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Largest undersea landslide revealed on Great Barrier Reef

7 February 2017
Scientists likened their discovery to a detective story.

The largest underwater landslide along the slope bordering the famous reef has been discovered, about 30 times the volume of Uluru. Modelling shows such a failure could yield a wave of about 27m but more research is needed. 

Fly-through near Innisfail

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The oldest fossil corals were 302,000 years old – which means the landslide that caused these knolls must be older
Lead researcher Dr Angel Puga-Bernabéu
North-westerly view of the Gloria Knolls Slide and Gloria Knolls off Innisfail. Depths are coloured red (shallow) to blue (deep), over a depth range of about 1700 metres.

View of the Gloria Knolls Slide and Gloria Knolls off Innisfail. This content is released under the Creative Commons Attribution 4.0 International Licence. Credit:

An international group of scientists has helped discover the remnants of a massive undersea landslide on the Great Barrier Reef, approximately 30 times the volume of Uluru.

The remains, known as the Gloria Knolls Slide, were discovered 75km off the north Queensland coast while the scientists were working from the Marine National Facility’s blue-water research ship Southern Surveyor.

A debris field of large blocks, or knolls, and numerous smaller blocks, lies scattered over 30km from the main landslide remains, into the Queensland Trough, to a depth of 1,350m.

“The oldest fossil corals recovered off the top of the knoll were 302,000 years old – which means the landslide event that caused these knolls must be older,” said lead researcher Dr Angel Puga-Bernabéu, a former postdoctoral researcher from the University of Sydney and now with the University of Granada.

The findings were published recently in Marine Geology.

University of Sydney Associate Professor Jody Webster, who had supervised Dr Puga-Bernabéu’s work in the School of Geosciences, likened the investigation to a detective story – first finding the knolls, then using later mapping to reveal the landslide source of the knolls.

He said the team went on to model a potential tsunami for a sudden under-sea mass failure on this scale, yielding a wave elevation of about 27m.

“The impact of any resultant wave would likely be dampened significantly by the presence of the relatively modern, 9,000-year-old formation we call the Great Barrier Reef, but this remains to be assessed systematically,” Associate Professor Webster said.

He said more seabed mapping and sampling was also needed to locate, characterise and determine the timing at which the submarine landslides occurred.

Co-author from James Cook University, Dr Robin Beaman, said the group had been amazed to discover the cluster of knolls while they were 3D-multibeam mapping the deep seafloor.

“In an area of the Queensland Trough that was supposed to be relatively flat were eight knolls, appearing like hills with some over 100m high and 3km long,” Dr Beaman said.

“This is all that remains after the massive collapse of sediment of about 32 cubic kilometres’ volume more than 300,000 years ago.”

The research was a collaborative effort between James Cook University, University of Sydney, University of Granada, University of Edinburgh and the Australian Nuclear Science and Technology Organisation. 

Download the fly-through animation

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