The TêTE ROUSSE GLACIER (French :
* 1 Geography
* 2 1892
The glacier is located on the northwestern slopes of the Aiguille du
Goûter , on the northern side of
The glacier is frequently crossed by mountaineers on their way to the
Tête Rousse mountaineering hut , which stands at the side of the
glacier at an altitude of 3,167 metres. It is also crossed by many
more climbers attempting the 'normal' route of ascent to the summit of
1892 MONT BLANC GLACIER FLOOD
Joseph Vallot (fr), the glaciologist and Director of the Mont Blanc Observatory at the time of the incident, published detailed accounts of his investigations into the Catastrophy of Saint Gervais. Measurements and photographs taken shortly afterwards showed that part of the glacier's snout (terminus ) had been torn away, revealing a cavity 40 metres in diameter and 20 metres above its base. From this a 3 metre high tube led back some 85 metres and at a 36° angle to an even larger second cavity, up to 40m high and 50 m wide. Maps drawn up shortly afterwards confirmed a depression in the centre of the glacier. It was estimated that 100,000 cubic metres of liquid water had drained away during the glacier's collapse, plus a further 100,000 cubic metres of broken ice. Together with the soil and rock broken away by the force of the rushing water, Vallot estimated that a weight of 500 million kilograms of material had borne down on the villages. He also warned that a repeat of water build-up was quite likely to occur, and that this would become more dangerous as time went on. He advocated the use of explosives to ensure a permanent flow of meltwater away from the glacier.
In 1904 a second water pocket was discovered within the glacier, and a hole was drilled to drain away 22,000 cubic metres.
Opinions have differed as to the precise mechanism by which water had built up in such quantity and then had suddenly been released with such devastating consequences. For many years the accepted explanation was that proposed by Joseph Vallot. It was believed that meltwater had drained through the glacier and become trapped as an intraglacial cavity, i.e. as an underground lake within a crevasse which itself had then become enlarged and widened by the water. However, recent re-analysis of historic photographs, accounts and contemporary meteorological precipitation data and field measurements, including radar analysis and magnetic resonance imaging, has presented an alternative and more plausible mechanism in which meltwater collected much closer to the surface (as a supraglacial lake ) in a period when the glacier had a negative mass balance (i.e. was experiencing year-on-year melting and retreat). Prior to 1878 the glacier would not have been well-visited, so any surface lake could have gone unnoticed, and after 1878 the glacier experienced a positive mass balance (i.e. year-on-year accumulation of snow and ice) which would have hidden the lake from view until the eventual outburst flood in 1892.
MODERN DAY RISKS
In July 2010 a pocket containing 50,000 cubic metres of water was
detected in a glacial pocket, and some 48,000 cubic metres of water
were pumped out. A siren warning system was installed to aid
evacuation of those at risk in the valley below, and evacuation plan
was put in place. The final section of the
In 2011 water levels within the glacier were predicted to refill the glacial cavity before summer, and a further 25,000 cubic metres of water was drained away. Further research was carried out to study and monitor the origin of the water.
In 2012 results of research were presented showing that two water pockets existed within the glacier. On 17 August 2012 part of the glacier's surface collapsed inwards. This created a large hole through which a glacial lake could be seen. Paths across the glacier were diverted, including that used to reach the Gouter Hut and thence the summit of Mont Blanc.
At 1:47am on 29 July 2013 during a heavy storm, the alarm system on the glacier triggered, alerting the authorities to a serious flood risk. 95 firefighters and 70 soldiers of the gendarmerie were mobilised, and an evacuation plan put into effect, involving the townspeople of St Gervais, Sallanches and Passy Domanc gathering at pre-arranged assembly points. Inspection of the glacier revealed that no collapse had taken place and the warning notice was lifted at 4:30am the same night. Studies revealed that between 35,000 and 50,000 cubic metres of water were present in the glacier.
By 2014 another build-up of a water pocket was discovered, and the Mayor of St. Gervais reported that, since its rediscovery, a total of 6 million euros had been spent in monitoring and pumping out water from the Tête Rousse glacier to protect the 3,000 inhabitants in the valley below.
* ^ A contemporary account by J Vallot, cited here, states over 200 deaths, although modern publications repeat a figure of only 175.
* ^ A B C D Vincent, C. (2010). "Origin of the
Outburst flood from