Scars, indicating large-scale slope failures, are clearly visible at a depth of around 140 m in Cook Strait.
Undersea mapping in Cook Strait has revealed detail of massive rock movements around a huge canyon, Nicholson Canyon, less than 15 km from Wellington Airport.
Using state-of-the-art multibeam equipment, scientists have discovered that the canyon walls are very steep. The over-300 m high walls have clearly visible scars indicating a large-scale slope collapse or landslide. NIWA ocean geologist Joshu Mountjoy estimates that the volume of rock which collapsed into the canyon was immense – in the order of 10 000 000 000 cubic metres, or approximately four times the size of Wellington’s Mount Victoria.
“The potential for submarine landslides to generate hazardous tsunami is well documented, and numerical tsunami modelling will be undertaken to assess the future hazard,” says Joshu. “Also, accurate knowledge of the seabed is important for activities such as submarine cable-laying and installation of other marine infrastructure.”
Evidence of several other similar size undersea landslides has been found in the Cook Strait canyons, all within a 50 km radius of Wellington. The landslides are thought to be initiated during large-magnitude earthquakes.
The research was funded by the Foundation for Research, Science & Technology, NIWA’s Capability Fund and the NZ Tertiary Education Commission.