Down the Rabbit Hole – Caves

by Deb on November 11, 2010

These photos and factlets were inspired by our visit to the amazing Ngilgi Cave in the south-west of Western Australia.  I love caves, they really are another world.

  1. Most underground caves are made from limestone, which is calcium carbonate.  This dissolves in water and weak acids so over thousands of years it can be eaten away leaving big holes, or caves.
  2. Inside the cave system the water is carrying all the minerals and calcium carbonate it has dissolved.  This is deposited when the water is saturated (can’t dissolve any more) and creates the beautiful natural sculptures.
  3. Straws are thin hollow tubes.  They are how many of the sculptures get started, minerals are generally left around the edge of a drop so it starts building tiny walls, then a tube where the water runs down the inside.  They are very fragile, if they are blocked the water starts to run down the outsides, building shapes like the one on the left.Straws
  4. These uneven shapes become stalactites, the classic stones we imagine hanging from the roof of the cave.  A couple can be seen in the back of the photo.
  5. When water reaches the end of the straw or stalactite it drips onto the ground, starting a stalagmite.  It’s easy to remember which is which if you think of ants in your pants – when the mites go up, the tites come down!
  6. Eventually the stalactites and stalagmites can reach and join, forming columns.  Column
  7. Sometimes there are lots of columns or the water is trickling over a wall in a sheet rather than a drip.  I don’t know if that has a technical name (anyone?) but this particular one was nicknamed the wedding cake.  Don’t forget this is stone – there are several tons here.wedding cake
  8. Or sometimes rather than dripping straight down the water runs along a ridge on the ceiling, creating a shawl or flowstone. These can get very complicated as water runs down both edges, they can even be translucent but are still stone. Shawl
  9. One of the stranger cave formations are helictites. There isn’t a definite answer on how they are made but a few different theories.  Something draws the water away from the tips of the straw, it could be wind, capillary action or even electrostatic forces in the crystals. helictite
  10. The most common mineral in caves is calcium carbonate but there are many others.  These are what create the beautiful colours like the reds and oranges above or this green. minerals
  11. Caves often have pools of standing water with deposits of crystals around them.  When a stalactite reaches into a pool it can be an anchor for crystals too.  These formed in a pool with different water levels, now gone.Crystals
  12. Because caves form over such long periods there can be many changes in the climate and environment around them.  Sometimes an ancient soil or palaeosol is buried in them, like the orange-brown in this photo. Palaeosol
  13. Unfortunately cave systems are very fragile.  People tramping through them and breathing affects the balance of water and minerals.  Touching anything leaves oils from our skin, which repels the water and leads to drying out and the end of the stone formations.  Chemicals in the oils can react with minerals in the stone and discolour it.  Caves are fascinating to visit, but leave them there for others to see. oil damage

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{ 6 comments… read them below or add one }

Brandt! November 11, 2010 at 11:31 am

beautiful pictures!!

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Rekaya Gibson November 11, 2010 at 3:05 pm

Fascinating! Thanks for sharing visuals. I love them!

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CountryDew November 11, 2010 at 10:01 pm

Oh, I love caves, too! We have many caves where I live in Virginia; this is big limestone country. Thanks so much for sharing this!
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Adelle Laudan November 11, 2010 at 10:07 pm

Fascinating and breathtaking. Thanks for sharing. Happy T13!

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Harriet November 12, 2010 at 3:15 am
Mistress B November 16, 2010 at 12:44 pm

I was talking to my mother about caves the other day (not sure why) and she was telling me that in some caves in drought affected nsw the cave managers are bucketing water into the caves because there is no ground water seeping into the caves to provide moisture to keep the stalactites and stalagmites or crystals growing.
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