Aletsch Glacier, the Alps’ largest and longest glacier, lying in the Bernese Alps of south-central Switzerland. Covering an area of 66 square miles (171 square km), it is divided into the Great Aletsch (main) and the Middle and Upper Aletsch (branches). The main glacier is 15 miles (24 km) long and 1 mile (1.6 km) wide. It extends generally southward from the Concordia Platz (where several other glaciers meet) to the Aletsch Forest (a nature reserve). Descending from the Aletschhorn (peak; 13,763 feet [4,195 m]), the Middle Aletsch reaches the main glacier nearly opposite Märjelen Lake, a small lake bordering the Great Aletsch and lying just north of the Eggishorn. The Massa River, a tributary of the Rhône River, issues from the Great Aletsch. Skiing, mountain climbing, and glacial excursions are popular in the region.
* From the western mouth flows the Great Aletschfirn, which runs along the northern foot of the Aletschhorn and Dreieckhorn. The Aletschfirn is supplied from the north by three notable firns: the Ebnefluhfirn, the Gletscherhornfirn, and the Kranzberfirn. All of these Firns have their starting points at around 3800 m. From the Ebnefluhfirns to the Konkordiaplatz, the Aletschfirn is 9 km long and is on average about 1.5 km wide. From the west, the Aletschfirn flows over the 3173 m high Gletscherpass, the “Lötschenlücke”, connecting with the Langgletscher, and then into the Lötschental valley.
* From the northwestern mouth flows the Jungfraufirn. This firn in fact represents the straight continuation of the Aletsch Glacier, yet is the shortest of the three tributary glaciers. It has its origin on the southern flank of the Mönch, at the Jungfraujoch and at the eastern flank of the Jungfrau. Up to the Konkordiaplatz, the Jungfraufirn is a scarce 7 km long, and returns to flank the Kranzberg in the west and the Trugberg in the east. At its highest point, it is 2 km wide, and further down it is still a good 1 km wide.
* From the northern mouth flows the Ewigschneefeld (Eternal snow field), where its starting point takes the east flank of the Mönchs. In an elbow, it flanks from Trugberg in the west and the Fiescherhorn and Grünhorn in the east, flowing on to the Konkordiaplatz. Up to here, it is about 8 km long and averages about 1.2 km wide. The mouth at the Konkordplatz it follows over a rise with a descent from 25 to 30 percent; here, the glacier is sharply split. Against the north is the Ewigschneefeld over the snow-covered pass of the Lower Mönchsjochs (3529 m high), connected with the catchment area of the Lower Grindelwald glacier. Through the Higher Mönchsjoch (3627 m high) between the Mönch and the Trugberg stands a connection to the Jungfraufirn.
Also at the mouth of the Konkordiaplatz from the east is the small but important Grüneggfirn (3 km long and averaging 600 m wide). This firn is connected in the over the glacier pass Grünhornlücke (3280 m high) to the Fiescher Glacier in the east.
From the Konkordiaplatz, the Aletsch Glacier has a width of approximately 1.5 km and moves at a rate of 180 m per year to the southeast on course with the Rhône valley, bordering the Dreieckhorn in the west and the great Wannenhorn in the east. It then takes a great right turn and bends ever closer to the southwest, running through the edge of the Eggishorn and Bettmerhorn of the Rhone valley. The lowest part of the great Aletsch Glacier is largely covered with detritus of the lateral and medial moraines. The glacier’s toe currently lies about 1560 m high, far beneath the local tree line. From it springs the Massa stream, which flows though the Massa Canyon and is used to generate hydroelectric power. It continues through the upper half of the Brig, eventually entering into the Rhone.
The great Aletsch Glacier shows considerable ice cover. At the Konkordiaplatz, it has an ice cover of more than 900 m, but as it moves to the south, the greater part of the ice melts, gradually decreasing the cover to around 150 m.
The characteristically dark medial moraine, situated almost in the middle of the glacier, runs protracted in two bands from the Konkordiaplatz along the whole length to the glacier’s toe-zone. This medial moraine is collected from the ice of three large ice fields, which all run together. The westernmost medial moraine has been named the Kranzbergmoräne, and the easternmost carries the name Trugbergmoräne.
On August 18th, 2007, photographer Spencer Tunick used hundreds of naked people in a “living sculpture” on the Aletsch Glacier in a photo shoot intended to draw attention to global warming and the shrinking of the world’s glaciers. The temperature was about 10 °C at the time of the photo shoot. The 600 participants on the shrinking glacier volunteered for Tunick (a collaboration with Greenpeace) to let the world know about the effects of global warming on the melting Swiss glaciers. The Aletsch Glacier receded by 100 m (330 ft) between 2005 and 2006.