Andreas Hasler from the Geographical Institute in Zurich says: “If spring and summer are very warm, the events of 2003 could well be repeated.” In plain language, there could be more rockslides on the Hörnligrat. On 15 July 2003, around 1'000 cubic metres of rock came down. Over 90 mountain climbers had to be helicoptered off the mountain and the climbing route was closed for several days. The rock mass of 1'000 cubic metres is equivalent to a cube with a size of 10 x 10 x 10 metres.
The “Hore” under close observation
For several years, a network of wireless sensors has been supplying data on rock movement on the Matterhorn. Researchers from the National Centre of Competence in Research «Mobile Information and Communications Systems» (NFS MICS) are now publishing their findings, which are helping to better understand rockslides and monitor risk zones in areas of permafrost.
In a media release, the SNSF (Swiss National Science Foundation) goes into detail about the mechanisms. The Alpine landscape will undergo great transformation in coming decades as a result of global climate change. The glaciers will recede even further and the number of rockslides must be expected to rise. Experts have been recording an increase in such events in the Alps for several years. This applies in particular to areas of permafrost, where the bedrock is permanently frozen. A rockslide occurred on the Hörnligrat ridge of the Matterhorn in the hot summer of 2003. Inspection of the breakaway point showed that the rockslide had exposed various frozen fissures. A team of researchers around Stephan Gruber from Zurich University thus took a more in-depth look at the unstable area on the Matterhorn.
In summer 2007, Gruber’s group, together with scientists from Basel University and the Swiss Federal Institute of Technology in Zurich, installed a network of wireless sensors on the Hörnligrat ridge. This was within the framework of the PermaSense project by the National Centre of Competence in Research «Mobile Information and Communications Systems» (NFS MICS) and also funded by the Swiss Federal Office for the Environment. The network allowed researchers to measure rock movement in the various fissures over several years. The researchers state that they determined a complex pattern of movement apparently influenced by two factors. When the rock warms in summer, it expands and closes the fissures. When the rock cools again in autumn, it contracts and the fissures reopen. This expansion and contraction gradually changes the geometrical arrangement of the fissure, with the result that over a period of time, the rock loosens.
“The measurement data of recent years gives us valuable information to better understand the processes in areas of permafrost,” says Stephan Gruber. “It will help us with the long-term and targeted monitoring of danger zones.” That frozen rock tends to be less stable in warmer temperatures is an obvious hypothesis. “But we still only know the basics of what is taking place underground.”
Consult local experts
For any Alpine expedition on the Matterhorn to be made in safety, it is advisable to obtain information from the Alpin Center. The local guides are experts on the Matterhorn. They can guarantee the greatest possible degree of safety for their guests; they know the routes and the risks of sudden changes in the weather and rockslides.