Puddingstones

By Alex Scott

Puddingstone from Ontario, Canada, by James St. John.

Puddingstone from Ontario, Canada, by James St. John.

Over 2 billion years ago, the Huronian glaciation was finally coming to an end after a 300-on-year global ice age. Originally caused by the evolution of oxygen-producing bacteria, this turbulent era may have been the catalyst for most living organisms today to evolve, including plants, animals, and fungi. 

As huge glaciers were retreating to the poles with the rising temperatures that signaled the end of the ice age, pebbles of jasper, chert, quartz, and other minerals were being consolidated in a quartzite matrix to form stones that, to humans evolving billions of years later, would resemble a Christmas pudding. 

Christmas pudding cake

When those humans arrived and another Ice Age occurred, the glaciers that stretched from the North Pole to Canada pushed these stones into Michigan, where they remained as the glaciers retreated once more. 

Puddingstone from Drummond Island, Michigan, by Paul Donelson.

Puddingstone from Drummond Island, Michigan, by Paul Donelson. 

 What remains are polka-dotted, multicolored Michigan puddingstones that are beloved not only by Great Lakes beachcombers but anyone with an interest in geology.

Puddingstone from Drummond Island, Michigan, by Paul Donelson.

Puddingstone from Drummond Island, Michigan, by Paul Donelson. 

Michigan isn’t the only place where you can find puddingstones—they are also found along the northeast coast of North America and in western Europe—but they remain some of the rarest and most interesting rocks in the world. 

uddingstone from Portugal by Bravo Ferreira da Luz.

Puddingstone from Portugal by Bravo Ferreira da Luz.

This article appeared in the Beachcombing Magazine March/April 2020 issue.

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