1. CO2 in Groundwater: Rainwater absorbs CO2 from the atmosphere and the soil as it percolates through the ground. This creates carbonic acid (H2CO3).
2. Carbonic Acid Reacts with Limestone: Limestone is primarily composed of calcium carbonate (CaCO3). When carbonic acid comes into contact with limestone, it reacts to form calcium bicarbonate (Ca(HCO3)2) which is soluble in water.
3. Dissolution and Cavern Formation: The dissolved calcium bicarbonate is carried away by the groundwater, leaving behind empty spaces in the limestone. Over time, these spaces enlarge and connect, eventually forming caves and caverns.
The chemical reaction:
```
CaCO3 (limestone) + H2CO3 (carbonic acid) -> Ca(HCO3)2 (calcium bicarbonate)
```
Key Points:
* The presence of CO2 in groundwater is crucial for the dissolution of limestone.
* This process is a major factor in the formation of karst landscapes, which are characterized by caves, sinkholes, and underground drainage systems.
* The rate of dissolution is influenced by factors like the concentration of CO2, the flow rate of groundwater, and the type of limestone.
