The Stromatolites of Hamelin Pool

In June 1954, a group of geologists discovered the stromatolites or 'living rocks' of Hamelin Pool which linked life on Earth today, with life on Earth 3.5 billion years ago.
Scientists who have studied fossils of stromatolites, once believed them to have been wiped out by intense competition with newer life forms like plants and animals.
While competition dramatically reduced stromatolites worldwide 550 million years ago, Hamelin Pool has provided a safe haven for stromatolite colonies for the past 5'000 years.
What are Stromatolites?

Stromatolites are layered limestone rock built by single-celled cyanobacteria (blue-green bacteria) which trap and bind sediments.
Some build craggy towers, others build flat spongy mats.

Stromatolites grow along the shore, usually right up to the highest tide mark.
They are fragile and can be easily damaged if you touch or walk on them.

At the entrance to Hamelin Pool is a massive sand bar called the Fauré Sill, which has built up over 6'000 years and restricted the tide flow into the Pool.
The shallow waters of Hamelin Pool evaporate quickly and create super-salty water.
In such harsh conditions, few sea snails can survive to graze on cyanobacteria.
Hamelin Pool has become a safe neighbourhood for cyanobacteria which build stromatolites of various shapes and sizes at different water depths.

In the Beginning stromatolites first appeared in a warm, salty sea like this.
Bacteria built our stromatolite empire which dominated the Earth for more than 2 billion years.
Without the oxygen they produced, life on land may not have evolved.

These red capped stromatolites stopped growing about 500 to 1'000 years ago when the sea level fell.
The reason for their colouring is a mystery.
One guess is it may have been iron in the water as they grew or the pigment of visiting bacteria.

All Stromatolite are built by cyanobacteria.
Those closer to shore tend to be flat and spongey while others in deeper water tend to build up layers to form rocky towers.

Stromatolite layers grow outwards, like the growth rings of a tree.
Their outer layer remains a thin strip of active life with a sticky film to trap and bind drifting shells and sand.
They slowly build up layers which harden into rock.
Scientists believe that their internal growth rings provide information on local environmental changes during their lifetimes.
Some scientists say that the growth rings in their ancient relatives reflect changes in the length of days, angle of the sun, even the rate at which the earth rotated.

Like humans, stromatolites come in various shapes and sizes.
Tidal movement, waves and the abrasive action swirling sand and shell help to shape them.
The club-shaped stromatolites prefer a deeper water habitat.



No liability for timeliness, integrity and correctness of this document is accepted.
Last updated: Thursday, 06.08.2009 4:29 PM