Scientists with the Marine National Facility's blue-water research ship Southern Surveyor found a debris field of large blocks, or knolls, and a number of smaller blocks. According to researchers, the natural calamity might have occurred almost 3,00,000 years ago due to a strong quake.
The research, based at Griffith University in Queensland, Australia, discovered that algae kills the corals through a potent chemical compound that poisons them.
Study researcher Robin Beaman, of James Cook University in Queensland, Australia, told Live Science: "We believe an natural disaster of sufficiently large magnitude was the most likely trigger for such a landslide event". Scientists revealed that they were able to locate eight undersea hills "in the middle of nowhere" and also found the crater while reconstructing and working out the contours of the nearby territory.
Fortunately, if a similar collapse were to happen today, the team says the effect might be not prove quite as risky for coastal communities - thanks to the existence of the coral reef itself.
"The oldest fossil corals recovered off the top of the knoll was 302 thousand years", says Dr Angel Puga-Bernabéu at the University of Granada and lead author on the study, "which means the landslide event that caused these knolls must be older".
He said future risk to the Queensland coast appeared unlikely because it was a "a very old event", but it was a worthy topic for future research.
Researchers have found that a "weed-like" algae is killing corals in the Great Barrier Reef because of increased carbon dioxide levels in the atmosphere.
A sediment sample taken from one of the scattered knolls identified both living and fossil cold-water coral species on the block, which came as a shock to the researchers, given the extreme, inhospitable depth of 1,170 metres (3,838.6 feet).
Perhaps luckily for creatures in the area, that tsunami wave would have been dampened by the surrounding reefs, the researchers said.
Already the team of global researchers have been surprised by the marine life they have found in the deep-sea conditions where temperatures can drop to 4 degrees Celsius and it is pitch black. The deep Great Barrier Reef will reveal a far more complex landscape than previously known.