WORK IN PROGRESS (Part 2) EarthCache
Hidden : 3/18/2013
Difficulty:
1.5 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

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Geocache Description:

The National Showcaves offer some of the best  examples of "speleothems" in Britain.

A speleothem commonly known as a cave formation, is a secondary mineral deposit formed in a cave. Speleothems are typically formed in limestone.

The National Showcaves Centre for Wales is situated within the Brecon Beacons National Park, and is a fascinating insight into the natural phenomena of cave formation.The coordinates to you to the rear of the dinosaur Park. You can choose by following the signs which caves you wish to explore

Getting here
 
N.B. SEASONAL ATTRACTION: PLEASE CHECK OPENING TIMES/DATES BEFORE SETTING OUT

Travelling from the South (M4)
Leave the motorway at junction 45, and follow the signs for the A4067 North (Pontardawe). You will then see the brown tourist signs for Dan-yr-Ogof Showcaves. Follow these signs all the way up the valley; from the motorway the journey time is approximately 25 minutes.
 
Travelling from the North
If travelling from the North, head towards Brecon. From Brecon, stay on the A40, travelling in the direction of Llandovery. You should leave the A40 just before Sennybridge (a left turn), looking for the brown tourist sign for Dan-yr-Ogof Showcaves. This takes you on to the A4067; from Sennybridge the journey time is approximately 15 minutes.
 
Or set your SAT NAV to SA9 1GJ
 
Typical limestone cave cross section


 
You will need to enter a cave to complete the cache and there is an admission fee. You will find it a worthwhile experience.
 
About the underground features
 
The bedrock at Dan yr Ogof is predominently carboniferous limestone, formed some 315 million years ago. Because the rock has cracks and fissures, water has been able to flow through it, dissolving the limestone and carving out the landscape we see today.
 
The rivers running underground in the caves cut new passages at lower levels and abandoned the higher levels. Cathedral cave is an abandoned higher level. The show cave at Dan yr Ogof  is formed in one of these lower levels and the river is still cutting its way down to form even lower cave passages.
 
The limestone is attacked along both 'bedding planes' - the layers of rock themselves - and along vertical fractures present in the rock from the times millions of years ago when south Wales was successively stretched and squeezed as continents collided and split apart. 
 
Limestone caves, where most stalactites and stalagmites are found, are mainly composed of calcite, a common mineral found in sedimentary rocks. Calcite molecules are made of calcium and carbonate ions, and are referred to as CaCO3, or calcium carbonate. When rainwater falls over a cave and trickles through rocks, it picks up carbon dioxide and minerals from limestone. If we add water, carbon dioxide and calcium carbonate together, we get this equation:H20 + CO2 + CaCO3 = Ca (HCO3)2  
Ca (HCO3)2 is known as calcium bicarbonate, and the water carries the substance, basically dissolved calcite, through the cracks of the roof of a cave. Once water comes into contact with the air inside the cave, however, some of the calcium bicarbonate is transformed back into calcium carbonate, and calcite starts to form around the crack. As water continues to drip, the length and thickness of the calcite grows, and eventually a stalactite forms on the ceiling. It can take a very long time for most stalactites to form -- they usually grow anywhere between a quarter-inch and an inch every century.
 
You can trace the words stalactite and stalagmite back to the Greek word "stalassein," which means "to drip." This is fitting because it describes how both are formed in nature. Although they look lifelike and a little creepy, stalactites and stalagmites grow simply because of water running over and through inorganic material.
 
The difference between a stalactite and a stalagmite.

They both occur in limestone caves. The stalactite is above, and hangs downward like an icicle; the stalagmite is below and sticks up. They grow in pairs, the slightly acidic water dissolves some of the limestone, carrying it downward. When the water evaporates, the limestone appears to have flowed downward.

Some of the water does not evaporate until it has fallen through the air, and landed on the floor, the remaining limestone building the stalagmite. Sometimes the stalactite is missing, as they sometimes break off and fall; you will often see their pieces on the floor. Or human visitors may break them off, and take them away. Often, the stalactite and stalagmite will connect, and become a column.



Other features

These caves full of different features. There are stalagmites, stalactites, cave bacon, flowstone, soda straws, columns, popcorn rock, and lots more. For example, ‘Cave bacon’ looks like real bacon, but it is not real bacon.Cave bacon can be found hanging out from walls and down from ceilings. Cave bacon is formed when water runs down a limestone cave wall or along a ledge. The water deposits calcite into delicate draperies, and the minerals like iron oxide make strips in the draperies. That is how cave bacon got its name.  Not all caves have this feature in them. Bacon strips can be different colors depending how pure the water is.

Soda straws are baby stalactites. They have the shape of soda straws and are generally translucent. They are also hollow and usually  straight. Soda straws are really fragile, so they can break with the slightest touch. Soda straws are known to grow up to 30 feet if left alone.

Stalactites grow downward from the cave ceiling. They are formed when drop after drop of water flows through cracks in the cave ceiling.

A column is a stalactite and a stalagmite that have joined each other. Some columns have been joined for so long that it is hard to tell if they were ever separate formations. Columns can be found where ever stalactites and stalagmites grow, but they are less common, because it takes a very long time for the formations to meet. Columns can be covered in popcorn rock. Popcorn rock looks like the popcorn we eat. They are round and bumpy.

Flow stone is round and sometimes it can have an opening in it. It can be found where water can flow over rock. Flowstone is almost always composed of calcite or other carbonate mineral. It forms in thin layers. Flowstone forms from actively flowing water in which carbon dioxide is lost and carbonate material is deposited. Impurities in the calcite may give a variety of colours to flowstone.

Stalagmites don't just emerge from the ground. The water dripping from the end of a stalactite falls to the floor of a cave and deposits more calcite into a mound. Soon enough, a stalagmite will form in a conelike shape. This is why you usually find stalactites and stalagmites in pairs, and sometimes they'll even grow together to form one big column.

Stalagmites grow upward from the cave floor. The word stalagmite comes from the Greek word "stalagma" which means "drop" or "drip". Stalagmites grow slower in caves than in artificial tunnels and basements. They usually have round tips. There are a lot of different kinds of stalagmites such as mushroom stalagmites. Stalagmites are generally a result of water dripping from overhanging stalactites. When stalagmites aren't a result of water dripping from stalactites they are formed by mineralized water that drips on it. As the water slowly evaporates, it leaves a small deposit of minerals. This is how stalagmites slowly form.
 


THE CACHE IS CALLED "WORK IN PROGRESS" BECAUSE THESE GEOLOGICAL PROCESSES CONTINUE EVEN TODAY AT AN IMiPERCEPTIBLE PACE.
 

Acknowledgements
 
Britainica Online

"The Wonders of Dan yr Ogof.” Sarah Symons    Y Lolfa
 
Thanks to the Showcaves management for permission to 'place' this earthcache.

 
 
Please EMAIL me the answers ~ From the guidelines: You do not need to wait for permission to log. Requiring someone to wait is not supported by the EarthCache guidelines. You should send your logging task answers , then log the EarthCache. When I review your logging task answers, if there is a problem, I will contact you to resolve it. If there is no problem, then your log simply stands."

1. The Dan yr Ogof  Showcaves offer examples of spectacular "decorations", or "speleothems", including aragonite crystals, cave pearls, columns, draperies, flowstone, helictites, popcorn, rimstone dams, soda straws, stalagmites, and stalactites.  
 
THIS ISN'T COMPLETELY TRUE, which features did you actually see? (Hint: use signs and guide)

Identify and NAME specific features:

2. FLOWSTONE is produced by sheets of calcite forming over sloping rock. The cave feauture that demonstrates this is ________

3. COLUMNS occur when a stalactite meets a stalagmite and they join. The cave feauture that demonstrates this is ________

4. CURTAINS are the result of water running across sloping rock, leaving minute layers of calcite behind. A good example of this can be seen in ____________

5. Desribe any one of the above features you have identified in terms of size, shape, colour, texture, surrounding area etc.

Please do not include any answers in your log.  
 

Additional Hints (No hints available.)



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