To start with it seemed to me that in this complex world, my rock was literally a solid base on which I could anchor my thoughts – as Richard Dawkins says: “In the beginning was simplicity”; before anything else existed on planet earth, there was rock. But now of course I realise that is just too simple. Yes, of course, rock existed before life, but life has gone on to make rock. Everything in the world is inter-connected. Now I understand that before my flint was a rock, it was alive…
“Flints were formed during a complex chemical process which began in the chalk seas millions of years ago when silica from the decomposing skeletons of sea creatures became incorporated in the accumulating chalk sediment. Under certain conditions the silica reacted slowly with oxygen in the water and hydrogen sulphide from decomposing organic material to form a precipitate which collected in the burrows and tunnels made by sea creatures.”*
And don’t forget Stromatolites.
“Stromatolites are rock-like structures formed by cyanobacteria and single-celled algae. The mucus secreted by the bacteria collects grains of sediment which become stuck together with calcium carbonate, also from the bacteria. This builds up into the structures seen in certain sea-shore bays. Cyanobacteria and algae can photosynthesise and the real significance of these microbes is that they are thought to be the first known organisms to photosynthesise and produce free oxygen and so were largely responsible for increasing the amount of oxygen in the primeval Earth’s atmosphere. After about a billion years, the effect of this, called the Great Oxygenation Event, actually killed off many organisms which could not live in oxygen, and led to the kind of environments we know today, where most organisms use and need oxygen.”**
NOW scientists and engineers are developing self-healing concrete, incorporating bacteria into the concrete mix along with a form of starch which acts as food. The bacteria lie dormant in the concrete unless a crack forms, allowing air and water to penetrate, then the bacteria are activated and start to metabolise the starch. They grow and reproduce and excrete a mineral form of calcium carbonate which bonds to the concrete and seals the crack.
Click on the image below to view a short GIF slideshow or view the full version of A Brief History of Rock at https://vimeo.com/255278513.