Formation of the Wairere Boulder Valley
see also about Geology

1.) Around 2.8 million years ago there was a volcano in this area which poured out a basalt layer, that covered the land which is known as Wairere valley. 2.) The layer was about 30 metres thick resting on a softer type of clay.  A first crack in the basalt formed and water erosion started under the basalt layer. 3.) The edges began to overhang and parts of the basalt layer fell into the crevasses underneath.
4.) Water running towards the sea started to form the creek or initial Wairere River and consequently widened the gap under the layer.  More and more parts of the initial lava flow broke off and the boulders placed themselves on the forming valley sides. 5.) Thousands of years passed and the valley widened even more with lots of rocks sitting all over both valley sides in soft clay.  They gently "floated" downhill towards the deeper parts in the middle of the valley.
6.) Rainwater falling onto the boulders moistened and softened the clay all around them and the weight of the boulders pushede them downhill,  like a cherry in a sloping pudding. 7.) Still today we observe that the boulders are "on the run" (they did not get very far in 2.8 million years).  The whole area shows many slips and minor land slides, which sometimes carried a boulder downwards. Finally the boulders arrived at the bottom of the valley. 8.) There they got stacked on top of each other.  The fluting pointing in very different directions indicates that the boulders must have been turned around many times during their journey to the valley floor.