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Volcanoes Allowed Dinosaurs to Conquer Earth

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Volcanic eruptions paved the way for dinosaurs to conquer the Earth, suggests a new study published in the journal PNAS.

The Rise of the Dinosaurs

Dinosaurs are known to have walked the Earth ever so freely following the end of the Triassic period: back then (around 200 million years ago), a massive extinction event had happened, leading to the disappearance of enormous creatures like scary crocodile-like reptiles, leaving behind dinosaurs which mysteriously survived the disaster. As the top predators had died out, the dinos filled the void. Thus did the dinosaur era begin.

The question remains, what caused the mass extinction of the other predators? Theories concocted by researchers mention a huge release of carbon dioxide into the air. According to the new study, this might have come from volcanic eruptions.

Artist’s impression of the Triassic period top predator Redondavenator (left) facing an aquatic phytosaur which went extinct at the end of that era. Photo credits: VICTOR O. LESHYK.

Global Impact of Volcanic Gases

Previous findings have revealed the existence of volcanic rocks with the same age as the extinction event; these rocks span across 4 continents, constituting the Central Atlantic Magmatic Province (CAMP). It was suggested that carbon dioxide released from volcanoes might have played a role in the disappearance of the creatures. However, scientists could not document the global impact of the volcanic eruptions. So, the researchers of the new study, a team from Oxford University, the University of Exeter, and the University of Southampton, set out to study the global effects of the major volcanic gas emissions, and their relation with the end of the Triassic period.

Scanning Rocks for Mercury, an Indicator of Volcanism

The scientists analysed the composition of sedimentary rocks left behind during the extinction; the deposits came from UK, Austria, Argentina, Greenland, Canada and Morocco. Their mercury levels were tested because volcanoes would normally emit mercury gas in huge amounts; this mercury is known to propagate globally in the air to ultimately settle in sediments. Sediments that would have been come from a massive volcanic eruption would, therefore, contain unusually high levels of mercury.

High Mercury Emissions at end-Triassic

The findings show that five of the six records display large mercury contents at the end-Triassic extinction era. Furthermore, the high mercury emissions appear to be contemporaneous with increases in carbon dioxide concentrations in the air, implying the release of the latter gas from volcanoes.

The authors, hence, conclude that their study support the theory of repeated volcanic eruptions at the end of the Triassic era, a volcanic activity which might have initiated the extinction event, explains lead author Lawrence Percival.

“This research greatly strengthens the link between the Triassic mass extinction and volcanic emissions of CO2. This further evidence of episodic emissions of volcanic CO2 as the likely driver of the extinction enhances our understanding of this event, and potentially of other climate change episodes in Earth’s history,” says Percival.

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