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Title    What Really Killed Dinosaurs and Other Life on Earth? Maybe Not an Asteroid Strike
Date    Wednesday September 21 2022, @12:18AM
Author    martyb
from the dept.

Arthur T Knackerbracket has processed the following story:

While some scientists think that asteroid and comet strikes are the cause of mass extinction events on Earth, new research from Dartmouth points to volcanic eruptions as the key driver.

What killed the dinosaurs 66 million years ago at the end of the Cretaceous Period? It has long been the topic of scientific debate, and many researchers have set out to determine what caused the five mass extinction events that reshaped life on planet Earth in a geological instant. Some experts believe that comets or asteroids that crashed into Earth were the most likely agents of mass destruction. Other scientists argue that immense volcanic eruptions were the primary cause of the extinction events. A new Dartmouth-led study published on September 12 in the Proceedings of the National Academy of Sciences (PNAS) reports that volcanic activity appears to have been the key driver of mass extinctions.

These new findings provide the most compelling quantitative evidence to date that the link between major volcanic eruptions and wholesale species turnover is not just coincidental. 

According to the researchers, four of the five mass extinctions are contemporaneous with a type of volcanic outpouring called a flood basalt. These eruptions flood vast areas—even an entire continent—with lava in a mere million years. In a geological time scale, that is just the blink of an eye. They leave behind massive fingerprints as evidence—extensive regions of step-like, igneous rock (solidified from the erupted lava) that geologists call “large igneous provinces.”

To count as “large,” a large igneous province must contain at least 100,000 cubic kilometers of magma. (One cubic kilometer is equal to 264 billion gallons or the volume of 400,000 Olympic swimming pools.) For context, the 1980 eruption of Mount St. Helens involved less than one cubic kilometer of magma. According to the researchers, most of the volcanoes represented in the study erupted on the order of a million times more lava than that.

The research team drew on three well-established datasets on geologic time scale, paleobiology, and large igneous provinces to examine the temporal connection between mass extinction and large igneous provinces.

“The large step-like areas of igneous rock from these big volcanic eruptions seem to line up in time with mass extinctions and other significant climatic and environmental events,” says lead author Theodore Green ’21, who conducted this research as part of the Senior Fellowship program at Dartmouth and is now a graduate student at Princeton.

[...] In fact, a series of eruptions in present-day Siberia triggered the most destructive of the mass extinctions about 252 million years ago, releasing an immense pulse of carbon dioxide into the atmosphere and nearly choking off all life. Bearing witness is the Siberian Traps, a large region of volcanic rock roughly the size of Australia.

Volcanic eruptions also rocked the Indian subcontinent around the time of the great dinosaur die-off, forming what is known today as the Deccan plateau. This, much like the asteroid strike, would have had far-reaching global effects, blanketing the atmosphere in dust and toxic fumes, suffocating dinosaurs and other life in addition to altering the climate on long time scales.

On the other hand, the investigators say, the theories in favor of annihilation by asteroid impact hinge upon the Chicxulub impactor, a space rock that crash-landed into Mexico’s Yucatan Peninsula around the same time that the dinosaurs went extinct.

Journal Reference:
Theodore Green, Paul R. Renne, and C. Brenhin Keller. Continental flood basalts drive Phanerozoic extinctions by Theodore Green, Paul R. Renne and C. Brenhin Keller, 12 September 2022, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2120441119

Original Submission


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