Volcanic eruptions caused ancient mass extinctions: Study

An international team of researchers has now uncovered evidence to suggest that this mass extinction was not a single event, but two separate events nearly 3 million years apart. Both events were caused by the same culprit: massive volcanic eruptions.

According to recent research published in the journal Earth and Planetary Science Letters, the researchers say their analysis provides evidence that oxygen-starved oceans precipitated two mass extinctions around 259 million and 262 million years ago during the Middle Permian Period.

Looming climate disaster

Researchers studying ancient extinctions can use their findings to predict the effects of current global warming on the ocean's food chain.

The study was led by Huyue Song, a former postdoctoral researcher at the University of Cincinnati, and Thomas Algeo, a professor of geosciences.

The researchers found that the Middle Permian Period experienced two mass extinctions, both caused by massive volcanic eruptions, which deprived the oceans of oxygen.

"Today, we are faced with several global change issues, including global warming, ocean hypoxia, seawater acidification, and biodiversity decline, which are similar to environmental changes during the Middle Permian interval of biological crisis, Song said.

Scientists have identified the five largest mass extinctions, including the most catastrophic of all 252 million years ago, called "the great death," which wiped out 90% of marine life and 70% of land animals. This disaster was also caused by massive volcanic activity that turned the seas into dead zones, Algeo said.

Volcanoes cause mass extinctions

Algeo said that the eruptions cause a temporary cooling period as ash in the upper atmosphere reflects sunlight, followed by a prolonged period of global warming. The emission of enormous amounts of greenhouse gases causes the warming of the oceans. As a result, warm surface water does not allow dissolved oxygen to reach deeper depths, leading to the collapse of the food chain.

"The ocean is teetering on the brink of anoxia," he said of this lack of oxygen. "Dissolved oxygen must be absorbed by the surface layer and supplied to the depths of the ocean. But warmer water has a lower density. When the density differential increases, it prevents any capsizing and there is no way to get dissolved oxygen to the deepest layers."

Mercury found in sedimentary layers is a valuable tool for researchers in identifying massive volcanic eruptions. Thomas Algeo, professor of geosciences at the University of Cincinnati, explains that "large volcanic eruptions spew mercury into the atmosphere that is transported around the Earth and deposited in marine sediments." This makes mercury a useful indicator of volcanic eruptions.

Scientists have traced the cause of the massive volcanic eruptions that led to two mass extinctions during the Permian to the Emeishan Great Igneous Province in southwest China.

Volcanic eruptions released massive amounts of greenhouse gases, heating up the oceans and starving them of oxygen, ultimately destroying the food chain.

Researchers identify these eruptions by looking for mercury in sedimentary layers, which is spewed into the atmosphere during volcanic activity and transported around the world. Geology is expected to continue to reveal mysteries of prehistoric life on Earth as new tools and more researchers contribute to the field.

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