Aletsch Glacier
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Aletschgletscher.JPG
Aletsch Glacier, the largest glacier in the Alps, covers more than 120 square kilometres (more than 45 square miles) in southern Switzerland. It descends round the south of the Jungfrau into the valley of the Upper Rhône; at its eastern extremity lies a glacier lake, Lake Märjelen (Gr. Märjelensee) (2,350 meters/7,711 feet above sea level). To the west rises Aletschhorn (4,195 meters/13,763 feet), which was first climbed in 1859. The Rhône River flows along the southern flank of the mountains.
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Description
The origin point of the great Aletsch Glacier lies situated in the 4,000 m high Jungfrau-Region. At the Konkordiaplatz, a six sq. km, slightly inclined iceflow, three large Firn (snow) fields come together:
- From the western mouth flows the Great Aletschfirn, which runs along the northern foot of the Aletschorn 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 tribitary 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's 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 Rhone 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 togther. The westernmost medial moraine has been named the Kranzbergmoräne, and the easternmost carries the name Trugbergmoräne.
Fluctuations in the glacier
In its high stage, during the "Little Ice Age" in the middle of the 1900's, the great Aletsch Glacier stretched about 2.5 km farther down into the valley. Due to the general warming trend since about 1870, the lower part of the Konkordiaplatz has been greatly reduced in volume, and the toe has retreated several kilometers. Today, the glacier's high tide can still be estimated by the nearly vegetation-free lateral moraine it has left before it. Since 1850, the thickness of the ice has decreased by over 100 m. Earlier, the ice flows of the Oberaletsch Glacier and the Mittelaletsch Glacier were also directly connected with the great Aletsch Glacier. In the lower region between the Strahlhorn and the Eggishorn lies Lake Märjelen, a glacial lake, or tarn, that accumulated at the high point of the glacier in the 1900's. This lake's sudden breakouts through the dam of glacial detritus have periodically caused surges of water into the Massa. These surges of water have repeatedly caused extensive flood damage.
Due to its large size, the glacier is relatively immune to short term climate fluctuations. While many other glaciers advanced from the end of the seventies to the beginning of the eighties, the Aletsch Glacier barely reacted to the temporary cooling - and just as little to the warm years since 1983. Due to the increasingly extreme heat of the last years, it is retreating - just like all other remaining Alpine glaciers - but is now nonetheless clearly strengthened.
Tourism
The Aletsch Glacier has long been considered a special place for travelers: a welcome area of exploration for the inquisitive. There have been research stations on the Jungfraujoch since 1937, and since 1976 on the Riederfurka above the Riederalp. Numerous wire cable cars have opened the region of the Berggrat between the Riederhorn and the Eggishorn. This area has a very beautiful view of the toe-region and lower part of the glacier. With the building of the Jungfraubahn on the Jungfraujoch (from the Sphinx 3571 m high) in 1912, tourists were also afforded a glance at the top of the glacier.
At the rock slope of the Fülbergs east of the Konkordiaplatz stands the 2850 m high Konkordia cabins of the Swiss Apine Club (SAC). They serve as an important embarkation point for the high Alps routes to the upper glacier from the Jungfraujoch or from the Lötschental valley into the area of the Grimsel Pass.
World Heritage status
On 13 December 2001 UNESCO declared the great Aletsch Glacier, as well as the Jungfrau-Aletsch-Bietschhorn, the unique Aletschwald and the surrounding regions, a Natural World Heritage Site.
References
- This article is based on a translation of the corresponding article from the German Wikipedia, accessed on various occasions during April 2005.da:Aletsch-gletsjeren