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Great Barrier Reef protecting against landslides, tsunamis

25 November 2015
The world-famous Australian reef is providing an effective barrier against landslide-induced tsunamis.

A tsunami has been found to have occurred up to 20,000 years ago, which could have impacted Aborigines living on the then fringe reef. Now the Great Barrier Reef provides a barrier to potential wave energy from submarine landslide-induced tsunamis. Details of the findings were published this week in the international journal Marine Geology.

Submarine landslide -70m causes tsunami

Credit: Dr Jon Hill, University of York.

The Great Barrier Reef is doing us a great service because of its ability to absorb potential wave energy.
Associate Professor Jody Webster

The world-famous Australian reef is providing an effective barrier against landslide-induced tsunamis, new research shows.

What has developed into the Great Barrier Reef was not always a barrier reef – it was once a fringing reef and did not offer the same protective quality. This is because the coast at this time was much closer to the source of the tsunamis, said lead author of the paper, Associate Professor Jody Webster, from the Geocoastal Research Group at the University of Sydney.

The research shows a shallow underwater landslide occurred 20,000-14,000 years ago, which caused a tsunami 2-3m high. The tsunami could have impacted Aborigines living at the time along estuaries and on islands off the paleo-coastline, which has since receded under the rising sea levels that followed the last ice age.

The 7km-wide landslide occurred off the edge of the continental shelf causing the tsunami on the paleo-coastline lying between Airlie Beach and Townsville.

Details of the discovery of the submarine landslide and tsunami were published this week in Marine Geology. The international team of researchers used sophisticated computer simulations to recreate what the tsunami would have looked like.

Associate Professor Webster said similar landslides under the sea could occur without our knowledge.

 “There is a relatively low chance that a similar submarine landslide with the potential to cause a tsunami of up to three metres or more would happen today,” Associate Professor Webster said.

“However, if one did occur, our findings suggest that the Great Barrier Reef is doing us a great service because of its ability to absorb some of that potential wave energy.”

Just how much energy would be absorbed and what the extent of damage could be done by rising sea levels and tsunamis or king tides is the subject of future research.

In reaching their findings, Dr Jon Hill from the University of York created visual simulations of the tsunami impact at today’s sea level, as well as at a depth of -70m, where the paleo-coastline was before it receded to its current position and was replaced at the shelf edge by the formation of the Great Barrier Reef.

The research team has named the submarine landslide the Viper Slide because of its location adjacent to Viper Reef.

Dr Robin Beaman from James Cook University and a member of the expedition that mapped the slide, said: “The discovery of the Viper Slide is the first solid evidence that submarine landslides existed on the Great Barrier Reef.”