Scientists have discovered evidence suggesting that a massive ancient underwater landslide occurred next to the Great Barrier Reef in Australia.

Gloria Knolls Slide

The Gloria Knolls Slide is just one of the seven undersea landslides that researchers have discovered in recent years but it is by far the largest. Scientists estimate that the event, which occurred more than 300,000 years ago, dumped about 8 cubic miles of rock and debris on the ocean floor.

Robin Beaman, from James Cook University, and colleagues found eight knolls that appear like hills in an area of the Queensland Trough, a deep basin running adjacent to the Great Barrier Reef, which was expected to be relatively flat.

Coral Community Hints Undersea Landslide Occurred More Than 300,000 Years Ago

Researchers were able to date the underwater landslide based on sediment sample from the largest knolls taken 4,000 feet below, which revealed the presence of a cold-water coral community.

Study researcher Angel Puga-Bernabéu, from the University of Granada, said that the oldest fossil corals that were recovered off the top were 302,000 years old hinting that the landslide that caused the knolls should have occurred earlier.

"The timing of emplacement of the first [Gloria Knolls Slide] GKS event, constrained by radiometric age of fossil biota from the surface of the largest slide block, was at least before 302 ± 19 ka," researchers wrote in their study. "Preliminary estimations suggest that unusually large seismic events were the most likely triggering mechanism for the GKS."

Scientists first discovered the remnants of the slip in 2007 during an initiative to produce a three-dimensional sea map of the trough. After discovering the knolls poking up from the seabed, the researchers mapped the area to discover the landslide that caused the underwater hills with depths ranging from 4,000 to 4,600 feet.

Beaman said that the landslide caused a catastrophic collapse that pushed debris about 20 miles from the base of the slip.

Ancient Landslide Powerful Enough To Trigger Waves As Tall As Eight-Story Building

Simulations of the event likewise showed that the ancient landslide was powerful enough to set off tsunami taller than an eight-story building.

The impact of the wave, however, was likely dampened by the Great Barrier Reef, if it existed at the time, which could have dispersed some of the surge's power.

"The Great Barrier Reef acts like a giant porous breakwater to reduce the energy [of ocean swell]," Beaman said. "If it was in existence at the time of this landslide, it would have done a similar job."

Implications Of The Discovery

The findings, which were reported in a study published in the journal Marine Geology on Dec. 27, 2016, offered insights on the deepest reaches of the Great Barrier Reef — the largest coral reef ecosystem in the world, which also serve as home to about 1,625 species of fish and about 1,400 coral reef species. Researchers said samples from Gloria Knolls reveal that life flourishes deep below despite the harsh cold and deep-sea conditions.

The research may likewise help scientists understand how often similar underwater landslides happen and whether or not these events pose risk to a populous coastline.

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