First stop today is Koekohe Beach on the Otago coast to see the Moeraki boulders. These are giant spherical rocks that Maori legend says are the remains from the wreck of the Arai-te-uru, one of the large canoes that brought the original human inhabitants to the island. Maori believed the eel baskets, calabashes, and sweet potatoes washed ashore; the rocky banks reaching out to the sea were thought to be the petrified ship hull, and a nearby headland was assumed to be the ship’s captain.
Scientific analysis is less intriguing but does nothing to reduce the unique nature of these giant round rocks. X-rays and electron probes reveal the boulders are made of mud, silt, and clay, held together by calcite (a major part of sedimentary rocks, often formed when a life form begins to decay).
It’s the calcite that gives the appearance of yellow seams.
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| Calcite gives the appearance of yellow seams holding the boulder together |
To give you an idea of the size of some of these boulders, here is a rare photo of the writer pushing (hah!) a boulder demonstrating its size and her need for vitamins and a good workout regimen.
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| The writer trying to move a boulder |
The Moeraki took about four million years to grow. Our guide tells us the spherical shape has nothing to do with the erosive power of the sea, but that the sediment and ‘calcite cement’ just grew equally in every direction. Some, like the one I’m trying (pretending?) to push are six feet or more in diameter
Geologists think the Moeraki formed in a layer of mudstone far below the surface of the water, and about fifteen million years* ago that layer was lifted above sea level. Gradually the breaking waves released the giant spheres from the rock and cliffs that held them. You can still see some of the boulders ‘trapped’ in the cliffs.
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| A boulder still trapped in a cliff |
The large seam-like calcite ‘cracks’ radiate from a hollow core lined with calcite crystals. The inside of the boulder seems to be weaker than the outside, so when one does break down, it looks almost as if collapsed, like the one below.
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| the 'inside' of a Moeraki boulder |
The boulders appear on the beach both individually and in clusters like those in the photo below.
Over many years, people have managed to take some of these marvels for souvenirs, etch their initials for posterity, and otherwise tamper with the unique formations. Since 1971 this area has been a legally protected scientific reserve to secure the unique Moeraki.
This video--https://www.youtube.com/watch?v=rMV3PH-wio8-- from http://www.moerakiboulders.com/ provides some good
images and info on the boulders, as well as additional history.
*"'Fifteen million years ago" I know I've said this many times throughout my blog, but when I am reminded of the vast history that came before me, I feel a sense of awe. Just the number 'fifteen million' can do that to me. Yeah, yeah, they're big round stones. But what amazing stones they are.
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