Mega tsunami 2025: 481 metre high monster wave - horror scenario like in an eco-thriller

The Tracy Arm Fjord on the Pacific coast in southern Alaska is a popular destination for cruise ships: The journey through the winding, approximately 50-kilometre-long inlet, framed by steep mountains, with the glacier tongue of the South Sawyer Glacier reaching into the water at its end, is considered spectacular.

A horror scenario like in an eco-thriller

It was all the more fortunate that none of the ships carrying several thousand passengers were on site on 10 August 2025 - otherwise the ensuing natural disaster could have had consequences only known from fictional eco-thrillers. Up to six of them usually visit the fjord every day during the summer season.

Early that morning, at 5.26 a.m., the northern escarpment below the mouth of the glacier suddenly began to slide: At least 64 million cubic metres of debris and earth crashed into the fjord in a massive avalanche. The shock was measured as a magnitude 5.4 earthquake.

The monster wave shaves the mountains bare

The water thus displaced in one fell swoop formed a breaking tidal wave, initially 100 metres high and travelling at a speed of 70 metres per second, which surged up the opposite wall of the fjord to a height of 481 metres and shaved all vegetation from the rock.

The run-up, as the height of the surge effect is called, is the second highest value ever documented: the record dates back to 1958, when a tsunami reached a height of 520 metres under similar circumstances in Lituya Bay in Alaska.

Climate change identified as the cause

The reconstruction of the actual event was carried out by scientists at the University of Calgary and published in the journal Science in an article published. In it, the research team led by geomorphologist Dan Shugar also points to possible reinforcing causes.

It is therefore likely that the retreat of the glacier caused by climate change played a role. Without the ice at their base, the steep cliffs would have lost an important support. This has decisively destabilised the slope.

"There will be a next time"

"The fact that the landslide happened so early in the morning was incredibly lucky. Next time - and there will be a next time - we might not be so lucky," said Shugar in Science.

Even though there were fortunately no cruise ships in the fjord, there were still witnesses to the event: strong currents and a rise in the water level were noticed on ships in front of the mouth of the fjord, where the tidal wave was "only" about two metres high.

The water washed around the tents

A group of kayak paddlers who had set up camp on Harbor Island, an island off the estuary, were awakened by water washing around their tents, taking a boat and almost all of their gear with it.

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