Wey-hey!! A chance for me to do microbiology lesson 101........ :clapclap:
This ain't going to be a short reply guys, so bear with me and hope it answers some of your questions.
cave shrimp said:
But. I've now been informed that the colouring is some form of bacteria which is decaying
SamT said:
What I do know is that some caves are not actually formed by water flow but by acid secreting bacteria such as the cueva de villa luz in mexico and i think - lechuguilla
Quite right, SamT. Most limestone caves are dissolved into formation by carbonic acid, a mixture of carbon dioxide and rainwater, which disolves Limestone (rich in Calcium Carbonate) into Calcium Bicarbonate (Cave Formation Lesson 1!!). Some, however, are created by a more corrosive acid - one that results from bacteria deep within the Earth, feeding off oil deposits.
These bacteria, called extremophiles because they live in extreme conditions, expel Hydrogen Sulphide gas (H2S).
IMPORTANT NOTE - EVERYONE SHOULD BE AWARE OF THIS: Hydrogen Sulphide is a colorless gas with an offensive stench which smells like rotten eggs. Be carefull of high concentrations in Cave systems - breathing in the gas at concentrations greater than 500 ppm (parts per million) can be fatal within just a few breaths. Death is usually preceded by a loss of consciousness after one or more breaths, although a loss of consciousness does not necessarily mean that death will follow. Hydrogen Sulphide is considered to be a "broad spectrum" poison. This means that it can poison several different systems in the body. This variety of activity may be the reason that no single antidote, or treatment, has been found for Hydrogen Sulphide poisoning. Hydrogen Sulphide can be especially dangerous because at concentrations over 100 ppm you might not be able to smell it, and therefore you would not realize that you were being overexposed.
If you are exposed to lower concentrations of Hydrogen Sulphide, the symptoms that appear, such as eye irritation, a sore throat and cough, shortness of breath, and fluid in the lungs, will usually subside within a few weeks, but other changes such as memory problems may occur. Breathing in Hydrogen Sulphide on a long-term basis may result in fatigue, loss of appetite, headaches, irritability, poor memory, and dizziness. It is also a flammable gas and can be ignited by Carbide Lamp operation.
This gas is carried up by groundwater into caves. The Hydrogen Sulphide mixes with Oxygen to form Sulphuric acid. The corrosive acid eats away at the limestone rock, leaving behind Gypsum, which is normally white, colourless or grey, but can also be found in shades of red, brown and yellow. Small crystals of Gypsum can gather in droplets of water and produce discolouration.
Bacteria also live within some of these pitch-black caves. Unlike their cousins in the oil deposits, these bacteria feed off the Hydrogen Sulphide, combining it with Oxygen to form even more Sulphuric acid, therefore producing even more Gypsum. Other types of microbes eat minerals within the rock (Sulphur and Manganese, for example) accelerating even further the cave-eating process.
Several years ago, scientists found bacteria and the acid it generated in Mexico's Cueva de Villa Luz (Cave of the Lighted House), still alive and still eating away the caves walls. Lechuguilla Cave in New Mexico (most of whose 100 miles+ passages have only been discovered since 1986), bore all the signs of being carved out by Sulphuric acid, though there was no acid still present within the cave and therefore no proof that it was the main factor behind the formation of that system.
Tubby Two said:
Going on a similar, but not the same, vein, i saw some extereme archeology program on the box last week with some people exploring an old mine in Anglesey, on the roof and beams there was lots of slime, dripping down like rubber curtains - they said it was some kind of carbohydrate from a bacteria. is this true?
Yes. The slime is bing formed by cave-dwelling microbes. In some cases the bacterial growth is so abundant the walls drip with slime. The bacteria is producing a sort of biofilm in which it exists.
Caves provide one of the most constant of environments; the temperature and humidity remain the same. But in some caves, Hydrogen Sulphide combines with Oxygen to produce Sulphuric acid, as previously mentioned. Some bacteria add their own acid as a waste product. To protect themselves from all this acid, certain bacteria produce their own microenvironment within the slimy biofilm.
It acts as a place for them to conduct their own little chemistry labs, so to speak, regardless of what is going on outside of the film. We protect ourselves against the byproducts of our metabolism and in essence, the bacteria are doing the same thing. The slimy projections produced by these microbes are sometimes amusingly referred to as "Snottites" (Honest!! Check out the bottom of the page at
http://www.chm.bris.ac.uk/sillymolecules/sillymols2.htm if you don't believe me........
).
:worthy:
