Global Cooling

April 21, 2008 7:29 PM

In 1987, the Caltech biomagnetist and paleomagnetist Joe Kirschvink gave undergraduate Dawn Sumner a rock sample [from South Australia] to study for her senior thesis. The apparent glacial origin of this rock lead directly to the theory that periodically the Earth has been thoroughly glaciated from the poles to the Equator: the so-called Snowball Earth events. A website dedicated to this theory includes detailed teaching slides, a FAQ, and many other resources on this interesting period in Earth's history.
posted by Rumple (7 comments total)

The BBC show Horizon covers it, starting here.
posted by Rumple at 7:37 PM on April 21, 2008

Slushball Earth
posted by lukemeister at 8:09 PM on April 21, 2008

Geologists are famous for extrapolating mountain ranges from molehills, but this seems pretty extreme. From study of one rock they're trying to claim something this radical?
posted by Class Goat at 10:21 PM on April 21, 2008

I'm a geology post-grad student in South Australia, and I've done some field work around the area where I believe this sample came from. We visited an outcrop of tidal rhythmites which were, I'm told, of the same age as this snowball earth sample. These tidal rhythmites have discreet layers that reflect individual tidal deposits, which means that at this point in time there was not complete glaciation.

It's not hard proof, of course- neither side of the argument has yet to put forward truly compelling evidence- but I think it's an interesting example of science at work. There are competing theories, each of which are conceivable and have some supporting evidence. Over the coming years (potentially decades) we'll see the body of knowledge added to gradually until it becomes apparent that one side of the debate is a far more likely explanation.

This isn't quite as dramatic, but I think of it as like being alive when the theory of gravity, or continental drift, or relativity was put forward. We take it for granted now, just as people a century from now will take it for granted that snowball earth did (or did not) happen.
posted by twirlypen at 10:55 PM on April 21, 2008 [4 favorites]

Class Goat, the links make it clear that there's a lot more evidence for it than just one rock.
posted by Chanther at 4:04 AM on April 22, 2008

Perhaps it migrated.
posted by Gungho at 6:06 AM on April 22, 2008

Oh. I thought it was going to be covered in coconut.
posted by dowcrag at 5:58 AM on April 24, 2008