Another visit to the Château de Calamès trail today. No other people - so we could well explore the cave at the foot: http://youtu.be/c-tzgjehhvw .

Conclusions:

(1) some parts of the cave's walls resemble hardened clay;

(2) other parts of material inside the cave consist of soft clay mixed with rounded pebbles like those you find in a mountain river (e.g. Ariege river) or on a sea shore. The clay is so soft that I could extract a stone from the mass with my fingers, and the stone was round and smooth. Means, it was polished by water before it became part of this cave;

(3) there is a distinct line where the 'facade' of the cave meets 'the ground' (the relatively flat terrace in front of the cave's entrance). Looks like the huge rock fell from above, and a part of it became hollow (became the cave). Further to that, all caves seem to have a flat 'floor', as if the rock fell on this 'floor' and made the top of the cave;

(4) when looking down on the valley at the foot of the mountain range, the valley is almost flat, with a distinct line between the edge of the valley and the wall of the mountain. This means the whole valley was a huge river, then gradually turned into soil, but the smooth round pebbles fill the soil.

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