Geology and Earth ScienceStudy: Volcanic warming may have caused extinction
Thursday, January 20, 2005 Posted: 3:04 PM EST (2004 GMT)
WASHINGTON (AP) -- An ancient version of global warming may have been to blame for the greatest mass extinction in Earth's history.
In an event known as the "Great Dying," some 250 million years ago, 90 percent of all marine life and nearly three-quarters of land-based plants and animals went extinct.
Scientists have long debated the cause of this calamity -- which occurred before the era of dinosaurs -- with possibilities including such disasters as meteor impacts.
Researchers led by Peter Ward of the University of Washington now think the answer is global warming caused by volcanic activity. Their findings are reported in Thursday's online edition of the journal Science.
They studied the Karoo Basin of South Africa, using chemical, biological and other evidence to relate layers of sediment there to similar layers in China that previous research has tied to the marine extinction at the same period.
Studying a 1,000-foot thick section of exposed sediment, Ward's team found evidence of a gradual extinction over about 10 million years followed by a sharp increase in extinction rate that lasted another 5 million years.
Ward's team believes the extinctions were caused by global warming and oxygen deprivation over long periods of time.
Massive volcanic flows in what is now Siberia brought on the warming while, at the same time, geologic action caused global sea levels to drop, Ward explained in a telephone interview.
"Once you expose a huge amount of underwater sediment to the atmosphere, two very bad things happen -- a huge amount of carbon in the sediments is released and also methane. Once (methane) hits the atmosphere it's the most efficient greenhouse gas on the planet," he said.
That provided a one-two punch of warming and a decline in oxygen levels, he said.
"Some of us have been toying with the idea that dinosaurs evolved to be a low-oxygen adaptation," resulting from this era, Ward said. "We know birds can live at much lower oxygen concentrations than we do, and we and think there were similar lung adaptations in dinosaurs."
Currently the atmosphere consists of about 21 percent oxygen, but the addition of gases at that time could have lowered levels to 16 percent or less, Ward said.
"If you didn't live on the sea level you didn't live," he commented, reflecting the fact that oxygen concentrations decline with altitude. The result would have been to eliminate half the living space on the planet, said Ward.
Scientists theorize dinosaurs evolved from the Earth's " Great Dying."
The more recent mass extinction that killed the dinosaurs -- 65 million years ago -- has been linked to an impact by a large asteroid or comet that struck in an area off the coast of what is now Mexico and left a distinctive layer of dust worldwide.
Some researchers have argued that the Great Dying might also have resulted from such an impact, but Ward's team said it could find no evidence for such an event.
That doesn't mean there wasn't one, argues Luann Becker of the University of California at Santa Barbara, commenting that "the absence of evidence isn't evidence for absence."
Becker, who was not part of Ward's research team, said "they did a nice job of presenting the paleontological data and the stratigraphy, which seem to show some indication of an evolutionary change going on for a prolonged period of time." However, she added, she doesn't believe that addresses the subject of cause and effect.
"I think that this is an ongoing discussion," said Becker, who previously reported on a crater off the northwest coast of Australia that shows evidence of a large meteor impact at about the time of the early extinction.
Ward's research was funded by the NASA Astrobiology Institute, the National Science Foundation and the National Research Foundation of South Africa.
WASHINGTON (AP) -- An ancient version of global warming may have been to blame for the greatest mass extinction in Earth's history.
In an event known as the "Great Dying," some 250 million years ago, 90 percent of all marine life and nearly three-quarters of land-based plants and animals went extinct.
Scientists have long debated the cause of this calamity -- which occurred before the era of dinosaurs -- with possibilities including such disasters as meteor impacts.
Researchers led by Peter Ward of the University of Washington now think the answer is global warming caused by volcanic activity. Their findings are reported in Thursday's online edition of the journal Science.
They studied the Karoo Basin of South Africa, using chemical, biological and other evidence to relate layers of sediment there to similar layers in China that previous research has tied to the marine extinction at the same period.
Studying a 1,000-foot thick section of exposed sediment, Ward's team found evidence of a gradual extinction over about 10 million years followed by a sharp increase in extinction rate that lasted another 5 million years.
Ward's team believes the extinctions were caused by global warming and oxygen deprivation over long periods of time.
Massive volcanic flows in what is now Siberia brought on the warming while, at the same time, geologic action caused global sea levels to drop, Ward explained in a telephone interview.
"Once you expose a huge amount of underwater sediment to the atmosphere, two very bad things happen -- a huge amount of carbon in the sediments is released and also methane. Once (methane) hits the atmosphere it's the most efficient greenhouse gas on the planet," he said.
That provided a one-two punch of warming and a decline in oxygen levels, he said.
"Some of us have been toying with the idea that dinosaurs evolved to be a low-oxygen adaptation," resulting from this era, Ward said. "We know birds can live at much lower oxygen concentrations than we do, and we and think there were similar lung adaptations in dinosaurs."
Currently the atmosphere consists of about 21 percent oxygen, but the addition of gases at that time could have lowered levels to 16 percent or less, Ward said.
"If you didn't live on the sea level you didn't live," he commented, reflecting the fact that oxygen concentrations decline with altitude. The result would have been to eliminate half the living space on the planet, said Ward.
Scientists theorize dinosaurs evolved from the Earth's " Great Dying."
The more recent mass extinction that killed the dinosaurs -- 65 million years ago -- has been linked to an impact by a large asteroid or comet that struck in an area off the coast of what is now Mexico and left a distinctive layer of dust worldwide.
Some researchers have argued that the Great Dying might also have resulted from such an impact, but Ward's team said it could find no evidence for such an event.
That doesn't mean there wasn't one, argues Luann Becker of the University of California at Santa Barbara, commenting that "the absence of evidence isn't evidence for absence."
Becker, who was not part of Ward's research team, said "they did a nice job of presenting the paleontological data and the stratigraphy, which seem to show some indication of an evolutionary change going on for a prolonged period of time." However, she added, she doesn't believe that addresses the subject of cause and effect.
"I think that this is an ongoing discussion," said Becker, who previously reported on a crater off the northwest coast of Australia that shows evidence of a large meteor impact at about the time of the early extinction.
Ward's research was funded by the NASA Astrobiology Institute, the National Science Foundation and the National Research Foundation of South Africa.
7 Comments:
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Earth’s “Great Dying” is still a huge mystery, and considering how long ago it happened, it is possible we might never know how it happened.
The theory about how the dinosaurs may have used lower levels of oxygen than we do is interesting, and it does provide basis for belief about the “Great Dying” being caused by atmospheric changes. It mentions that birds can survive at much lower oxygen concentrations, and there is much speculation that birds have evolved from dinosaurs. Granted, birds could have adapted their lower oxygen need over the thousands of years since the dinosaurs existed, but it doesn’t make the fact any less true.
If you lower the oxygen concentration level enough, then not much is going to survive. By adding the carbon and the methane to the air, you more or less choke the life out of a lot of organisms. Considering there’s very little evidence to support the meteor theory for this “mother of all extinctions” like there is for the extinction of the dinosaurs, this theory involving levels of oxygen concentration to be decreased 250 million years ago sounds plausible.
The extinction happened gradually, like most extinction tends to do, but then over the last five million years there was a sudden increase in extinctions. Considering there was much volcanic action in what is now Siberia, and global warming caused sea levels to drop dramatically, the amount of methane and carbon in the air could have accumulated to the point where suddenly, most of the life that once existed on earth vanished a lot quicker that it previously had.
This entire theory does seem to have some back bone, but I do believe that more evidence is needed, maybe even another theory to fight it, to prove it’s worth and weight. Considering ninety percent of all life disappeared then, it is unlikely we could find evidence in today’s life forms.
This article was quite interesting especially the theory of oxygen levels. What I wonder is if the extinction was occurring over about 15 million years why evolution could not help these animals to survive. You would think that there lung structures would have changed and developed to the new environment. I guess that just adds to survival of the fittest. The last 5 million years of extinctions happened rapidly I suppose with not enough time for evolution. But even so you would think they would have kept changing. That is why I agree with the fact that dinosaurs evolved from the great dying. At the risk of sounding stupid I can’t help but think that maybe the extinctions were actually mutations cased by the methane intake over so many years. It turned sea life into sea creatures and land life into land monsters. Or as we call them, dinosaurs. How else could such massive animals just appear?
Wow this caought my eye. Who nows if volcanoes causes a massive extention. even though oxygen levels changed it may not be the only reason I think there are other reasons why there was a extinction. One way i think is the formation of pangea causing a ice age. this reason becauese not all animals were able to adapt to the friggid weather. A second reason can be the meateor of the mesosoic witch could of killed 90 percent. It shore did kill all the doinosaurs and all plant life in this time but who nows if it killed alot more. Thats leaves me with a major question did the volcanoes really kill 90 % or were there more reasons?
I think that this article is very interesting and should be of great concern to the global community. The research done by Peter Ward brings to light a possibility that we could be facing in our lifetime or our children’s lifetime. Although the environmental issue of pollution and its harmful effects on the O zone that could result in global warming has been around for quite some time now, I don’t believe that people and governments around the world have taken it very seriously. But as more researches like this are performed every year, new evidence is brought to light of other things that are beyond our control that can cause this global warming to occur again. This adds to the list of things that we need to worry about that could start mass extinction again.
Right now we are left to think over this new possibility. Even if we were to shut down all the factories in the world and stop using cars we could still face the same threat because one or more our volcanoes could erupt setting forth mass extinction. And we already have people watching space for any asteroid or comet that could be heading our way (even though it’s not a guarantee but at least we are taking some measures). We can monitor volcanoes and know (not with much time to spare) when they could erupt but we have no way to stop it. We would be left to watch helplessly as what possibly happened 250 million years ago repeats it self. It almost seems that this planet goes through a recycling period every few hundred million years
I am very glad that research like these are performed. Even though they are not conclusive, they are part of a puzzle that one day we will be able to put together. The more we learn about the past our earth the more we can understand it and hopefully predict and prepare for what we know will probably repeat itself.
This leaves me to wonder if we, as species, could adapt to such a drastic change in our oxygen levels. Somehow I doubt it and the thought of it all is pretty scary. And even if we survive many other species as we know them would be gone. It seems like the only way to prepare for such an event is to try and find a way to reverse a greenhouse effect. I hope that there are scientists researching this right now and that this concern is shared among the global community. And maybe that a bigger effort is made in researching new ways to possibly avoid these catastrophic disasters. After all, our survival as a species as we know it, is on the line.
The great dying is something that we may never know why or what happened to cause mass extinction. Could a meteor have caused it just like the dinosaurs? Was it due to a global warming? Maybe an Ice age? We may never know because of the fact that it happened so long ago there could be a lot of erosion that went on and therefore it may result in an unconformity so we may never know what went on. What does interest me is why did more marine animals die off rather than land animals? Sure the sea level may have dropped but then the marine animals could have been pushed back a little into the sea. In a sense the marine animals have there own environment. They wouldn't be that much affected if plants and animals on land died off or diminished. So why did more marine animals die than land animals.
I had no idea that the "Great Dying" was before the era of Dinosaurs. According to the article, two posibilities came about as to what te cause was. Meterorited and global warming supposedly are the top two mos known motives. I do not think meteroites caused the extinction, although they did lead to an Ice Age. Can a meteor really kill off the entire earth though? Recently, i have learned that proto earth had barely any oxygen, i believe it was during the Hadean era. The gases that were presend were harmful and deadlyl i do not know why anything was actually alive at this time. Everything needs some form of oxygen in order to be living right? Or unless, they were just cells. What kind of fossils or evidence would they have left behind? Still, when oxygen was finally present, all the other harmfuk gases had to have been eliminated in the atmosphere in the form of acid rain... That alone is deadly. The dinosaurs came after this, so why would they be considered to be evolved into a low oxygen level creature? Exposed sediment of one thousand feel did show evidence of gradual extinction ovre time and subsequently showed a sharp increase in the extinction rate. Obviously, something extreme had to happen in order for organisms to die suddenly. What exactly did it? Will we ever knoe the truth? The whole thought of this scares me. What would happen if it happens to us? Did those creatures who were alive suffer? Did they seriously choke to death like the article says?
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