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The Glandon Pass

Toponymy

The Glandon Pass (FR-73-1924) takes its name from a locality in the commune of Saint-Colomban-des-Villards.
An eponymous torrent rises at the pass.

Geographical location

Massifs

 The pass lies on the border of the Belledonne and Arvesto the west of the Croix-de-Fer pass. 

Geology

The Col du Glandon and the Col de la Croix de Fer are geographically very close, less than 3 km apart and both located in the Grandes Rousses massif.

But they are very different in geological terms. If you follow the road between these two passes, located in the Eau Dolle valley, the change in the nature of the rocks - crystalline in the south and sedimentary (limestone) in the north - is reflected in a very perceptible difference in the vegetation and the shape of the relief. The entire massif to the south (Rochers de la Curiaz) sinks beneath the sedimentary mantle from the Col du Glandon to the Chalets d'Olle. 

Readers interested in this subject should refer to the comprehensive article by geol-alp.com 

Hydrography

South side (Isère side) Eau d'Olle valley.
L'eau d'Olle is a tributary of the Romanche, which rises near the Col de la Croix de Fer.

North side (Savoie side) : the Glandon rises near the Col and flows down the Villards valley before emptying into the Arc at Saint-Avre after crossing the A43 on a canal bridge.

It is a capricious torrent :

Access

Isère side

Access is shared with the Col de la Croix de Fer as far as the D926 / D927 junction (alt. 1907 m), 200 m from the Col du Glandon and 2.7 km from the Col de la Croix de Fer.

The D526 leaves Rochetaillée (30 km away, alt. 711 m), crosses Allemond (27 km away), passes over the Verneys dam and runs alongside the lake (left bank), crosses the Rivier d'Allemond (15 km away - alt. 1264 m), near the Grand'Maison dam (7 km away - alt. 1720 m) then follows the right bank of the lake, becoming the D926 as it crosses the Rieu Claret (4 km away, Isère / Savoie border, alt. 1773 m) before joining the junction with the D927 towards the Col de la Croix de Fer.

Savoie side

The D927 gives access to the Col du Glandon (FR-73-1924) from the Maurienne (Saint-Etienne de Cuines 21 km away - alt. 450 m) via Saint-Colomban-des-Villards (10 km from the pass - alt. 1100 m).

Modification of access

Isère side (shared with Col de la Croix de Fer)

The road was built in 1898 (and extended to the Croix de Fer pass in 1912).

At the end of the XX^th century two changes:

• The route was changed with the construction of the Grand-Maison dam from 1978 to 1985. The road slightly overhangs the lake (around fifty metres) before descending slightly towards the Eau d'Olle.
• On 23 April 1989, a Landslide from Pic Bunard  (300 to 400 m³ of rocks) swept away the road (right bank of the Eau d'Olle) above the Rivier d'Allemond at the Maupas waterfall. The road was rebuilt on the left bank over 2 km, with a descent (62 m in 600 m) to cross the torrent and then a fairly steep ascent (11% for the first kilometre). The old road can still be seen along the right bank of the mountain. (It was a year with Marmotte and BRA. A new road was built in 2 months! A miracle of decision).

Savoie side

In Roman times Glandon pass provided a link between the Oisans and Maurienne regions, descending through the Villards valley.

What to see - tourism 

Isère side (shared with Col de la Croix de Fer)

La Grand'Maison power station is a Pumped Energy Transfer Station (PETS).

A higher restraint (Grand'Maison lake(1,695 m) is connected by penstocks to a lower basin, the Le Verney reservoir, 900 m below the level of the power station (Lac du Verney725 m, 15 million m³ of water). During periods of high consumption, the power station turbines water from the upper reservoir. The water then flows into the downstream reservoir. During off-peak periods, mainly at night and weekends, water from the lower reservoir is pumped to the upper reservoir.

In this way, the system can store energy and respond quickly to peak demand.

The most powerful dam in Europe, it produces the equivalent of 2 old-generation nuclear reactors.

Le EDF Hydrélec Museum between the road and the Lac du Verney has been awarded the Museum of France and presents unique collections from the Alpine Arc dating from the 19th century to the present day.^e century and xx^e century. A scenographic tour pays tribute to the scientists, engineers, technicians and labourers involved in the creation of hydroelectric power stations and dams.

At the pass

A memorial at the top of the pass recalls that in July and August 1944, as the Provence landings were being prepared, mobile group no. 5 of the Oisans maquis temporarily repelled a German attack near the pass.

Above the Col du Glandon car park, four pillars have been erected to give a straight view of Mont Blanc.

Administrative status

Currently

Both sides of the pass are in the Savoie department (Commune de Saint-Colomban-des-Villards).

The Isère / Savoie boundary is located on the Isère side at the Pont du Rieu Claret (1730 m), 3.8 km from the pass.

History

Why isn't the Isère / Savoie boundary on the Arc / Isère LPE? (i.e. the Croix de Fer and Glandon passes)

According to "oisans.com

Until 1860, the Sabot pass marked the border between France and Savoie. Vaujany, on the route des cols, was then equipped with a border office to protect the province of Dauphiné. ... / ... Where the Grand'Maison reservoir now extends, in the past, vast alpine pastures were shared between the French and Savoyards. The Grand'Maison was a large building used to house shepherds. Information completed by " Isère-Tourisme " Behind the Col du Sabot was a border post, some of whose ruins still exist. 

ChatGPT completes this information (without citing sources):

"The region around the Croix de Fer and Glandon passes is an area of mountain pastures where Savoyard and Dauphinois farmers have practised agriculture for centuries. The inhabitants on both sides of the mountain had a close relationship and often shared pastures and farmland.

When the border was defined as part of the Treaty of Turin in 1860, it was important to minimise disruption to the local population. Fixing the border on the Rieu Claret, a clearly identifiable watercourse, made it possible to maintain the traditional use rights of farmers on both sides of the border".

Cycling and cycle tourism

Tour de France

The Tour de France climbed this pass for the first time in 1947.

BRA

In its traditional version, the BRA did not use the Col du Glandon (it passes through the crossroads 200 m from the pass on the road to the Col de la Croix de Fer).

However :

• In 2015, with the closure of the Chambon tunnel making it impossible to use the Col du Galibier, Plan B was implemented, with the Col du Glandon, the 18 Montvernier laces and the Cols du Mollard and de la Croix de Fer.
• In 2019, after the refreshment check at the Col de la Croix de Fer, there will be a U-turn and a descent of the Glandon to climb the Montvernier switchbacks.

Marmot

From its inception in 1982 to 1999, the "La Marmotte" cyclosportive race was run over the Col de La Croix de Fer, before moving on to the Col du Glandon.

In 2023, the Glandon was no longer on the programme, and the route took in the Col de la Croix de Fer (and the Col du Mollard).

Profile

There are many profiles of the Col du Glandon on the internet. The percentages given are quite... variable.

The best way to do this is to plot your route on Openrunner and click on "see altimeter profile" ... as here between Rochetaillée (Isère) and La Chambre (Savoie) :

And, finally, a few images about the Croix de Fer and du Glandon

An article by Gérard Galland (and Bernard Giraudeau for the geology section)