### Volcanic Winters, Not Carbon Dioxide, Blamed for Triassic-Jurassic Mass Extinction

Recent research challenges the longstanding belief that warming due to carbon dioxide was the primary driver of the Triassic-Jurassic mass extinction 201.6 million years ago. Instead, it suggests that intense volcanic activity caused rapid cooling, leading to the extinction event.

The extinction, which erased three-quarters of Earth's living species, coincided with immense volcanic eruptions that fragmented the supercontinent Pangaea. This geologic upheaval, spreading over approximately 600,000 years, led to the formation of modern-day Americas, Europe, and North Africa. The resulting volcanic phenomena marked the conclusion of the Triassic period and ushered in the Jurassic era, which saw dinosaurs rise to dominance.

Traditionally, experts believed that the volcanic eruptions spewed vast amounts of carbon dioxide into the atmosphere, causing global temperatures to soar and ocean waters to acidify. However, a new study, published in the Proceedings of the National Academy of Sciences, posits that rapid and extreme cooling caused by sulfate particles from the eruptions played a more critical role.

Lead author Dennis Kent and his team from the Lamont-Doherty Earth Observatory correlated magnetic data from volcanic deposits in Morocco, Nova Scotia, and New Jersey. Their findings indicate that the first pulses of lava, associated with the Central Atlantic Magmatic Province (CAMP), were brief yet momentous, each lasting under a century but releasing enough sulfates to drastically cool the planet.

These volcanic winters, characterized by sunlight-reflecting sulfate aerosols, led to abrupt temperature drops that devastated many species. Although carbon dioxide later contributed to a gradual warming, it was the rapid cooling that had the most immediate and catastrophic impact on the global ecosystem.

The study compared the CAMP eruptions to the historic 1783 eruption of Iceland's Laki volcano, which caused significant agricultural collapse. The initial CAMP pulses were found to be hundreds of times greater in magnitude, highlighting their capacity for environmental disruption.

Lying beneath the CAMP layers are fossils from the Triassic era, including various large terrestrial and semi-aquatic reptiles, as well as tropical plants. After the eruptions, these species vanished, giving way to small feathered dinosaurs, mammals, turtles, and true lizards — organisms that likely survived by seeking refuge in burrows and other sheltered environments.

Co-author Paul Olsen noted the significance of the rapidity of these volcanic events, suggesting that concentrated volcanic activity over short periods can have overwhelmingly detrimental effects compared to more spread-out phenomena. This insight enhances our understanding of how prehistoric volcanic events can shape Earth's biological history.

The research marks a significant shift in our understanding of the mechanisms behind the Triassic-Jurassic extinction and underscores the profound implications of concentrated volcanic activity on global climates and ecosystems.