Pasterze Glacier. Fold structures visible in the foliation of the ice of the Pasterze Glacier. Glaciers are rivers of ice that form when compacted snow from high ground turns into ice and flows downhill under its own weight. Many years of snowfall are contained in the ice of the largest glaciers. This glacier, over 8 kilometres in length, is one of the longest in Austria. It is currently retreating, decreasing in length by about 10 metres per year. Photographed in Hohe Tauern National Park, Austria. This national park is in the Hohe Tauern mountain range in the eastern Alps.