[M-IS20] Tsunami deposit

[MIS20-01] Rethinking tsunami deposits

★Invited Papers

*James Goff^1,2 (1.University of New South Wales, Australia, 2.University of Southampton, UK)

Keywords:Historical tsunamis, Geological evidence, Enhanced analytical techniques, Environmental data, Archaeological/Anthropological data

The 21^st century has seen tsunami research go from strength to strength. There have been many large tsunamis that have devastated coastal communities, destroyed livelihoods, killed thousands of people, caused the relocation of entire settlements, and redefined what it means to live and work at the coast. These large events have also left behind a geological legacy that has provided us with a modern-day laboratory for us to hone our skills, to find new ways of investigating a tsunami’s characteristics, and for us to be complacent. In the early days of tsunami geology research most scientists did not have the luxury of a recent event to learn from. Researchers made fortuitous discoveries, they constructed a kind of toolbox to understand and identify a past tsunami deposit and in many cases managed to link these events to a source that had been studied by other disciplines such as seismology or marine geology. In many ways, having new events to study has distracted us, we have become detail focussed, finding more and more innovative and different techniques to unravel the intricacies of a deposit – increasingly sophisticated geochemistry, the rise of environmental DNA and biomarkers, a growing suite of microfossils, and so on. These are all commendable advances, and such research must continue, BUT if we truly want to learn more about ancient deposits, we need more. Our focus on modern deposits divorces us from all the other lines of evidence that we can use that tell us more about the magnitude of such events. How were people affected and how did they respond? How was the landscape affected and how did it respond to such a catastrophic threshold change? Palaeotsunami research now stands at the stage where off-deposit data are as important or more so as their in-deposit counterparts. If we use the full suite of tsunami evidence that we see in modern events for the study of palaeotsunamis then we may surprise ourselves with how much better we understand them.

Figure: 15th century cave painting of a sea monster eating a human: Part of the Māori Traditional Environmental Knowledge from New Zealand about a devastating tsunami (after King & Goff 2010. Natural Hazards and Earth System Sciences, 10, 1927-1940)