An undistinguished stone house in the middle of a bare karst landscape hides the entrance to a cave 12 m under the surface. Although it is not very long if compared to other caves, only 110 m deep, the Biserujka cave has everything that is characteristic of karst phenomena. It has lots of typical features such as stalactites and stalagmites, and also a gallery or hall, which is suitable for the holding of concerts.
Stalactites are formed by the deposition of calcium carbonate and other minerals, which is precipitated from mineralized water solutions. Limestone is calcium carbonate rock which is dissolved by water that contains carbon dioxide, forming a calcium bicarbonate solution. The chemical formula for this reaction is:
CaCO3(s) + H2O(l) + CO2(aq) ? Ca(HCO3)2(aq)
This solution travels through the rock until it reaches an edge and if this is on the roof of a cave it will drip down. When the solution comes into contact with air the chemical reaction that created it is reversed and particles of calcium carbonate are deposited. The reversed reaction is:
Ca(HCO3)2(aq) ? CaCO3(s) + H2O(l) + CO2(aq)
An average growth rate is 0.13 mm (0.005 inches) a year. The quickest growing stalactites are those formed by fast-flowing water rich in calcium carbonate and carbon dioxide, these can grow at 3 mm (0.12 inches) per year.
Every stalactite begins with a single mineral-laden drop of water. When the drop falls, it leaves behind the thinnest ring of calcite. Each subsequent drop that forms and falls deposits another calcite ring. Eventually, these rings form a very narrow (0.5 mm), hollow tube commonly known as a "soda straw" stalactite. Soda straws can grow quite long, but are very fragile. If they become plugged by debris, water begins flowing over the outside, depositing more calcite and creating the more familiar cone-shaped stalactite. The same water drops that fall from the tip of a stalactite deposit more calcite on the floor below, eventually resulting in a rounded or cone-shaped stalagmite. Unlike stalactites, stalagmites never start out as hollow "soda straws." Given enough time, these formations can meet and fuse to create columns
referenz by wikipedia
First log your visit and then send me the answers per email. Please do not write the answers into your log!
- Photo with you in front of the house or inside the caves. (optional)
- In this cave you got stalactites and stalagmites, which ones are growing upwards?
- Whats the name of the last room in the cave?
- Whats the average temperature in the cave?