From Eurekalert: Caltech-led team debunks theory on end of ‘Snowball Earth’ ice age
Finds that rocks used as key geologic evidence were formed deep within Earth millions of years after the ice age ended
PASADENA, Calif.—There’s a theory about how the Marinoan ice age—also known as the “Snowball Earth” ice age because of its extreme low temperatures—came to an abrupt end some 600 million years ago. It has to do with large amounts of methane, a strong greenhouse gas, bubbling up through ocean sediments and from beneath the permafrost and heating the atmosphere.
The main physical evidence behind this theory has been samples of cap dolostone from south China, which were known to have a lot less of the carbon-13 isotope than is normally found in these types of carbonate rocks. (Dolostone is a type of sedimentary rock composed of the carbonate mineral, dolomite; it’s called cap dolostone when it overlies a glacial deposit.) The idea was that these rocks formed when Earth-warming methane bubbled up from below and was oxidized—”eaten”—by microbes, with its carbon wastes being incorporated into the dolostone, thereby leaving a signal of what had happened to end the ice age. The idea made sense, because methane also tends to be low in carbon-13; if carbon-13-depeleted methane had been made into rock, that rock would indeed also be low in carbon-13. But the idea was controversial, too, since there had been no previous isotopic evidence in carbonate rock of methane-munching microbes that early in Earth’s history.
And, as a team of scientists led by researchers from the California Institute of Technology (Caltech) report in this week’s issue of the journal Nature, it was also wrong—at least as far as the geologic evidence they looked at goes. Their testing shows that the rocks on which much of that ice-age-ending theory was based were formed millions of years after the ice age ended, and were formed at temperatures so high there could have been no living creatures associated with them.
“Our findings show that what happened in these rocks happened at very high temperatures, and abiologically,” says John Eiler, the Robert P. Sharp Professor of Geology and professor of geochemistry at Caltech, and one of the paper’s authors. “There is no evidence here that microbes ate methane as food. The story you see in this rock is not a story about ice ages.”
To tell the rocks’ story, the team used a technique Eiler developed at Caltech that looks at the way in which rare isotopes (like the carbon-13 in the dolostone) group, or “clump,” together in crystalline structures like bone or rock. This clumping, it turns out, is highly dependent upon the temperature of the immediate environment in which the crystals form. Hot temperatures mean less clumping; low temperatures mean more.
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  IMAGE: This is a view from one of the cap dolostone collection sites in south China, looking along the cliffs of the Yangtze Gorges.
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“The rocks that we analyzed for this study have been worked on before,” says Thomas Bristow, the paper’s first author and a former postdoc at Caltech who is now at NASA Ames Research Center, “but the unique advance available and developed at Caltech is the technique of using carbonate clumped-isotopic thermometry to study the temperature of crystallization of the samples. It was primarily this technique that brought new insights regarding the geological history of the rocks.”
What the team’s thermometer made very clear, says Eiler, is that “the carbon source was not oxidized and turned into carbonate at Earth’s surface. This was happening in a very hot hydrothermal environment, underground.”
In addition, he says, “We know it happened at least millions of years after the ice age ended, and probably tens of millions. Which means that whatever the source of carbon was, it wasn’t related to the end of the ice age.”
Since this rock had been the only carbon-isotopic evidence of a Precambrian methane seep, these findings bring up a number of questions—questions not just about how the Marinoan ice age ended, but about Earth’s budget of methane and the biogeochemistry of the ocean.
“The next stage of the research is to delve deeper into the question of why carbon-13-depleted carbonate rocks that formed at methane seeps seem to only be found during the later 400 million years of Earth history,” says John Grotzinger, the Fletcher Jones Professor of Geology at Caltech and the principal investigator on the work described. “It is an interesting fact of the geologic record that, despite a well-preserved record of carbonates beginning 3.5 billion years ago, the first 3 billion years of Earth history does not record evidence of methane oxidation. This is a curious absence. We think it might be linked to changes in ocean chemistry through time, but more work needs to be done to explore that.”
In addition to Bristow, Eiler, and Grotzinger, the other authors on the Nature paper, “A hydrothermal origin for isotopically anomalous cap dolostone cements from south China,” are Magali Bonifacie, a former Caltech postdoc now at the Institut de Physique du Globe de Paris, and Arkadiusz Derkowski from the Polish Academy of Sciences in Krakow.
The work was supported by an O. K. Earl Postdoctoral Fellowship, by the National Science Foundation’s Division of Earth Sciences and its Geobiology and Environmental Geochemistry program, and by CNRS-INSU (French research agency).
Excuse me Moderator but what does GTFA, used in your snip above, stand for?
My mind boggles. I know I live in a backwater but I do try to keep up.
Kindest Regards
[Hint: G = Go… A = Away. I should have not lost my temper. Sorries all around.
~ dbs]
ferd berple says:
May 25, 2011 at 7:06 pm
Everyone knows what ended snowball earth. It was folks driving around in V-8′s creating CO2 pollution and warming the earth.
=========================
Various UFO related groups insist that there have been advanced technological civilizations preceding ours by many millions of years.
Clearly it was the CO2 stripping geo-engineering projects which caused the snowball in the first place and it was only their re-invention of the v8 engine (biofuel powered for greater CO2 emission) which ended the snowball.
Ok ok…
/snark
Earths Atmospher: N2 is 780,800 ppm, O2 is 200,950 ppm, Ar is 9,300 ppm, H20 varies 1,000 to 30,000 ppm, CO2 is 395 ppm and CH4 is 1.7 ppm. Looks like whatever runs the water vapor is the key: the other Greenhouse gases are just plain scarce.
One more word of caution, if I may. After a career in rock-related geochemistry, I humbly realise that many aspects of even a simple-sounding mineral like dolomite are just beginning to be understood. Unfortunately, its understanding has probably been slowed by the drain of brains into the near-compulsory environment scene of the last few decades. It would take just a few minutes to sketch out a dozen projects for PhD theses about dolomite. We know that there are many unknowns.
Therefore, on a general blog like this, good as it is, do lock your keyboard before firing off a retort that involves high specialism, unless you can add to it. Carbonate isotope clumped thermometry is such a specialism, most probably.
But don’t read this as if I’m a party pooper. Have fun, keep well.
From my hazy recollection, I thought that there were cap dolomites over a couple at least of the Neoproterozoic glaciations. If true, that would imply, given the new interpretation of cap dolomite formation as I understand it here, that the same non-methane associated processes of cap dolomite formation must have occurred several times, not just at the end of the Marinoan.
Ciao
John
Wholeheartedly agree with Bill Illis! Invoking great earth-changing climatic events on changes in the gas contents of the atmosphere just doesn’t make sense from an energy budget point of view.
Cheers
John
a jones says:
May 25, 2011 at 10:19 pm
“Excuse me Moderator but what does GTFA, used in your snip above, stand for?”
Something like….Leave this area using groin jerking movements to someplace distant ;=)
“Excuse me Moderator but what does GTFA, used in your snip above, stand for?”
I think it means “go away”
GTFA – could mean Go The F… Away
[Reply: My apologies for losing it. Moderating thousands of comments a week can get tedious, but that is no excuse. The poster in question is a banned site pest who hides his URL. Info here. ~dbs, mod.]
I always thought that volcanic outgassing was a major factor in thawing out snowball Earth.
Bill Illis says:
May 25, 2011 at 9:58 pm
There is only one solid proxy measurement of CO2 as the last Snowball was ending and this is only 12,000 ppm. It had no impact on the Snowball ending at these low levels because it needed to be close to 250,000 ppm to overcome the temperature decline caused by all that ice.
I like the understatement! it puts our current 380 ppm in a correct perspective.
Was there not a Huronian “snowball earth” event about 2 billion years ago. How did that start and end? CO2 must have been pretty high back then.
From a jones on May 25, 2011 at 10:19 pm:
It’s a very old English expression, “Get thy foulness away!” Not surprising that you haven’t heard it. I believe Shakespeare may have used it, but don’t take my word for it, go ahead and check yourself. 😉
[Reply: Yes, that’s it. That’s it exactly ☺. ~dbs]
The Snowball Earth theory failed some years ago by two separate universities in the UK. The Open University Geological Dept. did a study in Scotland and found evidence of dropstones in the sediments of that time. Dropstones are stones picked up by glaciers, transported over open sea in icebergs and dropped as the berg melts. Since open water is required for this to happen, as well as temperatures for berg melting, the theory of complete ice cover of the planet was shown to be wrong.
Imperial College, London, also calculated that recovery from total planetary ice cover would be such a prolonged period that we could still covered by ice.
Nice to know they are correct. Solar and Milanchovian changes were to blame as they are now.
GTFA = Guam Track and Field Association
[That’s also correct. ~dbs]
@Bill illis
12,000 ppm? Can you confirm this is not a typo? 120 ppm or 120,000 ppb (parts per billion).
Coldish,
See the explanation in AdderW’s post above. And as an American protectorate, Guam folks know that GUAM means: “Give Us American Money!”☺
As always, America complies.
The volcanic outgassing theory for the ending of the postulated c.600Ma b.p. snowball earth episode has been presented by P.F.Hoffmann and D.P.Schrag of Harvard Univ. I only have a German translation of one article to hand (Spektrum der Wissenschaft, Dossier 1/2002, pp. 34-41), but I’m sure the authors have also published their work in English language journals.
The authors argue that with the world ocean 100% ice covered (itself IMO a speculative idea, not proven) the steady CO2 output of volcanoes could not be dissolved in the ocean and would accumulate in the atmosphere until the latter became so warm that it melted the ice.
The main piece of empirical evidence to support this theory is the observation in several parts of the world of substantial carbonate deposits – in some cases primary aragonite CaCO3 rather than dolomite CaMg(CO3)2 – overlying the supposed glacial tillites and dropstone beds. These deposits are explained by the rapid incorporation of the excess atmospheric carbon into marine carbonate once the ocean was re-exposed to the atmosphere.
I don’t buy the theory, but IMO it does deserve to be taken seriously.
Bahahaha… and not smart enough to know that changing his workstation/laptop IP makes no difference as to get to the internet. The outbound connection NATs it to a public address other than his own 99% of the time. And also not smart enough to understand DHCP leasing but will try to use it as a tool. No wonder he posts there.
Apology – the q tag did not work so well.
REPLY: The slash ALWAYS goes before the q, not after, same for B and i
– Anthony
From John Marshall on May 26, 2011 at 2:46 am:
Yet it was previously reported here in 2010 that evidence suggested global glaciation during an earlier ice age than the one mentioned above, aka a “snowball Earth.”
Yowzer! “sea ice extended to the equator 716.5 million years ago”
The pics with that post are not loading for me, so here is the Science Daily version of the press release with what should be the second pic in the WUWT post going by the captions. From it:
So it looks like “snowball Earth” happened before, the planet warmed up, so why couldn’t it have happened about 100 million years later?
To note it, the Imperial College specified “total planetary ice cover” while the “snowball Earth” was said to still have patches of open water, thus the differences may come from comparing “snowballs” and “ice balls,” the Imperial College calculations started with something that is considered unrealistic.
I am sorry to be Mister Picky, but the Earth cannot have looked like that image shown back then, assuming Mr Wegener was right, & was in Pangea state!
We know Snowball Earth must have occurred under current theories as evidenced by the presence of drop-stones in palces like South Africa, which was at one time believed to have not undergone glaciation, however the drop-stones suggested otherwise. Of course BBC’s Horizon programme some years ago, demonstrated this (before it succumbed to the AGW faith) in an excellent prog. They did also show that life can exist on the microbal scale & even life scale, with evidence of sea-life existing in Antarctica under the ice. Of course it soon started showing theories of mass extinctions being caused by Siberian lava flows/eruptions of millions of years that warmed the planet by 5°C, which then caused methane clathrates in the sea bed to melt raising the temperature by another 5°C, which would do the trick priming us for AGW catastrophe, except the methane didn’t keep rising. All very well as a theory I suppose.
Whilst the Shakespearean reference to GTFA is most eloquent, I prefer the other definition, being of Anglo-Saxon decent! However, the moderator could always refer to VHF radio parlance by advising the perpetrator to “Foxtrot Oscar”, rather as Richard North of EU Referendum is prone to do! At times a really good swear is good for the soul & I for one would not criticise anyone for so doing on the right occasion!
Bill Illis pretty well says it all – we used to be a giant Antarctica before we broke into pieces. Also, do you have to be an old geologist to be aware of dolomitization of calcareous limestone – a high risk development for old Ca-limestones – seawater is loaded with Mg++. GHG seems to be dolomitizing young geologists’ brains (and young physicists, chemists ….) The literature of the past few decades seems to be largely cotton candy.
George said on May 26, 2011 at 3:41 am:
That’s putting it mildly. Full quote marks around every page element after your use, even blank lines… Try using “blockquote” next time, apparently people often mess that up without messing up the page. It seems wordpress automatically fixes blockquote when a comment is posted.
However it’s not all bad, as it brought a nice corollary to Murphy’s Law to mind:
If you make it, they will break it.
☺
And I thought the science was settled, Methane caused Snobal Warming!
The original theory that I saw for the end of snowball earth was that the ice had suppressed volcanic activity to the point that it began to cause massives eruptions through the ice sheets, emitting massive amounts of CO² into the atmosphere which then warmed the earth and later became incorporated as dolomite