Alaska was lucky to avoid disaster after a landslide and tsunami. What about next time? | Alaska

TThe landslide that sparked a powerful tsunami in the interior passage of Alaska early on August 10 was a careful call, say scientists, tour operators and agency officials, with the risk of such events apparently increasing as the glaciers are withdrawn due to climate change.

“This is a historic event,” said scientist Dennis Staley of US Geological Survey of the slide, which occurred in the 50 miles (80 km) arm in the south of Juneau.

“I have the impression that we dodged a bullet,” he continued, to report that no one had been injured, to a destination that can see more than 500,000 annual visitors.

Staley studies the dangers of landslide in Alaska, including in popular tourist areas. Tracy Arm is a close fjord of 30 miles (48 km), with transparent walls looming thousands of feet above the water. It ends on the face of the South Sawyer glacier. The dramatic landscape, which is part of the Tongass national forest, attracts kayakers, boaters and a constant flow of packed cruise ships. But the canal was apparently empty at 5:30 am in the morning on Sunday August 10, while without warning a colossal piece of the Fjord Wall collapsed.

Staley says it is too early to know the precise size of the slide. But by analyzing his seismic signal, he and others estimate up to 100 cubic meters of rock, or more, fell near the face of the South Sawyer glacier. He threw a wave of ocean water an incredible 1,400 feet (425 meters) on the opposite side of the fjord, which will probably make one of the largest waves of this type ever recorded. Staley can see its impact on trees and brushes in satellite imaging and aerial photographs.

A few seconds later, a tsunami estimated up to 100 feet (30 meters) high in the entrance, undressing the forest and brushing from one or the other shore. Thirty miles away, the wave was still 15 feet high (5 meters) while influenced against the island of distant port, a few centimeters from a tent where Sasha Calvey and two other kayakers were camped.

The kayakers woke up to find half of their equipment that had been swept away. A kayak suspended from a bluff, another was stuck against a tree and a third swung in the ocean a quarter of a mile. The water remained chaotic for hours, explains Calvey.

Although they had to be rescued, ending a 78 -day expedition from Washington’s state, Calvey knows they were lucky. If the tsunami had occurred only three hours earlier, when the tide level was 10 feet higher, they may not have survived.

Jeffrey and Christine Smith had planned to anchor their 65 -foot tour, David B, for one night in Tracy. But the rainy weather led them to anchor about 45 miles from there instead. On the morning of the slide, they saw the water rising 10 feet along the shore near their anchorage.

“We felt a little fatal,” said Christine Smith after learning how much they missed the slide.

The landslide occurred a few hours before a tourist ship from Juneau and a National Geographic Tour boat, each with a capacity of more than 100 passengers, had to visit Tracy Arm. Two cruise ships carrying thousands of passengers had each visited the area less than 24 hours earlier. Another cruise ship was scheduled for the next day.

Staley and others marvel at luck, where bad weather, timing early in the morning and a tide has apparently conspired to prevent victims. In another little luck, part of the slide landed on the South Sawyer glacier. If its weight had struck the water, says Staley, the tsunami could have been even greater.

But some geologists fear that luck will run out. The landslides near retirement glaciers seem to increase, in Alaska and elsewhere. A possible cause is that the ice ice, which can have hundreds of feet thick, can help support the mountain walls above them. Scientists struggle if a rapid ice retirement, as in Tracy Arm and around the world can be performed “can take off from mountains” by removing support ice that has been in place for centuries.

Climate change also thaws high altitude permafrost worldwide. When the Pergélison Déget, explains Staley, changes in pressure, temperature and hydrology can cause deep instability in steep slopes. Scientists believe that the Dégel du Pergélisol contributed to a massive landslide and the collapse of the glaciers which destroyed the Swiss village of Blatten earlier this summer.

Staley underlines that it is too early to say what led to the slide from the Tracy arm.

“We have to be careful,” he says. “We cannot say with real certainty what has triggered this event.”

Michael West, the state seismologist who directs the center of earthquakes from Alaska to Fairbanks, is appropriate that it is too early to identify a trigger for the slide, which he calls “incredibly huge”. But he says that it should be noted that this and other landslides causing tsunamis have occurred near the retreat in recent years. He says that it is reasonable to explore the ideas of the denigration and defrosting of permafrost in the Tracy arm, as well as other factors such as recent rain in the region.

In 2015, a landslide near a glacier decreased in Taan Fiord in southeast Alaska sent water to 630 feet on a neighboring slope. A landslide in 2024 near Prince William Sound’s surprise glacier, more than 500 miles northwest of the Tracy arm, caused a small tsunami.

And last summer, a large landslide alongside the Pedersen Glacier declined in the Kenai Fjords National Park near Seward, Alaska, sparked a wave estimated at 60-180 feet.

Scientists also have a suspicious eye on a weak slope recently discovered above the retreating glacier, an hour south-east of anchorage. If he fails, according to the researchers, he could trigger a tsunami in Lake Portage which could slam in a reception center in Chugach National Forest which sees up to 1,000 people a day in summer.

They also monitor an unstable 3,000 -foot slope in the Barry Arm Inlet at Prince William Sound. If he fails, modeling shows that it can trigger a tsunami comparable to that of Tracy Arm. Barry Arm and the surrounding waters are also popular among boaters, kayakers, cruise ships and others.

Since the instability of the Barry arm was discovered in 2020, scientists have installed high -tech equipment to follow precipitation, the movement of slopes and other conditions on the mountain. They hope that work will improve understanding of the links between landslides, glaciers and climate change.

Although no instrumentation of this type was present at Tracy Arm, West says that work at Barry Arm helped geologists quickly identify the event by analyzing the data in real time of more than 250 seismic stations around Alaska.

“This is a new capacity,” said West, explaining that scientists have taken days to locate the Taan Fiord 2015 slide. But using the new method, they identified the location of the Tracy arm shortly after the calls came from boats in the region.

“But that’s where it becomes wild,” continues West.

He says that the examination of seismic surveillance sites shows that a seismic “bursting” occurred on the Tracy Arm site for about 24 hours before the slide, with hundreds of small detectable signals at 100 miles away. They suddenly ended with the slide.

“Not all landslides do this,” explains West, who hopes to seek this phenomenon to better understand possible warning signals.