Eight residences have been swept away by a vast landslide that struck in Norway.
The incident occurred on Wednesday, June 3, 2020, at Kråknes, Alta, a municipality in northern Norway. The landslide struck unexpectedly after a rainfall that occurred on the morning of the same day. It measured around 800 meters in length and 40 meters in height. Fortunately, there were no casualties as most of the structures were utilized as vacation houses and there were uninhabited at the time.
Jan Egil Bakkeby, a local, noticed what appeared to be a tensile crack the day before the major slide. He decided not to evacuate his house but to stay and monitor the situation. He managed to record the incident on camera and provided a stunning video. “I stormed out and fled up the mountainside where I saw it all from a distance. You could say I ran for my life,” Mr. Bakkeby stated. Click the video in the Media section below to watch the moment that the slide sweeps away the residences towards the sea.
A rescue operation immediately began and a man was saved. The landslide movement lasted for hours obstructing emergency crews from entering the affected area. However, authorities ensured that there were no additional people that could have been trapped. “They (rescue crews) have searched visually and using camera equipment. No discoveries have been made,” Sten-Rune Nikolaisen, an on-duty commander, stated.
The mechanism and the causes of the slide have not been officially identified yet, however, it is highly probable that it was a quick clay slide. According to the American Geophysical Union, the incident caught on camera is the second stage of the landsliding, since the footage shows existing damage both at the toe and at the lateral sides of the landslide mass.
Quick clay is a glaciomarine formation that can be found in various locations across the world including Norway, Russia, Finland, Canada and the United States. It is a type of clay that is prone to landsliding since it experiences a loss of strength when it is disturbed. This characteristic property is known as soil sensitivity and is expressed by the strength ratio of the undisturbed and the disturbed material. In quick clays, this ratio can be more than 30 (very sensitive). When disturbed, the material's structure is lost and it tends to behave like a liquid.
Quick clay landslides are extremely hazardous since they occur suddenly and affect large areas. Quick clay may depart from its stable form due to multiple triggering factors (overloading, erosion, rainfalls, slope undercutting, earthquakes etc). Identifying a quick clay slide is challenging as the stratum is usually covered by topsoil and thus, soil sampling and testing should be conducted on the underlayer.
The Norwegian Water Resources and Energy Directorate (NVE) is monitoring the conditions on the surrounding area and is also recording the seabed level. In the following week, soil samples will be retrieved from the area to derive the properties of the material.