A slice of paradise, …

A: Accumulation zone

In the accumulation zone, the snow never melts away completely even in summer, and this part of the glacier remains covered by snow all year round. Over the years, the snow becomes more and more compacted and eventually turns to glacial ice. So the accumulation zone is where new ice is formed and the glacier increases in volume.

B: Ablation zone

In the ablation zone, the snow melts away completely during the summer. Consequently, the glacial ice is exposed to the heat and the sun with no protection and also begins to melt. So in the ablation zone, the glacier decreases in volume.

C: Equilibrium line

The equilibrium line separates the accumulation zone from the ablation zone. When the snowline has reached its highest point at the end of the summer, that is the equilibrium line. Weather conditions can vary greatly from one year to the next, so the position of the equilibrium line also changes. Because it determines the size of both the accumulation and ablation zones, the equilibrium line gives an indication of the glacier's mass balance for that particular year. For the glacier to form as much new ice in the accumulation zone as it loses in the ablation zone, with the result that its mass balance remains stable, at least half of the surface of the glacier would have to remain covered in snow throughout the whole year.

D: Glacier snout

The glacier snout is where the meltwater leaves the glacier. Here the glacial stream begins. On warm days, numerous little rivulets form on the surface of the glacier which eventually tumble into a crevasse and continue on their way along the bed of the glacier, i.e. between the glacier and the ground beneath it. By the time it reaches the glacier snout, a considerable volume of water has usually accumulated.

E: Glacial stream

This begins at the glacier snout, where the water leaves the glacier. A glacial stream is typically milky in colour, due to the fine-grained "rock flour" that occurs in and under the glacier. That's why the meltwater from a glacier is sometimes called glacial milk.

F: Glacier forefield

The glacier forefield extends from the current glacier snout down as far as the position occupied by the glacier when it was at its maximum length in about 1860. This is a "young", barren landscape consisting of loose scree and boulders. Nevertheless, soon after the ice melts away, plants quickly begin to colonise the newly exposed ground. Whereas only a few, highly specialised pioneer species are found near the glacier snout, in the lower part of the Morteratsch forefield the larch and pine trees that are typical of the region are already present.

G: Medial moraines

Medial moraines begin where two glaciers meet or where the ice flows round a boulder. They are made up of stones which fell away from the cliff faces and landed on the glacier. Medial moraines look like long, narrow ribbons that follow the course of the glacier. The curving medial moraines on the Pers glacier can be clearly seen from the Diavolezza.

H: Lateral moraine from 1860

The last time that the glaciers in the Alps really advanced significantly was during the so-called "Little Ice Age". They reached their greatest extent between 1850 and 1860. The mighty lateral moraines still indicate today how far out the edge of the glacier reached along the sides of the valley. They show us just how massive the glacier was at that time.

I: Hanging glaciers

Hanging glaciers are like balconies of ice adhering to the steep walls of the valley and they are easily recognised by their vertical faces where the ice breaks off. Thanks to their altitude, they barely melt at all and grow all the time, but their ever-increasing weight is literally their downfall: blocks of ice, large and small, are constantly breaking away. Typical hanging glaciers can be found on Piz Palü, Piz Bernina and Piz Morteratsch.

J: Transverse crevasses

Glacial ice is plastic and flows gradually down the valley due to gravity. Where a rocky ledge occurs beneath the glacier, the surface breaks open into transverse crevasses, because the ice moves slightly faster on the steeper section than it does above the ledge. As the name suggests, these cracks are at right-angles to the direction of flow of the glacier. Beneath the ledge, the rate of movement slows down again, and the crevasses close up again.

K: Longitudinal crevasses

These are formed in the same way as transverse crevasses but parallel with the direction of flow. Typically they form where the glacier broadens out again after a narrow section.

L: Seracs

Seracs are columns of ice that form where transverse and longitudinal crevasses intersect. The result is often a chaotic-looking jumble of towers. The columns of ice are very unstable and usually collapse after a short time.

M: Marginal crevasses

Marginal crevasses open up where the glacier is slowed down at the edges by intense friction but the middle part of the glacier flows faster.

N: Bergschrund

The bergschrund is the crevasse at the top of the glacier. Officially, the bergschrund is regarded as the start or the highest point of the glacier, because it is from there that the ice begins to flow. Often the bergschrund can be seen as a narrow strip just below the summit or the cliff face.

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