Word Wednesday: Stromatolite

Nearly every biology class that I have ever taken has mentioned stromatolites. They are an essential part of the history of the Earth and are an easy term to understand.


Stromatolite breaks down into two parts: stromato and -liteStromato comes from the Greek word ‘stroma‘ which means bed or mattress and lite comes from the Greek word ‘lithos‘ which means stone. In other words, stromatolites were mattresses of stone.

Stromatolites growing in Hamelin Pool Marine Nature Reserve, Shark Bay in Western Australia. (Wikimedia Commons)

Stromatolites were microorganisms that lived up to 3.5 billion years ago and are some of the oldest fossils. They are ‘laminated organo-sedimentary structures formed by the trapping and binding, and/or precipitation of minerals by microorganisms‘, specifically by cyanobacteria (blue-green algae). In other words, they are made of layers and layers of cemented cells. They were typically no more than half a meter tall, but in some places were as large as 5 meters tall! Cyanobacteria is thought to have contributed to the high level of oxygen in the the atmosphere by undergoing photosynthesis. You can find these ancient fossils in places such as the Black Hills of South Dakota and the Upper Peninsula of Michigan. Today, the best known modern stromatolites are found in Shark Bay in Western Australia.

To learn more about stromatolites, check out the links below!

UC-Berkeley: Fossil Record of the Cyanobacteria

Shark Bay

AMNH: A stromatolite from Mauritania


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