We're going out to survey a new cave this evening. It contains the only helictites I've ever seen locally, which makes me wonder what conditions permit their formation. What can I look for to help me understand why these formed when there are no others in the area?
The Cave Minerals of the World book has excellent descriptions of how many speleothem types form. When you see helictites check the walls and ceiling for an obvious solid calcite coating that they would grow out of. One of the better explanations I read is that a thin layer of pressurized water gets in between the bedrock wall and the calcite layer and then it seeps out to make the helictites. The same hypothesis has also been applied to popcorn growth.
muddyface wrote:The same hypothesis has also been applied to popcorn growth.
Popcorn growth is connected with not equal saturated vapour pressure on concave and convex surface of popcorn. In conditions with very high concentration of aerosol in air. The airflow transporting the aerosol could help too.