Courmayeur · Italy
The height that changes
Mont Blanc does not possess a fixed height. The rock beneath does not move, but the summit is made of snow and ice, and that cap changes thickness from year to year with the wind and the snowfall. Since 2001 a team of French surveyors has measured it every two years with GPS, and each time the figure comes out slightly different: a few tens of centimetres either way, sometimes a few metres across a decade. It is a singular condition for a mountain, which ought to be the definition of what stays still. The figure you find written down therefore depends on the year in which it was printed. What is observed from here, by contrast, is always the same.
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How high is it now?
Somewhere around 4,805 to 4,810 metres, depending on the year of the survey. The official figure is updated after each campaign, and recent surveys have come out lower. The rock under the snow sits a little above 4,790.
Why measure it so often?
Partly scientific curiosity, and partly because the shape of the cap reveals the behaviour of wind and precipitation high up, which is hard to observe any other way. It has also become a tradition: the measuring expedition is a small event every couple of years.
Does the summit move as well?
Yes, slightly. The highest point of the snow cap is not always exactly above the same point of rock: the wind moves the snow and the summit migrates by a few metres. The survey teams record that too.
Where it is
More stories in Courmayeur
- The Aiguille Blanche
- The Aiguille Noire
- Duke of the Abruzzi Alpine Museum
- The Brenva Spur
- The Guides' House
- Church of Saint Pantaléon
- The quiet col
- The Col de la Seigne