Moeraki Boulders

Moeraki Boulders Facts

• The Moeraki Boulders comprise an unusual geological feature comprising a rather startling collection of large boulders along a section of beach on the coast of Otago.
• The majority of the surprising boulders lie in large clusters. Each of these boulders also measures roughly spherical in shape.
• In addition, some of these geological marvels also possess large fissures, as well.
• These fascinating and rather remarkable features occur in the sovereign island nation of  New Zealand, off the coast of Australia.
• Fortunately for posterity, the section of beach that they appear on now forms a protected reserve.

Moeraki Boulders Physical Description

The eye-catching Moeraki Boulders have long fascinated those who encounter them. The great majority of them fall into two distinct size ranges.

Approximately 30% of them measure between 1.6-3.3 ft (0.5-1.0 m) in diameter, while the vast majority of the rest all stay in the range of 4.9-7.2 ft (1.5-2.2 m).

Yet they do have one basic factor in common. All of the boulders display a dark gray color, due to the particular nature of their composition.

Most of these unique objects have a roughly spherical shape, yet a rather small percentage of them possess a slightly elongated shape.

Moeraki Boulders Composition and Origin

The astonishing Moeraki Boulders formed as septarian concretions. They consist of a combination of silt, clay, and mud, bonded together by calcite.

Beneath the extremely hard outer shell, they remain relatively soft, as they are less compacted.

A few have also broken open, and their interiors eroded by the elements. Further, the inner cores of many of these formations have linings of calcite crystals.

The Moeraki Boulders were formed during the Paleocene Era as the calcite deposited in the mud on the seafloor. As further mud layers deposited, the pressures began their formation.

The process required millions of years. Coastal erosion then exhumed them from the sea mud.

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