Professor David Tappin made his remarks on July 17, the 20th anniversary of a tsunami which claimed the lives of 2,500 people in Papua New Guinea, which was the result of the little-understood phenomenon.
Most tsunamis – such as the one which resulted in the deaths of 220,000 people in the Indian Ocean in 2004 – are the result of earthquakes above a magnitude of 7.5.
However, the tsunami which hit Papua New Guinea was preceded by one measuring 7 on the scale – almost six times less powerful, raising suspicions that something else was happening.
Dr Tappin said: “Although at the time some scientists argued for an earthquake mechanism for the local tsunami, it was generally agreed that the earthquake magnitude was too small to generate the recorded tsunami elevations.
“It was not a ‘tsunami’ earthquake, where the tsunami is much greater than expected from the source magnitude.
“Thus the most likely alternative tsunami mechanism was a submarine landslide.”
A series of investigations, undertaken by a team of marine geologists, followed, and this provided the evidence scientists were looking for – although more work needs to be done to establish precisely how comparatively minor quakes produce such dramatic results.
Dr Tappin explained: “Photographs and video imagery of the seabed revealed recent movement within the amphitheatre from fissures and cracks in sediment and limestones, and an associated proliferation of chemosynthetic faunas such as mussels and tube worms.
“These data confirmed this area as the most likely location for a slump-generated tsunami.”
These occur when large, unstable mounds of silt and other matter under the surface are disturbed, sending it crashing to the sea bed and creating huge waves in the process.
Dr Tappin explained: “Shaking can destabilises the water bed.
“Basically the material collapses downwards and pushes the water up.”
Many tsunamis which are known to have occurred in prehistory, including off the coast of Norway 8,000 years ago, are likely to have been the result of subterranean landslides.
There is also a risk of similar events happening in the Atlantic Ocean east of the United States.
Since the 2004 tragedy, as well as the one which hit Japan in 2011, the danger posed by tsunamis has been taken much more seriously, and warning systems are now in place in most of the world’s oceans which can detect earthquakes which have the potential to trigger them.
However, Dr Tappin added: “There does need to be more work done to use the methodology used to extend these warning systems to subterranean landslides.
“Unfortunately it’s like anything – it takes something major to get people’s attention.”