On Earth’s Oldest Known Wildfires
The Earth had experienced wildfires at a time when there were not many trees, but only little bushes, on its surface. Scientists recently found that the oldest wildfires had taken place 430 million years ago during the Silurian Period. They have found evidence of this in southern Wales and Poland, thanks to 430-million-year-old charcoal deposits. Scientists have discovered parts of burnt bushes in some ancient mud stones. Paleobotanist Ian Glasspool of Colby College in Maine (the US) and his colleague Robert Gastaldo have published a study in Geology magazine, giving the global community valuable insight into what life on Earth was like during the Silurian Period. According to a previous study, the first wildfires had broken out 10 million years ago. However, the latest research has proven it wrong.
Glasspool explained that although there were no big trees on the Earth during the Silurian Period, the ancient fungus, called Prototaxites, were there. Prototaxites are thought to have been able to grow as high as 9mt (or nearly 30ft) tall. According to Glasspool, the wildfires would have burned through very short vegetation, plus the occasional knee- or waist-high plant. He stressed: “It looks now as though our evidence of fire coincides closely with our evidence of the earliest land plant macrofossils. So as soon as there’s fuel, at least in the form of plant macrofossils, there is wildfire pretty much instantly.” He further said that wildfires need fuel (plants), an ignition source (it would have been lightning strikes at that period of time), and enough oxygen to burn.
Glasspool and his co-researchers have found evidence that the fire spread over a large area not only in Wales, but also at Winnica in Kielce region of Poland. Scientists are of the opinion that the fires had managed to propagate and left charcoal deposits from which researchers have come to know that atmospheric oxygen levels of the Earth were at least 16%. Currently, the level is at 21%, as it has varied during the course of Earth’s history. On the basis of this analysis, scientists have come to the conclusion that the atmospheric oxygen levels of the Earth might have been 21% or even higher 430 million years ago.
Meanwhile, Gastaldo claimed that increased plant life and photosynthesis would have contributed more to the oxygen cycle around the time of these wildfires. He stressed that this useful information would help paleontologists know the details of the oxygen cycle across time, and get a better idea of how life might have evolved. “The Silurian landscape had to have enough vegetation across it to have wildfires propagated and to leave a record of that wildfire. At points in time that we’re sampling windows of, there was enough biomass around to be able to provide us with a record of wildfire that we can identify and use to pinpoint the vegetation and process in time,” added Gastaldo.
Of course, the landscape of Europe has changed a lot in 430 million years. The two sites, used by the researchers for their analysis, would have been on the ancient Avalonia and Baltica Continents at that time. One should keep in mind that wildfires would have contributed significantly to the cycles of carbon and phosphorus, and also to the movement of sediment on the Earth’s surface. However, the latest discovery would help researchers go into the details of the complex combination of processes. “Wildfire has been an integral component in Earth-system processes for a long time and its role in those processes has almost certainly been under-emphasised,” said Glasspool.
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