When millions of tons of rocks fell a kilometer into an Alaskan fjord last year, it started one of the biggest. tsunami ever recorded, a monstrous wave 481 meters higher than the CN Tower’s highest viewing platform, a new study shows.
Dan Shugar, an associate professor at the University of Calgary and corresponding author of the study, says the scale of the Tracy Arm Fjord tsunami shows the catastrophic potential of such waves and why their risk should be a stronger focus for policymakers, especially in British Columbia.
“On the West Coast, we have Prince Rupert and Port Alberni, we have cities at the head of some of these fjords,” Shugar said.
“There’s also a pretty big ecological impact, you know, there’s a lot of trees that were completely wiped out and habitat and maybe animals, etc., that were wiped out by this tsunami.”
The study, published in the journal Science on Wednesday, finds that the tsunami in the southeast Alaska region near the northwest border of BC might not have happened but for the rapid retreat of a glacier that would have been in the path of the landslide.
He concludes that continued warming, along with “increasing exposure due to expanding infrastructure and cruise ship tourism”, means that landslide-triggered fjord tsunami risks are increasing.
Get the latest national news
Get the latest Canadian news in your inbox as it happens, so you never miss a trending story.
“Similar risk cascades could result in future disasters,” he says.
The study says that at 5:26 a.m. on August 10 last year, a landslide of more than 64 million cubic meters fell 1,000 vertical meters into the narrow and deep Tracy Arm fjord.
The resulting wave had the second highest wave – or height on land above sea level – ever recorded at around 481 metres.
The fiord usually sees about three cruise ships a day, but in the summer months more than 20 ships visit the nearby Tracy Arm and Endicott Arm fiords daily.
Fortunately, the only cruise ship in the fjord at the time was not in the path of the tsunami — it would have been “unsurvivable” for cruise ships at the head of the fjord, said Shugar, an associate professor of earth and environment at the University of Calgary.
The landslide lifted the fjord like water running down the sides of a bathtub, Shugar said.
The research, which also involved academics from Alaska, Denmark, Britain and elsewhere, found that the South Sawyer Glacier near the slide had retreated significantly, about 500 meters, in the months before the landslide.
If it hadn’t retreated, the landslide would have collapsed onto the glacier’s ice or not fallen at all, he says.
Shugar said the warming near the fjord in the past 200 years or so could be blamed almost entirely on humans, and that this had led to the thinning and retreat of the glaciers.
He likened the landslide to a child cleaning out their room by filling the closet full of teddy bears and other junk — then closing the door.
“The door is the rock wall, but it’s being held there by the latch, isn’t it? And the latch is the glacier,” he said.
“And you pull the icicle, you open the door and the door opens and all the teddy bears fall out.”
Shugar said he doesn’t believe the potential tsunami should stop cruise ships and tankers off the Canadian coast.
However, with cruise tourism on the rise and the potential for increased tanker traffic — amid talk of a new oil pipeline on the BC coast — there may be a threat from such tsunamis.
“We really need to look at these slopes very carefully to assess the risk or danger they pose and think about investing in all kinds of instruments that might be able to provide early warning,” he said.
He said the Geological Survey of Canada is already studying the fjords’ hazard potential, but that it should be considered by policymakers on a national scale.
&copies 2026 The Canadian Press
