Re: Question, what do things do when they freeze?


"Timberwoof" <timberwoof.spam@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:timberwoof.spam-4A3277.01421525042007@xxxxxxxxxxxxxxxxxxxxxxxxxxx
In article <f0m98t$176$1@xxxxxxxxxxxxxxxxxxxxxx>,
"Landy" <noone@xxxxxxxxxxx> wrote:

"Timberwoof" <timberwoof.spam@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:timberwoof.spam-C0E6AC.17424424042007@xxxxxxxxxxxxxxxxxxxxxxxxxxx
In article <2dlXh.14652$Pq5.13742@xxxxxxxxxxxxxxxxxxxxxx>,
"George" <george@xxxxxxxxxxxxxxx> wrote:

Secondly, there is no evidence that the Earth's crust has overturned
catastrophically in the way you envision, and asided from that fact,
the
evidence that the crust of Venus has overturned catastrophically is
questionable, at best.

Well, the Earth did suffer an "Iron Catastrophe": The earth was mostly
or all molten from the heat of cometary impacts, and the denser iron
sank to the center, leaving a crust of other stuff on top. But that was
quite early in the Earth's history. The event neatly answers the
question of how mantle convection started up ... and slowed down.


The iron catastrophe theory went out the window 20 years ago!
Unfortunately it still appears in many texts.

Oh. I didn't know that. What is the current explanation for how the
Earth differentiated and stratified into core, mantle, and crust? Point
me to a reference?

Wel maybe it wasn't 20 years ago! But most planetary geologists these days
prefer a protracted accretion / continuous core formation with iron bolides
sinking through either a molten mantle (unlikely) or a plastic solid mantle
(more likely). There are some useful PDF's produced for a geochemistry
course by the Rensselaer Polytechnic Institute:
http://www.rpi.edu/~watsoe/courses/handouts/
cheers
Bill


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