Sunday Herald Sun, July 6, 1997

An Aboriginal legend long thought by historians to mark the arrival of white men in Australia may refer to a giant tidal wave. Geologist Professor Ted Bryant believes the legend of a "white wave" that wiped out Aboriginal culture more than 200 years ago tells of a natural disaster that devastated the south coast of NSW after a comet strike in the Tasman Sea.

Most historians had assumed the legend referred to the coming of white men to Sydney Cove in January, 1788. Prof. Bryant told a major international research conference in Melbourne this week that the tidal wave was one of two giant tsunamis that hit the NSW coast in the past 1000 years.

The Wollongong University geologist estimates the tsunami was moving at about 350kmh when it hit the coast. He believes the earlier tsunami, which struck about 850 years ago, was probably even bigger.

Prof. Bryant linked the legend with a tsunami after he and a colleague found two telephone booth-sized boulders jammed one behind another in a crevice below a cliff face at Haycock Point near Merimbula. The boulders were well above any normal storm surge.

"This legend talks about a white wave falling out of the sky and destroying their culture," he said.

"To an observer, a wave overtopping a headland and falling into an embayment would seem to come out of the sky."

"We know it happened at daytime, around midsummer, because the legend describes how the white wave came when it was very hot and sultry, and people were lying around resting."

"The legend describes how people went down to the coast the next day and found large new sea caves gouged out all along the cliffs."

Prof. Bryant said the tsunami may be linked with a massive underwater mudslide on the continental shelf 50km off Wollongong, which left a debris fan 20km long and 10km wide on the sea floor -- its collapse was presumably triggered by a big earthquake.

"A slide of that volume would be big enough to give us our tsunamis," he said.

But as Prof. Bryant and Dr. James Nott of James Cook University searched the Australian coastline for more evidence of tsunamis, another, almost incredible possibility emerged.

"You find the signs all around the coast, once you know what you're looking for, and we found tsunami debris on the south coast, in Western Australia and around Cairns, and all the radiocarbon dates were similar," Prof. Bryant said.

"You can't have one big tsunami approaching different parts of the Australian coastline from opposite directions. Unless these things are much more frequent than we think, there must be another explanation."

"We're toying with the idea that the tsunamis were created by a comet that broke into a couple of fragments that hit the oceans around Australia."

Prof. Bryant said if giant tsunamis occur once every 600 years, there was a 15 per cent chance of one big tsunami in any century.

The frequency is consistent with recent evidence about the frequency of comet or asteroid-fragment impacts around the world.

Prof. Bryant told the 1997 Joint Assemblies of the International Association of Meteorology and Atmospheric Sciences (IAMAS) and the International Association for Physical Sciences of the Oceans (IAPSO) that the impact of a tsunami on today's densely populated coastline, and coastal cities such as Sydney, Wollongong and Newcastle, would be enormous.

"Waves this big would ride right over Sydney Heads and get into Sydney Harbor, or could flood into Port Phillip Bay," he said.

"Once these things get into harbors, you can get four-metre waves that slosh back and forth for many hours, causing great damage, especially in low-lying areas."