Coming One Day Near You -
A Mega-Tsunami

By Michael Christie

WOLLONGONG, Australia (Reuters) - One day, a giant wave traveling at 125 mph across open water could crash into Sydney harbor, wipe out the beaches of California or plough across the golf courses of northeast Scotland.
Mega-tsunamis have happened with greater frequency than modern science would like to believe, and no coastline in the world is safe, says Canadian geologist-geographer Edward Bryant.
He said he had found signs of giant waves sweeping over 425 feet high headlands in southeast Australia, roaring down the U.S. West Coast and carving into the bedrock of the Scottish coastline north of Edinburgh.
"I believe St. Andrews golf course is a tsunami deposit," Bryant, head of geosciences at Wollongong University south of Sydney, told Reuters.
Over the past 2,000 years, tsunamis have officially killed 462,597 people in the Pacific region alone, with the largest toll recorded in the Japanese islands.
Of the top recorded events, the Lisbon earthquake of 1755 is said to have triggered a 15-meter high wave that destroyed the port of Lisbon and caused widespread destruction in southwest Spain, western Morocco and across the Atlantic in the Caribbean.
Modern science blames the killer waves on earthquakes and most countries believe they are immune.
But in his book, "Tsunamis -- The Underrated Hazard," Bryant argues that submarine landslides, underwater volcanoes and even the potentially catastrophic scenario of a meteorite impact must also be taken into account when evaluating tsunami risk.
That means a destructive tsunami moving at 250 meters per second in deep water, 85 meters per second across continental shelves and at 10 meters per second at shore could strike an unprotected coastal metropolis anywhere, killing thousands.
In 1989, Bryant was dabbling into the coastal evolution of rock platforms and sand barriers along the New South Wales coastline of eastern Australia when he noticed something strange.
Giant boulders, some the size of boxcars and weighing almost 100 tons, were jammed 33 meters above sea level into a crevice at the top of a rock platform sheltered from storm waves.
Further field work found gravel dunes on a 130-meter-high headland and other massive boulders more than 100 meters inland. Bryant then examined bedrock that had been savagely eroded and found that headlands carved into inverted toothbrushes, where a gap had been roughly gouged in the middle, existed from Cairns in the far northeast to Victoria state in the south.
This could not be explained by normal wave action or storms.
"But a tsunami could do this," Bryant said.
"From being a trendy process geomorphologist wrapped in the ambience of the 1960s, I had descended into the abyss of catastrophism," Bryant writes in his book.
Similar toothbrush headlands exist in northeast Scotland and gravel has been dumped up to 30 km inland in Western Australia.
To the scorn of many modern scientists, Bryant says it is "naive" to base what we know about tsunamis simply on documented history.
In North America and Australia, official history only goes back as far as white colonization. We may be ignoring the legends of the Indians of North America, the Aborigines of Australia or the Maoris of New Zealand at our peril, he said.
We ignore all oral record and it's probably a significant oversight," Bryant told Reuters. One Aboriginal tale tells how one of the four pillars holding up the sky collapsed in the east and the sea also fell in.
The Maoris of New Zealand have long spoken of a time of fire that burned the land to a crisp.
A legend told by the Kwenaitchechat people of the U.S. Pacific Northwest tells of a great shaking of the earth that led to the sea receding and then coming back in a great wall.
Using dating techniques, Bryant argues there is evidence that eastern Australia was struck by a mega-tsunami around 1500, which would coincide with the Aboriginal tale of a "great white wave."
The Aboriginal accounts of fire in the sky mean a comet crashing into the South Tasman Sea could have been responsible.
Carbon dating indicates a great fire ravaged New Zealand at the same time, giving further weight to the theory of a comet.
And Bryant said Japanese researchers probing past tsunamis had found evidence of a massive earthquake off Oregon in January 1700 that would coincide with the Indian tales, and with a Pacific seismic zone where the Juan de Fuca tectonic plate grinds under the North American plate in a process called subduction.
"We now know the Oregon subduction zone goes every 300 years. 17002002?" he wonders with raised eyebrows.
Bryant's suspicions of meteor and comet impacts a relatively short time ago rile many in the scientific community who believe the chances of Earth colliding with space debris are tiny.
But Bryant says computer modeling suggests a meteor would not have to be a "dinosaur killer" to cause a mega-tsunami. A chunk 100 meters in diameter moving at 20 meters per second could theoretically produce a tsunami that is 27 meters high at source.
Focusing on extreme scenarios such as meteorite impacts may also underestimate the risk of a mega-tsunami.
Contentiously, Bryant argues that underwater landslides, which can involve thousands of cubic km (miles) of material, may have the power alone to generate the giant waves.
A 1998 earthquake off northwest Papua New Guinea has been blamed for a tsunami that killed around 2,000 people near Aitape.
But according to conventional scientific wisdom, the 7.1 magnitude was too small to be responsible for the 15-meter wave that at some points swept 500 meters inland.
Bryant says a submarine landslide was the likely villain.
Another landslide-induced tsunami may have been responsible for shaping the Scottish coastline, including the dunes of St. Andrews, 7,000 years ago.
Scientists have found indications of a large submarine landslide at Storegga off the east coast of Norway that Bryant says could have sent a wave originally measuring 8-12 meters roaring into the North Sea and across the Atlantic.
Worryingly, he says geologists at the University of Sydney have recently mapped around 170 submarine landslide zones off Sydney, Australia's largest city with four million inhabitants. What's more, he has found signs that tsunamis have struck the New South Wales coast with alarming regularity every 500 years.
If you take the risk seriously, it does not take much to save human life from tsunamis.
Chile, Japan and Hawaii already have warning systems and evacuation drills. Seabed sensors can send tsunami warnings via satellite triggering bells, alarms and telephones within minutes.
"The only guarantee or prediction is that they will happen again, sometime soon, on a coastline near you," Bryant concludes.
"Tsunami are very much an underrated, widespread hazard. Any coast is at risk."

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