Modeling what happened after a massive asteroid struck the Yucatan, a landscape that can cause mass extinction: stifling dust, immense tsunamis, and enough debris to leave the atmosphere to trigger global fires , However, the question remains as to whether the impact alone has dinosaurs extinction or whether it has ended the work that was triggered by a massive volcanic eruption in India.
The Deccan traps cover an area of about half a million square kilometers and the eruptions created over a million cubic kilometers of rock. Immense outbreaks such as these have been blamed for mass mortality in the past, as they pump a lot of toxic chemicals into the atmosphere and cause rapid rocking of cooling and warming. And the Deccan traps are no exception: people have argued that they have already killed the dinosaurs or so emphasized the ecosystems that they created the conditions for a mass extinction. But not everyone has believed this idea, and some have suggested that the asteroid collision actually caused changes in the Deccan Traps outbreaks.
To sort out all this, a better grasp of the timing of the outbreaks is needed than occurred at the time of the impact and extinction. In today's issue of Science two newspapers try to narrow down the timing. Unfortunately, their results are not completely consistent.
What and when?
Both articles rely on radiometric dating, but the articles use different types, each with its own boundaries. One of them deals with the decay of uranium trapped in zircons that form during volcanic activity. The strength of this method is that it is very precise. The disadvantage is that zircons form at high temperatures, which means that the zircons are underground before the eruptions and not during the eruption. So you do not specify an exact date for the outbreak.
To get around this problem, an Indian-Swiss-American team examined huge amounts of zircons and compared their data with their specific location in the series of eruptions the Deccan traps. A statistical analysis then identified outliers ̵
This suggests that the deccan traps were built in pulses with a large eruption about 100,000 years before the asteroid impact. Immediately thereafter, an even bigger one took place.
A second crew, this from India-UK-USA, dated Argon. The gas only starts when a rock solidifies, so it essentially starts the timer during the outbreak. The problem is that sometimes the gas can slowly escape the rock over time, which is less of a problem for zircons.
Overall, this group finds a large picture that overlaps with that of the group performing zirkon dating. However, there are differences in the details, and some are significant. For example, the researchers find that the deccan trap outbreaks overlapped with the mass extinction that occurred both before and after the event. However, they do not see any signs of impulses; Instead, they see almost uninterrupted eruptions. Most of the material (~ 75 percent) was used after the mass extinction.
The researchers' data are also consistent with a significant shift in the properties of the erupted rock that occurred simultaneously as the impact. This supports the assumption that the effects of the impact on the entire planet have been achieved.
Outbreaks like these release huge amounts of sulfur and carbon dioxide. These have opposite effects. The sulfur forms aerosols that reflect a lot of sunlight and cause a cooling. However, this cooling is short-term since aerosols in the atmosphere do not have a long life. Carbon dioxide does this and generates warming by the greenhouse effect. It is believed that this climate change has contributed to some mass extinctions.
The second article provides an analysis that correlates the outbreaks with the signs of climate change, but notes that they are not well positioned. The authors conclude that either something else was going on with the climate or that the release of gases did not always match the volume of the leaked lava. This result raises the question of how far the Deccan outbreaks would have contributed to ecological disturbances. Overall, it seems that we have much more information, but this does not necessarily lead to a clearer picture. The results confirm that major outbreaks occurred before the mass extinction, but the largest of them seemed to happen afterwards, and the impact of outbreaks on remote ecosystems is unclear. And we do not know if the outbreaks were a small series of huge outbursts or a relatively stable drumming of smaller events.
The good news is, if you're a fan of dinosaurs and want to know how they've come to an end there is still science left to do.
Science 2019. DOI: 10.1126 / science.aau2422, 10.1126 / science.aav1446 (About DOIs).