Recent history has shown us the true nature
of trans-Pacific tsunamis. The 2011 Tōhoku-oki tsunami from
Japan was almost 5 m high in Dichato, Chile, and the 2010
Maule tsunami from Chile was up to 2.0 m high in Japan. A few
hundred years ago and we see the 1700 AD Cascadia tsunami
inundating Japan - geological evidence in the Pacific
Northwest supported by historical evidence from Japan. These
were caused by subduction zone earthquakes, but we have argued
for many years that volcanic-related tsunamis have been
something of a "blind spot" in our understanding of the
Pacific tsunamiscape. It is with no feeling of smugness that
we now look back on the recent proof of this assertion -
Tonga, neighboring islands, and even distant locales such as
Peru were devastated by the tsunami(s) associated with the
January 2022 eruption of the Hunga Tonga-Hunga Ha'apai
volcano, one of thousands of similar Pacific Ring of Fire
volcanoes.
So where are the prehistoric ones, those that rely solely upon
the geological record, they must exist? It is here that the
problems start. First of all, just because the 2011 and 2010
events reached across the Pacific does not mean that they left
any sedimentary evidence behind. This means that when looking
into prehistory we are dealing with a fragmentary record of
these rare phenomena with geological evidence probably not
extending across the entire Pacific basin. Second, assigning
links between disparate points across the Pacific can be
hampered by chronological control. However, pragmatically,
since these are rare events the mere presence of tsunami
deposits and other evidence that date to around about the same
time across the Pacific can allow us to cautiously explore
potential trans-Pacific palaeotsunamis. And then, if we are
delving into prehistory, what about some more esoteric
examples. Submarine landslides can leave behind some
interesting clues, and then there is the occasional asteroid
that finds the Pacific a target too big to miss. The Pacific
Ocean covers about a third of the earth's surface, it also has
the honour of being home to the Pacific Ring of Fire. I have
spent a career chasing ancient tsunamis throughout the region
and slowly but surely we are making headway, and there are
some interesting stories to tell.
About the Speaker:
Professor James Goff is Honorary Professor
of Tsunami Research at the University of New South Wales
(UNSW), Sydney, Australia and Visiting Professor at the
University of Southampton in the UK. Up to 2016 he was Deputy
Director of the PANGEA (Palaeontology, Geobiology and Earth
Archives) Research Centre, and Director of the
Australia-Pacific Tsunami Research Centre at UNSW. He has
published four books and well over 300 peer-reviewed
publications.
https://www.bees.unsw.edu.au/our-people/james-goff
https://ptdb.niwa.co.nz/