In September 2023, Earth rumbled .

Seismic monitoring all over the globe registered a strange signal that repeated every 90 seconds over a whopping nine days, petering out in a way never before seen.

Then the same thing happened a month later. Subsequent analysis of those signals determined that the cause of that trembling was likely a giant megatsunami rocking back and forth, slapping against the sides of a fjord in Greenland – generating a standing wave known as a seiche .

Now, scientists have finally actually seen the event, in satellite data captured while the event was in progress. It's the observation needed to confirm that the cause of the seismic signal was indeed a seiche, giving us an answer to the age-old question: if a seiche forms in a Greenland fjord and no one is

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