A collaboration of Australian and Swedish scientists have found that current carbon dioxide (CO2) emission rates are 200 times greater than those of the most catastrophic ancient supervolcano event. Known as the “Great Dying”, this event around 252 million years ago wiped out at least 90% of species on Earth and 96% of marine animals.
But not all supervolcanic events are linked to mass extinctions.
Recent to research led by Dr Qiang Jiang, then at the School of Earth and Planetary Sciences at Curtin University, Australia, indicates that some past supervolcanic events involved a slower rate of CO release.2 or less CO2 overall, or both, and that it was not related to the size of the rash.
To investigate these ideas, Jiang and his team looked at the two largest supervolcanic regions of the past 540 million years – roughly when complex life forms emerged on Earth.
The largest, Ontang Java province, is now divided into three parts around New Zealand and the Solomon Islands, says study co-author and Curtin geology researcher Dr Hugo Olierook, the major part being underwater or inaccessible. The team therefore turned their attention to the second-largest volcanic province, known as the Kerguelen Grand Volcanic Province – a body of solidified lava three times the size of France in the southern Indian Ocean.
The researchers dated samples taken from Kerguelen using Argon-Argon datingwhich indicated an age of about 120 million years.
“The new age data revealed that the Kerguelen eruptions were, in fact, active throughout the global oceanic anoxic event 120 million years ago,” says Professor Fred Jourdan, director of the Western Australian Argon Isotope Facility at Curtin. “But although they rapidly degraded the environment for marine organisms, it did not lead to a deadly mass extinction.”
Armed with powerful microscopes and lasers, the team then looked deep inside the basalt samples for tiny (10 micron diameter) frozen magma drops called inclusions and measured the pockets of volatiles – molecules that easily change. in gas (water, CO2 and hydrogen sulphide, for example) – released from the drop of magma during its solidification and contraction.
Compared to similar gas studies of supervolcanoes associated with mass extinction events, Jiang and his team found that Kerguelen Province emitted at least five times less CO2 and at a rate 30 times slower than the volcanic eruptions that wiped out entire life forms.
Out of five major extinction events since animals first appeared, four are attributable to supervolcanoes, which deplete the oceans of oxygen and cause global climate change on time scales too small for the evolutionary adaptation of many land and sea animals.
The Earth has mechanisms by which carbon is drawn into oceans, rocks and soils, Olierook explains. “Shells embed carbon into their structure, and the oceans themselves pull carbon into the ocean floor, but this happens on the order of a few hundred thousand years.”
When CO levels2 emissions far exceed the sampling cycle – as during CO2-rich in supervolcanic events, then the balance is broken.
So why are some supervolcanoes rich in CO2?
There are a few likely reasons. When hot magma rises to the surface, it can interact with the rock layers it passes through. In the case of CO2-rich in supervolcanoes, Olierook says the magma intruded through “organic-rich sedimentary basins, heating them up and turning into a kind of peat and coal, the type of material that easily becomes CO2”. In the case of the two largest supervolcanoes, they “sat in the middle of the ocean. So there wasn’t really a lot of organic-rich material there,” he says.
It’s also possible that the rising magma itself is carbon-rich — something Olierook hopes to investigate further in the future.
Finally, the research team compared current levels of CO2 with those of supervolcanic events that resulted in catastrophic mass extinctions.
“Alarmingly, our calculations also show that we are currently emitting carbon dioxide 200 times faster than the supervolcanic eruptions that have caused the most severe mass extinctions,” Olierook says.
While this sounds like bad news, it also contains a faint glimmer of hope.
“If we are able to slow down our CO2 emissions now, we’ll actually see the effects of a slowdown now,” says Olierook. “We are definitely not on the verge of having the highest CO ever.2 in our atmosphere, however – there was much more CO2 in the atmosphere, say 100 million years ago.
“So if we can focus on slowing the rate of CO2 emissions, we could reach a level where our planet can cope with the CO emitted2.”
