The Moeraki Boulders are a number of huge naturally formed spherical stones, found strewn along a stretch of Koekohe Beach near Moeraki. They originally formed in ancient sea floor sediments around 60 million years ago. It’s thought they took around 4 million years to form and consist of mud, fine silt and clay, cemented by calcite. Once formed they lay hidden under a layer of up to 50m of sedimentary mud on the sea floor and are now being exposed from the mudstone they sat in due to natural erosion. (which can be seen in the pic)
The hard calcite outer is littered with cracks known as septaria which are filled with yellow calcite, dolomite and in some cases quartz. They vary in size up to 2m in diameter – these were about 1.5m to 2m in diameter.
A brief visit by us as we made our way on up to Oamaru, and as always the weather, tide and timing of our visit proved just spot on to capture them like this.
Sony a850, 15sec, at f13, iso100 + B&W x1000 10stop filter