Alpine glaciers

Alpine glaciers can be straight rivers of ice, long sweeping rivers, spread in a fan-like shape (Piedmont glaciers), and curtains of ice

that hang from vertical slopes of the mountain peaks. The stress of the movement causes the ice to break and crack loudly, perhaps explaining

why the mountains were believed to be home to dragons in the medieval period. The cracking creates unpredictable and dangerous crevasses, often invisible under new snowfall, which cause the greatest danger to mountaineers.[49]

Glaciers end in ice caves (the Rhône Glacier), by trailing into a lake or river, or by shedding snowmelt on a meadow. Sometimes a piece of glacier will detach or break resulting in flooding, property damage and loss of life.[49]

High levels of precipitation cause the glaciers to descend to permafrost levels in some areas whereas in other, more arid regions, glaciers remain above about the 3,500 m (11,483 ft) level.[50] The 1,817 km2 (702 sq mi) of the Alps covered by glaciers in 1876

had shrunk to 1,342 km2 (518 sq mi) by 1973, resulting in decreased river run-off levels.[51] Forty percent of the glaciation in Austria has disappeared since 1850, and 30% of that in Switzerland.[52]