Mastering the spring water
In the area of Saint-Nectaire, deep cracks allow volcanic magma to surge from the upper mantle. That magma, cooling down, maintains a heat flux in the underground and dissolves the mineral elements (calcium, sodium, iron).
Deep down, between 3000 and 4000 meters, the warm waters mix with carbon dyoxyde coming from the upper mantle. Lightened by that ascending gas, after a-40-year-subterranean course, those waters join the ground surface through the volcanic cracks. At the top of those cracks, the springs are harnessed, channeled through a network of subterranean galleries toward the petrification ladder.
By creating a series of small waterfalls, the ladders allow water to ventilate, causing the evaporation of carbon dyoxyde and calcium carbonate to settle into the prepared moulds.