Ancient volcanic eruptions unveil a fiery story of a twin mass extinction

Volcanic eruptions millions of years apart wiped out much of life on Earth.

Massive volcanic eruptions millions of years apart caused two mass extinctions during the middle Permian period, according to a study of uranium isotope profiles in marine samples. The findings highlight the potential effects of modern-day global warming on ocean food chains and the importance of addressing environmental issues to prevent further extinctions.

Long before the dinosaurs appeared, the Earth was dominated by animals that were in many ways more amazing.

Carnivores like the Titanophoneus, or “giant killer,” hunted formidable buffalo-sized armored reptiles.

Many of these animals died out in a mass extinction during the Capetian era, about 260 million years ago.

An international team of researchers says the evidence indicates that this mass extinction was not one but two events, separated by nearly 3 million years. Both were caused by the same culprit: massive volcanic eruptions.

By studying the uranium isotopic profiles of marine samples collected in the South China Sea, scientists have identified two “pulses” where the oceans became starved of life-giving oxygen.

In a study published in the journal Earth sciences and planetary messagesThe researchers say their analysis provides evidence that oxygen-deprived oceans triggered two mass extinctions about 259 million and 262 million years ago during the middle Permian period.

A climatic catastrophe is on the horizon

By studying these ancient extinctions, researchers can better predict how modern-day global warming will affect the ocean food chain.

“We’re studying the biotic crisis in the Permian period, but similar warming is occurring today because of human events,” said Thomas Algeo, a study co-author and professor of earth sciences at the University of Cincinnati. “Humans mimic the effects of volcanic eruptions as a result of the release of carbon into the atmosphere.”

The study was led by researcher Huyue Song of China University of Geosciences, a former postdoctoral researcher at UCLA.

“Today, we are faced with many global change issues, including global warming, ocean hypoxia, seawater acidification, and biodiversity degradation, which are similar to the environmental changes during the biological crisis period in the Middle Permian,” Song said.

Scientists have identified the five largest mass extinctions, including the most catastrophic of all extinctions that occurred 252 million years ago called the Great Dying, which wiped out 90% of ocean life and 70% of land animals. Algeo said this disaster was also due to massive volcanic activity that turned seas into dead zones.

“The Capitanian extinctions are not among the big five, but they are significant,” Algeo said.

How do volcanic eruptions lead to extinction?

Algeo said the massive eruptions create a short period of cooling of ash in the upper atmosphere that reflects sunlight, followed by much longer periods of warming. The release of huge amounts of greenhouse gases has caused the oceans to warm. Warm surface waters did not allow dissolved oxygen to reach lower depths, which eventually destroyed the food chain.

“The ocean is teetering on the verge of anoxia,” he said of this lack of oxygen. “Dissolved oxygen has to be absorbed by the surface layer and supplied to the ocean depths. But warmer water is of lower density. When you increase the density difference, you prevent any inversion and there is no way to get dissolved oxygen into the deeper layers.”

One way researchers identify these massive volcanic eruptions is by looking for mercury in sedimentary layers.

“Mercury has been shown to be a useful proxy for volcanic eruptions,” Algeo said. “Large volcanic eruptions spew mercury into the atmosphere which is carried around the land and deposited in marine sediments.”

Scientists say that the volcanic eruptions that caused the Great Death originated in Siberia. The volcanic eruptions that caused the double mass extinction occurred in the Permian period in southwest China in a place known as the large volcanic province of Emishan.

“Over the past 40 years, we’ve made huge strides in understanding Earth’s past.” – Thomas Elgew, University of California College of Arts and Sciences

Algeo said he would like to know if any terrestrial evidence supports the conclusions drawn from their study of the ancient oceans. He is optimistic that geology will unlock more mysteries about prehistoric life on Earth.

“Over the past 40 years, we’ve made huge strides in understanding Earth’s past,” Algeo said. “Part of it is because we have all these new tools that we can apply. And we have many more people working in this area than we had a generation ago.”

Researcher Song said the twin disasters in the Permian period show the devastating effects that global warming can have.

“We must pay attention to these environmental issues and prevent a sixth mass extinction,” he said.

Reference: “Global Oceanic Hypoxia Associated with the Marine-Capitane (Middle Permian) Mass Extinction” by Huyue Song, Thomas J. Algeo, Haijun Song, Jinnan Tong, Paul B. Wignall, David PG Bond, Wang Zheng, Xinming Chen, Stephen J Romaniello Henji Wei and Ariel D. Amber, March 30, 2023, Available here. Earth sciences and planetary messages.
DOI: 10.1016/j.epsl.2023.118128