Quick clay forms when glacial marine clay, deposited when Scandinavia was still rebounding from the weight of the Ice Age, loses its salt content through centuries of freshwater leaching. The result is a material that appears solid but can liquefy instantly when disturbed -- stable enough to build on, until it is not. Gjerdrum municipality sits on layers of this clay, and landslides are not new to the area. One destroyed farms and 1,600 meters of road in 1924. Another struck Ask itself in 1973. A third in 1980 hit near the southern edge of where the 2020 slide would occur, and yet another destroyed two houses in 2014. The pattern was clear. In 2008, hydrologist Steinar Myrab warned the municipality about soil erosion and landslide risk, calling for a halt in construction at Nystulia. His warnings went largely unheeded.

The first emergency calls came at 3:51 a.m. Residents reported their homes shaking, then tilting, then moving. The landslide carved a massive scar across Ask village, swallowing several buildings -- most of them homes and apartment complexes where families were sleeping. Ten people were injured in the immediate aftermath, and initial reports listed 26 missing, a number later revised to ten. Emergency responders from across Norway converged on the site: fire crews from Upper and Lower Romerrike, urban search-and-rescue teams from Oslo, Bergen, and Trondheim. On New Year's Day, a 14-person Swedish rescue team arrived to assist. Helicopters from the Royal Norwegian Air Force, including Sea Kings and the newer SAR Queens, circled the devastation.

The first body was recovered on New Year's Day. By January 3, the death toll had risen to seven. On January 5, Norwegian authorities announced they no longer held hope of finding survivors, though three people remained missing. The search continued for months, hampered by the instability of the ground itself. Two more bodies were found on February 9. The last victim was recovered on March 22, 2021, nearly three months after the slide. The names of all ten victims were made public with permission from their families -- a Norwegian practice that gives the dead their dignity rather than reducing them to anonymous statistics.

In the aftermath, a pattern of institutional failure became impossible to ignore. The area had been designated high-risk for landslides as early as 2005. A reassessment was scheduled for 2021 -- one year too late. Construction projects had continued despite the known hazards, and in November 2020, just weeks before the disaster, heavy machinery was used to build a hiking path 150 meters from the eventual slide area. The neighboring municipality of Nannestad had evacuated a hamlet on December 15 after a smaller landslide nearby. Experts and engineers publicly criticized both local and national government for allowing housing developments in areas they had known were dangerous for fifty years. In 2022, police charged Gjerdrum Municipality. King Harald V, Queen Sonja, and Crown Prince Haakon visited the disaster site on January 3 to meet rescuers and displaced families, and the king dedicated part of his New Year's speech to those affected.