Although the Mediterranean seems a calm sea, throughout history it has demonstrated that it is a destructive force. This is what can be deduced from remains found recently during an archaeological excavation in Estepona which shows that the town was hit by at least two tsunamis, one in the ninth century and the other between the first and fourth.
Archaeological excavations normally bring to light information about ancient civilisations, but geo-archaeology is different: it studies geological phenomena such as the formation of rivers, mountains, earthquakes, volcanic eruptions and other natural occurrences. In one of the many excavations which are being carried out in the oldest part of Estepona, a layer of sediment has been found which could correspond to a seaquake.
Experts from the Autonomous University in Madrid and the University of Cambridge have confirmed that Estepona suffered a tsunami in the ninth century, around the year 881, during the Moorish period, and they believe there could have been a previous one centuries before. If this is proven, it would be the first and only geo-archaeological finding of a tsunami in southern Spain at those times.
Dr Carlos Arteaga, of the Autonomous University of Madrid, who is coordinating these works, believes the first seaquake took place in Roman times. Afterwards, the sediments showed that it formed a dune, the land stabilised and the second seaquake possibly took place in the ninth century.
"Until now there was nothing to indicate that there had been this tsunami, only indications from the Moorish period," he says.
In order to detect a paleotsunami and differentiate it from a major storm or wave there needs to be, as well as the sediment, material from very deep under the sea and continental material. According to Dr Arteaga, the material from a simple storm would only reach a depth of 20 metres and the waves no more than six metres, maximum. In a tsunami, however, the waves would be about ten metres high. They would go far deeper than 20 metres and also, as the wave retreated, it would drag continental material with it. It would also drag the base ground, which in geological language is called an 'erosive scar'.
For the inhabitants of Estepona in the ninth century, this must have been a catastrophe because it would have destroyed a large part of the town. However, Dr Arteaga says that although a gigantic wave, 12 or 13 metres high, would have caused destruction, thanks to the city walls the population was protected. "The protective dykes they use in Japan today have the same effect as the ancient walls," he explains.
The experts say these findings are important because they will help to predict future catastrophes, "because if they happen once they can happen again". They also provide extra information about the seabed.
Sean Teylor and Sayontani Neogi, of the University of Cambridge, say more will be known when the findings are examined in a laboratory. They will remove complete blocks of the floor, using extreme caution, because they have a high sand content and could easily crumble. The archaeologists will then impregnate them with resin to solidfy them and cut them into very fine layers for examination under a microscope. "That way we will see what minerals there are, whether there are bones, and lots of small details which will provide us with a great deal of information," says Teylor.
Arteaga stresses that it was a very "lucky" discovery, finding evidence of two natural and such outstanding events in the same place.
The mayor of Estepona, José María García Urbano, says this finding "puts Estepona on the international scientific map because anyone who wants to study these natural phenoma is going to have to come here to do it".
The municipal archaeologist, Ildefonso Navarro, and the university experts say the work of the Arqueotectura company deserves praise, because these levels, where only earth can be seen, often pass unnoticed by the archaeologists who are looking for pieces of ceramics or iron.
Navarro, who is an expert in the history of Estepona, says that a Moorish author in the 10th century mentioned this seaquake, but in a generic fashion for the whole of Al-Ándalus.
The Lisbon earthquake of 1755, which resembled a seaquake in the Atlantic, was documented, but in the Mediterranean the effects were only felt on land. They were serious enough to demolish the church of Los Remedios in Estepona.