Volcanic provinces as drivers of mass extinctions

Volcanic provinces as drivers of mass extinctions

The Deccan Trapp in India is considered to be one of the causes of the mass extinction 66 million years ago. © Theodore Green, Paul Renne, Brenhin Keller, and Andrea Marzoli (University of Padova, Padua, Italy)

The earthly environment often had to accept setbacks - mass extinctions repeatedly destroyed large parts of the flora and fauna. Now there is new evidence of the causes of such events: Researchers have found a significant correlation between the eruptions of large magmatic provinces and the timing and intensity of the extinction waves. The larger the eruption of the volcanic provinces and the release of volcanic gases, the more severe the subsequent mass extinction was. This association is maintained even when you factor out the five major mass extinctions, the team said. In their view, the degree of agreement is too great for mere coincidence and speaks for a causal relationship.

Whether the Deccan Trapp in India, the Siberian Trapp or the Central Atlantic Magma Province: Large magmatic provinces are the largest volcanic areas on earth. When they erupt, these supervolcanoes can release more than 100,000 cubic kilometers of lava and trillions of tons of volcanic gases such as methane, carbon dioxide and sulfur dioxide. Therefore, at least some of these events have long been suspected of having been the cause of large-scale mass extinctions. "At least four of the five major mass extinction events occurred simultaneously with such flood basalt eruptions," explain Theodore Green of Dartmouth College in New Hampshire and his colleagues. For example, the eruption of the Siberian Traps around 252 million years ago coincided with the mass extinction event at the end of the Permian Era, the Central Atlantic Magma Province with the end of the Triassic, and the Deccan Trapp eruption with the end of the Cretaceous.

No coincidence

But is there a causal connection behind these coincidences? To investigate this further, Green and his team first categorized the eruptions of all known major magmatic provinces in terms of their eruption intensity and duration. Then they put this in relation to all known faunal transitions in the history of the earth and determined the degree of correlation with the help of mathematical-statistical methods. The result: "We find that the correlation between the eruptions of the large magmatic provinces and the times of the faunal transitions is far beyond chance," the researchers report. On average, one in 1.64 eruptions coincided with an extinction event. This association remained significant even after the team excluded the five major extinction events from the data set.

"This demonstrates that the observed correlations between magmatic provincial eruptions and Phanerozoic faunal transitions extend to smaller extinction events and are not solely driven by large-scale mass extinctions," Green and his colleagues state. Phases of extensive oxygen depletion in the oceans, so-called oceanic anoxic events, also corresponded to large volcanic eruptions. "It is extremely unlikely that this correlation is due to chance alone," the researchers said. For comparison, they also performed the same analysis for major asteroid impacts in Earth's history. A connection with extinction events was shown for individual impacts such as the Chicxulub asteroid 66 million years ago. However, this changes when it is excluded from the analysis: "We do not find a similarly robust correlation between the radiometric ages of large impact craters and mass extinctions," the team writes.

The stronger the outbreak, the worse the extinction

More detailed analyzes showed that the intensity of the eruption played a major role. The consequences for the environment and living environment were most serious when a lot of lava and volcanic gases were thrown out in a short time during the eruptions. "The linearity of this correlation suggests that the fatal consequences of flood basalt eruptions were generally directly proportional to their volumetric eruption rate," Green and colleagues write. Particularly eruptive events include the eruptions of the Siberian Trap 252 million years ago and the Deccan Trap 66 million years ago, but also the eruptions of the Central Atlantic Magma Province 201 million years ago and the Emeishan Trap 260 million years ago. "They appear to have had far greater environmental impacts than the volcanic provinces, which erupted slowly but over long periods of time," the scientists explain.

Her study also sheds new light on what happened at the end of the Cretaceous period — the mass extinction event that wiped out dinosaurs and around 75 percent of all marine species. "The correlation we found between eruption rates and extinction severity suggests that the Deccan Trapp could have caused a significant extinction wave at the end of the Cretaceous - even without the coincidence with the Chicxulub impact," say Green and his colleagues. They believe the eruption of this Indian volcanic province started the great mass extinction event, and the impact of the Chicxulub asteroid made it even worse.

Source: Theodore Green (Dartmouth College, Hanover, New Hampshire) et al., Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.2120441119

Recent Articles

Related Stories