I saw a really interesting doodad on The Science Channel the other day about how there is very strong evidence to support the theory that the entire planet was frozen over for approximately 10 million years about 600 or 700 million years ago. It was a crazy story, but the evidence seemed pretty convincing. I'm not much of an earth sciences guy but that whole story is fascinating. Here's a link: http://www.sciam.com/article.cfm?articleID=00027B74-C59A-1C75-9B81809EC588EF21 Have you heard about it? What do you think?
A bit of discussion about this subject happened in this thread http://www.sciforums.com/showthread.php?t=34939 Thanks for that URL which seems to be one of the best summaries of the concept I've seen.
The owner of Orion's Arm, Alan Kaslev, has another website which discusses this snowball Earth scenario in detail http://www.palaeos.com/Proterozoic/Snowballs.html here.
It is a compelling and dramatic theory, which one feels a desire to believe in. There are doubts, though: for one thing, the occasional large impact would have vapourised vast quantities of ice and produced a water vapour layer in the atmosphere, which would itself provide a considerable greenhouse effect and melt more ice. Objects up to 1 km across probably strike the Earth every 100,000 years on average, so a global whiteout might not have been able to last as long as the theory states.
There was quite a long and arduous study done which may actually still be going on called Earth Radiation Budget Experiment using some satellites specifically designed and launched for the study, if I recall correctly, that looked into the greenhouse effect of clouds and high altitude ice crystals. One of the major findings was that clouds and high altitude ice crystals reflected more heat back into space than they trapped via greenhouse activity. As far as water vapor goes, that is a different thing isn't it? Enough water vapor and you will get clouds of water droplets but the vapor itself, does that have greenhouse activity? I know it is invisible to the naked eye.
Fascinating article Wes. Thanks for posting legitimate science not crap dreamed up by the writers of the Observer and the like. But let me climb down from my soapbox..... From what I can recall of my climate and geochemistry, the article makes sense. I can follow the mechanics for coming out of the snowball Earth. However, I am curious how it all started. If the atmosphere was approximately the same composition as it is today, what would trigger the vast accumulation of ice? There are all sorts of contributing factors to glaciation such as solar precession, Milankovitch cycles, etc. but these are not on the same time scale as the length of the supposed ice age (10K to 100K years as opposed to ~10 Ga).
well, it's all about the glacial cycles I guess. i only skimmed the article, but in the thing on the science channel they emphaisized a critical percentage of planetary glaciation (?) from beyond which the snowball is inevitable. they didn't say what it was, but it hinged upon the fact that the white snow reflects the much needed solar energy back to space as compared to non-glaciated land/water. at some point, the white is too much, reflects too much back into space and the snowball is on. i'm probably just telling you what you already know. the question becomes at that point, how did the glaciers get far enough toward the equator as to cross the critical percentage. i gotta say I have no idea. hmmm. could be any number of extraneous factors that could push an ice age over the limit I'd guess. I wonder if orbital mechanics could have had anything to do with it, solar radiation differences, blah la blah. maybe the sun was in a particularly cool period at the same time the earth was in ice age or something. i was particularly impressed with the CO2 greenhouse effect explanation for the diffusion of the snowball and stupefied to think that the 'whatever explosion' that created the diversity of species directly follow this event. if the theory is true, it's quite likely that we would not exist if it were not for the earth having frozen over completely and almost all life on earth having been extinquished. quite daunting at the same time. i agree that it's fascinating though. simply amazing really.
Yes, the Sun was 6% cooler back then than it is now; as the amount of helium in the core builds up, the Sun will continue to get warmer until the red giant phase 5 billion years from now. But the event that caused the Phanerozoic snowball may have been a function of the tilt of our world, or the disposition of the continents immediately after the break up of the primeval continent Rodinia; back then the Earth/Moon system will have been very different, with the Moon a lot closer, giving shorter months; and the Earth rotated more quickly too. It is not possible to calculate the exact orbital characteristics of the Earth/ Moon system back then as the chaotic effect of the ocean tides makes the variables in the system too large; it might well be that the glaciation was a result of the characteristics of our orbit and spin. ---------------- SF worldbuilding at http:www.orionsarm.com
"But the event that caused the Phanerozoic snowball may have been a function of the tilt of our world" precisely. just because they found out the equator was frozen a long time ago doesnt automatically mean the entire earth was covered in ice (although it is possible) what is more probable, and ebura mentioned this- is a TILTING of the earth, possibly Exposing what we call the Equator to the north. Hence a TILT can place different parts of the earth as the POLE (freeze) and move what were the POLES to a new location. the CONCEPT of the show was interesting, although the show itself wasnt too great. just like the Bermuda Triangle show, it was biased and incomplete. but hey, nice try !
Couple of things bother me about this. During that period the MAGNETIC north pole moved from the Caribbean, through the centre of South America to Antarctica. How does this tell you where the tropics are? On line 3 it states "but ice grows a kilometer thick in the 50 degree Celsius cold". 50 deg Celcius (Centigrade) is a bit hotter that you can comfortably keep your hands in dishwashing liquid. Hardly cold. Should it be Kelvin? (bit too cold) or -50 degrees C?
I found this interesting in explaining C13 and C12 (nothing to do with carbon dating). http://ethomas.web.wesleyan.edu/ees123/caiso.htm IIUC fractionation between C13 and C12 is mainly through photosynthesis. If living matter 'prefers' C12 then a plummeting in C13 means a release of C12 and hence less living matter. This assumes the total does not change. But what about the solubility of CO2 in ocean water at differing temperatures? Any ideas?
It's official! http://news.bbc.co.uk/2/hi/science/nature/3721481.stm "The Ediacaran begins at the end of the last ice age of Snowball Earth, or Cryogenian Period, a term given to a series of glaciations that covered most of our planet between 850-630 or 600 million years ago."
Then one could say that the global glaciations were a cold shock, which awakened life on Earth to its full evolutionary potential? By letting only the toughest and most adaptable organisms survive, the glaciers cleared the stage for an explosion of diversification.
"Then one could say that the global glaciations were a cold shock, which awakened life on Earth to its full evolutionary potential? " Yes. I certainly believe in advancement evolutionwise via catastrophe. But you might have guessed that?!
I believe the solubility of CO2 would be higher with higher temperatures. This would explain why we get more rapid limestone precipitation in warmer climates. (It is also attributable to a larger area of shallow seas and a lack of polar ice.)
"This would explain why we get more rapid limestone precipitation in warmer climates" This is the opposite too. You get more precipitation in warmer conditions because the solubility is lower there.
