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


"George" <george@xxxxxxxxxxxxxxx> wrote in message
news:nIAXh.4172$np4.2826@xxxxxxxxxxxxxxxxxxxxxxxxx

Yes, but that occurred before the crust formed, and so the crust could
hardly have overturned catastrophically as a result. And yes I think that
convection has likely been going on deep inside the earth since it formed
4.56 bya.


Some questions I have; the oldest part of the sea floor, due
to spreading and supposedly subduction, is only some
200 million years old. I assume the super continent broke
up and started drifting apart around then. What about
before 200 million years? Has sea floor spreading been
present since the earth cooled? When did it start?
I've read the crust and oceans formed within
the first two hundred million years after formation
of the earth, what has been the shape or extent
of the continents during all that time? Also, the
sun was some 30% cooler when the earth
formed, how has the additional heat over time
been taken into account? I've read the earth
absorbs more heat than it gives off, how does
that play into plate tectonics? And what was
the diameter of the earth before it segregated
and was still of fairly uniform density?
Once it segregated into layers of varying
density did the diameter change?
Was the crust ever fully rigid and if so, when?
If the crust was rigid at some point, are
the current continents what's left from
eons of erosion, or pushed up?

On Mars it appears the northern half of the
planet was a sea, while the southern half
was highlands. Could that have been the case
on earth?

I've looked for most of these answers with
little success. If only half of these questions
have yet to be answered, I would say geology
is still in it's infancy as a science.




George



.

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