We’re all fascinated with the story of the end of the Dinosaurs, which corresponds with a really big impact, and possibly other catastrophes. The death of the dinosaurs is not only a puzzle, it is the event that made room for mammals and puny humans to evolve.
But there was also a mass extinction that cleared the way for the great adaptive radiation of dinosaurs. At the end of the Triassic period, about 200M years ago, there was a massive extinction of animals. The dinosaurs rose after this catastrophe.
This month a team of British scientists published new evidence that there was a huge sequence volcanic eruptions at that time, which would have been devastating for living things. This event has been suspected from other evidence of huge lava flows, global cooling (due to volcanic material in the atmosphere), and, of course, mass extinctions.
The new study uses a new techniques which measures mercury (Hg) in the rocks. This element is highly correlated with volcanic activity, which spews Hg into the air. The mercury falsl out and is incorporated into rock, where it persists for long periods of time–hundreds of millions of years.
Careful measurements indicate high levels of mercury in the period between the extinctions at the end of the Triassic, and the beginning of the Jurassic. In other words, a very clear suggestion that the volcanic disaster caused the extinctions, and the end of the episode was followed by the rise of the dinosaurs.
A key aspect of this work is to trace mercury deposits to many locations around the world. Furthermore, the deposits should be temporally aligned, rising and falling at the same time. These signatures are consistent with large volcanic “pulses”.
The researchers report that the “Hg excursions are recorded in five of the six sections studied”, and that “The onset of Hg enrichment occurred synchronously across the globe, coincident with the end-Triassic extinction and associated global carbon cycle perturbation.“ (p.5)
In other words, there is clear evidence of very widespread effects of volcanism at the precise time of the mass extinctions.
As Rebecca Morelle puts it, “The onset of Hg enrichment occurred synchronously across the globe, coincident with the end-Triassic extinction and associated global carbon cycle perturbation.”
And, evidently, ancestors of the dinosaurs survived this catastrophe, and “once the volcanoes had simmered down, few of their competitors were left, allowing the age of the dinosaurs to begin.”
The dinosaur age began and ended in world-wide catastophe that wiped out most living species, clearing the way for another burst of speciation.
The “age of mammals” started with the catastrophe that killed off the dinosaurs. It is ending now with the sixth extinction, and, most likely, a spike in global temperature.
- Rebecca Morelle, Volcanoes ‘triggered dawn of dinosaurs’, in BBC News: Science & Environment. 2017. http://www.bbc.com/news/science-environment-40333902
- Lawrence M. E Percival, Micha Ruhl, Stephen P. Hesselbo, Hugh C. Jenkyns, Tamsin A. Mather, and Jessica H. Whiteside, Mercury evidence for pulsed volcanism during the end-Triassic mass extinction. Proceedings of the National Academy of Sciences, June 19, 2017 2017. http://www.pnas.org/content/early/2017/06/13/1705378114.abstract
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