Quick Dips

A Breakthrough In Time

More accurate historical dates of ice ages, volcanic eruptions, earthquakes and other historical events in the southern hemisphere could result from a study being done at Waikato University. The study could also lead to more accurate predictions of earthquakes and volcanic eruptions in the future.

In one of the most significant and far-reaching scientific studies attempted in New Zealand this decade, the university's radiocarbon dating laboratory is collaborating with the Queen's University of Belfast laboratory to recalibrate the radiocarbon time scale over the last 1,000 years using New Zealand trees.

Radiocarbon dating plays a significant role in understanding New Zealand history, calculating the timing and pattern of Maori occupation, ice ages which mould the landscape, expansion and contraction of forests in response to climate changes, raising and lowering of sea levels, volcanic activity and earthquakes.

But radiocarbon ages can vary from solar ages by up to 10% because of cyclic atmospheric fluctuations. The errors can be corrected by dating wood of a known age to convert radiocarbon years into solar years.

In the Northern Hemisphere, tree-ring calibration of the radiocarbon time scale is already well advanced using trees such as the Irish oak, but an extensive on-going programme has never been attempted in the Southern Hemisphere.

Recently the director of the Belfast laboratory, Dr Gerry McCormac, and Steve Robertson of the Quaternary Dating Research Centre at the Australian National University in Canberra, visited the Waikato laboratory to help staff establish a high precision dating system similar to the Belfast system.

The first step of the study is to count the tree rings from a recently felled New Zealand cedar tree to provide wood samples of a known historical age for radiocarbon dating. The scientists then obtain high precision radiocarbon dates on selected tree rings to plot a calibration curve. Duplicate tree ring wood samples will be analysed in both laboratories, along with Irish oak samples, to match the two hemisphere sequences.

Director of the Waikato laboratory Dr Alan Hogg says there is some evidence to suggest the northern hemisphere calibration curve may not be accurate for New Zealand conditions.

"For instance, we know the Taupo eruption was about 2,000 years ago, but the corrected solar date may be inaccurate because it was obtained from the Northern Hemisphere calibration curve" he says. "From this study we will be able to obtain more accurate solar ages, which will give us more reliable information about past geological and prehistoric events."