Research Supports "Snowball Earth" Hypothesis

u2boy_nl writes, "A new U.S. study finds evidence for 'Snowball Earth,' the hypothesis that the entire Earth was ice-covered for long periods on several occasions, most recently 600-700 million years ago. The icy conditions (Earth's oceans frozen completely with ice more than a kilometer thick) ended violently under extreme greenhouse conditions — snowballearth.org suggests the meltdown could have occurred in as little as 2,000 years. Snowball Earth challenges long-held assumptions regarding the limits of global change. Wikipedia has more on the hypothesis."

Comments

Snowball Earth and the Fermi Paradox

[Jerf]

The Wikipedia article has some interesting connections to the Fermi Paradox, though the article doesn't call them out.

(If you don't know what the Fermi Paradox is, look, Wikipedia!)

One of the possible answers to the Fermi Paradox (which I note doesn't show up in the Wikipedia article) is that life is common in the universe, but the worlds are either hospitable towards the life, resulting in no selection pressure towards complexity, or so hostile that the life totally dies out too often to advance. The general image is of a universe full of oceans full of simple, utterly stable bacteria, which by most standards is still basically lifeless. (We're really interested in other intelligent life, not a universe of little germs.) It has been hypothesized that the best scenario for complex life is a recurring series of disasters that almost, but not quite, kills off life each time, resulting in a strong selection pressure for the requisite complexity to handle such environmental pressures.

Connect that idea with:

The carbon dioxide levels necessary to unfreeze the Earth have been estimated as being 350 times what they are today, but would be able to accumulate due to the opposite of the effect mentioned earlier as a possible mechanism triggering the freeze in the first place; if the Earth was completely covered with ice, silicate rocks would not be exposed during erosion, and carbon dioxide would not then be removed from the atmosphere. Eventually enough CO2 would accumulate, perhaps after an era of increased volcanic activity (a prodigious producer of this greenhouse gas), that the oceans around the equator would finally melt, which would produce a band of open ice-free water, much darker than the highly reflective ice, which would absorb more energy from the sun. This would in turn heat the Earth more, melting more water to absorb more light, and so on. Concurrently, the abundance of CO2 would provide plenty of food to feed a cyanobacterial population explosion, resulting in a relatively rapid reoxygenation of the atmosphere to feed the following Cambrian Explosion with the new multicellular lifeforms. This positive feedback loop would melt the ice in geological short order, perhaps less than 1000 years; replenishment of atmospheric oxygen and depletion of the CO2 levels would take more thousands of years.

However, the carbon dioxide levels would still be two orders of magnitude higher than usual. Rain would wash CO2 out of the atmosphere as a weak solution of carbonic acid, which would turn exposed silicate rock to carbonate rock, which would then erode easily, wash into the ocean, and form deep layers of carbonate sedimentary rock. Thick layers of exactly this abiotic carbonate sediment can be found on top of the glacial till that first suggested the Snowball Earth.

Eventually the carbon dioxide level would get so low that the Earth would freeze over again. This cycle went on until Rodinia had dispersed so much that the Earth's land was no longer strung out along the equator and the primary cause of Snowball Earth would no longer operate.

The next section of the Wikipedia article mentions the effect this could have had on evolution.

(I find the Fermi Paradox interesting because I believe it is actually by far the biggest problem facing science as a whole; science says life should be plentiful and easy and populating the stars ought to be possible at significant fractions of the speed of light, so where is the life that is doing so? It's easy to become numbed to the problem because it seems somewhat abstract, but it's not. Something is fundamentally wrong with at least one of biology, astronomy, cosmology, sociology, and/or the intersections of those disciplines we don't have names for, and we don't know what.)

Global Warming vs Religion

[DiscoLizard]

I find it amazing that people who believe in something with basically no verifiable proof of existence (i.e. God) have such a tough time believing in something that is so demonstrably happening in front of them.

If ever there was proof of the power of man to delude himself, denying that we have a large and thus-far detrimental effect on climate change would be it.

Re:Global Warming vs Religion

[nametaken]

That was a little out of left field, no?

I know plenty of people who believe both. In fact, I think there's actually LESS of a rivalry between religion and science than people suggest.

I think little things like this are important evidence for what I'm saying...

"John Paul insisted faith and science could coexist. In 1996, in a message to the Pontifical Academy of Sciences, he said that Darwin's theories were sound as long as they took into account that creation was the work of God and that Darwin's theory of evolution was "more than a hypothesis.'"

Cue the right wing wackos

[plopez]

I can't wait till they get a hold of this one. Regardless of all the other evidence they will use it as a way to slag on evironmentalists, the Kyoto treaty, liberals, democrats, gay marriage, stem cell research and find creative ways to link all of them to terrorism. And champion corrupt corporations as being the benign benefactors of all humanity. This should be fun.

The climate is dynamic. The question is: "are humans having a serious negative impact on the global climate?" And there is a bunch of evidence stacking up saying "yes."

Re:Troubling Question

[Anonymous Coward]

Bloody hell, learn to read:
"the meltdown could have occurred in as little as 2,000 years"