Glacier National Park: Stromatolites

Glacier National Park is home to a unique type of fossil called stromatolites. They were organisms of blue-green algae that lived in warm shallow seas in ancient times. Although they look as though they are fossils of ancient cabbages and range in size from a few inches to several feet in diameter, stromatolites are some of the earth's oldest fossils. They can be found in the pale gray cliffs of Siyeh limestone that dominate much of the high country of central Glacier National Park. You can see stromatolites around Logan Pass and along the trail to Hidden Lake.

Six species from three genera of stromatolites are preserved in the rocks of the park. The fossils are so well preserved that paleontologists from around the world come to Glacier specifically to study them. The fossils provide a window into what the earth was like during a period of 800 million years that began over a billion years ago. From these fossils, scientists learn about preservation, diversity, and antiquity.

These primitive blue-green algae are believed to have paved the way for modern plant and animal life. Blue-green algae absorbs atmospheric carbon dioxide, creates organic matter, and releases oxygen into the air. The stromatolites were the first plants responsible for starting the long process of removing carbon dioxide from the air and replacing it with oxygen that animals can breathe. Without the stromatolites, we wouldn't exist.

The Siyeh limestone in which the stromatolites exist, is dark in color because it contains a lot of organic matter. In some places, there is so much organic matter that freshly broken rock releases a foul odor. Every atom of carbon buried in the sedimentary rock must balance every molecule of oxygen in the air to account for the original carbon dioxide. Thus, the foul smell is a reminder of how we got the air we breathe.