fjord landslide – A huge landslide in Alaska’s Tracy Arm triggered a long-lasting seiche and tsunami-like waves, underscoring risks in busy tourist waters.
A massive landslide into a fjord generated enough force to send tsunami-like waves rolling through the surrounding region, in a rare sequence of events that was strong enough to register worldwide.
The collapse involved about 63.5 million cubic meters of rock plunging into the water.. As the impact transferred energy to the fjord, the resulting seismic activity propagated across the planet.. Sensors around the globe recorded the cascading waves, and the measured energy was comparable to that of a magnitude 5.4 earthquake.
Inside the fjord, the water did not simply surge and settle. Instead, the disturbance produced a 66-second long-period seiche, a standing wave that reverberated back and forth. That oscillation persisted for roughly 36 hours, meaning the fjord kept “ringing” long after the initial rockfall.
Researchers warned the danger could have been far worse if the timing had aligned with peak activity in the area. The report emphasized that Tracy Arm is among the most heavily visited tourist zones, with frequent boat traffic and dense human presence during summer months.
During the summer, more than 20 boats can pass through the Tracy and Endicott arms each day.. The traffic includes up to six large cruise ships. and the report noted that a landslide occurring only a few hours later—during the height of tourist activity—could have turned the event into a catastrophic disaster.
Even though the collapse happened early. at 5:26 in the morning. it was still intense enough to terrify people near the water.. On Harbor Island, about 55 kilometers away, kayakers noticed water moving past their tents roughly 20 minutes after the landslide.. The sudden flow was strong enough to carry off some gear. and one of the kayaks was taken in the surge.
The disturbance also appeared in other nearby locations. In No Name Bay, observers aboard a motor vessel reported wave activity coming from the direction of Tracy Arm: a cresting wave estimated at about 2 to 2.5 meters moving toward the beach, followed by a second wave around 1 meter.
Farther from the source. a small cruise boat anchored at Fords Terror. about 85 kilometers away. encountered a surge that rose and then receded.. The crew reported water pouring over a nearby sandbar. lifting their vessel by roughly three meters even as the tide was falling.. They said the surge lasted until about 11 a.m.. after which their skiff was left stranded on dry ground within minutes of the water pulling back.
At the mouth of the fjord. a cruise ship carrying around 150 people was anchored in dense fog when the event unfolded.. The captain described seeing strong currents, white water, and a noticeable amount of ice and debris along the fjord edges.. Importantly. the report pointed out that shallow. jagged seabed near the fjord’s mouth can act like a speed bump—reducing wave energy before it reaches ships offshore.
Because that “energy sink” effect helped blunt the waves near the fjord entrance, the report said people aboard the cruise ship were able to avoid injury. The account characterized the outcome as a rare combination of conditions that limited harm.
The fact that a rockfall-generated wave event could both be detected as seismic energy worldwide and also produce prolonged oscillations inside a single fjord highlights how quickly hazards can couple across different physical processes.. Here, a single impact set off planetary-scale seismic signals while simultaneously locking water into a long-lasting standing-wave pattern.
For a tourist region, timing and geography together proved decisive.. Early-morning hours reduced the density of people on the water compared with midday traffic. but the documented impacts—gear lost. vessels lifted. and shorelines affected—show that even relatively quiet conditions do not guarantee safety.
The observations from multiple distances also underline how wave behavior can vary widely over short spatial scales. Some areas saw multi-stage wave crests, others experienced surges capable of lifting boats, and at the fjord mouth, local seabed shape appears to have helped dissipate energy.
Overall. the event provides a sobering reminder that landslide hazards in fjords can generate not only sudden surges but also waves that continue to reverberate for hours.. With daily boat routes in place during the summer. the report’s warning—that the risk could escalate rapidly if such a landslide occurs during the busiest hours—lands with particular urgency for communities and operators navigating these waters.
fjord landslide tsunami seiche Tracy Arm cruise ship safety seismic waves Alaska tourism hazards long-period waves