Why would groundwater that remains in one place and does not circulate not result in a cave in limestone?

• A. It would become saturated with CaCO3 and would no longer dissolve the limestone
• B. It would remain unsaturated and continue dissolving limestone
• C. It would lose CO2 and become less acidic
• D. It would evaporate before dissolving limestone

Answer: (A)

Groundwater dissolves limestone only while it remains undersaturated with calcium carbonate. When water rich in dissolved CO2 percolates through limestone, it forms carbonic acid that dissolves CaCO3, producing Ca2+ and bicarbonate. As this process continues, the water accumulates dissolved calcite and approaches equilibrium with solid CaCO3. If the water sits in one place and isn’t renewed or flushed away, it will reach saturation and can no longer dissolve more limestone. Without ongoing dissolution, a cavern won’t form, because cave growth depends on flowing water removing dissolved minerals and keeping the solution undersaturated downstream. So stagnation prevents continued dissolution, whereas flow maintains dissolution and cave development.