Mer de Glace

The glacier lies above the Chamonix valley. The pressure within the ice is known to reach at least 30 atmospheres.{{cite journal|last=Nye|first=John Frederick|author-link=John Nye (scientist)|title=The Mechanics of Glacier Flow|journal=Journal of Glaciology|date=1952|volume=2|issue=12|page=82|doi=10.1017/S0022143000033967|bibcode=1952JGlac...2...82N|url=http://web.gps.caltech.edu/~tsai/files/glacial/Nye_JGlac1952.pdf|access-date=13 January 2016|doi-access=free}} The Mer de Glace can be considered as originating at an elevation of {{convert|2,100|m}}, just north of the {{ill|Aiguille du Tacul|fr}}, where it is formed by the confluence of the {{ill|Glacier de Leschaux|fr}} and the {{ill|Glacier du Tacul|fr}}. The former is fed by the {{ill|Glacier de Talèfre|fr}}, whilst the latter is, in turn, fed by the Glacier des Périardes, the vast Glacier du Géant and the broad icefields of the {{ill|Vallée Blanche}}. The Glacier du Tacul supplies much more ice than the Glacier de Leschaux.{{rp|20}}

File:Fotografi av glaciären Mer de Glace - Hallwylska museet - 103137.tif

However, if the Mer de Glace is considered in its broadest sense (i.e. from source to tongue), it is a compound valley glacier, gaining ice from snowfields that cover the heights directly north of Mont Blanc at an altitude of around 4,000 metres. It flows for a total distance of 12 kilometres, covering an area of 32 square kilometres in the central third of the Mont Blanc massif.{{cite journal|last1=Nussbaumer|first1=S. U.|last2=Zumbuhl|first2=H. J.|last3=Steiner|first3=D.|title=Fluctuations of the 'Mer de Glace' (Mont Blanc area, France) AD 1500–2050|journal=Zeitschrift für Gletscherkunde und Glazialgeologie|date=2007|volume=40|pages=1–137|url=https://phzh.ch/MAPortrait_Data/131444/8/Nussbaumer_et_al_2007.pdf|access-date=13 January 2016|location=Innsbruck|issn=0044-2836}}{{rp|6,21}}

From the Aiguille du Tacul, the Mer de Glace flows north-north-west between {{ill|Aiguille du Moine|fr}} on the east and Trélaporte on the west. It descends below Montenvers, at which point it is approximately 0.5 km wide, and descends to approximately {{convert|1,500|m}}. The glacier was once easily visible from Chamonix but has been shrinking backwards, and is now barely visible from below.{{rp|20}} The surface topography of the Mer de Glace changed very little during the first third of the 20th century, but from 1939 to 2001 the surface of the glacier has lowered an average of 30 cm each year, corresponding to an equivalent loss of 700 million cubic metres of water.{{rp|126}}

File:Mer de Glace 1.jpg

When the tension in the ice increases as the slope increases, the glacier is unable to deform and crevasses appear. These are notably transversal and, when there is intense crevasse activity on the steepest terrain, blocks of seracs appear as the glacier breaks up. Crevasses are of variable depth, depending on their position, and may be as deep as fifty metres. Seracs always form in the same places, namely the steepest sections over which the glacier flows. As crevasses open and seracs tumble downstream, the supply of ice is renewed by the constant flow from upstream. Broad banding patterns, visible on the surface of the Mer de Glace, are known as ogives, or Forbes bands, and result from differences in summer and winter collapse rates of the serac fields. On 24 July 1842, Scottish physicist James David Forbes observed the pattern of light and dark dirt bands on the Mer de Glace from the nearby Aiguille des Grands Charmoz and began to consider whether glaciers flowed in a similar fashion to a sluggish river and with a viscous or plastic manner.{{cite book|last1=Shairp|first1=John Campbell|last2=Tait|first2=Peter Guthrie|last3=Adams-Reilly|first3=Anthony|title=Life and Letters of James David Forbes, F.R.S., D.C.L., LL. D etc|date=1873|publisher=Macmillan|location=London|page=[https://archive.org/details/lifeandlettersj00taitgoog/page/n558 527]|url=https://archive.org/details/lifeandlettersj00taitgoog|via=Internet Archive|access-date=13 January 2016}}

File:Mer de Glace sketchmap by John Tyndall, 1857, from 1896 edition.png explored the glacial tributaries feeding Mer de Glace in 1857]]

In the 18th and 19th centuries, the glacier descended all the way down to the hamlet of Les Bois,{{harvnb|Grove|1988|pages=121–122}}: "in 1820 ... sixty yards") where it was known as Glacier des Bois. At that time the river Arveyron emerged from the glacier under a grotto-like vault ({{lang|fr|grotte d'Arveyron}}){{harvnb|Tyndall|1896|page=38}}: "In former times the whole volume of the Arveiron escaped from beneath the ice at the end of the glacier, forming a fine arch at its place of issue." and, through the accounts of early writers and explorers,{{cite book|author=William Coxe|author-link=William Coxe (historian)|editor1-last=Pinkerton|editor1-first=John|chapter=Travels in Switzerland and in the Country of the Grisons (1776–1777)|title=A General Collection of the Best and Most Interesting Voyages|volume=5|date=1809|page=781 (640–992)|url=https://books.google.com/books?id=708nAAAAMAAJ|access-date=14 February 2016}} attracted many more visitors, painters and later photographers, for example J. M. W. Turner'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.

Mary Shelley's 1818 novel Frankenstein references Mer de Glace during Victor Frankenstein's hikes into the Mount Blanc massif. Dr. Frankenstein meets his creation twice during mountaineering on the Mer de Glace.{{cite journal | url=https://www.tandfonline.com/doi/abs/10.1080/09699089900200080?journalCode=rwow20 | doi=10.1080/09699089900200080 | title=A meeting on the mer de glace: Frankenstein and the history of alpine mountaineering | year=1999 | last1=Nardin | first1=Jane | journal=Women's Writing | volume=6 | issue=3 | pages=441–449 }} This episode inspired the 1991 opera Mer de glace by Australian composer Richard Meale to a libretto by his compatriot David Malouf.{{cite book|last=Hannan|first=Michael|author-link=Michael Hannan (composer)|year=2014|title=The Music of Richard Meale|location=Kingsgrove, New South Wales|publisher=Wildbird Music|pages=170–181|isbn=978-0987514516}}

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• Mer de Glace ice cave
• Arveyron
• Électricité de France
• List of glaciers
• Mont Blanc massif

{{Reflist}}

• {{cite book|last=Grove|first=Jean M.|title=The Little Ice Age|author-link=Jean Grove|year=1988|url=https://books.google.com/books?id=XLRR6-olZd0C|isbn=0-415-01449-2}}
• {{cite book|last=Tyndall|first=John|author-link=John Tyndall|title=The Glaciers of the Alps|year=1896|

publisher=Longmans, Green and Co.|url=https://archive.org/details/glaciersalpsbeing00tyndrich}} New edition reprinted as {{ISBN|1-4212-0908-X}}.

• {{cite book| last1=Fournier|first1=André|title=Mer de Glace|date=2005|isbn=2842062620|edition=English version|url=https://books.google.com/books?id=soKrxDgM1rcC&pg=PA7|access-date=18 January 2016|ref=none}}

• {{Commons category-inline}}
• [http://geoportail.fr/url/7FcpkQ Mer de Glace and associated glaciers on French IGN mapping portal]
• [http://www.google.com/maps/streetview/#mont-blanc/mer-de-glace 360° photo from surface of Mer de Glace on Google StreetView]

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Category:Glaciers of Metropolitan France

Category:Landforms of Haute-Savoie

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Category:Chamonix