Long before the dinosaurs appeared, the Earth was ruled by animals that were even more incredible in every way. Carnivores such as Titanophonus, or the “titanic killer,” preyed on huge buffalo-sized armored reptiles. Most of these animals died out in the mass extinction in Capitania about 260 million years ago.
Now, an international team of researchers says evidence suggests this mass extinction was not one, but two events, about 3 million years apart. Both were caused by the same culprit: massive volcanic eruptions. By examining uranium isotope profiles in marine samples collected in the South China Sea, scientists identified two “pulses” in which the oceans are deprived of life-giving oxygen.
In a study published in the journal Earth and Planetary Science LettersThe researchers say their analysis provides evidence that oxygen-deprived oceans caused two mass extinctions during the Middle Permian period, about 259 million and 262 million years ago. By studying these ancient extinctions, researchers can better predict how modern global warming might affect the ocean’s food chain.
“We’re studying biocrises during the Permian, but similar warming is happening today due to human events,” said Thomas Algeo, professor of earth sciences at the University of Cincinnati and co-author. “People are simulating the effects of volcanic eruptions as a result of releasing carbon into the atmosphere.”
The study was led by researcher Huyue Song of the University of Earth Sciences of China, a former doctoral student at the University of California.
“Today, we face many challenges of global change, including global warming, ocean hypoxia, seawater acidification, and biodiversity loss that are similar to environmental changes during the Middle Permian biological crisis,” Song said.
Scientists have identified five major mass extinctions, including the most catastrophic 252 million years ago called the Great Extinction, which wiped out 90% of ocean life and 70% of land animals. This disaster was also caused by large-scale volcanic activity, which turned the seas into dead zones, Algeo said.
“Captain extinction isn’t among the Big Five, but it’s significant,” Algeo said. Said.
Big eruptions create a short cooling period of ash in the upper atmosphere that reflects sunlight, followed by much longer periods of global warming, Algeo said. Large amounts of greenhouse gas emissions have warmed the oceans. Warm surface water prevented dissolved oxygen from reaching lower depths, which eventually destroyed the food chain.
“The ocean is rocking on the edge of anoxia,” he said of this lack of oxygen. “Dissolved oxygen must be absorbed by the surface layer and enter the depths of the ocean. But warmer water has a lower density. If you increase the density difference, you prevent tipping and there is no way to take the dissolved oxygen to the deeper layers.”
One way to identify these major volcanic eruptions is to look for mercury in sedimentary layers.
“Mercury has been shown to be a useful proxy for volcanic eruptions,” Algeo said. Said. “Large volcanic eruptions release mercury carried around the Earth and deposited in marine sediments into the atmosphere.”
Scientists say the volcanic eruptions that caused so many deaths originated in Siberia. The eruptions that caused the double Permian mass extinction occurred in southwest China in a place known as the Emeishan Great Magmatic Province. Algeo said he would like to see if any terrestrial evidence supports findings from their study of ancient oceans. He is optimistic that geology will reveal more secrets about prehistoric life on Earth.
“Over the past 40 years, we’ve made tremendous progress in understanding Earth’s past,” Algeo said. Said. “Part of that is because we have all these new tools we can apply. And we have a lot more employees in this industry than a generation ago.”
Researcher Song said the twin catastrophes in the Permian period showed the devastating effects of global warming.
“We have to address these environmental issues and prevent a sixth mass extinction,” he said.
Source: Port Altele
