In this morning’s Herald there’s an item entitled ‘Call to save hilltop boulders’. According to the people doing the calling, the boulders were placed at the top of what is now an Auckland hillock prior to Maori settlement by a group of fair-skinned people, claimed to be Celtic voyagers. Hmmm. One of those campaigning for the boulders to be saved is quoted as saying [It] sparked a lot of mystery over how they got there. They were concretion boulders, which can only form in sea sediments, yet they had made it to the top of this high, yellow clay hill. More hmmm – this makes it sound as if human agency is the only way for these big boulders to have reached the top of the hillock.
But there are other, simpler explanations. As Geological Society spokesman Bruce Hayward says (in the same article), there’s no mystery about how the rocks got there. After all, the land mass that is now New Zealand formed from sediments deposited on the sea bed, on top of much older rocks, off the east coast of what’s now Australia. The boulders themselves are 70 million years old & formed on the sea floor, to be raised up during the tectonic events that produced New Zealand. Over time, the sediments that they were enclosed in eroded away, leaving the boulders in their apparently anomalous position on an Auckland hilltop. (These geological processes are well-documented and well-understood, which is rather more than one can say for the alternative hypothesis involving Celtic seafarers & their calendar system.)
The scientific explanation for the placement of marine concretions – & of fossils – isn’t new. Back in the late 1600s Nicholas Steno recognised that these objects could be buried in marine sediments & subsequently raised up above sea level by land movements & then exposed to view by erosion. And before him the polymath Leonardo da Vinci offered the same explanation for the observation that fossils of marine organisms can be found on mountain-tops far above the sea: fossils were once-living organisms that had been buried at a time before the mountains were raised. He wrote "it must be presumed that in those places [mountains] there were sea coasts, where all the shells were thrown up, broken, and divided. . ." The overwhelming weight of evidence is in favour of these early interpretations. And yet for some reason these elegant, insightful, evidence-based explanations can still be rejected in favour of hypotheses that seem to fit a somewhat romanticised and more than slightly unlikely view of the past.
Update: you might like to read this post on the All Embracing blog.