In the Norwegian Geiranger Fjord lies one of the most patrolled mountains on the planet. It is not for nothing that Aknesfjället – or Aknes – threatens the collapse of millions of cubic meters of rock which, if they fell into the water, could generate a tsunami in the fjord, … a wall of water that would sweep away towns and tourist attractions in minutes. Models and studies have shown scenarios with waves that would reach Geiranger and Hellesylt in a few minutes, with heights that, in some points, could exceed several tens of meters. A possibility that made Aknes not only an object of academic research, but also a priority for civil protection in Norway.
For many generations, the crack was just a curiosity that children would go around by throwing stones to listen to its echo. But over time, the fracture lengthened and opened up, and by examining historical photos and measurements, scientists confirmed an alarming progression. Between the 19th and 20th centuries, there were episodes of minor landslides in the region; More precise modern measurements have revealed that the active zone extends hundreds of meters in length. There, science has learned to listen to the mountain as if it had a pulse: the previously ignored microtremors are now clues, the humidity of rock joints, the rupture of small plates, the slow and sustained acceleration of the crack… The Aknes/Tafjord project, initiated at the beginning of the 21st century and consolidated over the last decade, deploys a technological network combining field instruments and remote sensors. GPS stations and extensometers were installed to measure specific displacements; technology for high-resolution topographic reconstructions; seismic networks and geophones which detect microseisms associated with internal movements; and InSAR (satellite radar) and GB-InSAR systems and aerial photogrammetry to capture larger-scale deformations. In addition, the sensors and columns anchored in the massif send information in real time to an alert center which processes the data 24 hours a day, every day of the week. A wide overlap of methods that makes it possible to distinguish patterns, validate anomalies and define alarm thresholds.
Unstable Areas Laboratory
The monitoring is not only scientific: Norwegian authorities, in collaboration with geotechnical institutes and municipalities, have designed evacuation protocols and early warning systems. The objective is not to predict with absolute certainty a collapse, which remains impossible to predict today, but to obtain robust signals such as accelerations in the speed of movement, peaks in microseismicity or modifications in the hydraulic response of the massif, which make it possible to issue alerts sufficiently in advance to evacuate residents and tourists occupying the banks of the fjord. In the simulations, the time windows are narrow: in some models the first wave would reach Hellesylt in less than five minutes and Geiranger in less than ten, the warning and reaction capacity must therefore have chronometric precision. For all these reasons, Åknes has become a living laboratory for monitoring unstable slopes, providing methodologies applicable to other locations with similar risk.
About The Author
