A quick-clay landslide disaster occurred in the morning of December 30 in the village of Ask in the municipality of Gjerdurm in Norway. A number of houses have been destroyed and over a thousand people have been evacuated. Unfortunately, ten people remain missing, including children, and chances to rescue them are dimming. Gjerdrum mayor Anders Østensen estimated the number evacuees will likely rise to 1,500 as more danger areas are found, Euronews reports. According to The Guardian, the Norwegian prime minister, Erna Solberg, defined the disaster “probably one of the biggest landslides we have had, and with the biggest consequences”.

Quick-clay landslides are frequent in Norway, Canada, Russia and other northern lands, where many soil deposits have been left in metastable condition after the last deglaciation. These soils look hard and strong, and people have built farms on them for centuries. Quick-clay soils typically formed under the sea, where the salt conferred them a stable structure. After the last glaciation, many soil deposits originally submerged became uplifted, and now we find them in many coastal areas. Rainwater has been infiltrating these clays for millennia, washing away the salts that kept them stable. Construction and excavation works can disturb the delicate equilibrium of these clays. Like a castle of cards, they can collapse suddenly, expelling all the water they were holding in their pores, and transforming in a mud in a matter of seconds. The collapse often starts in a small area but quickly propagates, swallowing trees, houses and roads.

Because quick-clay landslides occur suddenly, they rarely give chances to those caught in the movement. In 2016, another fatal landslide happened in Sørum, some 35 km outside Oslo, where three men working in a farm managed to escape, while other three were buried by the rapidly flowing mud. Another impressive landslide happened last summer in the municipality of Alta, in northern Norway, fortunately without casualties. However, several cabins were lost, and a segment of a coastal highway was destroyed.