Ventifacts hold a little mystery

Ventifacts have been mistaken for everything from adzes to pieces of shattered asteroid. But the rocks, stones, and sometimes boulders, which get their interesting shapes from being sculpted and polished over thousands of years by exposure to wind-driven sand, are now helping scientists learn more about the past.

The study of the provenance and the shape of the rocks — found along the Whanganui and South Taranaki coasts — sheds light on the past but they are also worth something commercially.

In the 1970s, the Geological Society of New Zealand became concerned that people were taking trailer loads of the ventifacts away and selling them, and wanted to put a stop to it to preserve them. It’s now illegal to take ventifacts from the Nukumaru Domain.

Professor Vince Neall, an expert on the geology of the Taranaki region, says studies of these sorts of materials will continually be enhanced with new methods.

“I find it stunning that we can now figure out what people have been eating in the past by studying the isotope ratios in their bones as to whether they were eating fish or whether they were eating meat,” Neall said.

Although ventifacts are discovered in a variety places, the ones at Waitotara hold a little mystery.

“The real interest in these ventifacts is how they come to be here at Waitotara,” Neall said.

“This particular rock type, as far as we know, is not known anywhere else in the North Island.”

The best explanation is they were pushed by the sea along a “marine bench” 120,000 years ago.

The type of rock is the same as that found south of Ta¯kaka, at the top of the South Island. Their discovery in the North Island helps to explain a few things.

“During an ice age, sea levels would’ve fallen and you could’ve walked from north-west Nelson to Taranaki and this helps explain some commonalities in the flora between Mount Taranaki and north-west Nelson.”

While the ever-evolving science of studying rocks unlocks many mysteries of the past, there are other surprising applications.

If you want to see the ventifacts for yourself, some of the Whanganui Museum’s collection is on display.

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