What are Stromatolites?

Stromatolites: Geological Structures

Stromatolites are sedimentary rock-like structures that formed in shallow waters. They developed through the build-up of simple bacteria that trapped sediment over time.

Early bacteria formed thin, sticky layers on the seabed. As they grew, they formed a film on the surface that caught tiny grains of sand, mud, and minerals. Over time, the bacteria grew upwards through the sediment towards the light, allowing new sediment to settle on top.

As the bacteria continued to grow, more sediment became trapped, forming a new layer. This process repeated again and again, gradually building up a layered, rock-like structure. Today, these structures are known as stromatolites.

The bacteria in these structures began the process that eventually led to a dramatic rise in atmospheric oxygen.

The word stromatolite comes from the Greek for 'layered rock'. 

Stromatolites are amongst the oldest fossil records of life on Earth. They were common along shorelines around the world about 3.5 billion years ago. Some even older structures, found in the Pilbara region of Western Australia and dating to around 3.7 billion years, have been identified, although their biological origin is still debated by scientists.

Stromatolites represent some of the earliest evidence that life existed on Earth.