It makes you wonder what created all that CO2 millions of years ago.
From Louisiana State University
LSU researchers find new information about ‘Snowball Earth’ period
It is rather difficult to imagine, but approximately 635 million years ago, ice may have covered a vast portion of our planet in an event called “Snowball Earth.” According to the Snowball Earth hypothesis, the massive ice age that occurred before animal life appeared, when Earth’s landmasses were most likely clustered near the equator, precipitated relatively rapid changes in atmospheric conditions and a subsequent greenhouse heat wave. This particular period of extensive glaciation and subsequent climate changes might have supplied the cataclysmic event that gave rise to modern levels of atmospheric oxygen, paving the way for the rise of animals and the diversification of life during the later Cambrian explosion.
But if ice covered the earth all the way to the tropics during what is known as the Marinoan glaciation, how did the planet spring back from the brink of an ice apocalypse? Huiming Bao, Charles L. Jones Professor in Geology & Geophysics at LSU, might have some of the answers.
Bao and LSU graduate students Bryan Killingsworth and Justin Hayles, together with Chuanming Zhou, a colleague at Chinese Academy of Sciences, had an article published on Feb. 5 in the Proceedings of the National Academy of Sciences, or PNAS, that provides new clues on the duration of what was a significant change in atmospheric conditions following the Marinoan glaciation.
“The story is to put a time limit on how fast our Earth system can recover from a total frozen state,” Bao said. “It is about a unique and rapidly changing post-glacial world, but is also about the incredible resilience of life and life’s remarkable ability to restore a new balance between atmosphere, hydrosphere and biosphere after a global glaciation.”
Bao’s group went about investigating the post-glaciation period of Snowball Earth by looking at unique occurrences of “crystal fans” of a common mineral known as barite (BaSO4), deposited in rocks following the Marinoan glaciation. Out of the three stable isotopes of oxygen, O-16, O-17 and O-18, Bao’s group pays close attention to the relatively scarce isotope O-17. According to Killingsworth, there aren’t many phenomena on earth that can change the normally expected ratio of the scare isotope O-17 to more abundant isotope O-18. However, in sulfate minerals such as barite in rock samples from around 635 million years ago, Bao’s group finds large deviations in the normal ratio of O-17 to O-18 with respect to O-16 isotopes.
“If something unusual happens with the composition of the atmosphere, the oxygen isotope ratios can change,” Killingsworth said. “We see a large deviation in this ratio in minerals deposited around 635 million years ago. This occurred during an extremely odd time in atmospheric history.”
According to Bao’s group, the odd oxygen isotope ratios they find in barite samples from 635 million years ago could have occurred if, following the extensive Snowball Earth glaciation, Earth’s atmosphere had very high levels of carbon dioxide, or CO2. An ultra-high carbon dioxide atmosphere, Killingsworth explains, where CO2 levels match levels of atmospheric oxygen, would grab more O-17 from oxygen. This would cause a depletion of the O-17 isotope in air and subsequently in barite minerals, which incorporate oxygen as they grow. Bao’s group has found worldwide deposits of this O-17 depleted sulfate mineral in rocks dating from the global glaciation event 635 million years ago, indicating an episode of an ultra-high carbon dioxide atmosphere following the Marinoan glaciation.
“Something significant happened in the atmosphere,” Killingsworth said. “This kind of an atmospheric shift in carbon dioxide is not observed during any other period of Earth’s history. And now we have sedimentary rock evidence for how long this ultra-high carbon dioxide period lasted.”
By using available radiometric dates from areas near layers of barite deposits, Bao’s group has been able to come up with an estimate for the duration of what is now called the Marinoan Oxygen-17 Depletion, or MOSD, event. Bao’s group estimates the MOSD duration at 0 – 1 million years.
“This is, so far, really the best estimate we could get from geological records, in line with previous models of how long an ultra-high carbon dioxide event could last before the carbon dioxide in the air would get drawn back into the oceans and sediments,” Killingsworth said.
Normally, carbon dioxide levels in the atmosphere are in balance with levels of carbon dioxide in the ocean. However, if water and air were cut off by a thick layer of ice during Snowball Earth, atmospheric carbon dioxide levels could have increased drastically. In a phenomenon similar to the climate change Earth is witnessing in modern times, high levels of atmospheric carbon dioxide would have created a greenhouse gas warming effect, trapping heat inside the planet’s atmosphere and melting the Marinoan ice. Essentially, the Marinoan glaciation created the potential for extreme changes in atmospheric chemistry that in turn lead to the end of Snowball Earth and the beginning of a new explosion of animal life on Earth.
While previous work by Bao’s group had advanced the interpretation of the strange occurrence of O-17 depleted barite just after the Marinoan glaciation, there was still much uncertainty on the duration of ultra-high CO2 levels after meltdown of Snowball Earth. Bao’s discovery of a field site with many barite layers gave the opportunity to track how oxygen isotope ratios changed through a thickness of sedimentary rock. As the pages in a novel can be thought of as representing time, so layers of sedimentary rock represent geological history. However, these rock “pages” represented an unknown duration of time for the MOSD event. By using characteristic features of the Marinoan rock sequence occurring regionally in South China, Bao’s group linked the barite layer site to other sites in the region that did have precise dates from volcanic ash beds. Bao’s group has succeeded in estimating the duration of the MOSD event, and thus the time it took for Earth to restore “normal” CO2 levels in the atmosphere.
“To some extent, our findings demonstrate that whatever happens to Earth, she will recover, and recover at a rapid pace,” Bao said. “Mother Earth lived and life carried on even in the most devastating situation. The only difference is the life composition afterwards. In other words, whatever humans do to the Earth, life will go on. The only uncertainty is whether humans will still remain part of the life composition.”
Bao says that he had been interested in this most intriguing episode of Earth’s history since Paul Hoffman, Dan Schrag and colleagues revived the Snowball Earth hypothesis in 1998.
“I was a casual ‘non-believer’ of this hypothesis because of the mere improbability of such an Earth state,” Bao said. “There was nothing rational or logic in that belief for me, of course. I remember I even told my job interviewers back in 2000 that one of my future research plans was to prove that the Snowball Earth hypothesis was wrong.”
However, during a winter break in 2006, Bao obtained some unusual data from barite, a sulfate mineral dating from the Snowball Earth period that he received from a colleague in China.
“I started to develop my own method to explore this utterly strange world,” Bao said. “Now, it seems that our LSU group is the one offering the strongest supporting evidence for a ‘Snowball Earth’ back 635 million years ago. I certainly did not see this coming. The finding we published in 2008 demonstrates, again, that new scientific breakthroughs are often brought in by outsiders.”
Bao credits his research ideas, analytical work and pleasure of working on this project to his two graduate students, Killingsworth and Hayles, as well as his long-time Chinese collaborators. Bao brought Killingsworth and Hayles to an interior mountainous region in South China in December 2011, where the group succeeded in finding multiple barite layers in a section of rocks dating to 635 million years ago. This discovery formed a large part of their analysis and subsequent publication in PNAS.
“Nothing can beat the intellectual excitement and satisfaction you get from research in the field and in the laboratory,” Bao said.
Bao’s research is funded by the National Science Foundation and by the Chinese Academy of Sciences.
To read the original article, visit http://www.pnas.org/content/early/2013/02/05/1213154110.1.abstract.
To read more about Huiming Bao’s research, visit http://www.geol.lsu.edu/hbao/.
Even if say for example there was no CO2 in the atmosphere at the beginning of snow ball earth, but at the end of snowball earth there was hundreds of times more CO2 in the atmosphere than there is now, then since snowball earth lasted millions of years that implies that for millions of years CO2 was hundreds of times the concentration we have today, and millions of years at that heightened concentration was not enough to halt snowball earth for a long long time. Therefore, now over the last hundred years or so since we have increased CO2 presumably less than 100ppm, how is this infinetesimal amount of change over a short period magically have such a massive effect?
I have always felt that unexplained fluctuations in solar output was the most likely cause for the Iceball Earth conditions, and for it’s subsequent end. I still favor that explanation. Still, I can think of a possible mechanism for the theory he proposes here: Snowball Earth freezes, the oceans are mostly blocked from communication with the atmosphere due to the global ice sheet, and intense volcanic activity in part of the globe fills the atmosphere with gases that are never precipitated out due to the cloudless conditions. Under these circumstances the relative gas concentrations in the atmosphere could change rapidly.
I don’t think that makes his theory likely, but I think it makes it possible.
Coach Springer says:
February 28, 2013 at 3:01 pm
With everything covered by ice trapping CO2 in the land, the tundra, the marshes, the peat, and the oceans, it could have been the hand…
What peat? What marsh? There were no land plants then…
Bill Illis says (February 28, 2013 at 3:54 pm): “Perfectly explainable in logical simple sensible terms (and without any magical need to invoke CO2 at all).”
Aaaaawwwww…
Just kidding. Thanks for the references, Bill. Fascinating topic, plate tectonics.
Without understanding what caused the glaciation in the first place it is not possible to have a coherent answer about how it ended. Snowball Earth conditions are known to have occurred in two (geologically speaking) brief windows of time around 2.3 billion and 0.7 billion years ago. Chapter 6 of “The Chilling Stars” by Svensmark and Calder has a good discussion on how this was determined and an explanation for the beginning and end in terms of the galactic cosmic rays(GCR)/clouds hypothesis: “Astrophysicist Nir Shaviv demonstrated that the Snowball events coincided with episodes of intense star-making in the Galaxy. This lead to such exceptional levels of GCRs hitting the Earth that the Earth became cloudy and sunless enough to freeze over. Tens of millions of years after the star-making episodes GCR levels returned to low enough levels for the climate to warm again.” [paraphrased for brevity]
OK, so what about all those positive feedbacks and CO2 tipping points that the green cult are always clanging on about. If we had planet snowball and it was warmed by ultra high atmospheric CO2 levels, then why did it not keep warming until the earth was a blackened cinder like all the chicken little types claim will happen… Or do those positive feedbacks only work with magic human CO2?
What evidence is there that Snow Ball Earth ever existed ???
Given that earths original atmosphere must have been just like Venus at about 100 bar (earth being larger therefore holding more gas) and almost all CO2 as is Venus today, then its not beyond the realms of possibility that the atmosphere could have been 10 or 20 bar (or more) back then and therefore average temperatures could have been higher. The question has to be what caused the snowball, rather than why we came out, which seems obvious given we can deduce that the atmosphere was still much thicker at the time of the dinosaurs, and would have been at a pressure high enough to heat it up once the cause of the ice house had passed.
The question I have is are scientist thinking backwards because they are blinded by the green house effect.
interesting speculation, wrong conclusion.
“In a phenomenon similar to the climate change Earth is witnessing in modern times, high levels of atmospheric carbon dioxide would have created a greenhouse gas warming effect, trapping heat inside the planet’s atmosphere and melting the Marinoan ice.”
This is the obligatory grant-grubbing non-science BS which calls into question the motives and the results of the entire study. Too bad. They might actually be onto something.
wws says:
February 28, 2013 at 4:20 pm
I have always felt that unexplained fluctuations in solar output was the most likely cause for the Iceball Earth conditions, and for it’s subsequent end. I still favor that explanation. Still, I can think of a possible mechanism for the theory he proposes here: Snowball Earth freezes, the oceans are mostly blocked from communication with the atmosphere due to the global ice sheet, and intense volcanic activity in part of the globe fills the atmosphere with gases that are never precipitated out due to the cloudless conditions. Under these circumstances the relative gas concentrations in the atmosphere could change rapidly.
I don’t think that makes his theory likely, but I think it makes it possible.
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I think that mostly he’s added one more thing to the list of bizarre phenomena associated with the “snowball earth” — dramatic O17 depletion. I’ve wondered at times if perhaps the magnetic field somehow got decoupled from the rotational axis and the magnetic poles wandered down toward the equator. That would account for both the rapid apparent continental drift (the reference frame was moving) and glaciation at “equatorial” areas that were really polar. But that wouldn’t explain O17 depletion. I suspect it may be many decades if not centuries before we really understand this exotic period of the Earth’s past.
We know from 500 million years ago that CO2 levels were in the region of 15 times today’s levels but were drastically reduced as the plant world took hold.
As we did not burn up but greened up when CO2 was high the same thing will happen again…in fact NASA have noticed a greening of the planet…even on the edge of some desert areas.
Demonising the planet’s number one plant food has always been nonsense….apart from it’s logarithmic nature in creating heat there is the small matter of the lack of warming in the Troposphere.
Doesn’t the greenhouse effect require that visible light is first absorbed, then emitted as IR? If the earth really was a snowball, then there would be very little conversion of visible light to IR, and therefore a very weak greenhouse effect, even with very high CO2 concentration in the athmosphere.
Steven Mosher says: Wait.. I thought the sun was the cause of all climate change.
C’mon Steve, we all know climate change is driven by a wide variety of interacting terrestrial and extraterrestrial factors that exert varying degrees of influence through time.
We just don’t see convincing evidence that CO2 is a major player.
OMG….so the stegasaur,the bronto,etc breathed CO2.And just how did the “little” lizards survive in the seas? They would have been breathing solid carbonates! And what cheap drugs,besides the cAGW ones,is this guy on?
In reply to:
Steven Mosher says:
February 28, 2013 at 2:15 pm
Wait.. I thought the sun was the cause of all climate change.
William: Ion modulating phonemon. GRC for example varies ions in the atmosphere and GCR varies depending on the position of the solar system and the galaxy plane.
How’s this for a theory:
1. Our old earth was struck by a mighty meteor.
2. The crust broke into the plates, pushing and heaving creating the mountains and valleys we have today.
3. Oil and gas (which are created by reactions at the edges of the earth’s inner core – like Titan) breaks to the surface.
4. The oil/gas ignites and burns at the surface creating the CO2 (I’m assuming O2 was present as this article seems to imply).
5. The ice melts filling up the valleys creating the oceans we have today.
6. Snowball earth suddenly becomes very warm and when the fires go out the resultant remnants have all the ingredients for life.
7. The oil and gas is discovered by humans trapped where the cracks in the plates have allowed it to rise to the surface.
8. Humans use the oil and gas for energy and create more CO2.
With a few tweaks I think that settles it.
talldave2 says:
So… we should cut CO2 levels so we can all die in another Snowball Earth.
I’m sold.
Best comment ever!
I like the image of the modern day Earth covered in ice. In late Proterozoic times the landforms of Earth were unrecognizable from today’s image.
BaSO4 fans? How do you like these:
http://www.tysonsfineminerals.com/mineral-gallery/?id=43
These are gypsum “fans” that grow in the the glacial clays of Lake Agassiz in Manitoba, composed of CaSO4. So-called gypsum rosettes and Barite rosettes are well known to geologists. I think it might be a worthwhile extension of the authors’ work to determine the O17 isotope of these which were also associated with an ice age – the recent one. It would be a good test of the hypothesis. If the Agassiz clays gypsum also has higher O17, then a snowball earth would be proven to not be necessary for their formation. Presumably the ice itself would be higher in O17 and O18 with these reduced in the atmosphere even without a snowball earth. Upon melting, the ice water would bear the heavier isotopes in greater abundance and these would result in gypsum or barite crystals growing in clay from dissolved gypsum or barite in the the “Ice Age” water.bound up in the clay.
Why so much gypsum? There are well known large gypsum deposits to the north of the Agassiz clays that would have been ground up by the ice into clay sizes, mixed with other fine clays settling in Lake Agassiz. The clay would have abundant fine gypsum and the water would be saturated with CaSO4.
Also, since, presumably with the extra neutrons, The atomic radii of the heavier isotopes would be greater than that of the common O16. This means there could be at least a small tendency for different O isotopes to better fit into mineral crystal lattices. I’m not so sure anyone has done much research in this regard. The assumption is that the ratios are pretty fixed in general and deviations are interpreted as being because of temperature in the water and air. I would think that hot, hydrothermal, mineralizing solutions (barite is a common canditate for this) could also fractionate oxygen isotopes. Why not? The hotter mineralizing waters hitting a porous formation could result in preferential “loss” of the lighter O isotopes for the same reason that we see partition in climate-temperatured waters and ice. Unless someone can show me I am wrong in this, I remain sceptical…
I think it’s more likely, IF snowball Earth really existed, that whatever caused the extreme cold conditions in the first place changed (such as an orbital perturbation), and once the oceans were revealed again, CO2 started increasing dramatically in the atmosphere, outgassing from the oceans.
Tom G(ologist),
Ice cover descended down through most of the U.S. and Europe, but the equator wasn’t affected. Prof Richard Lindzen wrote: “There is ample evidence that the Earth’s temperature as measured at the equator has remained within +/- 1°C for more than the past billion years. Those temperatures have not changed over the past century.”
Free oxygen? This is an iron planet. Without plants where did free O2 come from back then?
How does the atmospheric oxygen react to form barite if ice separates the precursors?
“Normally, carbon dioxide levels in the atmosphere are in balance with levels of carbon dioxide in the ocean. However, if water and air were cut off by a thick layer of ice during Snowball Earth, atmospheric carbon dioxide levels could have increased drastically.”
No, as the water cooled, the CO2 would preferentially dissolve in the seawater depleting the atmosphere. After the ice formed, it would seal off the largest source for CO2 in the atmosphere. With no rotting plants on the land, the only source of CO2 would be volcanic activity. Volcanic activity may be the mechanism. It would both emit CO2 and a heck of a lot of dust that would settle on the ice and decrease albedo. CO2, with its logarithmically diminishing effect would not be a serious agent, especially with a very low water vapour content of the atmosphere in a snowball earth situation. Nice try but no dice, let the CO2 go in this scenario- it robs the more interesting part of your paper of “oxygen”.