Avenc Gran de les Alzines
A 70-metre-deep pit in Vallirana, with a 3x4-metre entrance in a doline.
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Avenc Gran de les Alzines
A 70-metre-deep pit in Vallirana, with a 3x4-metre entrance in a doline.
Vallirana · Baix Llobregat
Length: 120 m · Depth: 70 m
Updated record
https://espeleoworld.com/en/c/avenc-gran-de-les-alzines
Information can change. Always verify coordinates, access, weather, and cave conditions before setting out.
A 70-metre-deep pit in Vallirana, with a 3x4-metre entrance in a doline.
Topographic
Espeleoindex · CC BY-NC 4.0, https://creativecommons.org/licenses/by-nc/4.0/ · Image © its author.
Photos
Espeleoindex · CC BY-NC 4.0, https://creativecommons.org/licenses/by-nc/4.0/ · Image © its author.
Description
Morphology
The 3x4-metre entrance opens in the middle of a doline. The base of the last shaft is full of blocks, forming a 4x5-metre chamber, leaving a small hole in the middle. The sloping base ends up becoming impenetrable at -70 metres. The side route ends in a 4x4-metre chamber where a precarious plug of blocks can be seen in the ceiling.
Progression
It has a first 12-metre shaft; at the base, a small 2'5-metre shaft connects with a 10-metre shaft. Halfway along this we find a ledge that allows us to access a side route. Continuing along the main shaft, once at the base we find a new 5-metre vertical, from which the parallel route can be seen. A new 8-metre vertical at whose base we find a ramp that places us at a 2'5-metre rise. Here begins a new 6-metre vertical that opens into a wide 6-metre shaft. The small hole in the middle of the block chamber allows access to the last 15-metre vertical.
The side route begins in the third shaft; halfway along it we find a ledge, where on the other side we find the small entrance of a 6-metre shaft that links with another 15-metre one; at the base we find a crawlway connecting with a large chamber full of blocks, walking among them to the other end, we find a 12-metre climb that gives access to an upper gallery.
The chamber at -44 metres can also be accessed from the main shaft through a window located at -35 metres.
History
In October 1994, members of GIRES begin a first digging out in the collapse that was in the centre of the doline next to the already known cavity of l'esquerda de les Alzines. The digging out would continue from 21 January 1995; on 13 May of the same year they reach -52 metres. After the summer they return to the pit and due to the September rains they find the cavity obstructed at -14 metres. They decide to install a metal mesh in order to hold the ground and prevent landslides, and finally on 23 February 1996 they reach the current depth of -70 metres.
Later, and due to the work carried out by a group of archaeologists, the metal mesh has disappeared and the falls are constant, which means that to explore the cavity precautions must be extreme. Recently (2011) it seems that the area of the entrance has become quite consolidated due to erosion itself.
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Bibliography
- GIRES.-(2003). “Avenc Gran de les Alzines”. Passamà (2) : 43-47.
- Lloret Prieto, Jordi. (1979).-Catálogo Espeleológico del Pla d' Ardenya. (Tomo 1):1-106. Barcelona.
- Fotografia inici desobstrucció, facilitada per Federico de la Vega.
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Source: Espeleoindex (espeleoindex.com), modified. CC BY-NC 4.0, https://creativecommons.org/licenses/by-nc/4.0/