Instability and Structural Failure at Volcanic Ocean Islands and the Climate Change Dimension

Abstract

Abstract Keating and McGuire (2000) [Island edifice failures and associated tsunami hazards. In “Landslides and Tsunamis”, Birkhauser, Boston, pp. 899–956] presented and examined evidence for ubiquitous island edifice failures and their associated tsunami hazards. In this follow-up review, we examine the status of landslide, debris flow and tsunami research and find that significant progress has been made in placing constraints on physical parameters that will facilitate numerical modeling of tsunami, landslide and debris flow movements. Similarly, physical modeling has provided an important contribution to our understanding of slope failure and debris transport, with many features generated in laboratory experiments clearly identifiable in sonar images of mass wasting events. In particular, we address published evidence and proposed models supporting the rule of climate change toward the generation of ocean island and continental margin landslides. Evidence presented from the Canary Islands and the Madeira Abyssal Plain is supportive of such a relationship, while that from the Hawaiian archipelago provides a weak argument for this association, primarily due to age-dating limitations. Notwithstanding these, a comparison of the known rainfall pattern for the Hawaiian Islands and the distribution of mapped edifice failures, however, reveal no obvious link between either wet or dry conditions and the disposition of debris avalanches and slumps. Furthermore, contemporary observations from the Hawaiian archipelago show that sub-aerial landslides are common under both wet and dry conditions. A correlation between climate-related sea-level change and continental margin slope failures is supported via the mechanism of methane venting. A comparable link between variations in sea level and instability and collapse at coastal and island volcanoes may also be vindicated by correlation between the intensity of volcanic activity in marine settings and the rate of sea-level change during the late Quaternary. Our review reiterates strong evidence for abundant slope failures on the flanks of ocean islands. The existence and nature of a climate change link remains, however, to be firmly established. It is likely that this will need to await better constrained age determinations for submarine slope failures, provided—for example—by an extensive program of ash-layer dating within sequences associated with landslides, slumps and debris flows within the marine environment. We conclude by addressing the hazard implications of future major collapse in the marine environment, drawing attention to increasing evidence for a serious future threat to coastal zones from major landslide-induced tsunamis.