How do stromatolites form?

Cyanobacteria, or blue-green algae as they are sometimes known, are the architects behind some of Earth's oldest known life forms. These tiny, yet mighty organisms are at the forefront of stromatolite creation. Possessing the ability to conduct photosynthesis, they play a pivotal role in not just the formation of stromatolites but also in producing oxygen that ancient atmospheres lacked.

These bacterial communities start by colonizing surfaces within shallow marine environments. Here, they create thick layers known as 'microbial mats.' These layers are alive, teeming with cyanobacteria, and over time, accrete minerals and particles that fortify the structure. It is this process that marks the start of a stromatolite's life. As the cyanobacteria perform photosynthesis, they generate oxygen and secrete a sticky substance that aids in trapping particles, further cementing their role as ecosystem engineers of the distant past.

Understanding the underpinnings of sedimentary structures like stromatolites allows us to visualize Earth's early biosphere. They represent a tangible link to the primordial world. The stromatolite's layered design results from an intricate dance between the living (cyanobacteria) and the non-living (sediments).

As these microscopic engineers persist in their photosynthetic activities, they create a sticky web that captures wandering sediments. These particles settle and become intertwined with the microbial mats, and as more layers are added, a complex, sediment-based structure takes shape. Over time, this repetitive layering creates the stromatolite's distinct striped pattern, recording the passage of time in stone.

The history etched into stromatolites is significant; these structures serve as diaries of the distant past, chronicling the biological and environmental transformations over geological timescales. These hardened sedimentary formations, built layer by microbial layer, not only signify the presence of life but have been preserved across billions of years.

Found embedded in rock strata around the globe, stromatolites offer a lens through which scientists can peer back and observe the conditions of early Earth. Their presence in the geological record speaks to ancient climates, atmospheric changes, and the progression of life. The scientific study of stromatolites provides a unique perspective, as each layer may represent thousands of years, allowing us to piece together a timeline of our planet's life story and the role cyanobacteria played in preparing Earth for more complex life.