Volcano May Have Split Continent, Reshaped Life
The largest sustained volcanic eruption in Earth’s history--so powerful it split an ancient super-continent and created the Atlantic Ocean--spewed millions of square miles of searing lava that extinguished much of life on ancient Earth, according to research made public Thursday.
From hundreds of basalt outcrops that rim the Atlantic coasts, scientists have pieced together evidence of the titanic eruption 200 million years ago. The eruption set the fractured landmasses adrift and, by inexorably wedging them apart, gradually opened the gulf that created the Atlantic--giving the map of the world the form it has today, researchers said.
In the space of perhaps just a few million years, half of all marine species died, as did almost as many species of reptiles and other land animals. This set the stage for the age of the dinosaurs and the evolution of the first mammals.
The new research, published today in Science, adds weight to a theory that mass extinctions, which have plagued Earth repeatedly since the dawn of time, were caused not primarily by collisions with comets or errant asteroids, but by the fierce internal volcanics of the planet itself.
So far, three mass extinctions have been linked with such massive continental eruptions.
“I think the new research is a major advance,” said paleontologist Paul E. Olsen at the Lamont Doherty Earth Observatory of Columbia University.
“This is one of the biggest things that has ever happened in Earth’s history. This is a gigantic, igneous event, and it all seems to have occurred in an amazingly brief amount of time,’ Olsen said.
To reconstruct the ancient catastrophe, a team of scientists analyzed basalt dikes, sills and lavas from the New Jersey Palisades and the Brazilian Amazon to Spain and West Africa. The team was led by dating expert Paul Renne, director of the Berkeley Geochronology Center, and his colleague Andrea Marzoli.
By studying the chemical composition and precisely dating the residual radioisotopes in the rocks, the researchers determined that the formations all stemmed from the same eruption. Once they realized that the outcrops were linked, they were able to determine that, in the distant past, the rocks all had been located together at the center of an immense continent called Pangea that once stretched, unbroken, from pole to pole.
Lava Flows Covered Vast Regions
The newly identified eruption, called the Central Atlantic Magmatic Province (CAMP), appears to have been centered in what is now Florida. It is by far the most extensive known, with basaltic lava flows that encompass about 2.7 million square miles. The formations today are so badly eroded or deeply buried that the researchers suspect that they are only seeing a fraction of the remains, suggesting that the eruption was even greater than they can tell.
“It has never been appreciated before that this [eruption] constitutes one single event,” Renne said. “The fact that it coincides with one of the biggest extinction events we know about is pretty exciting.”
There are few things as certain in the geologic record of Earth as great, and so far unexplained, cataclysms that, with disturbing regularity, bring life on the planet to the brink of extinction.
Few things, however, are as controversial in the science of Earth as the effort to identify the mechanisms responsible for these catastrophes.
In their search for a suspect, researchers in recent years have fingered just about everything that an educated imagination can conceive: from Ice Age cooling, greenhouse warming, drops in sea level and a precipitous decline in the amount of oxygen in the atmosphere to recurring impacts with comets.
In the most devastating extinction event, which occurred at the juncture of the Permian and Triassic periods 250 million years ago, life on Earth was almost completely wiped out.
Known to paleontologists as “The Great Dying,” 80% or more of all species in the ocean and 70% of all vertebrate families on land disappeared forever. It was the closest that organic life has ever come to being erased completely from the planet. Yet nobody really knows why.
More well known, perhaps, is the extinction event that involved the demise of the dinosaurs about 65 million years ago, which cleared the world stage for the rise of mammals and, eventually, humanity itself. Recent research has all but proved that an immense asteroid that struck Earth in the vicinity of the Yucatan Peninsula at that time played a starring role.
Links to Other Major Extinctions
In the last two years, however, researchers like Renne and his colleagues have argued that vast lava flows--known as flood basalts--also may have been a critical factor in all the major extinctions.
The scientists have identified the remains of two other calamitous outpourings of lava in India and Siberia that appear to coincide with those two extinction events 250 million and 65 million years ago.
Now they have identified the CAMP eruption, which is half again as large.
Each time, rivers of magma flowed from many individual volcanic cones, all feeding from the same vast plume of subterranean molten rock.
As the lava boiled over the landscape, continent-sized clouds of toxic fumes and greenhouse gases like carbon dioxide steamed into the atmosphere, the scientists theorize. While the lava itself could have triggered a global conflagration, the gases also may have further disrupted the environment by triggering drastic ecological changes and altering the world climate.
As devastating as such extensive lava flows may have been, they may not have been enough by themselves to cause such wide-spread global disruptions, some experts argue. There are geologic hints that other cosmic objects may have struck Earth with enough force to have contributed to the periodic extinctions.
“This is still one of the most intriguing issues in geology,” said Renne. What is “the relationship between extinctions and cataclysms such as magma floods or asteroid impacts? What we have now is another piece of evidence that shows there was a relationship between flood basalts and biologic crises.”
In any event, while still not conclusive enough to persuade everyone, it is convincing enough for some scientists.
“It is still extremely controversial in my own mind,” Olsen said. “But it is truly a remarkable coincidence that the three largest mass extinctions in the last 500 million years coincide with the three largest known volcanic eruptions.
“It is hard to look at that and say it is an accident.”
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
Earth’s Biggest Bang
New research reveals evidence of a sustained volcanic eruption 200 million years ago so powerful it split the continents apart and caused the extinction of many life forms then on Earth.
