The Hunga Tonga–Hunga Ha’apai volcanic eruption in December 2021 was the most violent in 140 years, and we are still learning from its aftermath. A recent study focuses on the eruption’s incredible underwater flows, which damaged nearly 200 kilometers of underwater cables. From the cables’ locations and the time of service loss, the team calculated that gravity currents hit the cables at speeds as high as 122 kilometers per hour and with run-outs that lasted over 100 kilometers. These fast flows were triggered by material from the volcanic plume falling into the ocean, causing dense flows that swept down the submerged slopes of the volcano and seafloor.
Previously, a landslide broke underwater telegraph cables off Newfoundland and a coastal construction accident severed a cable in the Mediterranean. But neither of those incidents revealed the same level of speed, distance, and destructive capacity as the Tongan eruption. It seems that these underwater gravity currents pose an ongoing threat to submerged infrastructure. As more cables are laid in volcanically-active regions of the Pacific, we will need more extensive mapping and monitoring of the seafloor to protect against future disruptions. (Image credit: eruption – Tonga Geological Services, illustration – APS/C. Cain; research credit: M. Clare et al.; via APS Physics)
