14 September 2013: The result of the 7th Mont Blanc measurement campaign is in!
The current altitude of the summit of Mont Blanc is 4810.06 meters. This is 0.38 of one metre less than in 2011.
The result is reassuring for all those who believed that the Mont Blanc measures 4807 meters, as established in 1863 and commonly understood since that date. Anything less than 4807m is not going to sit well with many people!
Measuring the Altitude of Mont Blanc
In the year of 2001, Leica Geosystems tested their new mobile GPS equipment, in the extreme conditions provided by the summit, with surveyors from the French National Institute of Geoegraphical and Forestry Information (IGN) using geodesic technology.
It was determined that western Europe's highest mountain did not have a summit altitude of 4807 metres. The actual altitude of the summit was 4810 metres, some three meters higher!
This significant discrepancy led to an agreement that a new measurement should be taken every two years.
The 2013 Campaign
Twenty people participated in the 2013 campaign, led by High Mountain Guides from Chamonix and St.Gervais.
The purpose of the campaign is to detect any changes to the 'soft' summit of Mont Blanc. Data is collected on the volume of snow fall and the speed and direction of the wind, both of which impact on the thickness of the snowpack.
Also, the altitude of the underlying rock is measured. The Alps are tectonically dead but there is still an element of residual upthrust.
The current rock altitude is 4792 metres.
The snow peak of Mont Blanc is approximately forty metres to the East of the rock summit. This is because the prevailing wind, from the West, pushes the snow mass to the East.
Data is collected at the summit of Mont Blanc by a mobile GPS station and then analysed by a team of geologists, meteorologists, climatologists from the IGN.
They determine the volume of snow and any changes to morphology and density of the snowpack. This data allows the scientific community to better understand the impact of variations in the weather.
Philippe Borrel, a surveyor from Annecy and member of the 2013 campaign, explains that, "a large database of information is being gathered for future generations. This will allow us to determine whether or not the snow-capped summit of Mont-Blanc is affected by climate change."
Philippe reflects that, "the 4807 metres summit of Mont-Blanc was so embedded in our collective memories, that it seemed an immutable height. Still, the height of the peak does vary, more or less, depending on the amount of snowfall and wind. The rocky summit of Mont Blanc is 4792m, but the thickness of the "eternal snow" that covers the peak may vary from 15 to 20 metres."
Altitudes of Mont-Blanc
Since 1863, the official height of the Mont-Blanc has been 4807 meters.
In 1892, the altitude was recalculated on an ellipsoidal geopotential mean at 4807.20 meters.
Then, in 2001, Mont-Blanc was measured to an altitude of 4810.40m.
Two years later, in 2003, Mont Blanc had melted by 2 metres. For the next two years the official altitude was down to 4808.45 metres.
By 2005, the altitude of the summit of Mont Blanc had recovered to 4808.75 meters.
By 2007, it had increased still further, to a new record of 4810.90 meters.
In 2009, the altitude of the summit had reduced by 45 centimetres to 4810.45 metres.
In 2011, a very small decease was detected. The altitude was measured at 4810.44 metres.
By 2013, a further decrease of 38 centimetres was detected, when the altitude of the summit was measured at 4810.06 meters.
The rock summit of Mont-Blanc is 4792 meters