A new study, published in the journal Geology, presents evidence that suggests the first known mass extinction on Earth was triggered by dramatic volcanic eruptions in Australia. This extinction-- the Early-Middle Cambrian extinction-- occurred some 511 million years ago and caused a dramatic reduction in complex multicellular life on Earth, yet the precise reasons behind this event remained shrouded in mystery.
The investigation, which was led by Curtin University’s Fred Jourdan, involved using high precision Uranium-Lead and Argon-Argon dating to determine the age of lava flows from the eruptions of the Kalkarindji volcanic province, which smothered an area of greater than 2 million square kilometers in Northern and Western Australia. They found that the eruptions occurred at the same time as the extinction, around 511 million years ago.
According to Jourdan, this famous extinction wiped out 50% of all species on Earth and although previous studies indicated that this was due to climatic changes and depletion of oceanic oxygen, no one knew the mechanism behind these events.
“Not only were we able to demonstrate that the Kalkarindji volcanic province was emplaced at the exact same time as the Cambrian extinction, but were also able to measure a depletion of sulfur dioxide from the province’s volcanic rocks- which indicates sulfur was released into the atmosphere during the eruptions,” he added.
Jourdan detailed how a much smaller eruption in 1991 by volcano Pinatubo decreased average global temperatures by a few tenths of a degree for several years due to the sulfur dioxide released. “If relatively small eruptions like Pinatubo can affect the climate just imagine what a volcanic province with an area equivalent to the size of the state of Western Australia can do,” he added.
The team also hypothesizes that lava intrusions in oil and sulfate deposits could have triggered the release of a significant amount of both sulfur dioxide and methane which, married with the release of volcanic gases, could have caused oscillations in the Earth’s climate. According to Jourdan, these climatic oscillations would have made it difficult for many species to adapt.
Furthermore, the team extended this study by investigating other eruptions and extinctions that have been documented throughout history. “We calculated a near perfect chronological correlation between large volcanic province eruptions, climate shifts and mass extinctions over the history of life during the last 550 million years, with only 1 chance over 20 billion that this correlation is just a coincidence,” said Jourdan.
Jourdan also stresses the importance of research such as this in understanding the consequences of climate change. By looking at how huge gas injections into the atmosphere have affected climate and ecosystems in the past, we may be able to understand more about the possible long-term effects of human-induced climate change.