How long can the early initiation stage of solution-cave formation take?

The early initiation stage of solution-cave formation is a slow process during which groundwater moves through mechanical fractures in limestone. Because the water becomes nearly saturated with dissolved calcium carbonate, the enlargement of these fractures occurs at a very gradual rate.1

Calculations indicate that this phase typically requires between 3,000 and 10,000 years to enlarge a fracture from an initial width of 10 to 50 micrometres to a "pencil-sized" opening of five to 10 millimetres. Once a continuous pathway of this size is established from the water source to the outlet, the initiation phase is considered complete, marking the transition to an evolving conduit system.1