Introduction
The Great Aletsch Glacier is the longest glacier in the Alps, stretching approximately 23 kilometers through the Bernese Alps of southern Switzerland. It is the centerpiece of the Swiss Alps Jungfrau-Aletsch UNESCO World Heritage Site, a region of extraordinary alpine beauty and scientific importance.
Formed by the confluence of three smaller glaciers high on the flanks of the Jungfrau, Monch, and other 4,000-meter peaks, Aletsch flows in a sweeping curve through a deep valley. Its distinctive dark medial moraines, stripes of rocky debris where tributary glaciers merge, make it instantly recognizable from the air.
Geography & Dimensions
- Length: ~23 km
- Area: ~81 km²
- Maximum Thickness: ~800 m (at Konkordiaplatz)
- Volume: ~15 km³
- Elevation Range: ~4,160 m (Jungfraujoch) to ~1,560 m (terminus)
Aletsch Glacier begins at the Konkordiaplatz, a vast snow plateau at roughly 2,800 meters where three tributary glaciers converge. From there, it flows southeast for 23 kilometers in a broad arc to its terminus above the Massa gorge.
At the Konkordiaplatz confluence, the ice reaches approximately 800 meters deep, the thickest anywhere in the Alps. The glacier's surface area of 81 km² makes it the largest single glacier in the Alps by every measure. Its medial moraines create dramatic dark stripes visible in aerial photographs.
Formation & Movement
- Tributary Glaciers: Grosser Aletschfirn, Jungfraufirn, Ewigschneefeld
- Ice Speed: ~200 m per year at center
- Age of Deepest Ice: Several hundred years
- Firn Line: ~3,200 m elevation
The glacier forms from snowfall on the high peaks of the Bernese Alps. Snow accumulates above the firn line at approximately 3,200 meters, gradually compressing into glacial ice. The three main tributaries funnel this ice into the Konkordiaplatz basin.
Aletsch flows at roughly 200 meters per year in its central section, much slower than steep maritime glaciers but typical for large valley glaciers. The ice takes over a century to travel from the accumulation zone to the terminus, meaning ice melting at the snout today fell as snow when the Eiffel Tower was being built.
Climate Impact
- Retreat Since 1860: ~3.6 km in length
- Thinning: ~300 m thinner at Konkordiaplatz since 1860
- Area Loss: Lost ~25% of its area since mid-19th century
- Projected Future: Could lose 90% of volume by 2100 under high-emission scenarios
Aletsch has been retreating since the end of the Little Ice Age around 1860. The glacier has lost approximately 3.6 kilometers in length and thinned dramatically, with the ice at Konkordiaplatz about 300 meters thinner than it was 160 years ago.
Climate projections for Aletsch are sobering. Under high-emission scenarios, the glacier could lose up to 90% of its current volume by 2100, transforming the landscape of the Jungfrau region. Even under moderate warming scenarios, substantial retreat is expected. The Swiss Glacier Monitoring Network tracks Aletsch annually as a key indicator of Alpine climate change.
Surrounding Ecology
- UNESCO Site: Swiss Alps Jungfrau-Aletsch (824 km²)
- Forest: Aletsch Forest (ancient Arolla pine, up to 1,000 years old)
- Wildlife: Ibex, chamois, marmot, golden eagle, bearded vulture
- Vegetation Zones: Nival, alpine, subalpine, montane
The Aletsch Forest on the glacier's western flank is one of the highest and oldest Arolla pine forests in Europe. Some trees are over 1,000 years old, their gnarled forms shaped by centuries of harsh alpine conditions. The forest has been protected since 1933.
As the glacier retreats, new terrain is exposed and colonized by pioneer plants. Scientists study these glacier forefields to understand ecological succession. The broader UNESCO World Heritage area spans from 4,274-meter Finsteraarhorn to the Rhone Valley, encompassing a complete cross-section of Alpine ecosystems.
Exploration & Tourism
- Viewpoints: Jungfraujoch (3,454 m), Eggishorn, Bettmerhorn, Riederalp
- Jungfraujoch Railway: Highest railway station in Europe (3,454 m)
- Hiking: UNESCO trail system around glacier margins
- Annual Visitors: Over 1 million to Jungfraujoch alone
The Jungfraujoch railway station at 3,454 meters, the highest in Europe, provides dramatic views over the glacier's upper reaches. Built between 1896 and 1912 through the heart of the Eiger and Monch mountains, the railway is an engineering marvel in its own right.
For closer encounters, cable cars to Eggishorn and Bettmerhorn on the eastern side offer sweeping panoramas of the full glacier length. A network of hiking trails allows walkers to trace the glacier's margins, passing through the ancient Aletsch Forest and across moraine landscapes. The region sees over a million visitors annually.
Key Facts
- Aletsch is the longest glacier in the Alps at approximately 23 km.
- The ice at Konkordiaplatz is about 800 m thick, the deepest in the Alps.
- The glacier has retreated approximately 3.6 km since the Little Ice Age peak around 1860.
- The Aletsch Forest contains Arolla pines over 1,000 years old.
- Climate models project the glacier could lose 90% of its volume by 2100 under worst-case scenarios.
Fun Facts
- Ice melting at the terminus of Aletsch today fell as snow more than a century ago, around the time the Jungfraujoch railway was being built.
- The Jungfraujoch railway tunnel through the Eiger took 16 years to construct and cost the lives of 30 workers.
- The dark medial moraines on Aletsch's surface can be used like tree rings to read the glacier's flow history.
- In the Middle Ages, villages near the glacier held processions to pray for the glacier to stop advancing toward their homes.
Final Thoughts
Aletsch Glacier is the frozen heart of the Swiss Alps, a landscape-defining feature that has shaped both the geography and culture of the Bernese Oberland for millennia. Its accelerating retreat is a powerful visual reminder of climate change's impact on even the most iconic mountain environments.
