Cause of Antartica's giant underwater landslides solved — and they could trigger tsunamis

The tsunami-triggering potential of these events raises concerns, particularly in the context of climate change.
Sejal Sharma
Representational image
Representational image

Frank Günther/iStock 

Submarine landslides or underwater landslides are global geohazards. They can develop almost anywhere on the seafloor where sufficient sediment is deposited. 

They can displace vast amounts of sediment and give birth to tsunamis which often have massive socio-economic impacts through human displacement and destruction of infrastructure.

And now a team of researchers has identified uncovered layers of weak sediments some hundreds of meters below the seafloor, which are prone to failure and may create gigantic tsunami waves. Once again.

Researchers visited the area in 2017 and then again in 2018 as part of an international expedition and collected sediments extending hundreds of meters beneath the seafloor.

“The project aims to explore the history of planet Earth, including ocean currents, climate change, marine life, and mineral deposits, by studying sediments and rocks beneath the seafloor," said Laura De Santis, a researcher at the National Institute of Oceanography and Applied Geophysics in Italy and a co-author of the paper.

Using chronologic data, the team concluded that long-term climatic shifts during the Neogene period (23 million and 2.6 million years ago) and the Quaternary period (2.5 million years ago) may have been critical in forming distinct rock formations that formed weak layers.

Glacially influenced continental shelves, which means parts of the continent submerged under shallow water, comprise a fifth of Earth’s continental margin area and are particularly sensitive to climate changes. The team suggests that the abundant and fine-grained sediments were preserved during prolonged intervals of warmer-than-present climates. 

The researchers think history might repeat itself

Earth is witnessing long-term shifts in weather patterns and temperatures, including warmer climates, shrinking ice sheets, and rising sea levels due to climate change. This is a cause for concern.

Through analyzing the effects of past underwater landslides, the researchers believe that future seismic events off the coast of Antarctica might again pose a risk of tsunami waves reaching the shores of South America, New Zealand, and South East Asia, as per the statement.

"Giant submarine landslides have occurred both on southern and northern high latitude continental margins, including the Antarctic and Norwegian continental margins. More knowledge on these events in Antarctica will also be relevant for submarine geohazard evaluation offshore Norway,” said Jan Sverre Laberg, from The Arctic University of Norway and a co-author of the study.

The team believes their insights will inform future investigations of geohazards associated with continued climate warming and Antarctic ice retreat.

Study abstract:

Antarctica’s continental margins pose an unknown submarine landslide-generated tsunami risk to Southern Hemisphere populations and infrastructure. Understanding the factors driving slope failure is essential to assessing future geohazards. Here, we present a multidisciplinary study of a significant submarine landslide complex along the eastern Ross Sea continental slope (Antarctica) that identifies preconditioning factors and failure mechanisms. Weak layers, identified beneath three submarine landslides, consist of distinct packages of interbedded Miocene- to Pliocene-age diatom oozes and glaciomarine diamicts. The observed lithological differences, which arise from glacial to interglacial variations in biological productivity, ice proximity, and ocean circulation, caused changes in sediment deposition that inherently preconditioned slope failure. These recurrent Antarctic submarine landslides were likely triggered by seismicity associated with glacioisostatic readjustment, leading to failure within the preconditioned weak layers. Ongoing climate warming and ice retreat may increase regional glacioisostatic seismicity, triggering Antarctic submarine landslides.

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