Deep within a French glacier, a melted menace
IN SAINT-GERVAIS, FRANCE From time immemorial, the Tete Rousse Glacier has sparkled majestically on the slopes of Aiguille de Bionnassay, an icy symbol of the Alpine heritage that molded the culture and produced the prosperity of this mountaineering town in the shadow of Mont Blanc.
But the glacier, a 20-acre mass lying within a bowl-shaped rock formation at an altitude of nearly 10,000 feet, has suddenly turned menacing.
Partly because of global warming, a giant pocket of water has accumulated within the ice, threatening to burst out of its frozen enclosure and send a wall of water, mud, ice and rock down on the chalets of Saint-Gervais spread across the valley below.
"Nature is stronger than we are," explained the mayor of Saint-Gervais, Jean-Marc Peillex, calling on his sometimes skeptical townspeople to heed the threat. "No one can confirm the risk is imminent," he said in an announcement posted around the community, "but nor can anyone confirm that there is no risk."
As soon as experts from the National Scientific Research Center reported with certainty in mid-July that they had detected the water pocket, Peillex, acting on his own advice, set up an alarm system on the glacier, connected to sirens in Saint-Gervais. Many of the town's 5,740 inhabitants, joined by up to 25,000 visitors during summer climbing season, were assigned rallying points on high ground where they could flee if the sirens wailed.
Residents of the most exposed homes on the upper side of the valley would have only 10 minutes if the glacier walls gave way all at once, he estimated, and as many as 3,000 people could be killed if the worst scenario played out.
By August, teams of scientists with special equipment were drilling day and night into the glacier to relieve the pressure, in a $3 million operation financed by the Saint-Gervais town hall, the national government and the European Union. From some holes, the water bubbled to the surface, as if from an artesian well. Pumps were lowered into others, sucking out the trapped water.
After about four weeks of drilling, Peillex said, the scientists estimate they have reduced the pressure by about half.
But as the work progresses, the specialists have raised a new fear. The glacier reaches more deeply into the rocky pocket than previously believed; it is now estimated at more than 230 feet. By draining the water and reducing the pressure gradually, Peillex explained in an interview, the scientists worry they might weaken the walls of ice, leading to a collapse that would send the remaining water rushing out in a deadly wave.
"Here in the mountains, we don't control everything," said Rosend'al Garcia, an employee of the Mont Blanc Co. who directs hikers and climbers onto mountain trails after they alight from a little train that shuttles them up from the valley.
Nevertheless, Peillex said, local and national leaders will have to decide whether to continue at the present pace or, as the scientists have recommended, send up more equipment to accelerate the drilling and evacuate the water faster.
Using magnetic detection devices similar to the scanners that allow doctors to see within the human body, the specialists estimated the glacier had entrapped between 2.3 million and 2.8 million cubic feet of water, the equivalent of more than 20 Olympic-size swimming pools.