In virginia and some other parts of the world, water has carved vast caverns out of underground limestone deposits. water, however, must contain dissolved carbon dioxide in order to break down the limestone. what role does the carbon dioxide play

Naturally, limestone has a low solubility in water. However, water containing dissolved carbon dioxide produces carbonic acid according to the following reaction: H2O + CO2 = H2CO3. Carbonic acid is a weak acid, however, through time, it can significantly carve out limestone. Thus, carbon dioxide, which is present everywhere, play an important role in dissolving limestone.