About 252 million years ago, the world was going through a turbulent period of rapid global warming.
To understand why this is so, scientists looked at a specific event in which a volcanic eruption in what is now Siberia released massive amounts of greenhouse gases into the atmosphere.
However, there is evidence that the climate was already changing before that.
Sea surface temperatures increased by more than 6-8 °C in the hundreds of thousands of years preceding the Siberian outflow in Siberia. Temperatures rose again after that, to the point that 85-95 percent of all living species eventually became extinct.
The volcanic eruption in Siberia has clearly left its mark on the planet, but experts remain puzzled as to what caused the initial warming before that.
Our research reveals that Australia’s ancient volcanoes played a large role. Prior to the event in Siberia, catastrophic volcanic eruptions in northern New South Wales released volcanic ash across the east coast.
These volcanic eruptions were so large that they unleashed the world’s largest climate catastrophe ever – and the evidence is now hidden deep within thick sediment mounds in Australia.
our study, Posted today at temper natureasserts that eastern Australia was shaken by frequent “super eruptions” between 256 and 252 million years ago.
Super eruptions differ from the more negative Siberian event. These catastrophic eruptions released huge amounts of ash and gases into the atmosphere.
Today we see evidence of this in light-coloured layers of volcanic ash in sedimentary rocks. These layers are found across large areas of New South Wales and Queensland, all the way from Sydney to near Townsville.
Our study identified the source of this ash in the New England region of New South Wales, where remnants of eroded volcanoes are preserved.
Although erosion has removed much evidence, the now seemingly innocuous rock is our track record of terrifying volcanic eruptions. The thickness and spread of the resulting ash is consistent with some of the largest known volcanic eruptions.
What is the size of super eruptions?
At least 150,000 cubic kilometers of material erupted from northern New South Wales volcanoes over a period of 4 million years. This makes it similar to the giant volcanoes of Yellowstone in the United States and Topo in New Zealand.
To put it in perspective, the eruption of Mount Vesuvius in AD 79, which wiped out the Italian city of Pompeii, produced just 3-4 cubic kilometers of rock and ash. The eruption of Mount St. Helens in 1980 was about 1 cubic kilometer.
Australian blasts have been covered over and over again entire East coast in ash – meters thick in places. The massive influx of greenhouse gases would have triggered a global spark Climate change.
Ancient sedimentary rocks provide a timeline of environmental damage caused by eruptions. Ironically, the evidence is preserved in coal measures.
Present coal deposits in eastern Australia show that ancient forests were used to cover much of this land. After the massive eruptions, these forests were abruptly ended in a series of wildfires over the course of about 500,000 years, 252.5-253 million years ago.
Plant matter usually accumulates in swamps and then is buried under sediments. The burial process provided heat and pressure, which made it possible to convert the plant matter into charcoal.
Without forests, no plant matter would have accumulated. The ecosystem collapsed and most of the animals became extinct.
Subsequent eruptions in Siberia amplified the devastation caused by Australia’s giant volcanoes.
This collapse of ecosystems is not limited to Australia either. The catastrophic event affected all ancient continents. It had a great influence on the evolution of life – which eventually led to the emergence of dinosaurs.
The giant eruptions in Australia were a major sign of change in the ancient world. As we look to achieve a more habitable climate in the future, who knew that the keys to environmental disaster lay beneath our feet?
Acknowledgments: We would like to thank our colleague Phil Blevin from the Geological Survey of New South Wales for his contribution to this work.
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