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Topic: Snowball Earth

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	Snowball Earth - Wikipedia, the free encyclopedia
		Geological formations which "Snowball Earth" proponents point to as evidence of the hypothesis are iron-rich rocks like taconite deposits and carbonate cap rocks.
		The association of the Snowball Earth event with the Cambrian explosion (the sudden appearance of multicellular lifeforms between 570 and 530 million years ago) is also of great interest.
		An even less severe possibility would be that it was merely the Earth's magnetic pole that wandered to this inclination, as the magnetic readings which suggested ice-filled continents depends on the magnetic and rotational poles being relatively similar (there is some evidence to believe that this is the case).
	en.wikipedia.org /wiki/Snowball_Earth (2148 words)

	Snowball Earth
		A snowball earth would be not only the most severe conceivable ice age, it would be the most prolonged” (Hoffman and Schrag 2000, p.
		The Sturtian snowball period is shortly succeeded by the earliest unambiguous record of metazoan animals and, after an additional 170 Ma and two more low-latitude glaciations, by the appearance of shelly Cambrian faunas.
		Overall, the various snowball earth hypotheses have potential to explain diverse observations of the Proterozoic geological record: synchronous low latitude diamictites associated with carbonate deposits, carbon isotope excursions, banded iron formations, and so on.
	www.peripatus.gen.nz /paleontology/SnoEar.html (4762 words)

	BBC - Science & Nature - Horizon - Snowball Earth
		PAUL HOFFMAN: The beauty of the snowball Earth theory is exactly that it links the chemistry, the geology, the planetary science and bam-bam-bam, all of the facts are, are consistent with the predictions of the theory.
		Several years ago I saw the papers about the snowball Earth indicating the geological evidence that the Earth was ice-covered and had been ice-covered for millions of years, plus the evidence that there were organisms, bacteria and green algae, that survived this ice-covered state and that's the puzzle: how could these photosynthetic organisms survive?
		Although disciples of the theory accept the snowball would have been death to most things, they argue whatever life did survive would have emerged into a new world almost devoid of competition, the perfect conditions for an explosion of evolutionary change.
	www.bbc.co.uk /science/horizon/2000/snowballearth_transcript.shtml (5295 words)

	Snowball Earth: The Discovery of Evidence That the Earth Was Once Frozen Over from Pole to Pole
		Snowball Earth refers to the contention that in the distant past the Earth froze over from pole to pole.
		When Earth acquired oxygen in the atmosphere some of it dissolved in the oceans and combined to form iron oxide, which was insoluble in water and precipitated out to form a layer of iron oxice called ironstone.
		The temperature of the Earth is strongly influenced by the amount of greenhouse gases in the atmosphere; i.e., water, carbon dioxide and methane.
	www.applet-magic.com /snowball.htm (2774 words)

	BBC News \| SCOTLAND \| 'Snowball Earth' theory melted
		Geoscientists in Scotland say they have evidence to disprove the controversial "Snowball Earth" theory - the idea that the planet was completely encased in ice just over 600 million years ago.
		The controversial theory that for millions of years the Earth was entirely smothered in ice, up to one kilometre thick, has been kicked around for more than 50 years.
		The team examined rocks in Namibia upon which the Snowball Earth theory is based, as well as samples from County Donegal, Ireland, and Death Valley in California, which would have formed during the glaciations.
	news.bbc.co.uk /1/hi/scotland/1857545.stm (573 words)

	Scientists engage in great snowball fight — JSCMS (Site not responding. Last check: 2007-10-19)
		Nicholas Christie-Blick, Ph.D., chairman of the Department of Earth and Environmental Sciences at Columbia University, is a proponent of the "Slushball Earth" theory.
		Dissenters say evidence for Snowball Earth is thin and instead espouse a hypothesis called Slushball Earth, in which the planet was once a patchwork quilt of frozen continents and a mostly liquid ocean.
		For their part, the snowballers accept that there was life in the ocean during the glaciation--but they say it survived only in pockets warmed by hot springs and deep-sea vents.
	jscms.jrn.columbia.edu /cns/2006-01-10/schlesinger-snowball (899 words)

	Geotimes - April 2005 - Space dust and snowball Earth (Site not responding. Last check: 2007-10-19)
		The “snowball Earth” theory, the leading explanation for what happened during these glaciations, holds that, at least twice in Earth’s history, expanding ice sheets reflected back increasing amounts of sunlight, further cooling the planet in a “runaway albedo effect.” Eventually, the ocean surface froze and glaciers reached the equator.
		The ratio of carbon-13 to carbon-12 in carbonate rocks for tens of millions of years prior to the snowball Earth events is the highest ever in the planet’s history, Schrag says, indicating a high level of biological activity, which takes carbon-12 out of the cycle.
		He also says that Earth has a sufficient probability of encountering a dust cloud every 140 million years, which is consistent with the timing of the glaciations.
	www.geotimes.org /apr05/NN_spacedust.html (683 words)

	Tidepool \| Books \| Snowball Earth (Site not responding. Last check: 2007-10-19)
		Snowball Earth covers recent findings that transform what some took to be crackpot inductive hypotheses into deductive theory.
		Earth was enveloped in ice for millions of years, and not just a moderate cold spell such as in the recent Pleistocene Ice Age, but a whopper, -40 C for years without end, alternating with brief interglacial periods of boiling +40 C temperatures.
		It lurches and staggers, retests itself, renews itself constantly, and in the development of the Snowball Earth theory, we have an excellent illustration of just how messy it really is. Scientists are after all human, and humans have habits.
	www.tidepool.org /books/snowball.cfm (686 words)

	BBC - Science & Nature - Horizon - Snowball Earth
		There are some tantalising geological clues that show this theory may be true but the problem is, the clues and the Snowball Earth theory defy the laws of nature.
		Scientists now believe that the so-called Snowball Earth theory could hold the key to the evolution of complex life on this planet.
		On Snowball Earth there was no rain to wash this carbon dioxide out of the atmosphere.
	www.bbc.co.uk /science/horizon/2000/snowballearth.shtml (548 words)

	Harvard Gazette: Winds and waves sculpted a 'snowball Earth'
		The planet's population - primitive plants and animals like algae and bacteria - sheltered themselves around hot springs on the ocean floor, in surface ponds melted by volcanic heat, or in nooks where the ice was thin enough for the sun to seep through.
		A theory that has been around since 1992 proposes that the Earth was like this at least twice between about 700 million and 600 million years ago.
		Snowballers think this could have happened astonishingly fast, in decades rather than centuries.
	www.news.harvard.edu /gazette/2005/02.03/13-snowball.html (909 words)

	Cloggie :: Booklog 2004 :: Snowball Earth (Site not responding. Last check: 2007-10-19)
		It is thought that the snowball earth occurred at a time when the continents were clustered around the equator, so that there was no brake on ice development at the poles.
		In the second, the snowball earth theory itself and its evolution are traced.
		Chipper or not, Walker makes the snowbal earth theory sound plausible and is good at explaining the supporting evidence, as well as the objections against the theory and how they were incorporated into it.
	www.cloggie.org /books/snowball-earth.html (465 words)

	NASA - NASA Study Suggests Giant Space Clouds Iced Earth
		They would look at Earth's rocks to find layers that relate to the snowball glaciations to assess whether uranium 235 is present in higher amounts.
		It cannot be produced naturally on Earth or in the solar system, but it is constantly produced in space clouds by exploding stars called supernovae.
		The research outlined a scenario that begins as Earth passes through a moderately dense space cloud that cannot compress the outer edge of the sun's heliosphere into a region within the Earth's orbit.
	www.nasa.gov /home/hqnews/2005/mar/HQ_05066_giant_clouds.html (677 words)

	Penn State News
		Then, in about 1,000 years, the remainder of the Earth rapidly froze due to the great reflectivity of the already ice-covered areas and their inability to capture heat from the sun.
		Once the Earth is snow covered, it takes 5 to 10 million years for the natural activity of volcanoes to increase carbon dioxide enough to melt the glaciers.
		One reason that many scientists initially rejected the snowball Earth theory was that biological evidence does not suggest that the various forms of life on Earth branched out from the latest total glaciation.
	www.psu.edu /ur/NEWS/news/snowballearth.html (747 words)

	Grad Student Pokes Holes in Hypothesis
		Remains of photosynthesizing microbes in prehistoric rocks suggest Earth was not ice-bound, as long proposed by supporters of the ‘Snowball Earth’ theory.
		“Snowball Earth” proponents, who say that Earth’s oceans were covered by thick ice, explain the survival of life by hypothesizing the existence of small warm spots, or refugia.
		On the other side are supporters of a “Slushball Earth” that would have included large areas of thin ice or open ocean, particularly around the equator.
	www.usc.edu /uscnews/stories/11653.html (618 words)

	The Snowball Earth (via CobWeb/3.1 planetlab2.tamu.edu) (Site not responding. Last check: 2007-10-19)
		Budyko showed that if the Earth's climate were to cool, and ice were to form at lower and lower latitudes, the planetary albedo would rise at a faster and faster rate because there is more surface area per degree of latitude as one approaches the Equator.
		The relatively small amount of heat escaping from the Earth's interior is sufficient to prevent the oceans from freezing to the bottom, but would still allow a kilometer thick cap of sea ice to form, thicker at the poles and thinner at the Equator.
		The frequency of polarity reversals of the Earth's magnetic field is such that the glacial deposits must represent a minimum of several 100,000s and more likely millions of years, consistent with the time scale of a "snowball" Earth.
	www-eps.harvard.edu.cob-web.org:8888 /people/faculty/hoffman/snowball_paper.html (5383 words)

	Geological Society of America - Snowball Earth - Press Release
		The idea that the Earth was encased in ice some 650 million years ago has sparked much scientific debate in recent years.
		In the ongoing Snowball Earth "fight," scientists continually uncover and report new evidence that supports their respective views.
		The Snowball Earth hypothesis proposes that during several profoundly cold periods of Earth's history that occurred from 750 to 600 million years ago, the ocean was covered by a thick sheet of ice.
	www.geosociety.org /news/pr/01-63.htm (535 words)

	LiveScience.com - Early Life Survived 'Snowball Earth'
		Ancient relatives of today's plants and animals may have survived Earth's oldest, longest winter, when the planet was covered in a deep sheet of ice.
		The finding fits with a study last year that concluded bacteria actually caused the first snowball scenario by producing oxygen that destroyed a warm blanket of methane in the atmosphere.
		If they could live through the toughest, coldest models of Snowball Earth, such hardy microbes could probably make a living on the frozen moons of Jupiter, he said.
	www.livescience.com /animalworld/060607_snowball_earth.html (592 words)

	Snowball Earth Simulation
		In August of 1998, the theory of a "Snowball Earth" was first introduced in the journal Science by a group of researchers including Paul Hoffman, Alan Kaufman, and Daniel Schrag.
		The snowball slowly melts until it reaches a critical balance, after which the great majority of the ice quickly melts and the now thick carbon dioxide gas causes a temperature spike in a violent greenhouse backlash.
		In conclusion, although this is a relatively simplistic numerical model, it indeed supports the present day theory of "Snowball Earth," and in so doing serves to enhance the possibility that at one time the Earth was in fact a cosmic snowball for millions of years.
	www.cs.caltech.edu /~westside/ge/snowball.html (1535 words)

	Snowball Earth
		There is geologic evidence that, for about 10 million years, Earth was extremely cold, covered with ice at least a kilometer thick from the tropics to the poles.
		The scale of the cooling appears to be unprecedented, yet the Earth eventually warmed.
		Although scientists are still developing theories as to how this happened, a logical cause for the thawing of Snowball Earth is the addition of the greenhouse gas carbon dioxide to the atmosphere, contributed during a period of erupting volcanoes.
	eo.ucar.edu /basics/cc_3_a.html (97 words)

	SNOWBALL EARTH Muse - Find Articles
		Between 750 million and 590 million years ago, supporters of the "Snowball Earth" theory say, the climate may have swung back and forth between deep freeze and hothouse as many as four times.
		But on a frozen Earth, there would be no rain; instead of evaporating to form clouds, water would stay on the ground, cold and rock-solid.
		In 1992, Kirschvink wrote a paper outlining his ideas and coined the term "Snowball Earth" to describe that biggest of chills.
	www.findarticles.com /p/articles/mi_qa4136/is_200401/ai_n9355163 (917 words)

	Snowball Earth Part 3: Evidence Against
		A group of scientists led by Joseph Kirschvink hypothesized that the Earth was once encased in a global spanning glaciation.
		The global glaciation, a "Snowball Earth", lasted for millions of years and was finally broken by the accumulated build up of carbon dioxide in the atmosphere that eventually led to a runaway greenhouse event that melted the glaciers in the span of only a few hundred years.
		They present evidence that the Earth was not covered in thick sheets of ice, instead that the tropical oceans remained mostly ice-free.
	www.suite101.com /article.cfm/everyday_geology/100705 (424 words)

	Universe Today » Archive » Ancient Life Survived Snowball Earth
		Unfortunately, this was also a stage when our planet went through one of its “Snowball Earth” phases, when the entire planet was encased in kilometer-thick snow and ice.
		New research shows organisms called eukaryotes — organisms of one or more complex cells that engage in sexual reproduction and are ancestors of the animal and plant species present today — existed 50 million to 100 million years before that ice age and somehow did survive.
		This is not the first time biomarkers indicating that eukaryotes and cyanobacteria were alive before “Snowball Earth” have been found in ancient rocks.
	www.universetoday.com /2006/06/12/ancient-life-survived-snowball-earth (801 words)

	BBC News \| Sci/Tech \| Earth's huge 'snowball event'
		A research team from Harvard University in Massachusetts has proposed that a fall in the level of carbon dioxide in the earth's atmosphere 750 million years ago caused a drop in global temperatures which came close to wiping out all life on earth.
		The entire earth became covered with snow, which reflected the sun's heat and further accelerated the process of freezing - a phenomenon which has been dubbed a "snowball event".
		Simple living organisms were present on earth three billion years before animals emerged, but it took the profound environmental changes that signalled the end of a snowball period to provide the conditions for the evolution of new life forms.
	news.bbc.co.uk /1/hi/sci/tech/159988.stm (500 words)

	SNOWBALL EARTH
		Estimating duration and intensity of Neoproterozoic snowball glaciations from Ir anomalies.
		Hugh Rice proposes to visit the Neoproterozoic succession in Finnmark, northern Norway in association with IGC 2008 in Oslo and is looking for input on whether it should be pre- or post-meeting.
		Snowball Earth Conference, Ascona, Switzerland 16-21 July 2006
	www.snowballearth.org (114 words)

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