- Where
- Bernese Alps
Canton of Valais, Switzerland - Coordinates
- 46.4422° N
8.0772° E - Biome
- High-alpine glacial ice
- Length
- c. 22.6 km (2014 measurement)
- Status
- UNESCO World Heritage, 2001
- Best visited
- Late June–September
The short answer
The Aletsch Glacier is the longest glacier in the Alps, running roughly 22.6 kilometres through the Bernese Alps in the Swiss canton of Valais. It forms at Konkordiaplatz, where several firn fields converge and the ice reaches a measured thickness of around 900 metres, then flows southwest toward the Rhône valley and feeds the Massa river. It sits at the centre of the Swiss Alps Jungfrau-Aletsch World Heritage Site, inscribed in 2001, and it is retreating: roughly 1.3 kilometres of length since 1980 and 3.2 kilometres since 1870, along with more than 300 metres of thickness.
Why it's worth knowing
Every retreating glacier is a climate story, and after a while they blur into one another. What makes Aletsch worth a separate entry is the second-order consequence, which is genuinely strange and much less reported.
Ice is heavy, and a glacier of this size presses outward against the valley walls that contain it. Remove several hundred metres of thickness and that lateral support goes with it. Above the glacier's left flank at Moosfluh, near Riederalp, a slope that had been creeping imperceptibly for decades accelerated sharply in autumn 2016 — a mass of more than 200 million cubic metres of rock moving at more than twenty centimetres a day at its peak, opening visible cracks and forcing the closure of hiking trails.
That is the version of glacial retreat almost nobody pictures: not just less ice, but a landscape that had been leaning on the ice discovering it can no longer do so.
The field notes
Konkordiaplatz
The glacier is a confluence rather than a single stream. Several firn fields — the Grosser Aletschfirn from the southwest, the Jungfraufirn from the northwest, the Ewigschneefeld from the north, and by most counts the Grüneggfirn as well — meet at a broad flat plain of ice called Konkordiaplatz. Sources differ on whether to count three tributaries or four, depending on how the Grüneggfirn is treated.
What is not in dispute is the depth. The ice at Konkordiaplatz has been measured at roughly 900 metres thick, more than anywhere else in the Alps. Where the tributaries merge, the rock debris carried along each glacier's edge is folded into the middle of the combined flow, producing the long dark medial moraines that stripe the ice all the way to the snout.
The staircase
The Swiss Alpine Club built the first Konkordia Hut in 1877, on a rock shelf a few metres above the glacier surface. Climbers stepped off the ice and onto the doorstep.
The hut has not moved. The ice has. Today the hut stands roughly 150 to 200 metres above the glacier, reached from the ice by a long series of metal staircases bolted to bare rock — 467 steps by one recent count, with plaques fixed along the way marking where the glacier surface stood in earlier years.
No graph communicates this as efficiently. You climb the measurement.
A forest at the edge
At the glacier's lower margin lies the Aletschwald, a protected old-growth stand of Swiss stone pine and larch managed by the conservation organisation Pro Natura. Ancient forest growing directly against active glacial ice is unusual in the Alps, where the more common pattern at a glacier's edge is bare moraine and scree.
The nature centre for the reserve occupies Villa Cassel at Riederfurka, a summer villa built in the early twentieth century by the English financier Sir Ernest Cassel — tourism having reached the glacier's edge some decades before conservation did.
Four hundred and sixty-seven metal steps. The Konkordia Hut was built in 1877 a few metres above the Aletsch Glacier; it now stands roughly 150 metres above it, and the staircase bolted down the cliff carries plaques marking where the ice surface used to be. Climbing it is the only way in, and every step is a unit of loss.
Getting there
Fly to Zurich or Geneva, take Swiss rail to Brig and a local train to Fiesch, Betten or Mörel, then a cable car up to the car-free villages of Riederalp, Bettmeralp or Fiescheralp. From those villages, gondolas run to viewpoints at Eggishorn, Bettmerhorn and Moosfluh, which give the full length of the glacier without setting foot on ice. Late June to September is the practical window.
Walking on the glacier itself, or reaching the Konkordia Hut, is roped glacier travel and requires a certified mountain guide — the ice is heavily crevassed and snow bridges collapse through the summer. Book a guide through a Valais guide office well in advance, and check current avalanche and alpine-hazard bulletins before any high-alpine excursion. Note also that the Moosfluh landslide has closed trails in that sector at times; check locally before setting out.
Common questions
How long is the Aletsch Glacier?
The Aletsch Glacier is about 22.6 kilometres long according to a 2014 measurement, making it the longest glacier in the Alps. Swiss tourism material commonly rounds this to 23 kilometres. Its area was measured at roughly 81.7 square kilometres in 2011.
Is the Aletsch Glacier shrinking?
Yes. The Aletsch Glacier lost roughly 1.3 kilometres of length between 1980 and 2016, and about 3.2 kilometres since 1870, along with more than 300 metres of thickness since 1980, according to Swiss glacier monitoring figures. The retreat is sustained and well documented.
What is the Moosfluh landslide?
Moosfluh is a slope above the left flank of the Aletsch Glacier, near Riederalp, where a rock mass of more than 200 million cubic metres accelerated sharply in autumn 2016, moving at more than twenty centimetres a day at its peak. The acceleration is linked to the thinning glacier no longer buttressing the valley wall.
What is Konkordiaplatz?
Konkordiaplatz is the broad plain of ice in the Bernese Alps where several firn fields converge to form the main Aletsch Glacier. The ice there has been measured at roughly 900 metres thick, the greatest depth anywhere in the Alps. Sources count either three or four tributary firn fields depending on how the Grüneggfirn is treated.
Why does the Konkordia Hut have hundreds of stairs?
The Konkordia Hut was built by the Swiss Alpine Club in 1877 on a rock shelf just a few metres above the Aletsch Glacier. As the ice thinned, the gap grew; the hut now stands roughly 150 to 200 metres above the glacier and is reached from the ice by metal staircases running to 467 steps, with plaques marking former ice levels.
Can you walk on the Aletsch Glacier?
Only with a certified mountain guide and roped glacier travel. The Aletsch Glacier is heavily crevassed and snow bridges collapse during summer. Visitors who want to see the glacier without stepping on ice can take cable cars from Riederalp, Bettmeralp or Fiescheralp to viewpoints at Eggishorn, Bettmerhorn and Moosfluh.