volcanic eruptions cambrian extinction
May 31, 2014

First Mass Extinction Believed To Be The Result Of Australian Volcanic Eruptions

Alan McStravick for redOrbit.com - Your Universe Online

This week has certainly been heavy on extinction news. Seth Borenstein's enlightening AP article is one, detailing that the Earth may, in fact, be on the brink of the Sixth Great Extinction event. Citing the loss of species at a rate of 1,000 times faster than at any time prior to the rise of the human race, Borenstein's story states we are toying with disaster and whether or not humans make it out of this alive depends fully on decisions we make today.

It is knowledge of the above that makes this extinction story not only interesting but important as well.

A researcher from the Perth, Australia-based Curtin University has definitively shown how the first mass extinction event in the history of complex life was caused by ancient volcanic eruptions on his own continent some 510 million years ago

Associate Professor Fred Jourdan, who teaches in the school's Department of Applied Geology, working with colleagues across Australia and the world, employed radioactive dating techniques to arrive at a precise age for when the eruptions of the Kalkarindji volcanic province occurred. This volcanic region saw lavas from the eruptions spread across more than 2 million square kilometers in the Northern Territory and Western Australia. To put that into perspective, it is an area roughly larger than the entire state of Washington. Their results have been published in the prestigious journal Geology.

Through their precise dating, the team showed that the eruptions occurred in conjunction with the Early-Middle Cambrian extinction event 510 to 511 million years ago. This, as stated above, was the first extinction event that was responsible for wiping out complex multi-cellular life on this planet.

“It has been well-documented that this extinction, which eradicated 50 percent of species, was related to climatic changes and depletion of oxygen in the oceans, but the exact mechanism causing these changes was not known, until now,” Dr. Jourdan said in a university statement.

“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 sulphur dioxide from the province’s volcanic rocks – which indicates sulphur was released into the atmosphere during the eruptions," explained Jourdan.

“As a modern comparison, when the small volcano Pinatubo erupted in 1991, the resulting discharge of sulphur dioxide decreased the average global temperatures by a few tenths of a degree for a few years following the eruption," he added. “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.”

Once the team was able to determine the age and sulphur dioxide emissions of the Kalkarindji volcanic province they then compared it with other global volcanic provinces. These comparisons showed the most likely process for the first five mass extinctions was likely a rapid oscillation of the climate triggered by eruptions that spewed sulphur dioxide, along with the greenhouse gases methane and carbon dioxide.

“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 one chance over 20 billion that this correlation is just a coincidence,” Dr. Jourdan said.

Many species are adapted for a very narrow environment and any change, regardless of how minute, will stress that species, often to extinction. Dr. Jourdan claims it was the rapidly changing oscillation in climate caused by the volcanic eruptions that made it increasingly difficult for various species to adapt. Dr. Jourdan believes his research into an event 510 million years ago is, itself, particularly salient and significant to the predicament we currently find ourselves in today.

“To comprehend the long-term climatic and biological effects of the massive injections of gas in the atmosphere by modern society, we need to recognize how climate, oceans and ecosytems were affected in the past,” he said.