23
Jul
2004

Rock falls a higher risk as climate warms

JAMES REYNOLDS
ENVIRONMENT CORRESPONDENT

The Scotsman
July 22, 2004

MANY of the world’s most spectacular high-mountain rock faces could start crashing down at alarming rates due to global warming, scientists are predicting.

As well as changing the very shape and appearance of classic mountains, some of the climbs themselves could also disappear as higher temperatures destabilise the rocks by thawing the permafrost beneath them.

In Europe, concerns about disintegrating rock faces were brought into sharp focus last year when at least 50 people died in the Alps as a result of collapsing escarpments.

In a year that saw some of the highest summer temperatures for decades, many mountain paths, including classic routes on Mont Blanc, were closed because of the increased risk to mountaineers.

On the Matterhorn, the collapse of part of the Hornli Ridge, the easiest and the most popular route up the mountain, stranded 80 climbers who had to be airlifted off by mountain rescue services.

Because there was no unusual snowfall or rainfall to trigger the incidents, geologists suspected that thawing of the permanently frozen interior of the rocks was to blame.

Now, a new computer model, developed at the University of Zurich, adds weight to this explanation, the journal New Scientist reports today.

The scientists abseiled on to 22 rock faces in the Alps three years ago, drilling small holes and inserting devices to record the temperature of the rock.

After a year, they recovered 14 of these devices and used the data to fine-tune a computer model which shows how variations in climate affect the temperature of the rocks.

Stephan Gruber, one of the researchers, said: "Our model suggests that higher summer temperatures will heat some rock faces to such an extent that the permafrost, which glues the cracks and joints together, will melt and decrease the stability of the rock face."

Michael Davies, from the University of Dundee, found from his own work that rock faces could become unstable well before permafrost melts completely.

Ice normally acts like glue and helps to hold rocks together, but experiments he carried out showed that, as it begins to warm, permafrost loses its strength, making the cracks and joints in a rock face less stable. "This means temperatures don’t have to rise above freezing to make a rock face become unstable," he said. "Global warming could have an effect sooner than we thought."

One-quarter of the Earth’s land surface is frozen, with some of this permafrost in mountain ranges.

If global mean temperatures rise by as much as 1.3C over the next 20 years, as predicted, geographers believe that mountain ranges from the Himalayas to the Andes will be affected as permafrost starts to thaw.

Ian Hey, the technical and safety officer for the British Mountaineering Council, said: "Last summer was an unusually hot year, and it did seem that there were a greater number of rock falls of all sizes round the Alps.

"I saw a couple on the Petit Dru, an imposing and beautiful rock pillar that towered over the French Alpine resort of Chamonix, when I was out there last year. But the largest and most publicised rock collapse happened on the Hornli Ridge on the Matterhorn, the standard and easiest route up and down the mountain.

"Fortunately, no-one was hurt, but anyone above the collapse had no easy way down, so the Swiss mountain rescue service had to helicopter about 80 people off the mountain."

He added: "If this proves to be a long-term threat, then obviously it will have consequences for the sport of mountaineering and climbing.

"There have been years going back where very bad rock fall was also experienced, so I think it might be a bit too soon to say that it is a major problem," he went on.

"You could also look at the concern over lack of snow cover in Scotland in winter that is affecting skiing, which is obviously also a problem, and this has impacted on ice-climbing in the area as well."

//news.scotsman.com/scitech.cfm?id=836672004


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