- 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.
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- 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.
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- ORAL LEGENDS
-
- 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.
-
- SUBMARINE LANDSLIDES
-
- 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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