Moeraki Boulders – Legend or Science: Let’s Solve this NZ Mystery

Margie Jones

Moeraki Boulders at the turn of the tide on the South Island of New Zealand

New Zealand is full of mystery, wonder, and spectacular scenery. Moeraki Boulders, the huge spherical rocks on Koekohe beach on the east coast of the South Island, combine all three. There are several different theories as to how these giant rocks ended up here, ranging from a Moeraki Boulders legend to a conspiracy theory.

Even the timelines vary from 60 million years ago to only a few thousand years. And, of course, there are a few scientific possibilities.

Currently, there are over 50 boulders. Today, they are protected by laws; however, that wasn’t always the case.  The largest of the New Zealand Moeraki Boulders are up to three metres in diameter, and weighing several tonnes. Interestingly, the majority are almost perfectly round rocks.

Where did these almost perfectly round Moeraki Boulders really originate?

Well, that’s up to you. Have a read and decide for yourself.

But first, let us tempt you with the rest of our beautiful country…

The Moeraki Boulders legend and a few other theories

Regardless of which one you choose to believe, you have to admit these boulders are among the most unique things in NZ.

A Māori legend

Legend tells us that the boulders are remains of calabash (a gourd-bearing tree), kumara (a sweet potato), and eel baskets that washed ashore when a canoe was shipwrecked. The rocky shoals that extend seaward from nearby Shag Point (to the south, but not visible from Moeraki Beach) are the canoe’s petrified hull.

Nearly perfectly round rocks found on the South Island of New ZealandShag Point is beyond the outcropping when looking to the South.


Conspiracy theorists tell us the Moeraki Boulders in New Zealand are actually alien eggs sent from space or washed up by the ocean. What do you think? Could the image just below be a hatched egg?

Could this be a hatched alien egg? South Island of New ZealandCould this be a hatched alien egg?


Volcanic activity is a plausible explanation.

According to this theory, these New Zealand boulders were shot out of an ancient volcano, and Koekohe Beach is where they landed.

Large rock embedded in the earth in New ZealandA prior volcano seems possible when looking at this boulder.


Mass lightning strikes passed through the region, forming canyons, boulders and other unusual geological formations. High-powered electric arcs can smash matter, spinning it in a vortex and melting and/or compressing it into round shapes – or boulders.

Round boulder on a beach in New Zealand


Science classifies them as septarian concretions. Accordingly, the Moeraki Boulders formation began on the ancient seafloor sediments 60 million years ago, during the early Tertiary period.

Each may have started as a core of a fossil shell, bone fragment, or piece of wood. Lime crystals in the sea gathered on the core over millions of years and then accumulated other minerals around it to make the boulder shape.

Over time, the original mudstone seabed became uplifted and formed coastal cliffs. The captive boulders released as the cliffs eroded.

Moeraki Boulders in black and white on the South Island of New ZealandA black-and-white shot of the boulders at high tide adds a bit of mystery.

Practical information on Koekohe Beach and Moeraki Boulders

  • Stairs lead down to Koekohe “boulders” Beach. Access requires a $2 fee to use the stairs. Money collection is on an honour system and used for maintenance and upkeep.
  • Locals and other adventure seekers often park their car a kilometre down the road and walk along the public beach to access the boulders.
  • The Moeraki Boulders Cafe, an upscale New Zealand café, is at the top of the stairs.
  • Check the times for Moeraki Boulders tides before you plan your day. Ideally, arrive closer to low tide than to high tide.

Moeraki Boulders are better seen at low tide

Moeraki Boulders at high tide on the South Island of New ZealandAt high tideMoeraki Boulders just after the turn of the tide on the South Island of New ZealandJust a bit past the high tide, we could already see more of the boulders above sea level.

We first learned of the Moeraki Boulders legend in 2007. At the time, we were living on the South Island for the winter ski season, and the house we rented had a photo of them on the wall. They called to me, and I had to see them for myself. Back then, we arrived at low tide, a far better time for seeing the boulders.

Alien Egg? At Moeraki Boulders in New ZealandAt Moeraki Boulders in New Zealand's South IslandNew Zealand's Koekohe beach on the South IslandKoekohe beach in New Zealand

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