Bizarre Natural Phenomena Vol.25 - The Playing Marbles Of A Giant (Moeraki Boulders)

Welcome to another bizarre phenomenon my friends! Today I wanna start by showing you a picture...

(Image source: wikimedia.org)

Who can tell me what these huge stones are? They are definitely not garden decorations that ended up at a beach because someone got fed up with them. 

(Image source: wikimedia.org)

They aren't huge dinosaur egg fossils either (although they look like it).

These round ball-shaped stones are called Moeraki boulders and have been decorating the shores of Koekohe Beach in Otago coast (near Moeraki, New Zealand). Legend has it that those stones are the petrified remnants of baskets that passengers started to through in the sea when their canoe was caught in a storm and was about to wreck. Those were said to be the Maori ancestors that came to inhabit the area for the first time.

What are they?

Moeraki boulders are actually concretions, the result of cementation of marine mud of the Paleocene era (meaning they must be 56-66 million years old). The mud, fine silt and clay gradually started to petrify uniformly (that's what their round shape tells us) outwards thanks to the carbonate mineral calcite. As we move from the center to the outer layers, the spheres become harder. The spheres took about 4 million years to form and grew up to weigh as much as 7 tons (the heavier ones) with a diameter of 2 meters (the larger ones). 

Large cracks, called septaria, cover the spheres starting from their hollow center. We don't know why these cracks happened, but they are filled with brown and yellow calcite. There are also small amounts of dolomite and quartz in the cracks that came to fill them when seawater levels lowered and groundwater covered up for it.

(Image source: wikimedia.org)

The boulders have been unveiled due to coastal erosion that removed the covering layers and exposed the spheres that were made of thicker materials. Waves have been working for years and years before they finally dug out those mysterious formations. In the past, the number of boulders was much bigger, but today we can find almost 50 of them. People have been taking the lighter ones to use as decorations and you can even find one outside the Otago Museum (transported there in the early 19th century). Inside the museum there are some more, of smaller sizes. Today the boulders are legally protected. Such unique formations can also be found in Kettle Point (Lake Huron, Ontario, Canada).

Just try to picture it in a time-lapse in your head: The fine mud gathering calcite deposits that became harder and harder and started from the size of a ball to reach their 2-meter diameter. These balls were then covered in mudstone and kept there safely for millions of years until the erosion from air and water worked so persistently to bring them back to light. Isn't it just amazing?

You can view an amazing photo collection of Moeraki boulders in kuriositas.com! 

Watch the video below for more information:

References

kuriositas.com
wikipedia.org
dailymail.co.uk
moerakiboulders.com
kspcommunityculture.ca

Thank you for stopping by and giving this post a read. I hope you enjoyed it! If it got your curiosity-radar on, you can check some of the previous articles on this series:
20 - The Hessdalen Lights
21 - St Elmo's Fire  
22 - Penitentes
23 - Explosive Lake Nyos
24 - Ball Lightning

If you please, feel free to pay a visit to my blog and check out my short stories along with plenty of educational posts.

     

Until my next post,
Steem on and keep smiling, people!