Austria

Geology

The following work deals with the structure and dynamics of large-scale permafrost phenomena - rock glaciers. Rock glaciers are ice saturated unconsolidated material, flowing following the morphology of underlying terrain until they reach the border of permafrost occurrence (annual mean temperature around the 0 ° C).The three active rock glaciers at the north slopes developed at an altitude from 2500 to 2700 m SH. Of these forms, on a tongue shaped 600 m long and 200 m wide rock glacier, the Lazaun rock glacier morphological, geophysical and hydrological investigations were carried out.Using GPR, a 500 m-long longitudinal, and a 200 m long profile crossing the rock glacier was carried out. One of the main reflectors was observed in a depth of 30 m depth, and smaller ones in 4m and 6m. Also steep inclined reflectors propagating from the major ones were detected.Previous GPS measurements at 53 points on the rock glacier (zero measurement was made on 26.08.2006, the last measurement on 20.07.2007) showed an average movement rate of nearly 30 cm / a. The speeds were highest in the middle of the rock glacier with 50 to 70 cm / a , and diminished in direction of the borders.Temperature at the base of the winter snow cover, used for the determination of the energy balance of the rock glacier, showed in the winter 2005 - 2006 up to 6-8 ° C lower temperatures than outside the area of the rock glacier, with temperatures around -7 to -9 ° C. The exceptionally warm and snow-poor winter 2006 - 2007 showed in contrast around 3 ° C higher temperatures than the winter before.The hydrology of the rock glacier runoff reached maxima during the snow melt (June - July) with up to 138 l / s, with falling temperatures until late summer and in the winter the values dropped at 9 l / s.During summer rainfall the runoff experienced a momentary increase. Daily fluctuations are most pronounced during the snow melt, but can be seen also during summer until October, even if they decrease strongly in intensity.In the summer of 2006, the source rock glacier, the source version of the Lazaunhütte, the glacier water flowing creek with different side arms of Lazaunferners, a source at Moränenabhang and a source in front of a fossil rock glacier on the southern slope forehead sampled and measured conductivity and temperature.The observed increase in element (cations and anions) concentrations of the runoff suggest a possible melting of the subsurface ice, realising weathering residues. It is likely that the observed recent increase in the annual mean temperature in the Alps is the cause of the melting of permafrost in the actual lower limit of distribution.