Today there are more than 2,000 glaciers in the Alps with an ice-volume of 100 km², 342 of which can be found in the Hohe Tauern National Park. You can differentiate between various types of glaciers, such as kettle glaciers, slope glaciers, rock glaciers, avalanche glaciers and effluent glaciers.
When summer temperatures are not enough to melt the snow that fell in winter, glaciers are formed. Year by year layers of snow stack up, which then transform into corn snow and harden into ice by the increasing pressure. Glacier ice is thus not a rigid body and flows down into the valley because of gravity. When rises are overflowed, tugging forces are generated which are released through the opening of fissures.
The Hohe Tauern National Park is home to all different types of glaciers. The largest glacier in the national park is the Pasterze, the valley glacier of the Grossglockner. With a length of 7.5 metres and surface of 18.5 km² (as of 2002) the Pasterze glacier is the largest glacier in all of the Eastern Alps and counts among the "big alpine glaciers in the world", as it extends from the periglacial altitudinal belt down to the potential forest belt and thus can "hold its own" against glaciers such the Glacier Noir or Glacier des Bossons.
Glaciers perform many important functions. They have a bearing on the hydrologic balance, are significant to energy generation, effect the microclimate and are linked to natural hazards. Furthermore, they are increasingly sensitive indicators of global climate change as glacier retreat has been observed for some decades now.