|Scientists from Nanjing University in China and New York University believe they found a sixth mass extinction that wiped out nearly all life on the planet / Photo by: Puwadol Jaturawutthichai via 123RF|
An asteroid hitting Earth did not cause the largest mass extinction, a volcano eruption did—at least that's according to a new discovery.
Scientists from Nanjing University in China and New York University believe they found a sixth mass extinction that wiped out nearly all life on the planet. The researchers said a volcanic eruption in Asia during the Middle Permian raised the total number of extinctions in the geologic record.
Prior to the discovery, historians say extinction defined five geological eras: the Ordovician (540 million years ago), the Late Devonian (375-359 million years ago), the Permian (252 million years ago), the Triassic (201 million years ago), and the Cretaceous (66 million years ago).
The unknown volcanic eruption was dated about 260 million years, sometime between the Ordovician period and the Cretaceous era. Massive die-off events are usually tracked through fossil records, but the results of the recent study were derived from analysis of rocks from Hudson Bay, Canada formed billions of years ago.
Newsweek, a US-based weekly news magazine, reported that the researchers were looking at a mineral called barite that held information about the amount of oxygen in the atmosphere at the time. Analysis of the rocks showed a massive drop in the level of life on Earth about 2.05 billion years ago. The drop corresponded to the significant changes on the planet's oxygen levels, particularly the surge in the amount of oxygen in the atmosphere prior to the die-off about 2.4 billion years ago.
This event was known as the Great Oxidation Event and at the end of which, there was a dramatic fall in oxygen levels. Researchers said conditions to sustain life on the planet went from "feast to famine," which persisted for another one billion years, Newsweek said.
Study author Peter Crockford stated they were "very surprised" with the results. He added that there were no expectations on seeing "such a large signal, nor did we expect to find it in this specific type of sample.
"Over the 100 to 200 million years before this die-off event there was a large amount of life on the planet, but after this event, a huge portion died off. However, instead of recovering like more recent mass extinctions, the amount of life on the planet or size of the biosphere stayed small for the following billion years of Earth's history—about two billion to one billion years ago."
A Major Species Wipeout
When the Great Oxidation Event occurred, photosynthesis of the only surviving micro-organisms at the time altered the chemical composition of the atmosphere. This alteration then led to the massive surge of oxygen that the microorganisms could no longer sustain.
CNN said the microorganisms used up all the nutrients they needed to produce oxygen, therefore unbalancing the Earth's atmosphere. The news agency added that this eventually led to an "enormous drop" in the biosphere or the amount of life on the planet—the severity of which remains unknown.
Results of the Nanjing-NYU study showed that some 80 to 99.5 percent of organisms were wiped out by the end of the Great Oxidation Event. The number of microorganisms was too great, leading to the production of too much oxygen.
"Even our most conservative estimates would exceed estimates for the amount of life that died off during the extinction of the dinosaurs approximately 65 million years ago," co-author Malcolm Hodgskiss told CNN.
Their calculations surpassed that of the extinction of the Cretaceous, which saw about 75 percent of life on Earth disappearing and ending the reign of dinosaurs, and the Great Dying event of the Permian era that resulted in the loss of around 97 percent of species (70 percent of terrestrial life and 96 percent ocean dwellers).
|Results of the Nanjing-NYU study showed that some 80 to 99.5 percent of organisms were wiped out by the end of the Great Oxidation Event / Photo by: Weerapat Kiatdumrong via 123RF|
An Insight Into the Future
For NYU biology professor Michael Rampino, it's important to know the number of mass extinction events as well as their timing in investigating and determining their causes. "Notably, all six major mass extinctions are correlated with devastating environmental upheavals—specifically, massive flood-basalt eruptions, each covering more than a million square kilometers with thick lava flows," Rampino told the Daily Mail, a British daily middle-market newspaper published in London in a tabloid format.
"In terms of both losses in the number of species and overall ecological damage, the end-Guadalupian event now ranks as a major mass extinction, similar to the other five," he added.
The previously unknown volcanic eruption was said to have created the Emeishan Traps, a rock formation found in China, and supports the idea of an "oxygen overshoot." An oxygen overshoot is a theory believed to have spurred the development of life with massive production of oxygen from photosynthesis and weathering.
Researchers believe their discovery could provide an insight into how Earth will possibly change in the future. "In terms of both losses in the number of species and overall ecological damage, the end-Guadalupian event now ranks as a major mass extinction, similar to the other five," Crockford said, adding that oxygen levels will "absolutely change" in the next billion years (although not at a pace fast enough that humans will begin to notice).
|The previously unknown volcanic eruption was said to have created the Emeishan Traps, a rock formation found in China, and supports the idea of an "oxygen overshoot" / Photo by: Alyona Boiko via 123RF|