Gouffre P40 de la Dent de Crolles

The entrance shaft is actually 32 metres; its top is fairly narrow but positions the rigger directly above the void, and once the descent has begun, the shaft immediately widens and is descended in a single pitch. The Puits du Cabri is actually a vertical constriction about 4 metres high. The Galerie d’York begins with a flat-out crawl on a polished, slippery floor, then opens up and alternates between passages with blocks, passages at floor level and descending passages. The Puits des 3 Sœurs has rope rubs on the wall; a large suspended block is about fifteen metres further down. The 50-metre meander is slightly descending; the 90-metre meander is never very wide, but is even less so below. The meander “known as 23m” is considerably longer than the 23 metres given in most descriptions. The stalagmitic slab is beautifully thick.

You climb 3 metres to regain a stance on a beautifully thick stalagmitic slab.

In a room of fine dimensions, the sound of flowing water is heard for the first time since the entrance. The flood risk is very significant in the Puits du Balcon and at the Puits de la Douche (in the event of a storm or during the snowmelt period); the succession of shafts can be very dangerous in the event of flooding (storm, meltwater, …). The Puits de la Douche leads to the Salle de la Douche, the low point of this traverse.

The route of this traverse is very complex: some passages, if misinterpreted, lead to getting lost in other parts of the Dent de Crolles network; it is therefore essential to carry the survey, the description and a compass.

Stages: P40 - Puits du Cabri - Galerie d’York - Puits des 3 Sœurs - Méandre de 50 mètres - Puits des Orbitolines - Méandre de 90 mètres - Puits des Pompiers - Méandre « dit de 23m » - Puits du Balcon (x4) - Puits de la Douche - Dalle stalagmitique - Carrefour Puits de la Lanterne - Grande Galerie du Glaz.

Route: P40↓(32m) - Puits du Cabri↓(4m) - Galerie d’York - P4↑ - Puits des 3 Sœurs↓(20m+12m) - Méandre de 50 mètres - Puits des Orbitolines↓(8m+4m) - R3↓ - Méandre de 90 mètres - Puits des Pompiers↓(10m) - Méandre « dit de 23m » - Puits du Balcon↓(22m+16m+18m+25m) - Puits de la Douche↓(25m) - Dalle stalagmitique - Carrefour Puits de la Lanterne - Grande Galerie du Glaz.

A permanent handline gives access to the anchors (chain + quick link) at the top of the shaft. Once at the bottom of the entrance shaft, you find yourself with both feet on a scree slope; you must climb back up this scree slope and spot straight ahead a vertical fissure that starts at floor level. This fissure gives access to a small space, then to a small step down that you descend, before reaching the top of the Puits du Cabri (rope rigged in place), which must be descended; average and large builds will probably find it painful to get through. Once down the Puits du Cabri and facing the shaft, the continuation is also opposite (no other options possible): you enter the Galerie d’York, where you progress lying down or on all fours. The Galerie d’York currently has (date?) a somewhat aged but reliable marking, consisting of orange flagging tape and black arrows drawn on the walls; at each “key junction”, you will follow either the flagging tape or the black arrow, or sometimes both at once, depending on what presents itself. Towards the end of the Galerie d’York (and following a slightly descending passage), the caver will want to continue into a passage presenting itself straight ahead, but on the right-hand wall a black cross indicates that the continuation is not that way: the continuation is almost behind you, on the right, a new descending passage marked with a black arrow. You then quickly reach a final passage at floor level, which opens into a room of fine dimensions. In this room, above all do not commit yourself straight ahead (that is, into the descent where you hear the water flowing): the continuation is on the right, where a full-height passage followed by a short climb immediately gives access to a rope rigged in place, at the foot of the P4, which must be climbed. Once at the top of the shaft, you enter a short, comfortable meander; at its exit, you descend a 4-metre shaft, watered, then reach the top of the Puits des 3 Sœurs (the rigging allowing the abseils to be set being on the right-hand wall as you exit the meander). Most descriptions say to descend this shaft for 14 metres and above all not to go any lower: this information is erroneous, you must descend this Puits des 3 sœurs all the way to the bottom. It is difficult to avoid rope rubs on the wall and you must be careful with your positioning throughout the descent. The descent of the Puits des 3 Sœurs requires both 35-metre ropes. From the chained abseil at the top of the shaft, you must ignore the first shaft where the water flows and descend on the dry side of the shaft; once committed to the vertical section, on reaching the level of a large suspended block, about fifteen metres further down, spot on the right a rudimentary belay, the use of which avoids the risk of the abseil rope jamming on the suspended block; then, from this belay, descend a further ten metres or so to the base of the shaft. On arrival at the bottom of the shaft, with your back to the wall you have descended, you notice another watered shaft on the right and the start of a meander on the left: the continuation is to the left, and the meander is equipped with a handline. Progress in this meander begins with a right-hand bend and continues for a few metres; you then come up against a belay. You must descend about 3-4 m (do not descend any lower as that leads towards the Réseau des Polonais) and commit yourself into a low passage, facing you, leading to a suspended meander. This meander of about fifty metres, slightly descending, is easily passed by staying on the floor; you must be careful of several shaft openings in the floor, which must be stepped over along the way. At the end of the meander you reach 2 successive shafts of 8 and 4 metres which you descend: this is the Puits des Orbitolines. On arrival at the bottom of the second shaft, with your back to the wall you have just descended, the continuation is to the left (the right leads to the Réseau des Polonais); a few metres to the left you find the chain allowing you to descend a 3-metre step that brings you into the upper part of the 90-metre meander. You continue opposite the step you have just come from and progress along the top of the meander for about 50 metres; progress is fairly instinctive at this level. The decision to descend lower is generally made shortly after a series of right-left Z bends, and where you see the meander widening below and taking on proportions more suited to easy progress; you then descend gradually to the floor, which you will not leave until the Puits des Pompiers (the end of the 90-m meander) and which you descend. This shaft of about ten metres is a moment of respite between the meander you have just finished and the next one. This meander starts from the bottom of the Puits des Pompiers, opposite where you descended; it is travelled for the most part at floor level, sometimes a little higher, but not much. There is a small step to descend along the way; also be careful of shaft openings in the floor. You must ignore the ascending ropes that you encounter and you eventually reach a handline that leads to the top of the first Puits du Balcon. You will then descend a total of 5 shafts of 16 to 25 metres (4 Puits du Balcon and the Puits de la Douche), and not 4 as is often said in descriptions; these shafts follow one another and are very beautiful. The exit from the Salle de la Douche is via a short stretch of meander that starts a little below the room; you quickly reach a T-junction and you make out, on the left, a gallery high up. You climb the 3 metres to regain a stance on a beautifully thick stalagmitic slab; you continue on the left, in the slightly descending gallery, to head towards the Trou du Glaz. You encounter 2 significant junctions which you take to the left, before passing the access to the Puits de la Lanterne; you then continue in the main gallery for about 350 metres, until the exit at the Trou du Glaz.

Source: Spéléo SecourS Isère (SSSI), « Réseau de la Dent de Crolles - Descriptif détaillé de la Traversée P40 - Glaz »: https://www.sssi.fr/topos/P40-Glaz.pdf