Printed from: http://braemoor.co.uk/crolles/glaz.shtml on 20 Aug 2017
Copyright: © 2017 - 2017 John Gardner

Réseau de la Dent de Crolles

Trou du Glaz

Northing: 45.31736° Easting: 5.85146° Altitude: 1,697 m

How to find it

The easiest approach is from the Col du Coq. Simply follow the GR9 following the yellow sign posts. It takes about 45 minutes. When exiting from a pull-through, turn left along the path, and head down the zigzags at the first junction. If approaching from Perquelin, as is necessary if doing the through trip to the Guiers Mort without a second car, make your way towards the Guiers Mort, cross the stepping stones below the cave, and follow the obvious path which rises up to the cliff, and then ascend beneath it. It takes about 1¾ hours.

Map of Dent de Crolles showing position of Trou du Glaz

Showing location of Trou du Glaz on the IGN 1:25000 map 3334OT
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The entrance to Trou du Glaz
Photograph: Pete Monk

Showing the entrance of Trou du Glaz - Photograph: Pete Monk
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Puits Ferdnand, Trou du Glaz
Photograph: Stuart Hesletine

The pull-through chains used on Puits Ferdnand in Trou du Glaz - Photograph: Stuart Hesletine
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Further information

Trou du Glaz is at the heart of the system, and there are many possible routes available. It is the exit for the equipped through-trips from P40 and Pulpite on the plateau. It is also the starting point for a number of pull-through trips equipped with pull-through chains, pitch-head traverse lines, and way markings, which have been well described in route guides produced by Spéléo Secours Isère, the local rescue organisation. All these through trips pass through the lower storey of the cave, which can be reached by two routes - the traditional route which descends the Puits de Lanterne, and an alternative which descends the Puits de l'Ogive. Hence there are two versions for each of the through trips. The main routes in the Trou du Glaz are as follows:

Puits Lanterns - Puits Ogive round trip

This is a fairly short round trip in the Trou du Glaz which descends the Lantern shafts, and returns through the upper storey via the permanently rigged Puits de l’Ogive. It allows a leisurely look around the entrance series, as well as a reconnaissance for pull-through trips. The route is fully described in a Spéléo Secours Isère guide (a loose translation by the author is available here - use it at your own risk...). The trip takes 2 to 4 hours depending on how much poking around is done, and requires 2*30 metre ropes. The route mostly follows large fossil passages.

The head of the first Lantern pitch, Trou du Glaz
Photograph: Pete Monk

The head of the first Lantern pitch - Photograph: Pete Monk
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Trou du Glaz - Grotte du Guiers Mort

Like the Berger and the PSM, the Trou du Glaz to Grotte Guiers Mort traverse is one that should be on every caver's wish list. There are now a number of links between the two system, including the original route which was connected by Chavelier's team in 1940. This descends P60 and follows an active streamway to the master cave. The one most used now, and is fully equipped with pull-through chains, traverse lines, and waymarkings is that which descends P36, and traverses into the fossil series exiting through the Réseau Sanguin into the Guiers Mort. It was first made possible in 1983. It drops 356 m down a dozen pitches, and covers about 2 km of passage. It also ascends a permanently rigged 40 m pitch. It typically takes four to five hours, and requires 2*40 m of rope, and is not weather dependent. It is used for commercial caving, so in season one can be pretty confident that the fixed ropes will be in order. It is fully described in a Spéléo Secours Isère guide, A loose translation by the author is available here, use it at your own risk. To find the parking area in Perquelin from the Grotte du Guiers Mort, follow the path down from the entrance, and pick up the way marked path.

Puits Banane, Grotte du Guiers Mort
Photograph: Graham Coates

Negotiating the Puits Banane in Grotte du Guiers Mort - Photograph: Graham Coates
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Trou du Glaz - Grotte Annette Bouchacourt

This route was pioneered by Chevalier's team, with the link-up between the two caves finally made in 1946, and it follows a large fossil phreatic passage up-dip through the heart of the mountain from the western cliffs to the south-eastern cliffs. Originally the water ran down dip from the Annette to Trou du Glaz with four major phreatic uprisers which need to be abseiled. The two entrances are more or less at the same altitude.

It is probably the easiest of the pull-through trips in the Réseau de Dent de la Crolles, and it provides an excellent introduction to the system. The pitch heads are all equipped with pull-through chains and traverse lines, and the various traverses encountered en route are also equipped with traverse lines. There is one upward pitch which has a fixed rope on it (it can be free-climbed if necessary). The route is used for commercial caving, so in normal season one can be very confident that the fixed rigging wilol be there. The route covers about 2,300 m, and there is about 12 m difference in height between the entrances. It typically takes about four hours, requires 2*40 m of rope, and is not weather dependent. Older accounts highlight the danger of a mobile boulder choke in the Annnette entrance passage, but this has now been stabilised with some serious iron work (see photograph below). The traverse is fully described in a Spéléo Secours Isère guide (a loose translation by the author is available here - use it at your own risk).

To return to Col du Coq, traverse north from the entrance for 100 metres, and find a route that picks its way down the slope for 30 metres. This intercepts a path which contours below the summit cliffs of the Dent de Crolles to the Pas de l'Œille path. This joins the ascent route at the top of the zigzags.

The stabilised boulder choke in the entrance of Grotte Annette Bouchacourt
Photograph: Dave Checkley

The stabilised boulder choke in the entrance of Grotte Annette Bouchacourt - Photograph: Dave Checkley
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Trou du Glaz - Grotte Chevalier

Although the enormous Grotte Chevalier was first explored in 1942 by Chevalier's team, it wasn't connected to the main system until 1984, and them from passages climbed into above P36. The first half of this traverse is the same as for the Glaz-Annette. It is a little more challenging than the Annette traverse, and features a superb 50 m shaft and a tensioned traverse above a 30 m shaft. It drops into the end of Grotte Chevalier. It covers about 3 km of passage, requires 2*55 m of rope, and is not weather dependent. The traverse is fully described in a Spéléo Secours Isère guide (a loose translation by the author is available here - use it at your own risk...). To return to Col du Coq, traverse south from the entrance for a few metres, and find a route that picks its way down the slope for 30 metres. This intercepts a path which contours below the summit cliffs of the Dent de Crolles to the Pas de l'Œille path. This joins the ascent route at the top of the zigzags.

Negotiating the traverse above Puits de l'Oubliette in Grotte Chevalier
Photograph: Graham Coates

Negotiating the traverse above Puits de l'Oubliette in Grotte Chevalier - Photograph: Graham Coates
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