Introduction - Tsunami - page 7

Krakatau in 1883 is based upon historical scientific
records—mainly the diary of Van Guest, the colonial vol-
canologist. The Burin Peninsula story is linked to the Grand
Banks earthquake and tsunami of 1929. This event is known
more for the breaking of telegraph cables on the seabed
between New York and Europe than for the deadly tsunami
that struck the southeast coast of Newfoundland. Both sto-
ries also have elements of fabrication. While the individual
experiences of Van Guest and the telegraph master are true,
the descriptions of their feelings and eventual meeting at the
end have been embellished to produce a more colorful story.
The Krakatau eruption and tsunami are probably one of the
best-documented tsunami events in the scientific literature.
At least four articles about it have been written in Nature
and two in Science. However, there is still scientific debate
whether or not the largest tsunami that reached Anjer Lor
and other locations in the Sunda Strait was the result of the
eruptions in the early morning or the one at 9:58 AM. If
witnesses had not been wiped out by the earlier tsunami,
they more than likely did not see the last one because they
had fled inland to safety. Thick ash also obscured the last
event, turning day into night. Field surveys afterwards could
not discern the run-up of individual waves, but only the
highest run-up elevation of the biggest wave.
Readers may also be willing to accept the story from Papua
New Guinea because it, like the Newfoundland one, is based
upon interviews with eyewitnesses. Scientists have cobbled
the story together from newspaper reports and interviews.
Unfortunately, both stories are unreliable because inter-
viewers, unless they apply structured qualitative methodol-
ogy, can be prone to exaggeration. In essence, both the
Papuan New Guinea and Newfoundland stories represent the
early phases of an oral tradition or folklore about a tsunami
event that is being passed on by word of mouth, or in the 20th
century supported by written documentation. When there are
no witnesses to a notable event left alive and no written
records, then all these stories become legends. Legends have
an element of truth, but often the exact circumstances of the
story cannot be verified. The tsunami story by the Kwenait-
chechat native people is a legend. However, when the most
likely source of a documented tsunami in Japan on January
26, 1700 was evaluated—using computer modeling—as
being a giant earthquake off the coast of Washington State,
the legend suddenly took on scientific acceptability and
received front-page coverage in Nature.
The Aboriginal story incorporates numerous published
legends in the southeast part of Australia. One story actually
uses the colloquial word tidal wave for tsunami. Scientific
investigations along the southeast coast of Australia now
indicate that the Aboriginal stories are not myths, but leg-
ends of one or more actual events. While no Aborigine at
the time thought of writing up a description of any of these
tsunami events and publishing it as a scientific paper in

Nature or Science, the legends are just as believable as any
newspaper article or scientific paper. They are just briefer
and less specific. The sky may have fallen in the form of an
asteroid or meteorite shower with large enough objects to
generate tsunami tens of meters high. There is geomorphic
evidence along the southeast coast of New South Wales, the
northeast coast of Queensland, and the northwest coast of
Western Australia for mega-tsunami. Certainly the coastal
features are so different in size from what historical tsunami
have produced anywhere in the world in the past 200 years
that a comet or asteroid impact with the ocean must be
invoked. The subsequent floods also have veracity. Asteroid
impacts with the ocean put enormous quantities of water
into the atmosphere as either splash or vapourised water
from the heat of the impact. That heated vapor condenses
and falls as rain because it is not in equilibrium with the
pre-existing temperature of the atmosphere. Research is
beginning to indicate that rivers and waterfalls across
Australia have flooded beyond maximum probable rain-
falls—the theoretical highest rainfall that can occur under
existing rain-forming processes. Asteroid impacts with the
ocean may explain not only some of the evidence for mega-
tsunami, but also this mega-flooding.
The single thread running through all five stories is
tsunami. The stories have been deliberately selected to
represent the different causes of tsunami. The Aboriginal
legend refers to the impact of an asteroid and the associated
airburst. The historically accurate Krakatau story recounts a
volcano-induced tsunami, while the Kwenaitchechat legend
undoubtedly refers to a tsunami generated by an earthquake
of magnitude 9.0 along the Cascadia subduction zone of the
western United States in January 1700. The Newfoundland
tale refers to the Grand Banks earthquake and submarine
landslide of 1929—the only well-documented tsunami to
affect the east coast of North America. Finally, and more
worrisome, the origin of the Papua New Guinea event is still
being debated. The event is worrisome because the wave
was too big for the size of the earthquake involved. The
combination of downfaulting close to shore and slumping of
offshore sediments on a steep, offshore slope may have
caused the exceptionally large tsunami. Many countries
have coastlines like this. The event is also disconcerting
because our present scientific perception and warning sys-
tem—especially in the Pacific Ocean—is geared to earth-
quake-induced waves from distant shores. Certainly very
few countries, except Chile and Japan, have developed a
warning system for nearshore tsunami. The stories delib-
erately cover this range of sources to highlight the fact that,
while earthquakes are commonly thought of as the cause of
tsunami, tsunami can have many sources. Our present
knowledge is biased, even after the shock of the Indian
Ocean Tsunami of 2004. Tsunami are very much an

underrated, widespread hazard. Any coast is at risk.