ThrombolitesLiving Rocks Thrombolites, 'living rocks', are the most
common form of microbialites, which are rock-like
structures built by micro-organisms. One of the few
places in the world where the thrombolites grow is at
Lake Clifton in Western Australia's
Yalgorup National Park which is located 32
kilometres south of Mandurah. The lake is also one of
only two sites known where microbialites occur in water
less salty than sea water. The lake contains the largest
lake-bound microbialite reef in the southern hemisphere
which is over 6kms long and widens in parts to 120m. The
thrombolite structures reach heights of up to 1.3m.
How It All Began Millions of years ago, earth, as we know it
was a little different, there was no oxygen in the
atmosphere and there was no protective ozone layer.
Scientists believe that things began changing when tiny
organisms started to appear (from where, no one knows).
These tiny little organisms lived in water and produced
oxygen. This oxygen entered the atmosphere and over time
created the atmosphere we live in today. Now this process
didn't happen overnight, the organisms had to produce
large quantities of oxygen over a long period of time
before earth could sustain life . One of the ancestors of
these tiny organisms are in fact algae, yes those aquatic
plants. Stromatolites and thrombolites are created by
algae and represent the earliest record of life on earth.
What Are Thrombolites? Thrombolites are formed when the
micro-organisms photosynthesise. During this processs
they are able to precipitate calcium carbonate from the
waters of the lime-enriched lake to form the rock-like
structures. Luckily Lake Clifton has an abundance of
fresh ground water which is high in calcium carbonate
providing the perfect environment. Thrombolites form in a
different way than stromatolites which are found in Hamelin Pool at Shark Bay . Thrombolites have an internally
clotted texture whilestromatolites have a layered
(laminated) internal structure and are formed by
blue-green bacteria trapping sediment particles.
Thrombolites and stromatolites were the only known form
of life on Earth some 350 to 650 million years ago.
Microbes found in both thrombolite and stromatolite
formations are believed to be responsible for oxygen
production which allowed life to exist on the planet.
Thrombolites are the most common form of microbialites
and are formed by a variety of micro-organisms. They grow
at an average of 1mm a year.
The only place on earth where both marine
stromatolites and thrombolites exist is on a small private
island, Highborne Cay , in the central
Bahamas. |
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