Take a close-up look at Australia's earth; it's not just a load of old rocks!!
By George Seddon, Professor Emeritus in Environmental Science, University of Melbourne and Senior Honorary Research Fellow at the University of Western Australia. Professor Seddon's latest book is Land Prints and is published by Cambridge University Press.
I have just got home from looking at the beginning of the world. What's that again? Well, there's a road in the Pilbara from Port Hedland to Marble Bar (the Athens of the North). Before you get to Marble Bar, turn south on a rough dirt track and, after crawling in and out of too many steep-banked dry creeks, you come to an old mine site. Nearby, there are several outcrops of fossil stromatolites and they are up to 3.5 billion years old, among the oldest known evidence of living organisms.
The stromatolites are in the Warrawoona Group, which were mostly volcanic lavas, but with some layers of sediment accumulating in shallow seas. Beneath these rocks, there is an angular unconformity or ancient erosion surface (a page missing in the local journal of events); the eroded rocks have been dated to 3.515 billion years.
For erosion to take place they had to be at the earth's surface; this is the first reliably dated evidence of a stable crust. The world was beginning to assume its present form; we are watching the curtain go up. Of course, it must have gone up elsewhere, too, but this is the first record - first by more than half a billion years, in the East Pilbara.
What was it like? Steamy. Volcanoes erupting, cooling lava, shallow seas, igneous rocks, mostly granitic, heaving away like hot thick porridge. A reducing atmosphere, mostly nitrogen and carbon dioxide, with traces only of oxygen. Yet there was life, including the cyanobacteria quietly building their layer-cake mushrooms of alternating sediment and organic films.
They kept at it. Moving south and a billion years later, the stromatolites were abundant in what is now the Hamersley Basin. At some point they became photo synthetic, able to harness the energy of the sun - for all of us. This was a step of far more significance for our species than landing on the moon. Most of our energy, including all the fossil fuels (rocket fuels included), our wood fires, our food, are directly or indirectly dependent on it. But that is only part of the story. Oxygen was a toxic waste product for cyanobacteria, and they excreted it by combining it with the abundant ferrous oxide dissolved in seawater, precipitated as ferric oxide. This is abundant in the banded iron formations, over a kilometre thick, mined at Newman, Tom Price, Shay Gap, and exported in massive quantity. You may not be enthusiastic about stromatolites and the cyanobacteria, but given that they paid for your Nissan Patrol or Miele electric oven, your TV and your holiday in Provence, you might spare them a kind thought. Nearly one-third of Australia's export income comes from the sale of minerals from WA, and those little micro-organisms were working away quietly on your behalf some 2.5 billion years ago - not, of course, only in WA, but they are most spectacularly exposed in the Hamersleys. Working on our balance of trade was not their only positive contribution; as they locked up most of the ferrous ions in seawater, they released oxygen to the atmosphere, and this began the next major phase of global evolution.
An oxygenated atmosphere allowed the appearance of new kinds of organism. Simple cells somehow acquired a nucleus - a handy little command post and communications centre. Another major step was the appearance of sexual reproduction requiring genetic recombination - not as efficient as simple division, but definitely more fun and very useful in times of rapid environmental change.
Then, towards the end of the Pre-Cambrian, soft-bodied, multi-cellular creatures made their debut. Again, they were first found and are best displayed in Australia, but this time in the Flinders Range, in the Pound Quartzite at Wilpena. After that, the race was on; trilobites, primitive fish, early land animals and plants, the dinosaurs, the mammals, the mammoths, us .... all this in a mere 500 million years. When I was young, I read a book by Eleanor Dark, called The Timeless Land. Australia was the place where time stood still. But she got it wrong. Australia was the place where the clock started ticking. It is ticking away still: put your ear to the ground and you can hear it tick. One of the most notable features of the past few decades is the rapid growth of knowledge in all the historical sciences, from geology and evolutionary biology through to archaeology and anthropology.
Time's arrow runs through all of them, historicising our world picture ever more fully, and perhaps nowhere more dramatically than in Australia. So look at the Big Picture: it has been running here for 3.5 billion years.