Most
of the rocks that we see today up to an altitude of 3500m were slowly
formed, millions of years ago, in the sea that covered the area where
we now find the Alps.
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Coastal
sand-dunes were at the origin of the silica
peaks which border the Vanoise from North
to South: the Aiguille du Dôme, the Pointe de la Grande Glière, the
Aiguille Doran amongst others.
Curious sink-holes
give the impression of a lunar landscape to the Petit Mont-Blanc of
Pralognan and the slopes of the Tovière.
There are some astonishing rocky pinnacles
made from a porous sedimentary rock called cargneule; an example is
the famous monolith of Sardières. |
Monolithe de Sardières
© PNV / Anne-Lise Bard |
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There is plenty of limestone
in the Vanoise and it is extremely varied in colour and texture:
in the Passage des Eaux Noires, black blocks of limestone are found
next to pale yellow cargneules.
Going over the pas de l'Âne on the other hand, one comes across
pure marble veined with crimson;
perhaps the most surprising is the vermiculated limestone of the
Lac Blanc of Polset, where the fossilised tracks of an unknown sea-worm
remain to intrigue us.
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Vermiculated
limestone
at Lac Blanc de Polset |
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Not far away, at the Roc de la Pêche, the few fossils
that have been found tell us that this whole cliff of 800m is completely
upside-down! The most recent strata are in fact bried at the base
while the oldest ones are high up at the summit of the Roche Nue.
Perhaps easier to comprehend are the countless micro-folds
which appear in certain limestone formations, such as at la Grande
Motte; their tortured features bear witness to the tremendous upheaval
resulting from the collision of the African and European continents
some 60 million years ago.
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| Pointes
de la Glière |
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The west of the Vanoise, from Fourneaux to Bourg-Saint-Maurice
by way of Bozel is entirely bordered with formations dating from
the Carboniferous age.
Sandstones and shists are often the rather monotonous
background for ski-resorts such as those of the Three Valleys. In
certain places, the local people exploited the veins of anthracite
until the middle of the 20th century. Montagny has one of the best-known
deposits.
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