But having been explained, it s certainly not the sort of thing you would throw back, because the true story of New Zealand s origins is a delicious piece of geology and scientific deduction. I can usually count on an e-mail from the researchers university, but in Australia, that s all too rare. Luckily, the people behind the bimonthly Australian Journal of Earth Sciences are better organised than most, so this time, I got a heads-up and started reading. Most of New Zealand, it seems, washed off the east coast of Australia a quarter billion years ago, then got scooped up as the sea floor slid in under Australia before the relative movement changed and carried the sediments that make up most of New Zealand s eastern side, including all of the North Island, the Southern Alps, Canterbury Plains and Otago, away from Australia. Part of the answer lies in fossils because Chris Adams, a New Zealand isotope geochemist has shown that the eastern parts of New Zealand have warmer-water fossils than the rest, suggesting that the two parts formed in different places and came together later.
Zircons are small crystals which form in granite.
They contain tiny amounts of uranium as an impurity. Zircons are extremely tough and do not weather or release their lead and uranium as they erode out and get included in new sedimentary rock that erodes, and so on, over and over again. The emitted isotopes are focussed through a mass spectrometer and measured. That s right, an Australian invention yet another of those clever Australian ideas than nobody talks about. Sorry, I digress.