Novel Computer Analysis Suggest Volcanism as Potential Dinosaur Extinction Culprit, Contradicting Asteroid Hypothesis

For years, scientists have engaged in heated debates over the cause of the mass extinction event that wiped out the dinosaurs around 66 million years ago, marking the end of the Cretaceous Period. The central question has been whether it was an asteroid impact or massive volcanic eruptions that brought about this catastrophic event.

Now, a groundbreaking approach seeks to settle the dispute by employing computer-based analysis.

According to the outcomes of this computational investigation, the colossal outbursts of gas resulting from the Deccan Traps eruptions may have been the primary drivers behind the extinction event, as reported in the September 29th issue of Science. These eruptions, which spanned approximately a million years, discharged copious quantities of gas-laden lava across what is now western India.

Dartmouth computational geologist, Alexander Cox, explains that rather than preconceiving theories that either blame volcanoes or asteroids, the objective was to minimize human influence and bias in the evaluation process.

The approach involved a retrospective examination of evidence gathered from the event. Researchers possess a crucial piece of evidence - cores extracted from deep-ocean sediments containing geological data pointing to substantial gas releases into the atmosphere. These gases included planet-warming carbon dioxide and ocean-acidifying sulfur dioxide.

The contentious issue has been whether these gases originated from the asteroid impact, which incinerated surface rocks, or the Deccan Traps eruptions.

Prior investigations had primarily focused on timing, looking at when lava pulses occurred during the Deccan Traps eruptions. However, these efforts were challenged by uncertainty surrounding the initial gas content within the lava. Estimated concentrations of carbon dioxide in the lava exhibited significant variations, making it challenging to arrive at a conclusion from a lava-flow perspective.

To decipher the relative contributions of these potential factors, Cox and Dartmouth geologist C. Brenhin Keller deployed a statistical model called a Markov chain Monte Carlo approach. This method systematically evaluates the likelihood of various gas emission scenarios from different sources and converges toward potential solutions as simulation outcomes align more closely with geological observations.

The strength of their approach lay in utilizing 128 separate processors to concurrently explore scenarios, allowing for comparisons between their outcomes. This parallel computing capability drastically reduced the time required for computations from a year to mere days.

The researchers relied on data obtained from three sediment cores, each spanning the period between 67 million and 65 million years ago. These cores contained foraminifera, microscopic ocean-dwelling organisms with carbonate shells containing distinct isotopes of carbon and oxygen. The chemical composition of these shells offers insights into the ocean's historical conditions, including past temperatures, oceanic biodiversity, and carbon transfer between the atmosphere, ocean, and land.

Computer simulations concluded that the volume of gas released into the atmosphere by volcanic activity alone could adequately explain the temperature variations and carbon cycling changes indicated by the foraminifera data found in the sediment cores.

Contrarily, the analysis suggested that the asteroid impact, responsible for forming the enormous Chicxulub crater in modern-day Mexico, likely did not contribute significantly to increased carbon dioxide or sulfur dioxide levels.

Despite these compelling findings, some scientists remain cautious about accepting this as the definitive answer to the age-old question. Sierra Petersen, a geochemist at the University of Michigan, acknowledges that while the approach employed here is elegant and inclusive of multiple proxy records, model outputs are inherently contingent upon input data.

Petersen underscores that foraminifera shells may not be ideal proxies for ancient temperatures, as their oxygen isotope ratios can change due to factors beyond just temperature, including seawater composition. Consequently, different temperature proxies could potentially yield varying patterns of gas release in model simulations.

Regarding the extinction event's cause, Petersen believes it's somewhat premature to conclude that the study entirely rules out the asteroid impact as a contributor. Instead, the study suggests that the impact may not have been associated with a substantial gas release. Nevertheless, she points out that the asteroid could have induced other catastrophic effects on the planet's environment.

Clay Tabor, a paleoclimatologist at the University of Connecticut, underscores that the Chicxulub impact led to numerous devastating consequences beyond the emissions of carbon dioxide and sulfur dioxide examined in the study. These consequences include vast clouds of soot and dust generated from pulverized rocks due to the impact. Previous research has proposed that this debris might have significantly reduced the sunlight reaching Earth, triggering a sudden and severe cooling period that had dire consequences for plant life and ecosystems.

Furthermore, the study indicates that while the asteroid impact may not have had a lasting impact on the planet's carbon cycle, there was an abrupt decline in the abundance of foraminifera immediately following the impact. This abrupt change is believed to have been responsible for the event's severe effects on life on Earth.

Tabor concludes by noting that many geochemical records covering the extinction event, in addition to the modeling work presented here, may struggle to accurately capture the rapid rates of change associated with the Chicxulub impact. Although the asteroid impact may have released fewer overall gases compared to the Deccan Traps, the speed of this release could have been equally devastating.

Source : [ Study Link - sciencenews.org]