its process. Enjoy them but leave them intact for the next visitor! Take nothing but good memories and leave no trace of your visit.
Where they came from?

         Water seeping through cracks in a cave's surrounding bedrock dissolves certain compounds like aragonite, calcite and gypsum in which its rate depends on temperature on the amount of carbon dioxide held in solution among other factors. When the solution reaches an air-filled cave, a discharge of carbon dioxide may alter the water's ability to hold these minerals in solution, causing its solutes to precipitate. Over time, which may span tens of thousands of years, the accumulation of these precipitates forms speleothems like those you can appreciate at these caves.
         Depending on whether the water drips, seeps, condenses, flows, or ponds, speleothems take various forms some of them well like stalactites well know to all of us and other ones less known but also spectacular like Coralloids. Almost all speleothems are named for their resemblance to man-made or natural objects.

Why are they so different?

         Like all the things in the nature, many factors impact the shape and color of speleothem formations. Temperature and humidity inside the cave, the amount or rainfall, the density of plant cover on the surface, the rate and direction of water seepage, the amount of acid in the water, air currents, the above ground climate; all of this factors influences on speleothem shape and color formation. Like almost others caves, Aracena Wonder Cave chemistry revolves around the primary mineral in limestone; calcite (CaCO3). This mineral is slightly soluble and its solubility increases with the amount of carbon dioxide (CO2) and unlike the vast majority of solids, its solubility decreases as the temperature increases due to interactions with the carbon dioxide, whose solubility is diminished by elevated temperatures; as the carbon dioxide is released, the calcium carbonate is precipitated.
         Below we’ll describe you some of the speleothems that you’ll find on these caves. Please remember that they are extremely fragile and you should in any, what’s or ever touch them.

Stalactites

         Most anyone that's ever heard of caves knows what stalactites are, even if they can't keep them straight from stalagmites. (Some useful associations are that stalactites hang "tite" while stalagmites hold "mite", or that stalactites are on the ceiling, stalagmites on the ground.) What most people probably haven't thought about is the birth of stalactites. Actually it's more a coming of age, the natural evolution of a special type of stalactite and also another speleothem: the soda straw.
         Crystals of calcite in a soda straw are oriented longitudinally and grow downward, so lengthening the straw. Most soda straws, however, eventually conduct water along their external surface, as well, and there deposit radially oriented calcite crystals perpendicular to their outer surface. This leads to thickening of the soda straw into the classical "icicle" shape most people associate with stalactites. Internal flow may continue, but often ceases as external growth envelopes the former drip canal

   
    Stalagmites

         Stalagmites, another one familiar cave formations, are best known as upward-growing, massive calcite mounds deposited from drip water. As with all speleothems, stalagmites are identified not by their mineral composition, but by their outward form and internal structure. Thus, cavers also refer to aragonite and gypsum stalagmites, when we are lucky enough to come across them.
         Stalagmites are built up from many successive growth layers. Each layer is made up of tiny, elongate calcite crystals oriented roughly perpendicular to the growing surface. If drip water evaporates from the stalagmite surface, layers of minute aragonite crystals may also develop. Darkly stained layers attest to the episodic influx of impurities, usually organics.
         If you ever get a photo of stalactites and stalagmites and you forgot which way was up, look at the tips of the formations. Stalactites almost always have pointed tips, whereas stalagmites are usually rounded, or even flat.
         When one stalagmite joins itself to a stalactite, or vice-versa, we’ve one column formed.

Flowstone

         Flowstone is perhaps the most common of all cave deposits, and is almost always composed of calcite or other carbonate minerals. It forms in thin layers which initially take on the shape of the underlying floor or wall bedrock beneath, but tends to become rounded as it gets thicker. Flowstone masses are often fluted with draperies at their lower end, such as the area above the caver's head. Impurities in the calcite may give a variety of colors to flowstone, such as the reddish areas on the right (likely due to iron).
         Flowstone forms from actively flowing water (rather than water squeezed through cracks) in which carbon dioxide is lost and carbonate material is deposited. This is the basic mechanism forming stalagmites as well, and the two often form together.

   
    Baldacchino canopies

         Baldacchino canopies form where the surface of a cave pool has receded beneath a growing stalagmite or flowstone mound. Prior to lowering of the pool, pool spar is deposited on the underside of the flowstone. Under these conditions, pool spar tends to grow most rapidly close to the water surface, where diffusion of the incoming supersaturated solution within the pool is least and diffusion of carbon dioxide into the overlying air is greatest. The result is an overhanging belly of calcite, which has its widest girth at the pool surface. Such a belly can be seen at left in the upper photo, where the flanking pool of blue, calcite-rich water has receded, but only after the overlying stalagmite has ceased growing.
         The classic "canopy", however, is formed when seep water calcite envelopes the overhung spar following a drop in pool level. Rivulets of water that cascade along the overhanging surface then deposit fluted draperies. In the lower photo, we see that these draperies formed strictly below the level an old, stable pool surface, which is marked by a rim of shelfstone to the right of the canopy.

Draperies

         Draperies are deposited from calcite-rich solutions flowing along an overhung surface. Surface tension allows these solutions to cling to a wall or sloping ceiling as they stream slowly downward. Loss of carbon dioxide to the cave atmosphere then causes the solutions to become supersaturated with respect to calcite, which is deposited in a thin trail. Initial calcite trails, hanging slightly lower than the surrounding surface, become preferential routes for continued flow, and so develop into slender, delicate sheets.
         Ripples and folds in cave draperies, which reflect the erratic path of pioneer flow routes, are reminiscent of 'drapes' of supple cloth, and the likeness provided an obvious name for these formations. Another fitting name, however, is sometimes given to the multi-colored, translucent draperies seen in the photo below. The dark and light bands, generally a product of the waxing and waning supply of organic acids to the seep solution, remind many cavers of "bacon".

   
    Coralloids

         Coralloids are one of the most common form of cave formation, and can take a a variety of forms. The term encompasses all manner of knobby, globular, button-like, coral-like, or botryoidal type formations that can form either above or below water. One of the most common resembles popcorn and is often given that name, so we have a whole separate description devoted to it

Popcorn

         Popcorn is a common name for a very common type of coralloid. It can be recognized by its gregarious nature and knob-like shape, the latter of which it owes to its concentric layering of microcrystalline calcite. Though one of the most common of all cave formations, the origin of popcorn has been one of the more difficult to explain. Perhaps both the abundance and ambiguity of cave popcorn arise because it forms under so many conditions. Popcorn forms either in air (subaerially) or within still cave pools (subaqueously). In air, it is deposited from thin, evenly distributed solution films, but these films may be products of direct seepage, surface flow, drip water splash, capillary action, or condensation. Seepage, however, is probably the most common solution supply mechanism. Moisture within the underlying bedrock or cave calcite is wicked through the relatively porous matrix of a popcorn knob to its outer surface, where it feeds an array of growing crystal faces. The validity of this mechanism has been shown by laboratory experiments in which popcorn knobs have deposited precipitates from various solutions in which their bases are submerged. Unlike many forms of cave calcite, which grow chiefly due to the loss of carbon dioxide from their depositing solution, subaerial popcorn is largely the product of evaporation. As such, popcorn is often an excellent indicator of the subtle air currents that waft through even the deepest reaches of many caves. Evaporation will be fastest on surfaces that face 'upwind', and the observant caver comes to read popcorn's bushy growth on one side of a stalagmite not unlike the way a backpacker reads moss on one side of a tree trunk. Even more important to the cave explorer is the fact that where there is wind, there must be cave! Popcorn may not make tight crawling leads very comfortable, but it does make them more encouraging!

   
How can you log the cache?

To claim this cache as found you should send to this cache owner a message answering correctly the following questions:

  • Inside the cave you’ll see the “Nude Room”. How do you classify this speleothems. Why?
  • In your opinion, what are the two major threat of Aracena Cave. Why?
  • Inside the cave, you’ll find something that it’s not supposed to be there. How that appears? Is it a good sign, why?

If you believe you have successfully completed this Earth Cache goals and has already sent to this cache owner all the requirements as requested, Please, feel free to log it as found. Later we will verify the requirements sent and, if necessary, contact you in order to make the necessary corrections to your log.

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