Did these huge stored volcanic deposits originate from many large eruptions or some massive ones?  Courtney Sprain
Modeling that happened after a massive asteroid struck the Yucatan has painted a hell that can cause mass extinction: nitrogen dust, huge tsunamis and enough debris leaving and restoring the atmosphere to stop global fires. But the question is whether the effect alone drove the dinosaurs to extinction or if it just ended the job started by a massive volcanic eruption that occurred in India.
Deccan The traps cover an area of about half a million square kilometers and the eruptions that created them involved over a million cubic kilometers of mountains. Outstanding eruptions like this have become known for mass extinctions in the past, as they pump very toxic chemicals into the atmosphere and cause a rapid seesaw of cooling and heating. And Deccan Traps is no exception: people have claimed that they already killed dinosaurs or had stressed ecosystems in a way that set the stage for mass extinction. But not everyone has bought in on this idea, and some have suggested that the asteroid collision actually caused changes in the Deccan Traps deans.
Sorting all this requires a better sense of the outbreak time than when the impact and extinction occurred. In today's issue of Science two papers try to limit the timing. Unfortunately, their results do not fully agree.
What and when?
Both papers rely on radiometric dating, but papers use different types, each with their own limitations. One of them looks at the decay of uranium trapped in zirconia formed during volcanic activity. The strength of this method is that it is very accurate. Its disadvantage is that zirconia is formed at high temperatures, which means that the zircones are underground before outbreaks, rather than during the outbreak itself. So they don't give an exact date for the outbreak.
To get around this issue, an Indian-Swiss-American team saw huge amounts of zircon and linked their dates to their specific place in the series of outbreaks that built Deccan Traps. A statistical analysis then identified some outliers ̵
1; a younger zircon during an older layer, for example – and took them into consideration to build a model of the most likely years of various outbreaks.
This suggested that the deccan case was built in pulses, with a large outbreak occurring about 100,000 years before the asteroid impact. An even larger took place almost immediately after.
A second team, this from India-UK-USA, did argon dating. The gas only begins to be trapped when a stone solidifies, so it begins essentially the timer during the actual eruption. The problem is that the gas can sometimes escape from the rock slowly over time, which is less of a problem with zircon.
Overall, this group finds a large image that overlaps that of the group that made zircon dating. But there are differences in the details, and some of them are significant. For example, the researchers also find that the deans from Deccan Trap were overlapped with the mass extermination, both before and after the incident. But they see no signs of pulses; instead, they see almost continuous outbreaks. However, most of the material (~ 75 percent) that they argued was introduced after the mass eradication.
The researchers' dates also correspond to a large shift in the characteristics of the outbreak that occurs at the same time as the effect. This supports the idea that the seismic effects of the effect reached across the planet.
Fluxes like this emit large amounts of sulfur and carbon dioxide. These have opposite effects. The sulfur forms aerosols that reflect a large amount of sunlight, causing cooling. However, this cooling is short term, since the aerosol does not have a long lifetime in the atmosphere. Carbon dioxide does, and it gives a subsequent warming through the greenhouse effect. This climate seat is supposed to have contributed to some mass emissions.
The second document contains an analysis that correlates the outbreaks with signs of climate change, but it finds that they are not right. The authors conclude that something else is going on with the climate, or that emissions of gases do not always match the volume of lava outbreaks. So that the result gives rise to questions about how much the deccan outbreaks would have contributed to ecological disturbances.
Overall, it seems that we have much more information, but it does not necessarily lead to a clearer picture. The results confirm that significant outbreaks occurred before mass eradication, but the largest of them appeared to occur, and the outbreak effect on remote ecosystems is unclear. And we don't know if the outbreaks were a small series of huge outbreaks or a relatively stable drummer of minor events.
The good news is that if you are a fan of dinosaurs and want to know how they met their end,  Science 2019. DOI: 10.1126 / science.aau2422, 10.1126 / science.aav1446 (About DOIs).