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Barrier Reef seafloor breaking off

AFP-JIJI

A huge slab of seafloor near the Great Barrier Reef is in the early stages of collapse and could generate a tsunami when it finally breaks off, researchers warned Friday.

Marine geologists from Australia’s James Cook University have been using advanced 3-D mapping techniques on the deepest parts of the reef — below diving depth — since 2007 and have discovered dozens of canyons.

On a recent trip, they came across the 1-cu.-km slab of seabed, the remains of an ancient underwater landslide perched on the continental shelf.

“Undersea landslides are a well understood geological process, but we didn’t know there were any on the Great Barrier Reef,” geologist Robin Beaman said. “We found this one large block that stood out. It is sitting on top of a submarine canyon, cutting into the slopes, and it is in the preliminary stage of collapse.”

He stressed that no one knows when a collapse may occur, “whether tomorrow or even in our lifetime,” but cautioned that people should be aware that it is there.

“It is slowly giving way, although it remains stable under current conditions,” Beaman said. “But it is absolutely going to collapse, and when it does fall, it will fall 1 km into the adjacent basin. This will generate a localized tsunami that will affect the Queensland coastline, which is around 70 km away,” he said. “We’re not trying to alarm people, but we need to know it is there and what could happen when it falls.”

The geologists who made the discovery were traveling on the Southern Surveyor, an Australian maritime research vessel.