page_title: Alps
section_title: Glaciers
hierarchical_section_title: Alps / Glaciers
caption_attribution_description: English: Der Unteraargletscher, der grössere der beiden Quellgletscher der Aare im Berner Oberland.
context_page_description: The Alps are the highest and most extensive mountain range system that lies entirely in Europe, and stretch approximately 1,200 kilometres across eight Alpine countries: France, Switzerland, Monaco, Italy, Liechtenstein, Austria, Germany, and Slovenia. The Alpine arch generally extends from Nice on the western Mediterranean to Trieste on the Adriatic and Vienna at the beginning of the Pannonian basin. The mountains were formed over tens of millions of years as the African and Eurasian tectonic plates collided. Extreme shortening caused by the event resulted in marine sedimentary rocks rising by thrusting and folding into high mountain peaks such as Mont Blanc and the Matterhorn. Mont Blanc spans the French–Italian border, and at 4,809 m is the highest mountain in the Alps. The Alpine region area contains about a hundred peaks higher than 4,000 metres.
  The altitude and size of the range affects the climate in Europe; in the mountains precipitation levels vary greatly and climatic conditions consist of distinct zones.
context_section_description: In the Miocene Epoch the mountains underwent severe erosion because of glaciation, which was noted in the mid-19th century by naturalist Louis Agassiz who presented a paper proclaiming the Alps were covered in ice at various intervals—a theory he formed when studying rocks near his Neuchâtel home which he believed originated to the west in the Bernese Oberland. Because of his work he came to be known as the "father of the ice-age concept" although other naturalists before him put forth similar ideas.
  Agassiz studied glacier movement in the 1840s at the Unteraar Glacier where he found the glacier moved 100 m (328 ft) per year, more rapidly in the middle than at the edges. His work was continued by other scientists and now a permanent laboratory exists inside a glacier under the Jungfraujoch, devoted exclusively to the study of Alpine glaciers.
  Glaciers pick up rocks and sediment with them as they flow. This causes erosion and the formation of valleys over time. The Inn valley is an example of a valley carved by glaciers during the ice ages with a typical terraced structure caused by erosion. Eroded rocks from the most recent ice age lie at the bottom of the valley while the top of the valley consists of erosion from earlier ice ages. Glacial valleys have characteristically steep walls (reliefs); valleys with lower reliefs and talus slopes are remnants of glacial troughs or previously infilled valleys. Moraines, piles of rock picked up during the movement of the glacier, accumulate at edges, centre and the terminus of 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.
  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.
  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. The 1,817 square kilometres (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. Forty percent of the glaciation in Austria has disappeared since 1850, and 30% of that in Switzerland.
caption: Louis Agassiz's studies of the Unteraar Glacier in the 1840s showed that it moved at 100 m (328 ft) per year.[47]
exif: {}