Research shows Great Barrier Reef protects against tsunamis

Posted on Friday 27 November 2015

Dr Jon Hill, of the University’s Environment Department, was part of a team of scientists which discovered that the immense reef off the coast of Queensland provides an effective barrier against tsunamis induced by underwater landslides.

The study, which also involved researchers from the University of Sydney and James Cook University, established that what has developed into the Great Barrier Reef was once simply a fringing reef that did not offer the same protection because the coast 20,000 years ago was significantly closer to the source of the tsunamis.

The research, published in Marine Geology, 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.

Dr Hill created numerical simulations of the tsunami impact at today’s sea level, as well as when sea level was 70m lower which moved paleo-coastline closer to the landslide, before receding to its current position to be replaced at the shelf edge by the formation of the Great Barrier Reef.

He said: “Numerical modelling is a key tool to understanding how ancient events affected our ancestors and the ancient coastline as we can recreate these events in a virtual laboratory.”

Associate Professor Jody Webster, of the University of Sydney who led the research, 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. 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,” he added.

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

How much energy would be absorbed and the extent of potential damage caused by rising sea levels and tsunamis or king tides is the subject of future research.