DOOMSDAYWhat Killed Dinosaurs and Other Life on Earth?
What caused the demise of the mighty dinosaurs at the end of the Cretaceous Period 66 million years ago? Some scientists argue that comets or asteroids that crashed into Earth were the most likely agents of mass destruction, while others point fingers at large volcanic eruptions.
The biological history of the Earth has been punctuated by mass extinctions that wiped out a vast majority of living species in a geological instant.
Based on evidence in the fossil record, scientists have identified five such events that reshaped life on Earth, the most familiar of which brought about the demise of the mighty dinosaurs at the end of the Cretaceous Period 66 million years ago.
What caused these catastrophes remains a matter of keen scientific debate. Some scientists argue that comets or asteroids that crashed into Earth were the most likely agents of mass destruction, while others point fingers at large volcanic eruptions.
Assistant Professor of Earth Sciences Brenhin Keller belongs to the latter camp. In a new study published in PNAS, Keller and his co-authors make a strong case for volcanic activity being the key driver of mass extinctions. Their study provides the most compelling quantitative evidence so far that the link between major volcanic eruptions and wholesale species turnover is not simply a matter of chance.
Four of the five mass extinctions are contemporaneous with a type of volcano called a flood basalt, the researchers say. These are a series of eruptions (or one giant one) that flood vast areas with lava in the blink of a geological eye, a mere million years. They leave behind giant fingerprints as evidence—extensive regions of step-like, igneous rock that geologists call large igneous provinces.
To count as “large,” an igneous province must contain at least 100,000 cubic kilometers of magma. For scale, the 1980 eruption of Mount St. Helens involved less than one cubic kilometer of magma.
In fact, a series of eruptions in what is now known as Siberia triggered the most destructive of the mass extinctions about 252 million years ago, releasing a gigantic pulse of carbon dioxide into the atmosphere and nearly choking off all life. Bearing witness are 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, creating what is known today as the Deccan plateau. This, much like an asteroid strike, would have had far-reaching global effects, blanketing the atmosphere in dust and toxic fumes, asphyxiating dinosaurs and other life.
“It seems like these large igneous provinces line up in time with mass extinctions and other significant climatic and environmental events,” says Theodore Green ’21, lead author of the paper.
