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History Of Ice On Earth
By : shalu123 |
Members :7
Location : mumbai , India
Type : Public
Created on :
17 Dec 2012
Last Updated on :
31 Dec 2012 |
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Findfriendz / Clubs / Science and History / History Of Ice On Earth
History Of Ice On Earth
Primitive humans, clad in animal skins, trekking across vast expanses of ice in a desperate search to find food. That’s the image that comes to mind when most of us think about an ice age.
But in fact there have been many ice ages, most of them lo ng before humans made their first appearance. And the familiar picture of an ice age is of a comparatively mild one: others were so severe that the entire Earth froze over, for tens or even hundreds of millions of years.
In fact, the planet seems to have three main settings: "greenhouse", when tropical temperatures extend to the poles and there are no ice sheets at all; "icehouse", when there is some permanent ice, although its extent varies greatly; and "snowball", in which the planet’s entire surface is frozen over.
Why the ice periodically advances – and why it retreats again – is a mystery that glaciologists have only just started to unravel. Here’s our recap of all the back and forth they’re trying to explain. More
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