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 stromatolite, once believed them to have been wiped out by
intense competition with newer life forms like ants 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 5000
tears.
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.
At the entrance to
Hamelin Pool is a massive sand bar called the Fauré Sill, which has built up
over 6000 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.
Red Caps.
These red-capped
stromatolites stopped growing about 500 to 1000 years ago when the sea level
fell. The reason for their colouring is a family mystery. It may have been
because of iron in the water as they grew or the pigment of visiting bacteria.
Layers of history
Stromatolite layers
grow outwards, like the growth rings of a tree. The 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 the internal growth rings provide information on local environmental
changes during the stromatolites lifetime. Some scientists say that the growth
rings of very ancient stromatolites reflect changes in the length of days,
angle of the sun, even the rate at which the earth rotated.
Living rock
The cyanobacteria that
build us first appeared n earth 3.5 billion years ago when oxygen was scarce.
As the original stromatolite colonies expanded, they released more and more
oxygen into the atmosphere, eventually raising the oxygen level to 20% of all
atmospheric gases. This led the way for air-breathing life forms to evolve.
When the tide is in,
you can see little bubbles.
It was amazing to see
these stromatolites, and to think that we live are alive on earth today is
thanks to them is fascinating!
..............
We spent the night at the Hamelin Bay Station. It was really nice and calm there, and the owners were very friendly. It is in the middle of nowhere though! We wanted to go and buy some food but were told that the closest shop was more than 100km away!
The black swan is the state emblem, and the Swan
River was named after it, but sadly had very few, because most of the swan’s
preferred habitat, the shallows, has been destroyed.
Le Carnet de Voyage
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