Mer de Glace
Encyclopedia
The Mer de Glace is a glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

 located on the northern slopes of the Mont Blanc
Mont Blanc
Mont Blanc or Monte Bianco , meaning "White Mountain", is the highest mountain in the Alps, Western Europe and the European Union. It rises above sea level and is ranked 11th in the world in topographic prominence...

 massif, in the Alps
Alps
The Alps is one of the great mountain range systems of Europe, stretching from Austria and Slovenia in the east through Italy, Switzerland, Liechtenstein and Germany to France in the west....

. At 7 kilometres (4.3 mi) long and 200 metres (656.2 ft) deep, it is the longest glacier in France.

Geography

It originates at an elevation of 2400 metres (7,874 ft) where it is fed by the confluence of Glacier du Géant, Glacier de Lechaud, and Cascade du Talèfre, north of Mont Tacul, and descends to 1400 metres (4,593.2 ft). It flows north-north-west between Aiguille du Moine on the east and Trélaporte on the west. Le Grand Dru lies to the north east. It was once easily visible from Chamonix
Chamonix
Chamonix-Mont-Blanc or, more commonly, Chamonix is a commune in the Haute-Savoie département in the Rhône-Alpes region in south-eastern France. It was the site of the 1924 Winter Olympics, the first Winter Olympics...

, but has been shrinking and is now barely visible from below.

It lies in the Chamonix
Chamonix
Chamonix-Mont-Blanc or, more commonly, Chamonix is a commune in the Haute-Savoie département in the Rhône-Alpes region in south-eastern France. It was the site of the 1924 Winter Olympics, the first Winter Olympics...

 valley, it was the first place in the valley to have a ready-made tourist attraction.

The Mer de Glace, like all glaciers, it is constantly renewed under the effect of two phenomena: accumulation, notably due to snowfall and ablation, essentially due to melting. The Mer de Glace flows permanently under the effect of its own weight, crusting crevasse
Crevasse
A crevasse is a deep crack in an ice sheet rhys glacier . Crevasses form as a result of the movement and resulting stress associated with the sheer stress generated when two semi-rigid pieces above a plastic substrate have different rates of movement...

s, serac
Serac
A serac is a block or column of ice formed by intersecting crevasses on a glacier. Often house-sized or larger, they are dangerous to mountaineers since they may topple with little warning...

s or pockets of water to form, depending on the type of ground.

The glacier's speed, although not perceptible to the naked eye, is considerable. From more than 120 metres (393.7 ft) a year in its upper part, the Mer de Glace moves about 90 metres (295.3 ft) per year in the region of Montenvers
Montenvers Railway
The Montenvers Railway or Chemin de fer du Montenvers is a rack railway line in the Haute-Savoie region of France. The line runs from a connection with the SNCF, in Chamonix, to the Hotel de Montenvers station, at the Mer de Glace, at an altitude of ....

, which is about one centimeter per hour.

As soon as the tensions intensify, the glacier is deformed and crevasses appear. These are notably transversal. When there is intense crevasse activity, the breaking-up of the glacier by the crevasses forms blocks of seracs.

The unidentified objects, of variable depth, depending on their positioning, may reach fifty metres. They always form in the same place because of the shape of the glacial valley in which the glacier flows. Disappearing downstream, they are renewed upstream.

History

In the 18th and 19th centuries the glacier descended all the way down to the hamlet of Les Bois, where it was known as Glacier des Bois. At that time the river Arveyron
Arveyron
The Arveyron River is a left tributary to the Arve River, rising in the famous Mer de Glace just above Chamonix in south-eastern France. It flows into the Arve in Chamonix.-References:*http://www.geoportail.fr*...

 emerged from the glacier under a grotto-like vault (grotte d'Arveyron) and attracted painters and later photographers, for example Joseph Mallord William Turner
J. M. W. Turner
Joseph Mallord William Turner RA was an English Romantic landscape painter, watercolourist and printmaker. Turner was considered a controversial figure in his day, but is now regarded as the artist who elevated landscape painting to an eminence rivalling history painting...

's "Source of the Arveron in the Valley of Chamouni Savoy", 1816. The position of its front end fluctuated over the years but its maximum extent was in the mid-19th century.

Electricity Generation

Subglacial waters from the Mer de Glace are used seasonally by EDF
Électricité de France
Électricité de France S.A. is the second largest French utility company. Headquartered in Paris, France, with €65.2 billion in revenues in 2010, EDF operates a diverse portfolio of 120,000+ megawatts of generation capacity in Europe, Latin America, Asia, the Middle East and Africa.EDF is one of...

 for the generation of hydroelectricity
Hydroelectricity
Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...

. Tunnels bored under the glacier collect water from the base of the glacier and channel it down to a hydropower plant in the valley. This water is then discharged into the Arveyron
Arveyron
The Arveyron River is a left tributary to the Arve River, rising in the famous Mer de Glace just above Chamonix in south-eastern France. It flows into the Arve in Chamonix.-References:*http://www.geoportail.fr*...

further downstream.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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