New data on catastrophic tsunamis in the Mediterranean: history may repeat itself

The Mediterranean almost always seems like a calm sea but, as various recent studies have warned, the risk of major catastrophes is by no means ruled out. And one of the possible natural tragedies is a tsunami that reaches the Mediterranean coasts, for example, after an earthquake or a volcanic eruption.

In June 2022, during the presentation of the international Tsunami Ready system, the Secretary of the Unesco Oceanographic Commission (IOC), Vladimir Ryabinin, recalled that there is a high probability that in the next 30 years there will be tsunamis in the Mediterranean that They can be considered tsunamis. In fact, various scientific teams have studied the risk and possible consequences of this type of phenomenon on our coasts, such as the model presented in 2015 by experts from Italy and Greece.

A new historical review study now shows that the danger is not new, leaving of course that it can be repeated.

Specifically, this new contribution has been published in the Journal of Iberian Geology and its authors with Javier Lario, Professor of External Geodynamics at the UNED Faculty of Sciences, Chris Spencer (UWE Bristol) and Teresa Bardají (UAH).

In this work, from some deposits found in Cabo Cope, Murcia, the researchers have recorded an event, dated between approximately 800 and 1,400 years, that caused large accumulations of blocks in this region of the Murcian coast. From the results, it is clear that “catastrophic tsunamis have also taken place on the Spanish Mediterranean coast, phenomena that could be repeated today”, summarizes the UNED in an informative note.

Javier Lario points out that, knowing these data, the need to “implement alert plans in the coastal areas of the southern Mediterranean to educate the population and raise awareness is more justified.

“We are talking about 70% of the population living on the coasts. If it affects in summer, the floating population of coastal areas is much higher than that of winter. Clearly, a tsunami now would have a very big impact,” Lario said in a statement released by Sinc.

“We applied the methodology that we had developed to see if it could be due to large storms or tsunamis, since the Murcia area can have tectonic activity from earthquakes,” explains Javier Lario, “and we have seen that it could be the result of a tsunami.” Although the waves of a major storm may be greater than those of a tsunami, they would not have the capacity to drag these blocks up to 4 meters above sea level, which reach 17.7 tons. With his work, Lario and his colleagues are mainly trying to distinguish between these two types of phenomena. “It is interesting to differentiate it because with climate change we are seeing an increase in major storms and even hurricanes, which have a similar geological record”, comments the geologist.

On the other hand, they seek to focus on the risk that exists in the western Mediterranean belonging to the Spanish coast. “It is true that the geological record is very local,” says Lario, “but for that geological record to remain, it had to be something more regional. In fact, in the north of Castellón there are colleagues who have found deposits of the same type”. Although this region of the coast differs from other more active eastern areas of the Mediterranean – such as the area of ​​Italy, which has great volcanic activity, or Turkey -, there are active faults, especially in the Alboran Sea.

“Through the studies, what we try to show is that, although in the instrumental period no high-risk tsunamis have been recorded in the area, there is a nearby geological record that tells us that they have occurred,” explains Javier Lario. Thanks to these records, recurrence periods can be established to alert the authorities of possible phenomena similar to the historic Lisbon tsunami that devastated the Andalusian coast. “We are talking about 70% of the population living on the coast. If it were to affect summer, the floating population of the coastal areas is much higher than that of winter. Clearly a tsunami now would have a very big impact”, comments Javier Lario. “The population tends to be in the lower areas associated with the riverbanks or close to the beaches, which are easier to develop, in addition to also affecting the associated industry.”

Cities such as Huelva and Cádiz have begun to create evacuation plans, but Lario explains that it would be necessary to implement it in the southern Mediterranean coastal areas to educate the population and raise awareness. But the absence of a great tsunami in the historical memory of this region makes its implementation more complicated. Likewise, the erosion and degradation of the coast by human action could greatly affect the severity of a possible tsunami. “The processes of rising sea level or erosive processes of the beach and the natural protection that the coasts have make it more vulnerable in the event of a tsunami. If we have lost sand or a coastal area and the water can penetrate further inland, and when a tsunami comes, the effect will be worse”, warns the geologist.

The Ministry of the Interior together with the National Geographic Institute and the General Directorate of Civil Protection have developed a State Tsunami Plan, recalls the UNED. Through the analysis of the danger of tidal waves on the Spanish coasts, this plan represents a starting point for autonomous communities and localities that approve to implement their own action plans in the risks of tsunami flooding that could occur within their territories. . This informs society of the data extracted from investigations such as the one carried out by the geologist Javier Lario and also facilitates the dissemination of knowledge of general interest, such as the causes and consequences of events of this type.