Abstract
The 2022 eruption of Hunga Tonga–Hunga Ha’apai (HTHH) and the tsunami it generated was a graphic reminder of the power of volcanic tsunamis. While the volcanic meteotsunami (measured around the globe) was the most far-reaching, the near-field tsunami caused runup exceeding ten metres on several islands in the Tongan archipelago. This near-field tsunami was undoubtedly driven by multiple volcanic tsunami mechanisms including submarine explosive eruptive bursts, pyroclastic density currents (PDCs) generated by column collapse and the near-field pressure anomaly. Flank and caldera collapse may have also contributed. Understanding volcanic tsunami mechanisms is an important step in protecting people and communities from their effects. This is not a simple task as volcanic eruptions, especially submarine volcanic eruptions, are difficult to measure in ways that reveal their tsunamigenic potential. Even in the case of HTHH (probably the best measured volcanic tsunami in the world), the timeline of the eruption is not obvious. Likewise, volcanic tsunamis are infrequent, making collecting field data even more difficult.
While we cannot set off volcanoes in the lab, idealised physical and numerical experiments can increase our understanding of volcanic-tsunami mechanisms, and the size and characteristics of the waves they generate. This, in turn, can help us understand the hazards they pose. This presentation reports on the results of a 4-year project which studied volcanic tsunamis using both laboratory experiments and numerical modelling to understand how explosive submarine volcanoes and PDCs generate tsunamis. These include an in-depth look at PDCs generating tsunami waves, including the transfer of energy into waves and the factors that influence wave heights. We also consider the essential physics numerical models must capture to correctly simulate volcanic tsunamis and consider field-scale scenarios of potential volcanic tsunamis in Lake Taupō (a volcanic caldera and the largest lake in the North Island of New Zealand).