Grépon : Mer de Glace

Grépon : Mer de Glace


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Associated waypoints

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  • Swisstopo - 46 - Val de Bagnes
  • Swisstopo - 292 - Courmayeur
  • IGN - 3531ET - St-Gervais les Bains - Massif du Mont Blanc
  • IGN - 3630OT - Chamonix - Massif du Mont Blanc



route_types: loop_hut, traverse
durations: 1 day(s), 2 day(s)
rock_types: granit
configuration: face, pillar

quality: fine


    IV    P3 


elevation min/max : 2523 m / 3482 m

height_diff: +1000 m / -1100 m

height_diff_difficulties: 850 m

difficulties_height: 2600 m


glacier_gear: glacier_safety_gear


lift_access : yes




Extraordinary high mountain route on a big face. Historic route, the Knubel crack being the first V+ pitch in the Mont Blanc range. Not much gear in place, one needs to be good at route finding.


Approach 1h

From the Envers hut, go onto the Trelaporte glacier and traverse northwards under the Tour Rouge. Pass the bergschrund as far right as possible, (delicate) and traverse to the left, passing another bergschrund to gain the rock.

Route 8 to 10h

  • Climb leftwards up a series of chimneys and ledges, (4a to 4c) until at the level of the summit of the Tour Rouge. Follow a system of terraces obliquely leftwards to join a faint spur in the centre of the face.
  • Make a 20m abseil to get into a deep gully which one traverses to gain the line of the East spur, which is the key line of the route.
  • Climb this spur (pitches of 4c/5a) until the Balfour gap (some moves of 5c just below the gap). One can leave the sacks here.
  • Climb the Knubel crack (5c) to reach the summit virgin.

Descent 3h to 5h

Descent to the col des Nantillons

  • Regain the Balfour gap by a 20m abseil on the E side and pass on to the SW side to gain the descent route
  • Follow a series of ledges and abseils to reach an obvious shoulder. A 30m abseil leads to a deep gap, climb up 3m (3c) to a terrace. (CP).
  • Descend by a faint path and a system of ledges to near to the col des Nantillons.

Descent to the Plan de l'Aiguille

  • Go onto the glacier and descend it in the middle, (crevasses), pass under the Grand Charmoz and traverse (rapidly) under a band of threatening seracs.
  • Go onto the rognon (rock island) des Nantillons and climb northwards down it. At the end a 20 to 30m abseil brings one onto the glacier which is descended, avoiding some large crevasses until it is possible to get onto the S moraine.
  • Follow a contour path through the Blatiere glacier moraine and passing the glacier snout to the Plan de l'Aiguille cable car station


  • The route catches the sun.
  • Bergshrund can be difficult by headlights.

Sensitive areas
There are sensitive areas on this route. Please refer to the map.


  • Crampons, lwt. ice axe,
  • Abseil rope, helmet,
  • 7 quick draws, nuts and friends.


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