The Presses polytechniques et Universitaires Romandes have the good idea to publish this winter a new version of the fascinating book “A tsunami on Lake Geneva”, first published in late 2018. In reality, authors and publishers had no choice. Because, the pages of the first edition barely dry, new archaeological discoveries brought new elements confirming the thesis of the work.
“During the opening of the book, Professor Philippe Schoeneich, expert in the subject, tells us that during the digging of an evacuation canal in Noville, an emergency excavation revealed the presence of a Gallo building. Roman who could have been disturbed by the famous tsunami, remembers Pierre-Yves Frei, author of the book. I think I have turned pale. ”
Gigantic shock wave
But let’s remember the facts, as we can reconstruct them today. In 563, between 30 and 50 million cubic meters of rock stood out from the summit of La Suche, an eminence above Les Évouettes, in Chablais, on the left bank of the Rhône. The power of the fall of these materials into the soft soil of the Rhône delta causes a gigantic shock wave. It triggers a sub-lake landslide and 250 million cubic meters of sediment accumulated on the slopes of the lake collapse towards the depths.
The waves raised by these phenomena are monstrous. Simulations performed at the University of Geneva establish that the highest reached
“The great mountain of Tauredunum […] collapsed so suddenly that it crushed a nearby market town, villages and all their inhabitants at the same time “
How do we know all this? There are several sources of information. Two period texts, first of all, including that of Bishop Marius of Avenches, author of a historical chronicle covering the years 455 to 581 AD. About the 563 tsunami, the pious man had to collect testimonies. He writes: “This year, the great mountain of Tauredunum, in the diocese of Valais, collapsed so suddenly that it crushed a nearby town, villages and all their inhabitants at the same time. Its fall also set in motion the whole lake, 60 miles long and 20 miles wide, which, leaving its two banks, destroyed very old villages with men and cattle. The lake even demolishes many churches with those who served them. Finally, in his violence he swept away the Geneva bridge, the mills and the men and, entering the city of Geneva, he killed many men. ”
This testimony was confirmed in 2010 by two geologists from the University of Geneva, Stéphanie Girardclos and Katrina Kremer, who discovered and measured sediment deposits at the bottom of Lake Geneva from the catastrophe of 563 and deposited in a few hours. Carbon 14 dating of pieces of wood found in these sediments confirms the date of the event. For its part, the geological study of the hills that dot the Chablais in the Chessel, Noville and Rennaz triangle shows that they came from folds, waves of earth raised by the fall of the rocks of La Suche.
New evidence
Thus, when he got his hands on the first edition of his work, Pierre-Yves Frei regretted “the absence of terrestrial archaeological evidence in this file”. However, these were brought to him by archaeologists working in Noville shortly after, in the form of a fragment of wall and other elements of masonry, but also coins, ceramics and other objects, all caught in sediments disturbed by the collapse of the summit of La Suche.
“There, we realized that we had all the elements of the story in hand, notes Pierre-Yves Frei. In order to prepare a reissue of the book, we then returned to our sponsors, who allow us to sell it at 19fr.90. What interests us is that everyone can access it. “
“Now we can fully discover this story”
An extremely modest price for a work of this quality, it must be emphasized. Because Pierre-Yves Frei and his wife Sandra Marongiu, who designed the thing graphically and produced the numerous infographics, do not just tell the story summarized above in detail. The scientific journalist has embarked on a real and fascinating multidisciplinary study, making detours through the medieval manuscripts, Julius Caesar and Swiss migrations, sediment cores, the shaping of Lake Geneva by glaciers, controversies and other disasters of the kind.
“Now we can fully discover this story, with this desire to show that by merging the sciences, we can tell a great story,” he says. Add a rich iconography and the conclusion is obvious: a success.
Created: 12.01.2020, 09h02
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