Around 70 kilometres north of the elegant city of Dunedin (with its hexagonal city centre, castle and albatross nesting area) is one of nature’s more unusual travel wonders. As if walking into a giant’s game of marbles, huge spherical rocks are randomly scattered over Koekohe Beach. Unlike typical stones eroded smooth by the pounding oceans and coastal winds, the Moeraki Boulders (or Kaihinaki in Maori) have a far more exciting geological history.
Soon after the extinction of the dinosaurs, these rocks were formed in ancient seabed sediments a little like oysters form pearls. Around a bone fragment or piece of wood, layers of lime minerals, silt and mud coated the centre over time (well, lots of time – around four million years) creating large spherical shapes in a process scientists uninspiringly describe as septarian concretions.
More recently geological movements have uplifted the mud seabeds into dramatic coastal cliffs, wind and waves gradually extracting the embedded boulders haphazardly across a lonely stretch of beach.
Wandering around the Moeraki Boulders adds to the mystery. Some are in clumps while others sit isolated. Some lay buried in sand with their head peaking out like a bald head while other sit completely exposed. Like a creative playground, it is near impossible not to want to crawl and climb on them, jump from one to another, feel their roughened surface and perch on a rock pondering a strange geological phenomenon while gazing out to sea. A pod of Hector Dolphins may even skip along the shallows of the coastline seeking food or playing joyously in the chilly ocean waters.
Some of the Moeraki Boulders have split trying to revealing a hollowed centre while others have grown a stranger crystalline exterior giving them a tortoise shell-like skin. Some are quite a bit bigger than others varying from over two metres to under a metre in diameter.
Maori legend dictates that a canoe was wrecked along the New Zealand coast carrying a cargo of eel baskets, gourds and calabashes. These petrified into rock when they fell onto the land leaving a symbolic memorial to the ship’s loss.
Vibrant imaginations have offered descriptions like “giant gobstoppers”, “alien’s brains” and “Kiwi Stonehenge”. For me, I envisage a game of marbles for giants.
Whatever your reaction to the Moeraki Boulders, the geological phenomenon make a wonderful diversion on a drive between Dunedin and Oamaru. Their mysterious origins and strange appearance boggle the mind while enjoying a bracing stroll below the coastal cliffs wondering how many more of the giant’s marbles will be extruded from the cliffs by nature’s inevitable shaping of this dramatic shoreline.