Ice grotto glacier phenomena

On the tracks of the Stubai Glacier

Station 1

Glacier

Glaciers are fascinating formations. They shape our landscape.

At the glacier we find crevasses, mills, cones, moraines... At station 1 of the ice grotto we want to show you some of these phenomena, which you can see all around you at the Stubai glacier. Further along the way, we will show you how some of these special glaciological formations are created and how glaciers work.On the pictures below you can see some of these glacial phenomena.

Station 2

Ice flow

Glaciers flow towards the valley under the influence of gravity.
The annual flow speeds of our alpine glaciers range from a few metres to over a hundred metres per year. The glaciers flow fastest in the steep areas. During summer, the movement is faster than in winter because the melted water reduces friction on the ground, so the ice can slide faster over the glacial bed. If the mass balances are positive, the glacier gains mass, because more snow remains over summer than ice melts at the tongue.

As a result of positive mass balances, the flow rate of the ice also increases, the glacier advances. If more ice melts at a tongue than the flow movement of the glacier brings, the glacier becomes smaller.

The common expression "the glaciers are retreating" is misleading, as the ice naturally always flows downwards.

Station 4

GLACIAL MILK

The glacier grinds the rock into a fine flour. The sediments give the glacial streams their characteristic colour. The milky cloudiness of the glacial runoff has led to the term ‘glacial milk’. Each month, several tonnes of sand are transported into the glacial streams. For instance, suspended loads of between 150,000 and 240,000 tonnes per month were measured in the Ruetz river. This corresponds to around 10,000 to 20,000 truckloads.

Station 6

Exotic species

In the ice grotto, quite a few things are preserved in the eternal ice

As part of the excavations at the ice grotto, the Institute for Interdisciplinary Mountain Research at the Austrian Academy of Sciences took ice samples. One sample contained fungus spores. These were transported to the Schaufelferner by the wind more than 100 years ago, deposited in the snow and enclosed in the glacial ice. Time and time again, dust from the Sahara is transported by the wind in the Alps, deposited at the glacier and stored in the ice. Beetle mites and other arthropods are often transported to the glacier by the wind and enclosed in the ice. In the glacial areas that do not flow, very old relics can survive (e.g. Ötzi the Iceman for 5,000 years).

Station 7 

Stratification -  summer and winter

The ice in the cave shows seasonal stratification: in summer, the melting creates a dark layer that contains dust and sand, which is blown onto the glacier over the summer. The winter layer is light-coloured.

Station 8 

Balanced temperature 

The temperature at the glacier is constant at 0°C. This is why the temperature in the ice grotto seems cold to you in summer and warm in winter. In addition, every visitor gives off heat (100 watts) and thus warms the air in the ice grotto.

Station 9 

Optical features

When ice contains lots of air bubbles, it looks white. Blue light can penetrate furthest into the glacial ice. 25% of the blue light is still present behind an ice layer one metre thick, but only 1% of the red light. As the red light is absorbed fastest, the ice appears blue.

INSIDE THE ICE CAVE:

Please take the lamps at station 9 and light up the ice once with the red light and once with the blue. See for yourself the visual properties of the glacial ice.

Station 11

GLACIAL POLISH

The bedrock is polished by the glacier that flows above it and the rocks carried in the ice. The rock affected by the glacier has an unmistakable appearance and is referred to as glacial polish. The characteristic scratches in the rock are called striations.How pieces of rock can also be broken off. Using these traces, it is possible to determine the flow direction of the ice for Ice Age glaciers. An especially fine sediment is created when the rock is ‘polished’. This gets into the melted water and leads to the characteristic cloudiness of the glacial runoff, which is also referred to as ‘glacial milk’.

Station 12

Glacial retreat

The image below shows the changes to the Schaufelferner since 1850. At this time, the glacier reached its greatest expansion since the last Ice Age.This image clearly shows the side moraines after the last glacial expansion in 1850. Numerous impressive side moraine embankments still indicate this glacial peak.Among other places, you travel over a particularly clear example in the gondola in the 2nd section of the Eisgrat railway.

Development of the glacial climate

At the height of the last Ice Age around 20,000 years ago, the Alps were covered with ice up to the great lakes in the foothills of the Alps, with only the highest peaks protruding.10,000 years ago, it became warmer and the glaciers in the valleys melted. The glaciers that remained were of a similar size or smaller than those today. The Little Ice Age around 1250 led to cooling, and so the glaciers reached a peak within the last 10,000 years in 1850. Since then, the glaciers have been retreating, interrupted with brief advancements in 1870, 1920 and 1980.

The illustration shows the postglacial temperature development in the Eastern Alps region. The glacial expansion determined so far and the forest and tree lines were used to determine the development of the summer temperature (May-September) for the last 11,000 years. In over 65% of this time, the temperatures lay above the mean of 1980-90, which are the red areas in the graph.

Station 13

The glacier

Glaciers are created where snow does not melt for several years.

It remains on the ground and turns into glacial ice over several decades. The fluffy snow weighing 300 kg/m³ is compressed in a year into firn weighing 700 kg/m³.  Compression then continues slowly until, after around 30 years, the final stage ‘ice’ is achieved, weighing 917 kg/m³.  Under the influence of gravity, the ice is shaped and in constant movement. The glacier thus moves several metres a year towards the valley.

In some places, the forces are so great that the ice cannot react with plastic deformation, such as at the edge of the land and over rock hummocks in the ground. Then cracks form, called crevasses. he melted water creates channels in the ice. At the surface, melted water forms a meandering stream, which reaches the ground via the glacier mills (vertical channels in the ice) and then emerges again at the mouth of the glacier.