In a new study, an international team of scientists has gathered evidence that the mass extinction event that occurred about 260 million years ago was caused by two volcanic cataclysms, not just one. The colossal eruptions would have occurred over a period of 3 million years.
This is what they concluded when analyzing uranium isotopes in marine samples collected in the South China Sea. Scientists have identified signs that the oceans were deprived of oxygen on two occasions, once 262 million years ago, and again 259 million years ago, both in the Capitan period, during the middle Permian. The results are published in patrol Earth sciences and planetary messages.
According to the researchers, the study of ancient mass extinction events helps to understand current phenomena. Huyue Song, study leader and researcher at the Chinese University of Geosciences, says, in the current situation.
In the history of the Earth, no less than five major mass extinction events have been identified, the largest of which dates back to 252 million years ago, marking the transition from the Permian to the Triassic. The catastrophe, which was also caused by large volcanic eruptions, killed 90% of life in the oceans and 70% of land animals.
Massive, cascading volcanic eruptions can be deadly because they create a short period of cooling in the atmosphere, due to ash reflecting sunlight, followed by long periods of global warming, during which large amounts of greenhouse gases are released by volcanoes. As a result, the entire planet is heating up, including the oceans. And if the surface water temperature rises, the deeper layers of the sea will not be able to absorb the oxygen dissolved in the atmosphere.
“Dissolved oxygen has to be absorbed by the surface layer and supplied to the deep ocean. But warmer waters have a lower density. When you increase the density density, you avoid any disturbances and there is no way to get dissolved oxygen into the deeper layers.” explains Thomas Algeo, co-author To study and Professor of Earth Sciences at the University of Cincinnati.
One way to identify ancient, massive volcanic eruptions is to look for mercury in sedimentary layers. “Large volcanic eruptions expel mercury into the atmosphere, which carries it around the Earth and is deposited in marine sediments,” Algeo says. Samples collected by scientists indicate that the “twin” volcanic eruption in the middle Permian period occurred in southwestern China, in what is now the Greater Emishan Volcanic District.
Now, the team’s next step is to find ground evidence to support the study’s conclusion. For now, research not only helps us take a look at the planet’s past, but also helps us reflect on the devastating effects of global warming. “We must pay attention to these environmental issues and avoid a sixth mass extinction,” Song says.
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