David Biello reports that fire ranks among humanity's oldest and most powerful tools. Now the residue from all the oil and coal burned to power modern civilization may provide the best marker for the start of a new geologic epoch that highlights Homo sapiens’s world-changing impact, known as the Anthropocene, or "new age of humans." "We're actually changing and continuing to change how the Earth system functions and leaving markers that could still be found in a million years time," says Earth scientist Karen Bacon of the University of Leeds in England. "That's quite incredible to think about." (more).
The proposed marker is billions of microscopic black balls found from the high arctic to the bottoms of lakes in Chile. When a flame eats into the hydrocarbons known as coal or oil, not all the carbon atoms pair up with the oxygen that makes fire and carbon dioxide emissions possible. Some of that carbon remains bonded tightly to its fellow carbons, unburned, forming a little black sphere (more). These spheres are known as spheroidal carbonaceous particles (SCP) to environmental scientists and incomplete combustion products to fire engineers; the general public knows them best perhaps as soot (more).
That soot, fly ash or whatever you want to call it is borne aloft by the hot gases of combustion before settling gently back to Earth in lungs, into lakes and the sea or onto the landscape. The more coal and oil burned, the more black spheres formed, making such soot the perfect record of a swelling fossil-fuel pyromania. As CO2 changes the climate, one of humanity's biggest impacts on the planet as a whole, these pitted carbon balls mark the potentially irrevocable change. "In the very top of these sediment cores we take, we get these fly ash indicators," explains Leeds geologist Graeme Swindles, lead author of a paper published in Scientific Reports on May 28 (Scientific American and Scientific Reports are part of Nature Publishing Group.)
Swindles argues the SCPs are a marker for the start of the Anthropocene. For example, long boggy brown peat cores that record millennia of deposits suddenly turn black as night at their tops from the recent addition of sooty carbon. "These things are all over the place—they're everywhere," he adds, noting that he has found SCPs even in the far reaches of the Amazon rainforest, remote from any industrial activity, albeit at lower concentrations. "We have indicators that are basically like fossils that can be used to pinpoint the boundary."
Environmental scientist Neil Rose of University College London has been collecting such SCP records from lakes around the world for 25 years. On every continent more fly ash starts falling into the geologic record around 1950, Rose notes in a paper published by Environmental Science & Technology on March 19, even though we have been adding SCPs to the environment for roughly 170 years now.
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