Scientists have debated the causes of this extinction, often attributing it to a prolonged warming period due to high carbon dioxide levels from these eruptions. But a new study presents a different perspective, suggesting that initial volcanic activity led to extreme cooling rather than warming. According to the study, rather than unfolding over thousands of years, the first eruptions were rapid, lasting less than a century each and releasing sulfur-rich particles that cooled the Earth dramatically. Although atmospheric carbon dioxide eventually increased, leading to warming, it was the volcanic winters that initially devastated life on Earth.
"Carbon dioxide and sulfates act not just in opposite ways, but opposite time frames," said Dennis Kent, lead author and researcher at Columbia's Lamont-Doherty Earth Observatory. "It takes a long time for carbon dioxide to build up and heat things, but the effect of sulfates is pretty much instant. It brings us into the realm of what humans can grasp. These events happened in the span of a lifetime."
The study, published in *Proceedings of the National Academy of Sciences*, examines the mass extinction's link to the Central Atlantic Magmatic Province (CAMP) eruptions. In 2013, Kent and his team established a significant correlation between these eruptions and the extinction by examining polarity reversals in sediments just beneath CAMP lava flows, indicating the eruptions occurred almost simultaneously across vast regions. Further dating of volcanic rock placed the beginning of these eruptions at about 201.6 million years ago.
The recent analysis compared magnetic particle alignments in CAMP rocks from Morocco, the Bay of Fundy in Nova Scotia, and New Jersey's Newark Basin. Magnetic particles within lava point in the same direction if erupted in close succession, while those emplaced after thousands of years show a marked directional shift due to the gradual drift of Earth's magnetic pole. Researchers found five successive initial lava flows over 40,000 years, with each pulse showing a consistent magnetic orientation - suggesting each occurred in less than a century, fast enough to prevent magnetic pole drift from affecting the lava's magnetic record.
These rapid eruptions, the researchers argue, released sulfates that blocked sunlight and caused severe cooling. Unlike carbon dioxide, which remains in the atmosphere for centuries, sulfate aerosols settle relatively quickly, resulting in short but intense cooling spells. These volcanic winters devastated ecosystems, similar to, but vastly more intense than, the 1783 eruption of Iceland's Laki volcano, which caused significant crop failures. The initial CAMP eruptions, the researchers suggest, were hundreds of times larger in sulfate release.
Below the CAMP lava layers, Triassic fossils reveal the diversity of life before the extinction, including large amphibians, primitive reptiles, and tropical plants. After these layers, such species vanish, with small feathered dinosaurs and burrowing animals like turtles and early mammals surviving and eventually thriving.
"The magnitude of the environmental effects are related to how concentrated the events are," said study coauthor Paul Olsen, paleontologist at Lamont-Doherty. "Small events spread out over [tens of thousands of years] produce much less of an effect than the same total volume of volcanism concentrated in less than a century. The overarching implication being that the CAMP lavas represent extraordinarily concentrated events."
Research Report:Correlation of sub-centennial-scale pulses of initial Central Atlantic Magmatic Province lavas and the End-Triassic extinctions
Related Links
Lamont-Doherty Earth Observatory
Explore The Early Earth at TerraDaily.com
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