A Rockslide that Struck a Chord—Literally
On September 16, 2023, a massive 25-million cubic meter rockslide thundered down a mountainside at Hvide Støvhorn, East Greenland, before plunging into the Dickson Fjord. The resulting impact wasn’t just local — it echoed across the globe. While landslides causing tsunamis isn’t entirely new, what happened next was unprecedented. The collision created a 200-meter-high tsunami that eventually morphed into a “seiche” — a rhythmic oscillation of water within the fjord. But this was no ordinary seiche. It pulsed with such precision that it emitted a seismic signal at a constant 10.88 millihertz frequency, ringing like a bell around the Earth for nine consecutive days.
The idea that an event in Greenland could send vibrations detectable from seismometers as far away as Germany and Japan might seem like the plot of a science fiction novel. But it’s science fact — and it’s causing a shift in how geophysicists think about the relationship between water, land, and seismic energy. As stated by Alice-Agnes Gabriel (LMU): “climate change is shifting what is typical on Earth, and it can set cascading events into motion – to unravel the data these events produce we need to integrate simulations and data, as is one of the main project goals of DT-Geo.”
How a Seiche Becomes a Global Signal
To understand this event, imagine filling a bathtub with water. Now, picture pushing one end of the tub hard enough to send water sloshing back and forth. If the tub was long enough, that sloshing could continue for hours. In the case of Dickson Fjord, however, that “sloshing” — or seiche — lasted for nine days. Unlike the bathtub, the fjord is subject to gravity, water resistance, and complex geological structures, all of which combine to create a phenomenon as difficult to predict as it is rare.
The seiche wasn’t just contained within the fjord. It had a distinct pulse that acted like a metronome for the planet. This frequency (10.88 mHz) matched that of seismic Rayleigh waves, which can travel vast distances through the Earth’s crust. The rhythmic force of the seiche essentially “pushed” on the Earth’s crust like a person tapping a drum, sending that precise frequency around the globe.
Scientists have previously seen similar signals during volcanic eruptions, but nothing on this scale from a landslide. DT-GEO’s role in isolating and identifying this signal was pivotal. Using a combination of satellite imagery, fieldwork, and advanced modeling, they managed to reconstruct the series of events with clarity.
A New Chapter in Seismology
This discovery is much more than an isolated curiosity. It provides insight into how the cryosphere (Earth’s frozen regions) and hydrosphere (water bodies) can interact with the lithosphere (Earth’s crust) in a way previously unseen. With climate change accelerating the melting of glaciers, the frequency of landslides in polar regions is expected to increase. Each of these events has the potential to create more of these long-lasting seismic signals.
For DT-GEO, this work represents a landmark moment in the study of “natural laboratories” like Greenland’s fjords, where unpredictable environmental conditions offer a chance to observe Earth’s dynamic processes in real-time. Their findings suggest that these ultra-long-duration seismic signals might serve as an early warning system for future landslides, tsunamis, or seismic shifts.
Why It Matters for the World
This discovery isn’t just about Greenland. It’s about the entire planet. The ability to detect and interpret seismic signals like this could lead to better predictions of landslides, tsunamis, and even sudden shifts in tectonic plates.
For coastal communities vulnerable to tsunami events, it could be a game-changer. A seiche-generated seismic signal might offer early indications of pending disasters, potentially giving residents crucial minutes to evacuate. This is no small feat, as tsunamis often strike with little or no warning.
DT-GEO’s Role
DT-GEO researchers played a key role in the recent study, not just collecting data but leading the seismic modeling efforts that helped confirm the link between the fjord’s oscillations and the global seismic signal. This work illustrates their ability to bridge various scientific fields, from seismology to climate studies and disaster prediction. As Finn Løvholt (NGI) noted, “DT-GEO team members were involved in many different aspects of this interdisciplinary study, demonstrating the advantages of a project that connects scientists across disciplines.”
For DT-GEO, the approach to science goes beyond just observing the Earth — it’s about anticipating its behavior. By combining machine learning, advanced simulations, and fieldwork, the team showed how these tools can come together to deepen our understanding of natural events.
The project involved a large, international consortium of seismologists, tsunami modelers, geologists, acousticians, and others, all working together to combine data and models to solve the puzzle. This collaboration stood out for its efficient communication; whenever specific data or insights were needed, experts from different fields were able to provide them quickly.
DT-GEO was particularly involved in landslide and tsunami modeling, a critical component of understanding the event. One of the key approaches was using two different models to cross-check results, helping to confirm the seiche as the source of the long-period signal.
Read the full paper in Science: Science Paper Link
