The death of the vast Glossopteris forests that produced Australia’s coal, marks a point in time (252 million years ago) when 85-95% of all living things became extinct on this planet. The event corresponds to a geologically rapid period of global warming. Sea surface temperatures increased by 15^∘C. The cause of this catastrophic warming is mostly considered to reflect the voluminous outpouring of lava in Siberia, known as the “Siberian traps” that altered the Earth’s atmospheric composition. However, preceding the Siberian eruptions, species were already declining globally, and the climate was already changing. Scientists are unsure what caused this initial warming.  

Research completed by our team at the University of New England, together with the NSW Department of Planning, and Boise State University in USA have identified an additional trigger for global warming. The identification of a series of large-scale super-eruptions occurring in eastern Australia was recently published in Nature Geoscience.

Our recent study confirms, through precise age dating, that 257- 252 million years ago eastern Australia was being rocked by a culmination of repeated super eruptions, in the lead up to the Siberian event. Super eruptions, the largest eruptions of their kind, are different to the Siberian event, in that they are explosive and spew voluminous ash and gasses high into the atmosphere. The eruptions blanketed the land repeatedly with volcanic ash.

Utilising high-precision Uranium-Lead isotopic age dating of tiny crystals of the mineral zircon, new age relationships for the remnants of the volcanism establishes that at least 150,000 km³ of material was erupted in 4 million years. The ash-fall from these events is spread across eastern Australia. The volcanic ash can be observed interbedded with the prominent coal measures, that once formed ancient swamps and forests. Our study has confirmed the source of these ash layers is in the New England Region of New South Wales, where the eroded remnants of vast calderas are preserved.

The thickness and spread of the ancient volcanic material is consistent with some of the largest volcanic eruptions known to science. Eastern Australia 257- 252 million years ago was being rocked by repeated super eruptions. The scale and features of volcanoes  are overall similar in magnitude to that of the super volcanoes of Yellowstone in the USA or Taupo in New Zealand. The egress of substantial ash and greenhouse gas into the atmosphere of previous eruptions of these scales caused periods of pronounced climatic change in the past. The eruption of Toba 75,000 years ago in Indonesia nearly wiped-out early humans during a prolonged volcanic winter. A series of historically significant volcanic eruptions spanning 1400 – 1850 contributed to the recent ‘little ice age’. The Mt Tambora eruption in Indonesia in 1816 contributed to the ‘year without summer’. 

The period of super-eruptions in eastern Australia corresponds to changes in global temperatures and the onset of species die-off. Correlation of the results of the study to proxies of environmental change and species abundance are consistent with a link between the vast eruptions and ecosystem stress and initial extinction. The best indicator of the environmental upheaval is the abrupt termination of the vast Glossopteris forests, a key coal forming plant in Australia. Subsequently the eruption of the Siberia Traps led to even greater global warming and the catastrophic collapse of ecosystems worldwide.    

Chapman, T., Milan, L. A., Metcalfe, I., Blevin, P., Crowley, J. Pulses in silicic arc magmatism initiate end-Permian climate instability and extinction. Nature Geoscience (2022). https://www.nature.com/articles/s41561-022-00934-1