The Birth Of The Boulders
Around 2.8 million years ago a volcano at the site of Lake Omapere erupted. This eruption was so huge that a basalt lava flow was spread across a massive area, that extended to Horeke. In fact there may have been multiple eruptions that extended this far resulting in a deep basalt layer around 30m thick.
This basalt lava flow started to crack as the ground beneath it was eroded over time by the action of rain. The Wairere stream formed, widening the gap below the basalt crust, so more and more chunks of basalt broke off. The boulders started to move towards the valley floor. The underlying soil was clay and as this washed away from under the boulders they moved further down the valley, finally ending up at the valley floor in the river. It has taken the boulders 2.8 million years to get from the top of the hill to the positions they lie in today.