Tsunami wiped out historic knowledge

WORLD OF SCIENCE - BOB BROCKIE

OPINION: About 500 years ago New Zealand was hit by the mother of all tsunamis.

A wave of water 25 metres high swept ashore from the north. That's as high as an eight-storey building and 12 times bigger than the one that hit Samoa the other day. The water surged inland up to a kilometre and up to a height of 32 metres. It was still 10 metres high as it swelled through Cook Strait.

How do we know about this? Because archaeologist Bruce McFadgen has spent years scouring our coasts and reading scientific reports. He and other scientists have found evidence of the big tsunami from Northland and Bay of Plenty to Nelson. Near Wellington there are tsunami- generated marine gravel and rocks, pumice, seashells, driftwood and debris on Kapiti Island, in Palliser Bay and on D'Urville Island.

More evidence comes from eroded riverbanks, seaside cuttings, from dug holes, drilled cores and from buried Maori settlements. The evidence for a big tsunami is overwhelming.

Dr McFadgen is something of an expert on radiocarbon dating. He says that with more than 400 dates for catastrophic New Zealand events and more than 1500 dates for archaeological sites he has every confidence in dating the big tsunami in the 15th century.

In those days most Maori lived on the coasts of Northland, Auckland, Coromandel and Bay of Plenty - the very coasts that bore the full force of the tsunami.

To fill out the picture, he draws on many traditional Maori accounts of disastrous seas rising to the height of cliff tops, overwhelming their lands, drowning communities and sweeping away their fleets of canoes about 15 generations ago.

Dr McFadgen suggests the great wave would have carried away all canoes and fishing gear, gardens and stored food, buried shellfish beds and poisoned the soil with salt.

He thinks many coastal Maori would either have drowned or died of their injuries and, with the wholesale loss of food, many survivors would have succumbed to starvation.

The timing of the calamitous tsunami coincides with many changes that overtook Maori.

Before the disaster Maori built two-hulled canoes, afterwards only single-hulled boats.

The quality of stone adzes, fishing gear, ornaments and other artifacts declined after the tsunami, which Dr McFadgen attributes to the loss of many skilled craftsmen.

He also finds that the whakapapa of several tribes go back to the 15th century but no further, possibly because so many knowledgeable kaumatua and priests were lost in the waves. Dr McFadgen thinks the big tsunami triggered a significant transition from archaic to classical Maori culture, but this idea does not sit well with some archaeologists.

In all the wall-to-wall media chat about the recent Samoan tsunami, I'm astonished that no journo has thought to interview Wadestown's unassuming Bruce McFadgen. He knows more about tsunamis than you can shake a stick at.

* Bruce McFadgen's Hostile Shores: Catastrophic Events in Prehistoric New Zealand and Their Impact on Maori Coastal Communities is published by Auckland University Press.

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