Research involving our Departments of Earth Sciences and Geography has revealed how an explosive volcanic eruption triggered the fastest underwater flows ever recorded and led to extensive damage of seafloor cables.
Avalanche-like flows
The research team, which was led by scientists from the National Oceanography Centre (NOC), studied the huge eruption of the submerged Hunga Volcano in January 2022 which triggered fatal tsunamis and pressure waves that travelled around the globe. This was the most explosive eruption on Earth in over 100 years.
The study, published in Science, shows that there were major impacts far below the sea surface as erupted volcanic material plunged into the ocean, creating avalanche-like flows which travelled at speeds of up to 122km/hour along the seafloor.
This flow broke the only seafloor cable that connected the Kingdom of Tonga to the global telecommunications network, as well as the only internal cable within Tonga. These cable breaks severely hampered disaster relief efforts, and initially made it impossible for many residents of Tonga to contact their loved ones abroad.
Collaboration in a crisis
Subsea cables underpin our daily lives and carry more than 99% of all digital data traffic globally. Tonga's only international cable was abruptly served during the eruption disconnecting the whole nation from the rest of the world during a volcanic crisis.
Professor Peter Talling, an oceanographer in our Departments of Earth Sciences and Geography, brought together an international team of scientists and industry collaborators immediately after the eruption occurred to find out what caused the disruption.
The team sampled and surveyed the seafloor providing evidence to show that powerful and dense subsea currents caused the cable damage.
The study determined that the extremely fast flows were caused by collapses of the eruption plume, falling directly into the ocean onto very steep underwater slopes.
Their initial speed was so fast that these underwater flows were capable of running several hundred meters uphill and for at least one hundred kilometres across the seafloor, giving deeper insight into the widespread damage to the seafloor cables.
Future resilience
The timings and locations of the cable damage allowed researchers to determine the speeds of eruption-triggered seafloor flows for the first time and to better understand the hazards of other submerged volcanoes worldwide.
The insight from this research will help industry experts to understand risk better and improve the resilience of cable systems in other volcanically-active regions.
