Aletsch Glacier

The glacier is fed by three big snowfields high in the mountains.

The dark stripes are bands of rock on the ice.

UNESCO says the Alps here began to be pushed up and squeezed together 20 to 40 million years ago. Very old crystalline rocks, 400 million years old, were pushed over younger rocks as the African plate moved north.

The Commons description of this photo explains that the two dark lines on the ice are medial moraines: bands of rock that mark where ice from the glacier's three main snowfields comes together.

UNESCO: the High Alps formed by uplift and compression that began 20-40 million years ago; within an altitude range of 809 to 4,274 m the region shows 400-million-year-old crystalline rocks thrust over younger carbonates by the northward drift of the African plate, with U-shaped valleys, cirques, horn peaks, valley glaciers and moraines.

The photo's Commons description: the two dark lines near the middle are the medial moraines separating the ice of the three main firns; the western one is called the Kranzberg moraine and the eastern one the Trugberg moraine.

The Aletsch Glacier is getting shorter and thinner.

Pictures taken from space show how much ice has gone.

NASA compared satellite pictures taken in 1984 and 2024. According to the Swiss Glacier Monitoring Network (GLAMOS), the Aletsch has retreated more than 1,300 meters since 1984, and it has also thinned.

Its neighbors are shrinking too: since 1984, the Fiescher Glacier has retreated more than 1,000 meters and the Oberaletsch Glacier more than 240 meters.

NASA Earth Observatory paired Landsat 5 (2 September 1984) and Landsat 8 (6 August 2024) images. Per GLAMOS, the Aletsch retreated more than 1,300 m since 1984 and lost 43 m of water equivalent in four decades; Oberaletsch retreated more than 240 m and Fiescher more than 1,000 m. Central Europe lost 39 percent of its glacial ice between 2000 and 2023.

UNESCO notes that the varying retreat rates of the region's glaciers illustrate climatic change and open new ground for plant colonization.

When the ice melts back, new ground appears. Plants slowly move in.

There is also a forest, the Aletsch forest.

UNESCO says the region has many alpine and sub-alpine habitats, on both crystalline and carbonate rocks, with a dry southern side and a wet northern side.

As glaciers retreat, they leave new ground where plants can grow. UNESCO calls the way plants move in, step by step, an outstanding example of plant succession, and it points to the upper and lower tree lines of the Aletsch forest.

UNESCO: within its altitudinal range and its dry southern and wet northern exposures, the property offers a wide range of alpine and sub-alpine habitats on crystalline and carbonate substrates, with ecosystems that evolved without significant human intervention.

Plant colonization in the wake of retreating glaciers is an outstanding example of plant succession, including the distinctive upper and lower tree-line of the Aletsch forest.

Never walk on a glacier without a trained guide.

Wear sunglasses and sunscreen near the ice.

PlayOwl's advice: glacier ice can hide deep cracks, so only walk on a glacier with a trained mountain guide, and otherwise stay on marked trails above it.

The sun can be strong in the mountains. The CDC says UV rays reflect off snow, so wear sunscreen, sunglasses and a hat with a brim all the way around.

PlayOwl's advice: walk on glacier ice only with qualified guides and proper equipment; viewpoints and marked trails are the safe way to see it.

CDC sun safety: UV rays reflect off surfaces such as snow and water; use broad-spectrum sunscreen, UV-blocking (wrap-around) sunglasses and a wide-brimmed hat.