It gathers additional carbon dioxide as it moves through the soil. Water mixed with carbon dioxide is weak carbonic acid solution. As this solution of water and carbon dioxide seeps through the cracks and crevices, it dissolves the soluble rock and forms cavities and channels as it moves downward and laterally. After thousands of years of solution, underground rooms and chambers can be formed. Not all cave passages in soluble rocks form in precisely the same way.
Water enters the cave system through sinkholes, losing streams, and other points on the surface.
It travels underground and exits at a spring. Sometimes water moves very slowly underground, rather than rushing along underground streams. Many of the caves formed this way are mazes of passages with many interconnections. Water flowing vertically down cracks can develop passages almost like elevator shafts, except that the passages are circular or oval. As rain water falls through the air, it picks up carbon dioxide.