Basalt flows, like the black rock in this New Jersey quarry, are remnants of massive volcanic activity 200 million years ago.
Image: Paul Olsen/Lamont-Doherty Earth Observatory
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The mass extinction that wiped out many species at the end of the Triassic period some 200 million years ago made way for the dinosaurs' domination of Earth for the next 135 million years. Now, researchers have determined the timing of a possible trigger for that Triassic extinction event with unprecedented precision.
Scientists have long suspected a link between the Triassic die-offs — one of the five largest mass extinctions to have struck Earth in the past 542 million years — and widespread volcanic activity that occurred at around the same time. The vast amounts of lava spilled from those eruptions, which covered an area slightly smaller than Australia, can now be found on four continents.
Radioactive dating techniques used in previous studies haven’t been accurate enough to pin down exactly when those eruptions took place, says Terrence Blackburn, a geochronologist at the Carnegie Institution for Science in Washington DC. Some estimates have even suggested that the die-offs took place before the eruptions started, implying that the volcanism may have had only a peripheral role.
But by using a precise dating technique that charts the radioactive decay of uranium isotopes to lead in zircon crystals found within ancient lavas, Blackburn and his colleagues have determined that the volcanism took place in four phases. After examining lavas at seven sites in eastern North America and one in Morocco, the team concludes that the first and largest episode of volcanic activity began at the same time as the mass extinction. The results of the study were published today in Science.
Crystal clue
Zircons aren’t normally found within lava deposits, says Blackburn. But as extremely thick layers of magma cool, zirconium, uranium and rare earth elements become concentrated in still-molten layers within the solidifying lava, providing the source material from which zircons can crystallize.
The first phase of eruptions began in what is now Morocco around 201.56 million years ago, the team reports. Fossils of pollen and other spore-like structures appear in sediment layers there just below the massive lava deposits, also known as flood basalts — a sign that ecosystems in this area were intact and functioning just before the onset of volcanism.
Within about 12,000 years, the wave of eruptions had spread to areas that are now located along the US east coast. During the first 30,000 years of this phase of volcanism, and possibly over a much shorter interval, more than 1 million cubic kilometers of magma had spilled forth — enough to smother an area the same size as the lower 48 US states to a depth of more than 100 meters, says Blackburn.
Subsequent, smaller episodes of volcanism occurred about 60,000 years, 270,000 years and 620,000 years after the first phase had begun, the team estimates.
“This work has taken dating to a higher level with super precision,” says Paul Renne, a geochronologist at the University of California, Berkeley. “It adds to the notion that the [end-Triassic] extinctions and the flood basalts were linked.”
However, it is still unclear what ultimately caused the die-offs, says Renne. It might have been the drastic swing in climate between short-term cooling induced by volcanic aerosols and long-term warming caused by carbon dioxide emissions. Alternatively, the extinction might have been caused by the resulting acidification of the oceans, or any of a dozen or more ecological insults proposed in previous studies, he notes. “This is good circumstantial evidence, but in some cases that’s all you get,” Renne says.
This article is reproduced with permission from the magazine Nature. The article was first published on March 21, 2013.
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15 Comments
Add CommentIt's crazy that past changes in atmospheric and ocean chemistry take 10,000 years or more and we're doing something similar with CO2 emissions over the course of a couple centuries. Why would we want to use our planet to conduct an uncontrolled experiment like this? Mass extinctions like the Triassic extinction event are associated with massive releases of CO2, ash, and large areas paved over with lava. Does anybody think it's smart to try and recreate these conditions?
Reply | Report Abuse | Link to thisHow else can we prove that CO2 emissions cause mass extinctions? It may be the only way to convince the deniers...
Reply | Report Abuse | Link to thisQuestion: The zircon dating is dependent upon the magma not being radioactive, isn't it? And yet when they tested the Mount St Helens lava, they found it was radioactive.
Reply | Report Abuse | Link to thisWhich meshes completely with the De Meijer / Van Westrenen theory about georeactors, and hot spots. But if that is the case, then doesn't this throw off the dating?
Moreover, if -- for example -- the Hudson Bay/Caribbean plate is the scar from a supercritical georeactor explosion (a la De Meijer / Van Westrenen), and the African Karoo / Scotia Plate is the scar from another there, then wouldn't that throw off the dating around those, that is used to argue that the Permian extinction was a protracted event?
sault, I agree with current concerns about increased CO-2 levels, but I don't see how humanity has control over, or would be a threat to cause, massive releases of volcanic ash or "large areas paved over with lava".
Reply | Report Abuse | Link to thisOn the other hand, I'm surprised, from having read about the massive extent of these lava flows, and the relatively short time that it took for them to occur, that it took thousands of years for the effects to be felt.
It also begs the interesting question of what brought about these "eruptions" to begin with; I can't say I've encountered much information on this aspect of the topic.
Well, we're releasing all sorts of toxins into the environment, disrupting ecosystems and poisoning ourselves. We're also paving over large swathes of the Earth's land with concrete and asphalt, something akin to resurfacing by lava. So while we're going about it in a different manner, we are recreating A LOT of the factors associated with a period of extreme volcanic activity.
Reply | Report Abuse | Link to thisAnd these weren't just one-time eruptions, either. From the article:
"Within about 12,000 years, the wave of eruptions had spread to areas that are now located along the US east coast. During the first 30,000 years of this phase of volcanism..."
These are periods of intense eruptions lasting thousands of years. Meanwhile, we are currently releasing 100x as much as the Earth's volcanoes do each year and the attendant changes in atmospheric chemistry are occurring over decades to centuries now compared to tens of thousands of years with past mass extinctions.
To share an even more troubling detail, the End Permian Mass Extinction is another global extinction event that killed 95% of marine life and 70% of all life on Earth. Massive volcanic activity even greater than at the end of the Triassic is suspected in having a hand in this, the worst mass extinction in the fossil record. Even so, those volcanoes took 200,000 years to double atmospheric CO2 concentrations while we are set to do it in around 200...A THOUSAND TIMES FASTER than what set the stage for the greatest mass extinction! Are we insane?!
The end of Triassic times is known for being the time of the disruption of Pangaea 2. This extinction event happened in less than 10,000 years and occurred just before Pangaea started to break apart! The opening of the Atlantic must have released much of the heat trapped under the supercontinent, therefore leading to massive volcanism and environmental disruption. Large bolide impacts at that same time should not be diregarded either. We should remember that the coincidence (!) of large volcanic events and antipodal bolide impacts is the common feature of P-Tr and K-Pg mass extinctions... The Manicouagan impact event (sixth-largest confirmed impact crater known on earth, compared to fifth-largest extinction event...) happened apparently 12 million years before the end of Triassic, and could have helped in producing enhanced volcanism in the opening Atlantic by upper mantle shock wave disruption. Also the opening of the Atlantic should have rearranged global oceanic circulation, and therefore global climate patterns. All this, acting on a relatively fragile biosphere, with low biodiversity after the P-Tr mass extinction, and due to the low diversity of supercontinental habitats, must have been important too.
Reply | Report Abuse | Link to thisCO2 in my opinion is not a problem for life. On the contrary it is highly beneficial for food chains based on photosynthesis, as Arrhenius stated. Perhaps we should look at water vapour, or other things, maybe related to the large evaporite deposits that began forming at that time (increased albedo?), or perhaps at cosmic catastrophes, like supernovas, or other. Also, what about methane? Isn´t it typically related to massive fracture activity/volcanism (hydrothermal and dynamic alteration of basalts/serpentinization) and to strong greenhouse effects?
:-/
Cosmogeological factors should not be overlooked in favor of CO2 obsessions.
Ocean acidification due to increased ocean ridge activity sounds interesting too.
Relative sea level fall due to thermal bulging of the supercontinent is something I forgot to mention in the possiblee extinction causes, as well as the clathrate gun hypothesis.
Reply | Report Abuse | Link to this-Also some doubts on wether this extinction is the 3rd, 4th or 5th largest of Phanerozoic times...-
Tr-J charcoal and bonebeds of Tübingen, SW Germany, seem to indicate large wildfires (similar to P-Tr beds?), and might have been caused by important O2 levels (due to increased photosynthesis by high CO2?) and perhaps a large bolide impact as spark...
Reply | Report Abuse | Link to thisThe Rochechouart crater coincides in time with this extinction event, and although it is relatively small in size, it and might have ignited wildfires, and is near to Tübingen...
Reply | Report Abuse | Link to thisHere is a quick primer about what causes volcanics: http://www.elmhurst.edu/~richs/EC/102/Lectures/PlateTectonicsII.pdf - Push-Pull and Heat
Reply | Report Abuse | Link to thisInstead of mass extinction event, I like to think of it as a mass evolution event. The dinosaurs didn't go extinct, they evolved into chickens :-) Viva La Evolucion
Reply | Report Abuse | Link to thisSault said "It's crazy that past changes in atmospheric and ocean chemistry take 10,000 years or more"
Reply | Report Abuse | Link to thisWhere in this article did you find this?
The author does state that any of a dozen ecological insults could have been the cause.
@ amoore, comment number 2: What you reccomend is not the way of science. Forget about CO2 propaganda!
Reply | Report Abuse | Link to thisИз-за изменения формы Земли изменились скорость вращения Земли вокруг своей оси и угловой наклон это нарушило равновесие в системе Земля-Луна.Луна приблизилась к Земле настолько,что попала в область тяготения Земли(не путать с притяжением).Лунный прилив усилился многократно,земная кора пошла волнами как вода,все происходило со скоростью вращения Земли вокруг своей оси на тот момент(в настоящий момент скорость вращения Земли вокруг своей оси 1800 км.в час это выше скорости полёта винтовочной пули).Луна не доходя до точки Лагранжа одновременно с Землей сменила географические полюса и удалилась от Земли(смену географических полюсов Луны доказали сотрудники парижского Института Физики Земли (Mark Wieczorek,Matthien Le Feuvere).
Reply | Report Abuse | Link to thisЧитайте библейских пророков они написали как все происходило и как произойдет снова.С какой стороны ждать беды (все начнется во время лунного затмения в северном полушарии).
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