January 2022 witnessed the violent eruption of Hunga Tonga–Hunga Haʻapai submarine volcano in the South Pacific. With a volcanic explosivity index possibly equivalent to VEI 5, this represents the largest seaborne eruption for nearly one and a half centuries since Indonesia’s cataclysmic explosion of Krakatau in AD 1883. The Tongan eruption remarkably produced ocean-wide tsunamis, never documented before in the Pacific instrumental record. Volcanically generated tsunamis have been referred to as a ‘blind spot’ in our understanding of tsunami hazards, particularly in the Pacific Ocean. This event therefore presents a unique opportunity for investigating the multiple processes contributing to volcanic tsunamigenesis. It is argued that, although challenges exist, integrating theoretical, observational, field and modelling techniques offers the best approach to improving volcanic tsunami hazard assessment across Oceania.

Transported coastal boulders have increasingly come to represent a valuable element of investigations within the broader framework of multi-proxy approaches applied to coastal hazard studies. Through a case study on Taveuni Island in Fiji, this paper outlines some approaches and hindrances to effective timing of prehistorical high-energy marine inundation events (storms and tsunamis) on tropical coastlines from the evidence of reef-platform carbonate boulders. Various sources of errors are outlined that investigators must consider when attempting to use carbonate boulder ages as a surrogate for timing past events. On Taveuni, uranium : thorium dates with a high level of precision (1–7 years) suggest that major inundation events have a return period of approximately 40–45 years since 1650 AD. Of particular importance, considerably different age dates are provided by coral samples sourced from the top and bottom (i.e. opposite faces) of individual boulders, so highlighting interpretation biases that must be avoided.