Unsurprisingly, one of the major threats to a small group of islands east of New Zealand is that of a tsunami. At 1am on August 15, 1868, tsunami waves generated the previous day by an earthquake offshore from Arica, Peru – some as high as six metres, nearly the height of a two-storey house – smashed into the Chatham Islands. The Arica earthquake, estimated at about 8.5–9.0 magnitude, saw the Chathams subjected to devastating tidal waves that swept up to 6.4 kilometres inland leaving death and destruction in their wake.
Believed to be the only fatal tsunami recorded in historic times, this was one of the first such events in New Zealand to be documented in detail. Three destructive waves within an hour caused havoc as noted in a report from the Hawkes Bay Herald on September 12, 1868:
“… The third wave, which came rolling in with most awful grandeur and thousand-fold power, bearing down outbuildings and stout old akeakes, which broke and cracked beneath its fury like matchwood, carrying away young cattle, and scattering the debris of the ruins far away …”
GNS Science Risk Specialist Kristie-Lee Thomas reports that the entire Chatham Island coastline was affected by the 1868 tsunami. She says: