In the quest to unravel the mystery of the dinosaurs‘ mass extinction 66 million years ago, scientists have often debated whether a colossal asteroid impact or massive volcanic eruptions were the primary culprits. Dartmouth researchers have taken a novel approach to settle this age-old scientific dispute – they removed human biases from the equation and let computers decide.
In their ground-breaking study published in the journal Science, these researchers utilized a cutting-edge modelling method, powered by interconnected processors, to navigate vast amounts of geological and climate data without human intervention. Their goal: to pinpoint the key events and conditions that triggered the Cretaceous-Paleogene (K-Pg) extinction event, a cataclysmic episode that paved the way for the rise of mammals, including early humans.
Alex Cox, the study’s first author, explained their approach: “Most models in science move in a forward direction, but we took a different route. We adapted a carbon-cycle model to work in reverse, allowing it to find the cause through statistical analysis without any predetermined hypothesis or bias. In essence, we let the model guide us through the geological record.”
The modelling process was a colossal undertaking, involving over 130 processors that scrutinized more than 300,000 potential scenarios of carbon dioxide emissions, sulphur dioxide output, and biological productivity over a million years before and after the K-Pg extinction event. Using a machine learning technique known as Markov Chain Monte Carlo, which resembles predictive text on a smartphone, these processors worked collaboratively but independently to compare, revise, and recalibrate their conclusions until they uncovered a scenario that mirrored the events preserved in the fossil record.
The fossil record, rich with geochemical and organic remnants, vividly portrays the catastrophic conditions during the K-Pg extinction. This event, named for the geological periods before and after the disaster, witnessed a widespread collapse of ecosystems as animals and plants succumbed to extreme environmental fluctuations. The atmosphere fluctuated wildly, oscillating between frigid and sweltering conditions, laden with sun-obscuring sulphur, airborne minerals, and heat-trapping carbon dioxide.
While it is indisputable that this catastrophe occurred, the debate has long revolved around its cause. Early theories attributed it to volcanic eruptions, but the discovery of the Chicxulub impact crater in Mexico shifted the focus towards a massive asteroid strike as the primary culprit. Over time, however, these theories have begun to converge, suggesting a dual calamity where the Chicxulub impact compounded the devastation caused by the earlier massive volcanic eruptions in India’s Deccan Traps.
However, scientists have remained divided on the degree to which each event contributed to the mass extinction. To address this uncertainty, Alex Cox and his advisor, Brenhin Keller, an assistant professor of earth sciences at Dartmouth and a co-author of the study, decided to let the computer model make the determination.
Their model indicated that the Deccan Traps’ prolonged eruptions, releasing staggering amounts of climate-altering gases like carbon dioxide and sulphur dioxide, could have been sufficient to trigger the global extinction event. The Deccan Traps had been erupting for approximately 300,000 years before the Chicxulub impact. During this period, they emitted an estimated 10.4 trillion tons of carbon dioxide and 9.3 trillion tons of sulphur into the atmosphere.
Brenhin Keller, who had previously linked four of Earth’s five mass extinctions to volcanism, stated, “Our model independently analyzed the data and determined the quantities of carbon dioxide and sulphur dioxide needed to create the climate and carbon cycle disruptions observed in the geological record. These figures align closely with what we expect from emissions associated with the Deccan Traps.”
The model did reveal a significant drop in the accumulation of organic carbon in the deep ocean around the time of the Chicxulub impact, likely resulting from the asteroid’s devastating effects on various plant and animal species. The fossil record also displays a noticeable temperature decrease, a consequence of the vast amount of sulphur released into the atmosphere upon impact, which acted as a short-term cooling agent. The asteroid impact is believed to have emitted both carbon and sulphur dioxide, but the model found no substantial increase in emissions of either gas at that time. This finding suggests that the asteroid’s contribution to the extinction was not primarily linked to gas emissions.
In conclusion, the age-old debate over what caused the extinction of the dinosaurs continues, but this new computer modelling approach provides compelling evidence that the Deccan Traps’ volcanic eruptions may have played a more pivotal role than previously thought. By relying on an unbiased computational analysis of geological data, scientists hope to gain further insights into this ancient mystery, ultimately expanding our understanding of the Earth’s history.