A river landslide in Canada's Yukon last December caused a tsunami of ice slabs to fly over two soccer fields, damaging trees in the process.
Now new research shows that the damage from this “ice tsunami” was compounded by the destructive power of river ice. However, it was also limited to a smaller area than if the landslide had struck in the summer and created an ice-free wave.
The ice tsunami struck on December 17, 2024, when a steep slope above the Tahini River collapsed without warning. About 4.1 million cubic feet (118,000 cubic meters) of mud and rocks fell into the river, which was covered in ice at the time. The impact created an ice-covered tsunami that washed over 17.8 acres (7.2 ha) of the river and its banks. River ice broke up to 820 ft (250 m) away, and ice chunks over 43 sq ft (4 sq m) were found 656 ft (200 m) from the landslide.
The ice wave washed away vegetation from the banks of the river, demolishing all but the four largest trees on the bank opposite the landslide. Only trees with trunks larger than 11.8 inches (30 centimeters) in diameter remain on this slope.
Some pieces of river ice were overturned with 4 inches to a foot (10 to 30 cm) of sand stuck to them. These slabs froze to the bottom of the river, Kronmiller wrote, and the force of the tsunami tore the river bed along with them.
Landslides are usually caused by melting snow, rain or human activity, but Kronmiller found no evidence of an external trigger event on December 17. Instead, the slope suffered “brittle failure,” meaning it split without any sign of deformation or deformation.
Fortunately, no one was injured in the incident, which occurred 15.5 miles (25 km) northwest of Whitehorse, Yukon, in a rural area. However, the river is a place for active recreation. In winter, people ride along it on dog sleds and snowmobiles, and in summer, river rafting crosses Takhini.
The landslide narrowed the river by 50% and clogged it with debris that could pose a hazard to paddlers for years to come, Kronmiller wrote. A new study has found that the Tahini River will likely take more than a decade to work its way back through the landslide debris.
