What is the process in karst region?

A karst region forms when a weak acid dissolves carbonated bed rock such as limestone as it flows underground. Over time large voids are created in the lime stone rock beneath the surface creating an interconnected system of sink holes, springs, aquifers and caves.

Water is considered to very "corrosive" to dissolving carbonates. Temperature, Ph, Calcium and Carbonate content all affect the how corrosive the water will be.

Surface water, being in contact with the atmosphere. Subsurface water being more corrosive if CO2 levels are at 400 ppmv.

At lower temperatures calcite is more soluble.