Michael Avian

Recent and Holocene dynamics of a rock glacier system: The example of Langtalkar (Central Alps, Austria)

The Hinteres Langtalkar rock glacier (Gössnitztal, Hohe Tauern, Austria) has been part of a complex transportation system of debris and ice since the beginning of the Holocene and shows the highest creep rates of all rock glaciers measured in the Hohe Tauern Range. Results of movement analysis show that the entire rock glacier behaves very differently at different zones and that sudden temporal and spatial changes of velocity rates are a typical feature. Zones with high rates occur close to rather inactive zones and zones with low rates have rapidly accelerated within recent years. The increase in movement rates over time is probably caused by topography. These studies – especially the measurement of surface velocities and elevational changes – allow a differentiation of the rock glacier and a first attempt of a morphogenetic interpretation. In this context, it is important that the innermost part of the cirque was covered by a small cirque glacier during the Little Ice Age advance. This cirque glacier created a moraine complex which contributes to the material supply of the rock glacier. A first estimation of transportation rates is possible with the help of the measurement results available, leading to an estimation of a probable age of at least 4000 years.

Glaciological Studies at Pasterze Glacier (Austria) Based on Aerial Photographs

This chapter describes and analyses glacier recession observed at Pasterze Glacier, Hohe Tauern Range, Austria, for the time period 2003–2009. Pasterze Glacier is the largest glacier of the entire Eastern Alps, and it is highly indicative of ongoing glacier melt in the Alps. We evaluated three glacier stages (2003, 2006 and 2009) and the glaciological changes between them. The quantitative analysis is based on aerial surveys carried out during the summer of these years. The photogrammetric workflow provided high resolution datasets, such as digital elevation models and orthophotos of each stage. We evaluated the extent, surface elevation, flow velocity field, supraglacial debris cover, and geomorphological changes at the glacier surface and the adjacent paraglacial environment. The main numerical results can be summarized as follows: the glacier covered 17.3 ± 0.1 km2 in 2009, the mean surface elevation change was −1.31 ± 0.07 m a−1 for the period 2003–2009, the glacier surface flow velocity in two test areas at the glacier tongue decelerated from 2003–2006 to 2006–2009 (−4 % and −31 %), and the debris cover of the glacier tongue increased from 63 % (2003) to 72 % (2009). We conclude that Pasterze Glacier is far from equilibrium and that its glacier tongue will turn into a large dead ice body in the near future.