Variations in the flow of La Clamoux have no consequence in the bottom of the Gouffre, and this is due to the absorbent fissures, filled with sand, that regulate the flow. These natural filters permit to provide high quality drinking water at the bottom of the Gouffre.
After leaving the impermeable rocks, the water of La Clamoux is absorbed in the limestone fissures. So, nowadays, the cave is still being carved out, but we must imagine that this phenomenon of loss when it in contact with limestone is old and dates back to several millions of years. In those times, the valley of Cabrespine was not much carved out and the level of the river Clamoux had nearly the same altitude as the car park of the Gouffre, that is to say 200m higher than it is today.
That explains why the subterranean gorge had been carved out on such a height and the fantastic heights of the Gouffre Géant. What happened at the beginning of the carving out
And how can we explain the formation of the great chamber of the Gouffre? Water probably arrived from the “Red Chambers” and flew out through the black hole situated to the left of the entrance tunnel (the hole can be easily seen from the metal bridge). The vertical erosion already unblocked the great chamber since the debit of La Clamoux was much higher than the present-day debit. As waters were penetrating little by little, they used different more or less parallel ways. However, below, the immense vault alleviated from the water pressure has consequently found its balance again in accordance with the requirements of the types of rocks. As the water flow was reducing, the Gouffre looked like a mushroom, a classical shape known by all karstologists. The extraction of materials was so important that, in spite of collapse and rebalancing of the roofs and walls, the way of the underground river could be accessible for speleologists.
They followed kilometres of galleries which lie on different levels, intersect on nearly an altitude of 200m. The volume excavated by waters represents several dozens of millions of m³.