From Weekend: ANOTHER LIFE: The notably raffish atmosphere of Brighton, the seaside town where I grew up, attracted the concern of dogged Pentecostalists, urging repentance in the short time left to the world, writes Michael Viney
"Prepare to meet thy doom" and "The end is nigh", warned the placards they carried through the sinners on the promenade. In the sect's shop window near the railway station, an unchanging centrepiece haunted my childhood. It was a large steel engraving depicting the apocalypse: a lurid sky rent with lightning, the earth buckled and fissured, people falling.
Notwithstanding recent parallels, this early exposure to catastrophism and its tendency to overstate has helped me to resist too much alarm in the face of dire prophesies, even (perhaps, these days, especially) when they emanate from scientists.
Among the latest must be reckoned Tsunami: The Underrated Hazard, by Prof Edward Bryant, head of the School of Geosciences at the University of Wollongong, Australia. It is published by Cambridge University Press, which, I notice, also published the book beside it on my shelf, Understanding Catastrophe (1992), which dealt happily with storms, earthquakes and supernova explosions but overlooked the giant tidal waves that are now Bryant's concern.
The past few years of awesome television documentaries about the earth's tortured surface have brought "tsunami" tripping off the tongue as a peril by no means confined to Pacific coastlines - tsunami is Japanese for harbour (tsun) wave (ami) - and with several powerful causes.
Specially impressive for conoisseurs of catastrophe has been the scenario predicting an explosive eruption in La Palma, a steep-walled volcanic island in the Canaries, off west Africa, causing a giant landslide into the ocean.
This, it is proposed, could generate a mega-tsunami quite powerful enough to cross the Atlantic, swamping the east coast cities of North America, and sending other troublesome eddies up to western Europe and Ireland.
Bryant seems to have missed out on this particular premonition, though he does document some of the Canaries' more notable sea-slides of the past, and notes that a mammoth earthquake near Lisbon in 1755 sent a wall of water across the Atlantic to Barbados and sank ships in the English Channel with a four-metre wave from nowhere.
He closes his book, however, with a set of stories that "foreshadow or prophesy" the nature of tsunamis resulting from less considered causes. And one of these, a submarine landslide, comes uncomfortably close to home.
Out at the edge of the Continental Shelf west of Ireland are great canyons and slopes thickly rimmed with glacial sediment, much of it carried down at the end of the last ice age, when vast margins of seabed lay exposed. In the deeps of the Rockall Trough, within a few hundred miles of Ireland's north-west coast, huge slumps or slides of sediment lie piled on the seafloor or spread out into fans.
In 1996, the first comprehensive survey of the deep-water basins to the west of Ireland produced high-quality images of some 200,000 square kilometres of the sea floor. Along with the "ploughmarks" caused by ancient icebergs (one of them more than five kilometres long), they show the scars of massive slumps of sediment caused by "slope failure". One of these, at 2,000 metres down on the Rockall Bank, covers 11,000 square kilometres.
Tsunamis are already known to have resulted from huge slides at Storegga, on the Norwegian continental slope, in geologically recent times. The last-but-one shifted some 3,880 cubic kilometres of sediment, and the most recent, about 8,000 years ago, carried sand more than 80 kilometres inland up the estuary of the Firth of Forth on Scotland's east coast.
According 'to Bryant, there were also at least seven major submarine slides off the west coast of Ireland over the same timespan, between 30,000 and 8,000 years ago. In the dramatic scenario of his epilogue, a small Sunday earthquake that nobody notices, a mere three to four on the Richter scale, triggers a slide big enough to generate a tsunami. It takes two hours to reach the west coast of Co Donegal.
"Headlands along 350 kilometres of rugged coastline were swamped, while flat pocket beaches in sheltered embayments were totally eroded. The wave was amplified by funnelling in embayments such as Loughros More and Gweebarra bays, and into Lough Swilly running down to Letterkenny. Here the wave reared from eight metres along the open coast to over 15 metres inside embayments," he writes.
Further east, the death toll mounts: "University students living in the coastal communities of Portstewart and Portrush succumbed to the waves." And as for the countryside around Gweedore and Donegal: "The number of dead will never be known because rural marginalisation along one of the most isolated coastlines in western Europe ensured that many victims had no community contacts and hence went missing without being noticed." Ah yes, that's rural Co Donegal for you, as seen from Wollongong.
SCRAMBLING round the wilder shores of his native Australia, Bryant finds convincing geological signatures of tsunami "events" and one finishes his book quite satisfied with their role in shaping landscape and even human history and myth. But is his future scenario worth a place on the agenda of Donegal County Council (cost of seismograph, overtime for gardaí, etc)? I have my doubts.
What does he suggest you do if there is a tsunami warning? Along the northern coastline of Papua New Guinea, people have been encouraged to adopt a tree: "Notches can be cut into trees as toeholds, and people can easily climb a tree and lash themselves to the trunk in a matter of minutes." In cities, of course, the best bet is to dash to an office block: "Run to the lobby, push the elevator button, and go to the top floor."
Bryant, who has published more than 50 papers internationally on such topics as sea level, climate change and catastrophic agents of coastal evolution, is the clearly the man to advise the residents of Ringsend when the next heaping tide surges in.
What are slime moulds?
David F. Nolan, Santry, Dublin 9
They are fascinating organisms (myxomycetes) somewhere between animal and vegetable. For most of the time they lurk in the ground litter or in decaying stumps, but warm, humid weather can bring them climbing into view as brightly-coloured, often custardy, masses called plasmodia, each a giant cell containing millions of nucleii. They can creep about in search of prey such as bacteria and fungi and end up like a dried puffball full of spores.
About four months ago a wagtail arrived as a permanent resident of our windowsill. Most of its time is spent flying to the top of the window to hit the glass with its beak. Between attacks it feeds lustily from a tray of flake meal and scraps and takes nuts from a hanging feeder. Is this bird a trifle eccentric or just plain daft?
Felicity Smith, Kiltennel,
Gorey, Co Wexford
It is trying to drive off an intruder (its reflection) from its territory. You would do it a favour by moving its feeding tray away from the windowsill and hanging a cutout of a hawk inside the glass. It is using up energy attacking the window instead of looking elsewhere for a nesting site.
Eye on Nature is edited by Michael Viney, who welcomes observations sent to him at Thallabawn, Carrowniskey PO, Westport, Co Mayo. e-mail: viney@anu.ie.
Observations sent by e-mail should be accompanied by postal address.
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