* CO2 in the Ground: CO2 naturally dissolves in rainwater and is also released by decaying organic matter in the soil. This dissolved CO2 reacts with water to form carbonic acid (H2CO3).
* Carbonic Acid's Power: Carbonic acid is a weak acid, but it's strong enough to react with the calcium carbonate (CaCO3) in limestone. This reaction creates calcium bicarbonate (Ca(HCO3)2), which is soluble in water.
* Dissolution: The calcium bicarbonate dissolves into the water, effectively removing the limestone.
This process is responsible for the formation of caves, sinkholes, and other karst features. It also contributes to the erosion of limestone cliffs and other landforms.
In summary: It's the carbon dioxide in the groundwater, which creates carbonic acid, that allows the water to dissolve limestone.
