The skyscraper-sized tsunami that vibrated through the entire planet and no one saw

Dickson Fjord in August 2023. Just a few weeks later, a large chunk of the mountain would slide into the ocean. Wieter Boone / Flanders Marine Institute

Earthquake scientists detected an unusual signal on monitoring stations used to detect seismic activity during September 2023. We saw it on sensors everywhere, from the Arctic to Antarctica.

We were baffled – the signal was unlike any previously recorded. Instead of the frequency-rich rumble typical of earthquakes, this was a monotonous hum, containing only a single vibration frequency. Even more puzzling was that the signal kept going for nine days.