• Switzerland's news in English

'Geneva hit by tsunami' — 1,500 years ago

AFP · 29 Oct 2012, 10:44

Published: 29 Oct 2012 10:44 GMT+01:00

Facebook Twitter Google+ reddit

The incident suggests Geneva and Lausanne remain vulnerable today, as do other cities on the edge of mountain lakes and high-sided fjords, they said.

"The risk is underestimated because most of the people just do not know that tsunamis can happen in lakes," Katrina Kremer, an Earth scientist at the University of Geneva, told AFP.

In a letter to the journal Nature Geoscience, Kremer's team said they delved into the "Tauredunum Event," an episode that occurred in AD 563.

A contemporary account by a French bishop, Gregory of Tours, described a catastrophe that was as bewildering as it was terrifying.

A giant wave charged down the lake, destroying villages and herds of animals, and then passed over the city walls of Geneva, on the western tip, where it drowned several people.

Was this a "lake tsunami"? Some experts have argued so.

They point to evidence that part of a mountain slipped into the River Rhone about five kilometres from where it flows into Lake Geneva at the lake's eastern point.

Keen to find out more, Kremer's team swept the deepest part of the lake with high-resolution radar.

They uncovered a huge, oval-shaped pile of sediment, more than ten kilometres long, five kilometres wide and five metres thick.

The thickest point was in the south-east, indicating an origin in the "delta" where the River Rhone flows into the 73-kilometre long lake.

The team then took four cores of the sediment and carbon-dated tiny vegetal remains embedded in it. The estimated age of this debris is between AD 381 and AD 612.

"Since the AD 563 event is the only significant natural event recorded in historical accounts within our calculated age interval, we consider our dating results to be a strong indication that the deposit is linked to the AD 563 rockfall and tsunami," the letter said.

On that fateful day, believes Kremer, the shock of the rockfall caused the nearby delta's built-up slopes to collapse.

Long, narrow and crescent-shaped, Lake Geneva created ideal conditions for funnelling the maelstrom of mud and water into coherent, amplified waves.

"Our numerical simulations with a shallow water model show that delta collapse in the lake generates a large tsunami at various locations along the shore, where a wave of 13 metres is observed after only 15 minutes, and at Geneva where a wave of eight metres arrives 70 minutes after the mass movement is initiated," the researchers wrote.

Story continues below…

In the 6th century, a wave of this height would certainly have had the impact on Geneva that Gregory described, and today would completely inundate large parts of the inner city, they warned.

Over the last 10,000 years, several big slips have occurred, and they could happen again as sediment is building up on the delta slopes -- posing a threat to more than a million people living on the lake shores, said the letter.

"Our study highlights that not only cities located on sea coasts and fjords are at risk from destructive tsunamis, but so are densely-populated lake shores," it said.

Tsunamis are usually associated with an earthquake on the sea floor that occurs close to a coast. The quake raises or lowers the sea bed, and the displaced water forms waves.

But research since the 2004 Indian Ocean tsunami suggests that amplified waves can be created in a range of other scenarios, ranging from volcanic eruptions to dam breaks.

Facebook Twitter Google+ reddit

Your comments about this article

Today's headlines
'Protect Swiss waterways or lose our fish': WWF
Photo: Richi Stadelmann/WWF

Eighty-five percent of fish species in Switzerland are under threat, according to a report by the World Wildlife Fund (WWF).

SBB pilots new annual pass – costing 12,200 francs
The 'door-to-door' pass includes use of an electric car. Photo: SBB

Swiss federal railways (SBB) is looking for 100 people willing to pilot a new annual transport pass that includes use of an electric car.

Immigration to Switzerland falls as emigration rises
File photo: The Local

Immigration in Switzerland has fallen considerably this year, according to official figures.

Wawrinka aces his way into Basel quarterfinals
Photo: Fabrice Coffrini/AFP

The home favourite returns to the quarterfinals of the Swiss Indoors for the first time in five years.

Illegal immigrant dies after setting himself on fire
The victim was treated at University Hospital Zurich. Photo: University Hospital Zurich

The 45-year-old Tunisian was threatened with deportation.

Swiss government rejects call for second immigration vote
Photo: Justus Blumer/Christophe G

The Swiss government has rejected a popular initiative calling for a revote on plans to limit immigration.

Bern: companies should report salary inequality by law
File photo: Fabrice Coffrini/AFP

The Swiss government wants to force small companies to examine their rates of pay every four years.

Husband in custody after Orbe body identified
File photo: Bas Leenders

The deceased is a 55-year-old woman who lived in the house with her husband.

Presented by MoneyPark
How to get a mortgage in Switzerland
Houses in Zürich. Photo: Pixabay.

Ready to buy? Here’s what you need to know as an expat about Swiss regulations, how to finance your purchase, and why you should use a broker.

Autumn in Switzerland: ten stunning Instagram photos
Photo: Swiss Tourism/Jan Geerk

Switzerland is beautiful in all seasons, but as these photos show, autumn is a special time in the alpine country.

Photo: Unterirdisch Ueberleben
Inside Switzerland’s largest nuclear bunker – 40 years on
Sponsored Article
Last chance to vote absentee in the US elections
Photo: The Local
Ticino firefighters rescue cow from swimming pool
Photo: Antoni Da Campo
Vegan wins battle to be accepted by Swiss army
Photo: Swiss Tourism
Ten Swiss ski resorts named most expensive in Europe
Photo: Randy Kashka
Swiss women will ‘work for free’ for the rest of year
Photo: Swiss Tourism
Montreux throws hat in Olympic rings
Photo: Swiss Tourism
Seven things you’ll miss about Switzerland if you leave
Photo: Richard Juilliard/AFP
Man makes Geneva airport bomb threat ‘for a joke’
Photo: AFP
Solar Impulse team reveals plans for unmanned plane
File photo: Martin Abegglen
Swiss to vote on passport rules for 3rd gen foreigners
Photo: AFP
Swiss wingsuit hotspot Lauterbrunnen won’t impose ban
Photo: Swiss Tourism
Six reasons Switzerland isn’t as boring as you might think
Photo: Swiss Tourism
Report: Switzerland one of world’s best places for girls
Photo: The Local
Thief returns Swiss cow bells worth thousands
File photo: Wikimedia Commons
One in three rapists isn’t locked up: statistics
Photo: activistin.ch
Tampon-tax protest turns Zurich fountains red
Photo: AFP
Geneva police to lift ban on bearded officers
Photo: Marcel Gillieron/AFP
Suicide chef’s restaurant keeps Michelin stars
Photo: Lara de Salis
11 things the Swiss get tired of hearing abroad
Photo:  Ivo Scholz/Swiss-image.ch
Survey: expats in Switzerland have money but few friends
Photo: AFP
Swiss press criticize Bern’s 'capitulation' on immigration
Photo: Jura Trois Lacs tourism
German ex-policeman is Swiss city’s new hermit
Photo: Dmitry A. Mottl
Ticino votes to favour local workers over foreigners
jobs available