Mercury found buried in ancient rock suggests volcanoes are behind The Great Dying, the biggest mass extinction that ever occurred on Earth. The event killed off over 95 percent of life on the planet.
The Great Dying
In a new study published in the journal Nature Communications, scientists reported the discovery of a spike in mercury in the geologic record at nearly a dozen sites around the world. They said this provides persuasive evidence that volcanic eruptions caused the extinction event.
The Great Dying occurred between the Permian and Triassic periods 252 million years ago. The cataclysm killed off much of terrestrial and marine life that lived before the time of the dinosaurs.
The eruptions happened in the volcanic system called the Siberian Traps in what is now the present day central Russia. Many of the eruptions occurred through gaping fissures in the ground, and not in cone-shaped volcanoes.
The eruptions occurred frequently and were long-lasting spanning over a period of hundreds of thousands of years. The extended period of eruptions likely prevented the recovery of Earth's food chain.
Chemical Signature Of Earth's Biggest Mass Extinction
Scientists explained that a lot of mercury is released into the atmosphere when there are large explosive volcanic eruptions.
Volcanic eruptions ignited deposits of coal that released mercury vapor into the atmosphere. The element eventually dropped into marine sediments around the world creating a chemical signature of the catastrophe.
In their study, researchers dated the rocks where mercury was deposited using the fossilized teeth of conodonts, lamprey-like creatures that were decimated by the catastrophe.
"We measure mercury (Hg), assumed to reflect shifts in volcanic activity, across the Permian-Triassic boundary in ten marine sections across the Northern Hemisphere. Hg concentration peaks close to the Permian-Triassic boundary suggest coupling of biotic extinction and increased volcanic activity," study researcher Jun Shen, from China University of Geosciences, and colleagues wrote in their study.
Set Off A Deadly Climate Change
Researchers said the eruptions spewed so much ash into the air, and these erupted materials, particularly the greenhouse gases, warmed Earth by an average of about 10 degrees centigrade. Researchers said the warmer climate was the nail of the coffin that led to the extinction of many species.
"Volcanic activities, including emissions of volcanic gases and combustion of organic matter, released abundant mercury to the surface of the Earth," Shen said.