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uried deep in the untouched sediments of a lake in the Alps of northwestern France lay the clues to a geological mystery nearly 12,000 years old. But it took the combined efforts of mathematicians and geologists to not only  piece together proof of an ancient natural disaster but also help modern humans protect themselves from future catastrophes.

The origins of our recent study can be traced to 2016, when two geologists from the University of Savoy Mont Blanc (USMB) embarked on an expedition to Lake Aiguebelette. This lake had, until then, remained uncharted territory for sedimentologists, and its sediments held the promise of untold stories.

This initial exploration sparked the curiosity of Mathilde Banjan, whose Ph.D. thesis became a quest to unravel the geological history hidden beneath the lake’s tranquil surface. Over the course of her research, she meticulously analyzed sediment cores, performed radiocarbon dating and identified traces of several ancient earthquakes.

Denys Dutykh

Denys Dutykh is an associate professor of mathematics at Khalifa University.

Among these findings, one event stood out — a major underwater sediment landslide that occurred approximately 11,700 years ago. The triggering of this landslide by one of the detected earthquakes was established, yet one question lingered: Could this landslide have triggered a tsunami?

The enigma of this potential ancient tsunami remained unsolved at the conclusion of Banjan’s Ph.D. This is a mystery that begged further investigation, and thus, the quest continued.

In collaboration with USMB’s Pierre Sabatier, we embarked on a new journey, launching a graduate project to reconstruct this ancient event through numerical modeling. This endeavor was spearheaded by Muhammad Naveed Zafar, our Ph.D. student, under joint supervision. Our approach was systematic: First, we reconstructed the landslide event, validated by geological data. Then, by coupling this reconstruction with a hydrodynamic model, we simulated the generated wave field.

The results were nothing short of astonishing. The simulations revealed that the ancient tsunami produced waves up to 3.5 meters high.

Imagine the scale of such a wave in a serene alpine lake and the sheer force it would have unleashed upon the surrounding landscape. Thankfully, 11,700 years ago, the area around Lake Aiguebelette was sparsely inhabited, sparing ancient communities from what would have been a cataclysmic event.

These findings, published in the Journal of Geophysical Research: Solid Earth, shed light on the complex interplay between seismic activity, sediment dynamics and tsunami generation in alpine lakes. Our study underscores the importance of interdisciplinary collaboration, as it was the fusion of mathematics and geosciences that enabled us to solve this ancient riddle.

The implications of our work extend far beyond Lake Aiguebelette. The methodologies we developed are now being applied to larger alpine lakes, enhancing our understanding of past events and helping us better estimate future hazards in these regions. This research not only enriches our historical knowledge but also equips us with tools to mitigate potential risks.

As we continue to explore the geological mysteries of alpine lakes, we invite you to stay tuned for more exciting discoveries. Each new finding brings us closer to unraveling the intricate tapestry of Earth’s dynamic history, and we are thrilled to share this journey with you.

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