How can France be affected?

FOCUS- UNESCO considers that the possibility of a tsunami in the Mediterranean Sea in the next 30 years is very high.

Can a tsunami hit France? If the question may seem hypothetical, the risk is very real, according to UNESCO, which says that such an event is very likely to occur in the Mediterranean Sea in the next 30 years. This wave, caused by the rapid movement of the volume of water, can be caused by earthquakes, volcanic eruptions and even underwater movements.

Although rare, several tsunamis have occurred in Europe. To study the risks, the tsunami warning center CENALT (Atomic Energy and Alternative Energy Commission) analyzed historical precedents. What forms could they take today? What damage can they cause? For Tsunami Awareness Day this Saturday, November 5, we interviewed Hélène Hébert, the center’s national coordinator, who deciphered the different scenarios that could affect France.

Tsunami threat in the Mediterranean Sea

Earthquakes are the main cause of tsunamis. The Nice region is particularly prone to this, several cases of this type have already been reported. For example, in the winter of 1887, during the Nice Carnival, a tsunami reached the coast around 6 am, killing 8 people and injuring 55 in the Alpe-Sea islands. It was particularly deadly in the Italian region of Liguria, where 635 people died.

A house in Nice destroyed in the Riviera earthquake, 1887. Illustration for Our Place and Its Story, edited by Robert Brown (Cassell, 1890). Look and Learn / Bridgeman Pictures

Contrary to what we can imagine, the height of the waves did not reach 15 meters. “They measured one or two meters“, – corrects Hélène Hébert. “A sea current of 50 cm of water can be particularly devastating: it can reach speeds of 40 km/h and then carry away fragile people, the elderly and even children.“, adds Hélène Hébert, who adds that this scenario is particularly disturbing. “A flood of several meters will last for several hours and will have an economic impact and ultimately cause human casualties.»

Algeria edge in the south of the western Mediterranean Sea,it is also exposed to very significant seismic zones“, continues Hélène Hébert. We remember the strong earthquake in Algeria in 1980 or in 2003. The earthquake in Boumerdes on the Algerian coast caused waves that crossed the Mediterranean Sea: two to three meters high could be observed in the Balearic Islands. In France they were up to one meter high.Hundreds of boats were damaged in the Balearic Islands.

Tsunami threat in the Atlantic Ocean

If the Mediterranean Sea is most affected by the tsunami risk, the Atlantic Ocean is not left out. Here are the fieldstsunamigenicis listed. History reminds us of this with the tsunami that devastated the city of Lisbon in the 18th century.

On November 1, 1755, a very strong earthquake destroyed the city of Portugal. A few minutes or even a few hours later, a tsunami came with waves five to fifteen meters high. The port on the Tagus and the city center were also flooded. “The Gulf of Cadiz in Portugal, Morocco, Spain was in the foreground and at the same time it was affected by almost quite high waves. What we saw in Japan in 2011. The French West Indies also observed waves of three to four metersHélène Hébert commented. Between the earthquake, tsunami and fires, 100,000 people in Lisbon were victims of this earthquake and its indirect consequences.

Earthquake in Lisbon, Portugal, November 1, 1755. Colored woodcut. Granger/Bridgeman Pictures

This tsunami is one of the most significant natural disasters in the Atlantic Ocean. The French coast was more or less protected by the configuration of the Iberian Peninsula. “However, we believe that with numerical simulations, this tsunami could potentially affect certain coasts of the Atlantic coast. “, warns Hélène Hébert. “It happened three centuries ago, and is therefore as likely to happen again tomorrow as in a century or two. In this region, it is estimated that such tsunamis are possible approximately every 400-500 years.“.

The rock falls

Apart from earthquakes, tsunamis can also be caused by other factors such as rockfalls and avalanches. This is what happened on October 16, 1979, as a result of a landslide at the site of Nice airport: a tsunami flooded several districts of Antibes and Nice, an almost four-meter-high wave in La Salis caused material damage and the death of about ten people . “Up there, there is an underwater depression that causes the sea to swell. It is impossible to predict such a phenomenon. When it dissipates, large destructive effects occur in front of the source“, explains Hélène Hébert.

On October 16, 1979, the boats, driven by the tidal wave, climbed the floating bridges of the port of Nice. ERIC GAILLARD / ARCHIVE / AFP

Least likely scenarios: volcanoes and meteorites.

Other events can cause tsunamis, but are less likely. Volcanoes, especially:We have a recent example in Tonga with the 2022 Hunga Tonga eruption. The nearest islands received waves reaching a height of fifteen meters; Oceania, America and Asia were also affected by these waves.»

You have to understand that when a volcano explodes, the whole building turns to dust.It can create a wave both because it sinks to the bottom of the sea, and because the explosion is felt in the atmosphere, it creates waves. The combination between the atmosphere and the water layer is called a meteotsunami.“.

Eruption of Hunga Tonga in 2022. HANDOUT/REUTERS

The final scenario of a small possibility: a tsunami caused by a meteorite, like the one in the Gulf of Mexico 66 million years ago. The meteorite created a wave 150 meters high, which could have caused the extinction of the dinosaurs. It turns out that yes, in these cases, tsunami-type, more complex and cataclysmic events can occur.“. But this is very rare, concludes Hélène Hébert.

Leave a Reply

Your email address will not be published. Required fields are marked *