Submarine Slope Instabilities Coincident with Shallow Gas Hydrate Systems: Insights from New Zealand Examples

The potential of gas hydrate systems to play a role in submarine slope failure has been well-documented since the late 1970s. Several conceptual models exist for how the gas hydrate-free gas system might weaken submarine sediments, but there is no definitive evidence for gas hydrate-related processes being the primary cause of a particular submarine slope failure. We present a review of coincident gas hydrates and submarine slope instabilities on New Zealand's active margins. The examples we show represent different failure modes in a range of slope environments, including the upper continental slope and tectonic ridges, with the common factor being that the base of gas hydrate stability approaches the seafloor in these regions. We synthesise several proposed sediment weakening mechanisms and draw comparisons to other global models for gas hydrate-related slope instability. This contribution highlights diverse influences that gas hydrate systems could have on submarine sediment strength, while acknowledging gaps in our understanding of the potential role of gas hydrates, free gas and fluid flow on slope stability.