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#19542 - 03/25/07 07:27 PM 'Snowball Earth' Theory Out In The Cold
DA Morgan Offline
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Registered: 10/17/04
Posts: 4136
Loc: Seattle, WA
The theory that Earth once underwent a prolonged time of extreme global freezing has been dealt a blow by new evidence that periods of warmth occurred during this so-called 'Snowball Earth' era. Analyses of glacial sedimentary rocks in Oman, published online in Geology, have produced clear evidence of hot-cold cycles in the Cryogenian period, roughly 850-544 million years ago. The UK-Swiss team claims that this evidence undermines hypotheses of an ice age so severe that Earth's oceans completely froze over. Using a technique known as the chemical index of alteration, the team examined the chemical and mineral composition of sedimentary rocks to search for evidence of any climatic changes. A high index of alteration would indicate high rates of chemical weathering of contemporary land surfaces, which causes rocks to quickly decompose and is enhanced by humid or warm conditions. Conversely, a low chemical index of alteration would indicate low rates of chemical weathering during cool, dry conditions. For the full story Click Here .
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#19553 - 03/26/07 04:38 AM Re: 'Snowball Earth' Theory Out In The Cold [Re: DA Morgan]
terrytnewzealand Offline
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Registered: 08/02/06
Posts: 1031
Loc: Whangarei New Zealand
The first I read of the snowball earth theory placed it at the end of the Permian, 230 million years ago. Evidence of deep ice cover is found right up to the tropics in Southern and Western Africa, South America, Australia and India from that period. The argument fell down because they failed to take into accout the continents were in much different positions to what they are now. I think some people just like the idea of catastrophes. The idea may spring from biblical ideas that the world is going to end any day.

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