Extreme erosion by submarine slides

Submarine slides (including slides, slumps, and debris flows) pose major geohazards by triggering tsunami and damaging essential submarine infrastructure. Slide volume, a key parameter in hazard assessments, can increase markedly through substrate and/or water entrainment. However, the erosive potential of slides is uncertain. We quantified slide erosivity by determining the ratio of deposited (V-d) to initially evacuated (V-e) sediment volumes; i.e., slides that gain volume through erosion have V-d/V-e ratio >1. We applied this method to the Gorgon slide, a large (500 km(3)), seismically imaged slide offshore northwestern Australia, and reviewed V-d/V-e ratios for 11 other large slides worldwide. Nine of the 11 slides have V-d/V-e > 1 (median value = 2), showing emplaced volumes increased after initial failure. The Gorgon slide is the most erosive slide currently documented (V-d/V-e = 13), possibly reflecting its passage across a highly erodible carbonate ooze substrate. Our new approach to quantifying erosion is important for hazard assessments given substrate-flow interactions control slide speed and runout distance. The variations in slide volume also have important implications for submarine infrastructure impact assessments, including more robust tsunami modeling.

Automated summary

Submarine slides are major geohazards that can trigger tsunamis and damage submarine infrastructure. Our study quantified the erosive potential of submarine slides and found that the slide volume tends to increase after the initial failure. This has important implications for hazard assessments and impact assessments of submarine infrastructure.