The Triassic-Jurassic Extinction, occurring 201.6 million years ago, is often viewed as a gradual event caused by increasing temperatures and ocean acidification. However, a recent study suggests it was primarily triggered by volcanic winter.
Around 201.6 million years ago, one of the mass extinctions that shaped our planet occurred, leading to the sudden disappearance of about three-quarters of all species. This event coincided with significant volcanic activity that led to the fragmentation of Pangaea, a colossal continent that comprised nearly all of Earth’s landmasses. Over a span of about 600,000 years, a staggering volume of lava erupted, splitting what is now known as the Americas, Europe, and North Africa. This catastrophic period marked the transition from the Triassic period into the Jurassic, paving the way for dinosaurs to emerge and eventually dominate the Earth.
The specific causes of the End Triassic Extinction have long been a topic of debate. Traditionally, it was believed that the accumulation of carbon dioxide from volcanic eruptions had gradually raised temperatures to intolerable levels for many species while also acidifying the oceans. Contrary to this view, the new study proposes that the cooling effects of volcanic winter, rather than warming, were the primary cause. It offers insights indicating that instead of taking hundreds of thousands of years, the initial lava flows that marked the end of the Triassic were monumental eruptions lasting less than a century. These eruptions released large quantities of sulfate particles into the atmosphere, which reflected sunlight, leading to a rapid decrease in temperatures and causing freezing conditions for many species. While temperatures may have eventually risen in an already hot environment—where carbon dioxide levels were already three times higher than today—the researchers attribute the most significant damage to volcanic winters.
Lead author Dennis Kent from the Columbia Climate School’s Lamont-Doherty Earth Observatory explains, “Carbon dioxide and sulfates affect the climate in very different ways and on different timescales. It takes a long time for carbon dioxide to accumulate and heat the planet, but sulfates exert almost immediate effects. This helps illustrate the events in a timeframe humans can relate to; they unfolded within a human lifetime.”
The study has recently been published in the journal Proceedings of the National Academy of Sciences.
The extinction at the Triassic-Jurassic boundary has long been associated with the eruption of the Central Atlantic Magmatic Province, or CAMP. In a pivotal study from 2013, Kent and his team established one of the strongest connections between the two. By examining paleomagnetism, Kent found consistent changes in sediment polarity just below the initial eruptions of CAMP, indicating synchronized volcanic activity across large regions. By dating the volcanic activity to around 201 million years ago, scientists were left questioning the scale of the initial eruptions, with many assuming they occurred over extended periods.
In the latest research, Kent and colleagues analyzed samples from CAMP deposits in Morocco, Nova Scotia’s Bay of Fundy, and New Jersey’s Newark Basin. Their principal evidence came from the alignment of magnetic particles in the rocks, which reflect the historical shifting of Earth’s magnetic pole during the eruptions. Due to a series of complex processes, this magnetic pole is slightly offset from Earth’s rotational axis and shifts position a fraction of a degree each year. Consequently, volcanic rock formed within a few decades will align in one direction, while those formed thousands of years later will be oriented differently.
The researchers discovered five distinct initial lava pulses from CAMP occurring over roughly 40,000 years, with magnetic particles consistently pointing the same way. This alignment suggests that these eruptions happened in under 100 years, before magnetic pole drift could be observed. The researchers assert that these massive eruptions released immense amounts of sulfates in rapid succession, blocking sunlight and inducing sharp temperature drops. Unlike carbon dioxide, which lingers for long periods, volcanic sulfate aerosols typically dissipate within a few years. Thus, these volcanic winters, although short-lived, were devastatingly impactful. The researchers compare the CAMP eruptions to the sulfates from Iceland’s 1783 Laki eruption, which led to severe crop failures; they argue that even the early CAMP eruptions were hundreds of times more significant.
Buried beneath the layers of CAMP are fossils from the Triassic era, including large terrestrial and semiaquatic crocodile relatives, unusual tree lizards, giant amphibians, and many tropical vegetation types. Following the CAMP eruptions, these species vanished. Small feathered dinosaurs, having existed for tens of millions of years prior, managed to survive and flourish in the aftermath, growing larger alongside turtles, true lizards, and mammals, likely because their smaller size allowed them to endure in burrows.
“The degree of environmental impact correlates with the intensity and concentration of these events,” noted study coauthor Paul Olsen, a paleontologist at Lamont-Doherty. “Smaller events spread out over tens of thousands of years result in significantly less impact compared to the same total volcanic activity occurring within less than a century. This suggests that the CAMP eruptions were extraordinarily concentrated incidents.”
The research was coauthored by Huapei Wang from China University of Geosciences, Morgan Schaller from Rensselaer Polytechnic Institute, and Mohammed Et-Touhami of Morocco’s Université Mohamed Premier.
