License: Creative Commons - Attribution-No Derivatives Author: denisbin
The so called haystacks rocks are a series of dramatically weathered granite outcrops which are possibly as much as 1,500 million years old. They were named after Dennis Murphy the original landowner on whose property the rocks are located. The pillars are tall rocks with concave shapes that are now detached from the underlying bedrock. The pillars and boulders have side walls that are flared in shape. The flared shapes are the result of weathering by soil moisture from just beneath the land surface and along fractures. Because the near-surface soil dries out in summer the weathering is slower at the junction of the rock and soil compared with deeper down where soil moisture is always present. As wind erosion has removed surface layers of soil the exposed pillar walls emerge as concave in shape. In some cases the flared slope has advanced toward the centre of the rock from all sides to such an extent that the tops of the rocks are much wider than the remaining core near the soil surface.