Malta could be hit by a tsunami at any time, according to scientists who have found evidence that the northeastern coast was once struck by 20-metre high waves.
“Since earthquakes and tsunamis generated from them are so unpredictable, at the moment we’re not sure whether it could happen tomorrow, in 500 or 700 years. However, we do feel confident it is likely to happen again,” Malcolm Bray, who led the University of Portsmouth scientists, told Times of Malta.
Earthquakes and tsunamis generated from them are so unpredictable
“An earthquake could take place soon but the tsunami it causes might be very small, while, at the same time, an earthquake could happen in 100 years and the tsunami could be sufficiently large.”
The four scientists involved in the study have found geological evidence that historic tsunami waves swept over Malta’s northeast coasts reaching 20 metres above sea level in some places.
It was during a trip with students in 2009 that they noticed an unusual accumulation of boulders along the coastline. They spent three years examining the landforms on the northeastern coast with the support of the Department of Geography at the University of Malta and yesterday they published a paper in the international journal Zeitschrift für Geomorphologie.
The paper, by Dr Bray, Derek Mottershead, Philip Soar and Paul Farres, is called ‘Extreme wave events in the central Mediterranean: geomorphologic evidence from the Maltese islands of tsunami’.
The team identified boulders that had been detached from the shoreline and clifftops, some of which split after great impact and were carried inland for distances of up to 100 metres.
Evidence shows the tsunami reached onshore speeds exceeding 20 miles an hour, lifting 70-ton boulders, some of them shattering into smaller rocks as they crash landed.
The boulders were found in about 30 different locations and there was some excellent evidence on the northeast coast of Comino and the northeastern portion of the Marfa ridge, Dr Bray said.
One question that remains to be answered is when the waves actually hit the Maltese shores.
The senior lecturer explained that the team was carrying out carbon dating on marine organisms (shellfish) found attached to a very small number of boulders to understand when these rocks came out of the sea. If they manage to date them, they can then link the boulder to an event that could have led to the tsunami.
The last major tsunamis in 1169 and 1693 were triggered by earthquakes centred on the Malta escarpment (underwater cliff), southeast of Sicily, which directly faces Malta’s northeastern coast and is only 100 kilometres away.
A tsunami in Malta could also have been caused by seismic activity in Greece, where a major event occurred in southwest Crete in 365AD. There was also a tsunami in 1908 but it had only a limited impact on Malta, reportedly causing localised flooding around Msida and Marsaxlokk.
It appears that no event of the magnitude indicated by the new evidence occurred within the past 300 years.
Prof. Mottershead said it was highly likely that there had been other equally devastating waves previously and that there would be more in the future.
The study is not only interesting from a historical point of view, Dr Bray said. It was also of interest to the Maltese as the tsunami could happen again and hit anywhere exposed to the northeast, from Marsalforn through Għadira and Mellieħa Bay downwards.
The northeast coast was now Malta’s most densely populated region and if a similar sized wave struck today it could threaten thousands of people.
“It is not possible to predict earthquakes and if an earthquake does occur, you cannot be sure it will cause a tsunami.
“However, a sufficiently large earthquake could cause a tsunami. So anybody living along the coast who feels an earthquake should keep an eye on the sea and make plans to move to higher ground, which, fortunately, in Malta is never far away.
“In many tsunamis, but not all, the water retreats, exposing rocks or beaches that are usually covered by water. This could be an indication that the wave will come in minutes later,” Dr Bray said.
If a tsunami was triggered from the Malta escarpment, islanders would have about 35 minutes of warning or 80 minutes if it started in western Greece.
Although a warning system could be installed in the Mediterranean, it was very difficult to analyse the information and warn people in 30 minutes.
Dr Bray is hoping the new evidence will help the Maltese government make contingency plans to protect lives and livelihoods on the vulnerable northeastern coast.
Prof. Mottershead had already given a presentation to relevant government departments, including the Civil Protection Department, he added.