page_title: Aletsch Glacier
section_title: Formation and evolution
hierarchical_section_title: Aletsch Glacier / Formation and evolution
context_page_description: The Aletsch Glacier or Great Aletsch Glacier is the largest glacier in the Alps. It has a length of about 23 km, has about a volume of 15.4 km³, and covers about 81.7 km² in the eastern Bernese Alps in the Swiss canton of Valais. The Aletsch Glacier is composed of four smaller glaciers converging at Concordia Place, where its thickness was measured by the ETH to be still near 1 km. It then continues towards the Rhône valley before giving birth to the Massa. The Aletsch Glacier is – like most glaciers in the world today – a retreating glacier. As of 2016, since 1980 it lost 1.3 kilometres of its length, since 1870 3.2 kilometres, and lost also more than 300 metres of its thickness.
  The whole area, including other glaciers is part of the Jungfrau-Aletsch Protected Area, which was declared a UNESCO World Heritage Site in 2001.
context_section_description: The Aletsch Glacier resulted from the accumulation and compaction of snow. Glaciers generally form where snow and ice accumulation exceed snow and ice melt. As the snow and ice thicken it reaches a point where it begins to move due to a combination of gravity and pressure of the overlying snow and ice.
  During the last glacial periods, the Aletsch Glacier was much larger than now. 18,000 years ago the lower part of the ridge, between Riederalp and the glacier, was completely covered by ice. Only the summits of the Bettmerhorn, Eggishorn and the Fusshörner were above the glacier. After an important retreat, the glacier again advanced 11,000 years ago during the last glacial period. The glacier reached the Rhône valley, and its ice the Riederfurka. Remaining moraines are still visible in the Aletsch Forest.
  Since the last glaciation, the glacier generally retreated. However slight climatic changes happened and, in 1860, the glacier was 3 km longer and the ice level 200 m higher.
  As for many other glaciers, records show a major longer-term retreat trend. The Aletsch Glacier receded by 3.2 km (2.0 mi) since 1870, including 1.3 km (0.81 mi) since 1980. A record retreat of 114.6 metres (376 ft) happened in 2006 alone.
  Since the end of the Little Ice Age in 1850 the glacier has lost 20 percent of its ice mass, considerably less than other glaciers in Switzerland, which have lost up to 50 percent. This is explained with the large size of the Aletsch Glacier, which reacts much slower to climate change than smaller glaciers. It is however estimated that, by 2100, the glacier will have only one tenth of its 2018 ice mass.
caption: The retreat of Aletsch Glacier in the Swiss Alps (situation in 1979, 1991 and 2002), due to global warming.
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