Volcanic Eruptions Caused End-Permian Extinction, New Evidence Confirms
An international team of paleontologists from China and the United States has found high levels of mercury in the end-Permian marine sediments at nearly a dozen sites around the world, which provides persuasive evidence that volcanic eruptions were to blame for the mass extinction at the end of the Permian period, about 252 million years ago.
The end-Permian extinction, also known as the Permian-Triassic extinction event and the Great Dying, is the largest mass extinction event in Earth’s history.
The catastrophe killed off nearly 96% of all marine species on the planet over the course of thousands of years.
The main cause of the extinction is generally thought to be linked to severe environmental perturbations caused by eruptions in a volcanic system called the Siberian Traps.
Many of the eruptions occurred not in cone-shaped volcanoes but through gaping fissures in the ground.
The eruptions ignited vast deposits of coal, releasing mercury vapor high into the atmosphere. Eventually, it rained down into the marine sediment around the planet, creating an elemental signature of a catastrophe that would herald the age of dinosaurs.
“Volcanic activities, including emissions of volcanic gases and combustion of organic matter, released abundant mercury to the surface of the Earth,” said study lead author Dr. Jun Shen, a researcher at the China University of Geosciences.
“Typically, when you have large, explosive volcanic eruptions, a lot of mercury is released into the atmosphere,” added University of Cincinnati’s Professor Thomas Algeo, co-author of the study.
“Mercury is a relatively new indicator for researchers. It has become a hot topic for investigating volcanic influences on major events in Earth’s history.”
The researchers used the sharp fossilized teeth of lamprey-like creatures called conodonts to date the rock in which the mercury was deposited. Like most other creatures on the planet, conodonts were decimated by the catastrophe.
The eruptions propelled as much as 3 million km3 of ash high into the air over this extended period.
“In fact, the Siberian Traps eruptions spewed so much material in the air, particularly greenhouse gases, that it warmed the planet by an average of about 10 degrees centigrade,” Professor Algeo said.
“The warming climate likely would have been one of the biggest culprits in the mass extinction. But acid rain would have spoiled many bodies of water and raised the acidity of the global oceans. And the warmer water would have had more dead zones from a lack of dissolved oxygen.”
“We’re often left scratching our heads about what exactly was most harmful. Creatures adapted to colder environments would have been out of luck. So my guess is temperature change would be the No. 1 killer. Effects would exacerbated by acidification and other toxins in the environment.”
Stretching over an extended period, eruption after eruption prevented the Earth’s food chain from recovering.
“It’s not necessarily the intensity but the duration that matters. The longer this went on, the more pressure was placed on the environment,” Professor Algeo said.
“Likewise, the Earth was slow to recover from the disaster because the ongoing disturbances continued to wipe out biodiversity.”
“The mercury signature provides convincing evidence that the Siberian Traps eruptions were responsible for the catastrophe,” Dr. Shen said.
The study appears in the journal Nature Communications.
Jun Shen et al. 2019. Evidence for a prolonged Permian-Triassic extinction interval from global marine mercury records. Nature Communications 10, article number: 1563; doi: 10.1038/s41467-019-09620-0