page_title: Moeraki Boulders
section_title: Description
hierarchical_section_title: Moeraki Boulders / Description
caption_attribution_description: English: View of Moeraki Beach and boulders. A sense of scale is given to the boulders with the photographer Albert Percy Godber seated on one. Photograph taken by Albert Percy Godber circa 1925.
context_page_description: The Moeraki Boulders are unusually large and spherical boulders lying along a stretch of Koekohe Beach on the wave-cut Otago coast of New Zealand between Moeraki and Hampden. They occur scattered either as isolated or clusters of boulders within a stretch of beach where they have been protected in a scientific reserve. The erosion by wave action of mudstone, comprising local bedrock and landslides, frequently exposes embedded isolated boulders. These boulders are grey-colored septarian concretions, which have been exhumed from the mudstone enclosing them and concentrated on the beach by coastal erosion.
  In 1848, Walter Mantell sketched the beach and its boulders, more numerous than now. The picture is now in the Alexander Turnbull Library in Wellington. The boulders were described in 1850 colonial reports and numerous popular articles since that time. In more recent times they have become a popular tourist attraction.
context_section_description: The most striking aspect of the boulders is their unusually large size and spherical shape, with a distinct bimodal size distribution. Approximately one-third of the boulders range in size from about 0.5 to 1.0 metre (1.6 to 3.3 ft) in diameter, the other two-thirds from 1.5 to 2.2 metres (4.9 to 7.2 ft). Most are spherical or almost spherical, but a small proportion are slightly elongated parallel to the bedding plane of the mudstone that once enclosed them.
  Neither the spherical to subspherical shape or large size of the Moeraki Boulders is unique to them.  Virtually identical spherical boulders, called Koutu Boulders, are found on the beaches, in the cliffs, and beneath the surface inland of the shore of Hokianga Harbour, North Island, New Zealand, between Koutu and Kauwhare points.  Like the Moeraki Boulders, the Koutu Boulders are large, reaching 3 metres (10 ft) in diameter, and almost spherical. Similar boulder-size concretions, known as Katiki Boulders, are also found on the north-facing shore of Shag Point some 19 kilometres (12 mi) south of where the Moeraki Boulders are found.  These concretions occur as both spherical cannonball concretions and flat, disk-shaped or oval concretions.  Unlike the Moeraki boulders, some of these concretions contain the bones of mosasaurs and plesiosaurs.
  Similar large spherical concretions have been found in many other countries.
caption: Albert Percy Godber portrait of himself among the boulders circa 1925
exif: {}