An NUI Galway professor is investigating links between freak waves that have hit our shores and earthquakes. He tells Lorna Siggins, Marine Correspondent, about his research
On a calm, fine day in August 1852, 15 people were close to the limestone ledges of Inis Mór, the largest of the Aran islands, when a wave rose up out of the sea and swept them to their deaths. Two years later, there was a report of a giant wave striking the Wexford coast near Kilmore Quay.
And in 1909, a 15-year-old boy named M.J. Lyons described how he was travelling in a horse and cart with his brother and father into Westport, Co Mayo, when all three were thrown into the air. The coast road along Clew Bay had been hit by an enormous wave which was followed by a loud rumbling noise like thunder.
Prof Mike Williams of NUI Galway's geology department believes that there is a link between such incidents, and that link is the seismic occurrence which creates a tsunami. Associated with Japan and the Pacific region, tsunamis are caused by tremors or earthquakes on the sea floor, and their effect can be magnified if large masses of sediment slide down a continental slope as a result of the geological movements.
Perched on a "fairly stable" part of the Earth's crust, Ireland is not exposed to such phenomena - or so the theory went until the geologist began his research, as part of a project supported by NUI Galway's millennium fund.
It is research which has led him to believe that it may have contributed to the formation of the Aran islands off the Galway coast.
Yes, he says, the last volcano did erupt in Ireland about 50 million years ago, but earthquakes are "scéal eile". He points to the tremors which affected Dublin and Wexford in the 1980s, most of which were due to movements along the fault running down the Menai Straits between Anglesey and the Welsh mainland. One of the disadvantages of living on a relatively stable part of the Earth's crust is that "earthquake occurrences are more difficult to predict" - in contrast to areas like the San Andreas fault zone.
Waves generated by earthquakes in deep water can pass unnoticed, but their size can reach major proportions when they approach shallower waters. As Williams explains: "The earthquake shocks can be transmitted to areas where sheltered bays or inland lakes exist", and in this case the consequent vibration can create a giant wave called a "seiche" which can begin to oscillate from one end of the lake to another.
He cites as an example an earthquake in the area around Loch Ness in Scotland in the 18th century. "A large wave began to propagate down the narrow lake, gaining height as it went." It was so big that it almost - "but thankfully not quite!" - destroyed the local brewery at Fort Augustus.
It is this type of wave which may have hit Clew Bay in 1909 and given M.J. Lyons, his father and brother such a fright. The day after that happened, boats were found strewn across the roads, and the contents of warehouses were destroyed.
"All this had happened when the tide was out," Prof Williams says. He believes that an earthquake may have generated the wave which hit the Wexford coastline on September 15th, 1854 - and, similarly, the roller which caused such devastation on Inis Mór on August 15th, 1852.
Yet could these be simply rogue waves? Last year, New Scientist reported on research being carried out in the EU and by the US Office of Naval Research into rogue waves which, it is now believed, sank 22 supercarrier ships between 1969 and 1994, claiming 542 lives.
The best known fatality is the 295-metre long British-owned Derbyshire bulk carrier which vanished off the coast of Japan in 1980 and was a sister ship of the Kowloon Bridge which floundered off this coastline in 1986. It is believed that a large wave cracked open the main hatch, flooded the hold and led to the deaths of all 44 people on board.
The list of "ones that got away" is also startling, and includes a report of a 29-metre wave on the bow of the QE2 cruise liner en route to New York in 1995 - Capt Ronald Warwick compared it to colliding with the White Cliffs of Dover - and a report of a 21-metre wave which hit the British cruise liner, Oriana, in 2000 while it was responding to a Mayday call from a yacht some 600 miles west of Cork in the Atlantic.
The orthodox oceanographer's theory on rogue waves is that they are caused by "constructive interference" - as in small waves joining forces and building up, with ultimate size being influenced by the wind speed, length of time it blows and expanse of open water. This would explain the frequency off Cape Agulhas, South Africa, where the Atlantic and Indian oceans meet, and in the Gulf Stream, the Kuro Shio current south of Japan and the infamous Cape Horn area, where fast currents and countervailing winds produce some of the roughest seas.
However, this does not explain the reports of rogue waves in the North Sea, where there are no fast flowing currents. It is now being suggested that some sort of non-linear interaction or chaos may be responsible. Different types of non-linear mathematical models are being tested, such as the Schrodinger equation which was developed to describe the quantum behaviour of electrons in an atom, and it has been calculated that waves of four times the average height can "rear up from nowhere" and die down "just as suddenly" - substantiating some of the larger than life mariners' stories.
Prof Williams emphasises that his work focuses on seeking a link between seismic occurrences and historical reports of freak waves here. He has researched the details of one of the largest earthquakes to have affected Europe in recent centuries, the Lisbon earthquake of November 1st, 1755. It is believed that more than 50,000 people perished in minutes, as "buildings collapsed and three tsunamis crashed over the harbour area about half an hour after the initial ground shocks". The waves caused "devastation", not just in Lisbon but right down the Iberian coast and as far south as Morocco.
As he explains: "They then propagated in a radial pattern across the North Atlantic", and a giant wave as high as the second storey of houses was witnessed in the Bahamas. In Finland and Switzerland, lake levels "rocked backwards and forwards" and giant waves rolled up the English Channel and into the North Sea. Deposits from these waves discovered in the Scilly Isles suggest tsunamis of between five and 10 metres above high water marks, Prof Williams says.
A computer model suggests that they would have struck the western Irish coastline about two to three hours after the first ground shocks were felt in Portugal. The castle of Coranroo, belonging to the Hynes family near Kinvara on the south shore of Galway Bay is said to have collapsed into pieces as a result of the Lisbon quake.
Also, about 1640, "O'Flaherty of Ogygia" recorded that the sea came over Blind Sound on Inis Mór towards the north-west. Given that the cliffs to the south of this part of the island are between 20 and 30 metres above sea level, this would have been enormous. Suggested confirmation of this lies in an Earthquake Catalogue of the British Association, published in 1858 and written by an Irish scientist, Robert Mallet. He noted the occurrence of a large earthquake at 3.15 a.m. on April 4th, 1640 - the effects of which were felt in France, Belgium, Holland, and perhaps also Ireland.
Prof Williams has delved back further - and this is where the formation of the Aran islands comes in. The annals record an event in Co Cork in 830 AD where "the sea broke through its banks in a violent manner and overflowed a considerable tract of land". The island of Inisfadda was "forced asunder and divided into three parts". A similar event is part of the legend of how the Aran islands were formed, he notes. The legend, as recorded by T.D. Lawson in 1906, relates how "the outside ocean burst over the coast and united with the inland lake, Lough Lurgan (now Galway Bay), the denuded islands (Aran) marking the former coastline".
Though he notes that the timing of these events is a matter of speculation, there is evidence that the earthquakes generated in the active zone of the Gulf of Cadiz, such as that of 1755, affected the west Irish coast. This zone also suffered a significant earthquake with associated tsunamis in 216-218 BC, which was linked to the Gulf of Cadiz. "Perhaps this was why the Aran islands first became detached from the mainland," he suggests.