Coming One Day Near You: A Mega-Tsunami
One day, a giant wave travelling at 125 mph across open water could crash into Sydney harbour, 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 [not including the massive number of deaths caused by the Indian Ocean tsunami a few years ago – Ed], 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.
Geological Dabbler to Catastrophist
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. [This asteroid impact in the Tasman Sea between Australia and New Zealand has been dated to the 1520s by various other sources; the more recent huge wave in 1700, mentioned below, likely affected the entire Pacific and was caused by volcanic activity and underwater landslides emanating from Hawaii - Ed]
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. 1700 - 2002?" 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 modelling 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 kilometres 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 [at the time of writing; a few more exist now – Ed]. 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."
By Michael Christie
From Reuters via Rense.com
Big splash theory says meteors hit regularly
A LARGE asteroid or comet, the kind that could kill a quarter of the world's population, smashed into the Indian Ocean 4800 years ago, producing a tsunami more than 180 metres high - about 13 times as big as the one that hit Indonesia almost two years ago.
The startling claim is made by a group of researchers, including Australians, who cite as evidence a newly discovered crater, 29 kilometres in diameter, 3800 metres below the surface of 1600 kilometres south-east of Madagascar.
Most astronomers doubt that any large comets or asteroids have crashed into the Earth in the past 10,000 years. But the self-described "band of misfits" that make up the Holocene Impact Working Group say astronomers simply have not known how or where to look for evidence of such impacts along the world's shorelines and in the deep ocean.
Scientists in the working group say the evidence for such impacts during the past 10,000 years is strong enough to overturn estimates of how often the Earth suffers a violent impact on the order of a 10-megaton explosion. Instead of once in 500,000 to 1 million years, as astronomers now calculate, catastrophic impacts could happen every few thousand years.
The researchers, who formed the working group after finding one another through an international conference, are based in the US, Australia, Russia, France and Ireland. [In 2006] the group started using Google Earth, a free source of satellite images, to search the globe for chevrons - enormous wedge-shaped sediment deposits, that are composed of material from the ocean floor - which they interpret as evidence of past giant tsunamis.
Ted Bryant, a geomorphologist at the University of Wollongong, was the first person to recognise the palm prints of mega-tsunamis. Large tsunamis of 10 metres or more were caused by volcanoes, earthquakes and submarine landslides, Dr Bryant said, and their deposits have different features.
Deposits from mega-tsunamis contained unusual rocks with marine oyster shells, which could not be explained by wind erosion, storm waves, volcanoes or other natural processes, he said.
"We're not talking about any tsunami you've ever seen. Aceh was a dimple. No tsunami in the modern world could have made these features." Dr Bryant identified two chevrons found about six kilometres inland from the Gulf of Carpentaria. Both point north.
When Dallas Abbott, an adjunct research scientist at Lamont-Doherty Earth Observatory, in New York, visited a year ago, he asked her to find the craters.
To locate craters Dr Abbott uses sea surface altimetry data. Satellites scan the ocean surface and log the exact height of it. Underwater mountain ranges, trenches and holes in the ground disturb the Earth's gravitational field, causing sea surface heights to vary by fractions of a centimetre. Within 24 hours of searching the shallow water north of the two chevrons she found two craters.
She obtained samples from deep sea sediment cores taken in the area by the Australian Geological Survey.
"We think these two craters are 1200 years old," she said. The chevrons are well preserved and date to about the same time.
Copyright The New York Times
New Illuminati comments: Sooner or later IT WILL HAPPEN AGAIN. In the best of times, anyone who lives on the coast cares little for their life, and anyone who BUILDS on or near a coastline condemns themselves, their family or whoever buys their 'property' to untimely death - and this is no longer the best of times...
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