Speleotherms

               Cave formations are typically formed from calcite. When water seeps through the ground, it picks up carbonic acid from carbon dioxide leftover from dead plants and animals. The acidic water dissolves limestone, creating underground cavities. When water hits the air in these cavities, the carbonic acid is released as carbon dioxide leaving the remnants of calcite.

               Despite what many people think, some cave formations can form rather fast; some small formations are often even found in mines.  These formations have been known to grow as large as an inch in about 40 years. While this may seem to be rather slow, it is rather fast compared to the thousands of years some think it takes.