Avenc del Torrent Fondo

The cavity is formed by an “L”-shaped fissure, about 7 m long by 1.50 wide and -2.50 m deep. Through it, descending a step of -1.70 m, we will find ourselves on the upper level of the pit, where the mouth of the small -4 m pit is located, which once descended will leave us in a wide, sloping chamber, full of rocks, stones and a lot of earth. This chamber has dimensions of 6.5 m long, by 4.30 m at its widest part, with a height that oscillates between 1.70 m and 2.50 m.

There are also three chimneys to highlight. The first is located two metres after descending the small -4 m pit, rising about 3.50 m, and the remaining two are at the eastern end of the chamber. The first of these is a tall, narrow chimney, almost 5 m high, and the height of the second cannot be determined, because it is choked by large blocks of rock that block it. It seems as if this chimney had in other times been an old mouth that was open to the exterior and that later became plugged and choked by the action of the nearby torrent.

The vertical drop is 9.80 m.

In a fifth phase, an incipient reconstructive process would begin, localised in some specific points of the chamber, formed by small stalactites and above all flowstone in the two final chimneys.

Speleogenesis: The cavity has passed through various evolutionary phases throughout its formation. In a first phase, there was a fissure located in the middle of the bed of the Torrent Fondo, which collected its waters and acted as an active sink of the stream, working it in depth and causing an intense erosive process, which later would form the interior chamber. In the second phase we would find a period of filling and plugging of the cavity, due to the contributions of clastic materials from the stream, which would be precipitated inside the pit by the strong torrential currents that would take place in that area in past times. This would cause the intense accumulation of rocks, stones and earth in which the interior of the cavity is found. In a third phase, the torrent would shift until reaching the level it occupies at present, so the water and clastic material input inside the pit would cease. In a fourth phase, an intense period of corrosion and decalcification of the limestone would occur in the interior chamber. This process is well present on the ceiling of the chamber, where many rocks are currently hanging awaiting collapse due to the action of gravity. The chimneys that exist inside it were also formed at that time. The one that is blocked by large blocks, it has been speculated, could be another mouth, which would be choked. But this is on the exterior, without finding any indication of it.