[meteorite-list] Molten Core? Solid Core? Rocky Core? Blue Cheese!?

From: Meteorites USA <eric_at_meteoritecentral.com>
Date: Tue, 29 Dec 2009 20:02:02 -0800
Message-ID: <4B3AD0BA.5030906_at_meteoritesusa.com>

OK,

A friend and I were watching a show on Discovery or NatGeo a couple
months back. The program I think was about asteroids, and impacts,
perhaps even "How the Earth Was Made" or another program. Don't really
remember....

The point is during the show they said very matter-of-factly on three
separate occasions that the Earth's core was made of three different
materials. One scientist (or narrator I don't remember) said Earth had
a rocky core. Which we laughed at of course because we all know that the
Earth's core is Solid iron right? Then another scientist confirmed our
knowledge and stated what we already knew. The Earth core is made of
SOLID iron. "Of course we said!" Now that's right... Then not 10 minutes
more into the show another person stated that the Earth had a molten
iron core.

To make matters even more confusing the show went on to say that the
SOLID iron core was surrounded by molten iron with lighter "rocky"
materials "floating" out beyond that OK... sounded good at the time, but....

My question is simple. Which is it? Molten? Solid Iron? or Solid iron
surrounded by molten iron. And if it's the latter how is this possible?
Wouldn't the solid iron core NOT be solid if it were sitting in the
middle of a molten lake of iron? Does the core cool faster than the
surrounding material, and if so how is this possible considering this
the logic that says an object cools from the outside in.

Now, I'd like to stop there but I just read an interesting article on
National Geographic's website titled "North Magnetic Pole Moving East
Due to Core Flux" here:
http://news.nationalgeographic.com/news/2009/12/091224-north-pole-magnetic-russia-earth-core.html

At the end of the article it flatly states:

"...Wandering Pole -

Geologists think Earth has a magnetic field because the core is made up
of a solid iron center surrounded by rapidly spinning liquid metal. This
creates a "dynamo" that drives our magnetic field.

Scientists had long suspected that, since the molten core is constantly
moving, changes in its magnetism might be affecting the surface location
of magnetic north...."

I don't know about you, but this confuses me just a little bit...

Can anyone please clear this up for me? And perhaps the rest of the
world? ;)

Regards,
Eric Wichman
Meteorites USA
Received on Tue 29 Dec 2009 11:02:02 PM PST