What geological process allows for the gradual enlargement of cavities into caverns over time?

The gradual enlargement of cavities into caverns over time primarily occurs through the process of dissolution by acidic groundwater. When water that has absorbed carbon dioxide from the atmosphere and soil becomes acidic, it can effectively dissolve soluble rock types, such as limestone. As this acidic water seeps through cracks and pores in the rock, it gradually erodes the solid material, leading to the creation and expansion of underground cavities. Over long periods, this process can result in the formation of extensive cavern systems.

This process is fundamental in karst topography, where the landscape is characterized by sinkholes, underground rivers, and caverns. Factors such as the presence of organic matter and the concentration of carbon dioxide in the soil greatly influence the acidity of groundwater, enhancing its ability to dissolve limestone and contributing to the growth of these subterranean structures.