From: Bill Payne (bpayne15@juno.com)
Date: Wed Mar 26 2003 - 22:59:19 EST
On Wed, 26 Mar 2003 02:44:50 -0800 "Don Winterstein"
<dfwinterstein@msn.com> writes:
What I don't know, and maybe you do, is what fraction of the total
horizontal force on the plates comes from pressure generated by upwelling
rock. Perhaps it's negligible to begin with, or perhaps no one knows:
You can deal with this kind of thing only through modeling, not
measuring.
[Reply] I certainly don't know, but I have always assumed that convection
cells (driven by heat) dragging on the bottom of the crustal plates
provided the horizontal force to move the plates. As the plates separate
along the mid-Atlantic Ridge, the reduction in pressure allows the deeper
rock to liquify and flow to the surface, building the Ridge.
At work I have an incredible photo taken by the last shuttle crew of the
terminator (?) of daylight over Europe (if anyone knows where to find
this photo on the web please let us know). In this photo, most of Europe
is dark and the lights are on. The western edge of Europe and the
Atlantic are still in daylight. The incredible thing about the photo is
the fact that the floor of the Atlantic is plainly visible. You can see
the continental shelves, the Azores and Mariannas, and of course, the
mid-Atlantic Ridge. The interesting thing about the Ridge relative to
this conversation is the presence of the many strike-slip faults. I'll
have to look at the photo again, but I'm sure that the faults cut through
the Ridge, which suggest that they are the result of forces acting over a
wide area, not from thrusts produced by injected lava.
For anyone who may be interested, I recently composed the following notes
on those reefs (from memory, so an occasional detail or two may not be
strictly accurate):
[snip] Thank you, Don, for taking the time to provide this description.
If anyone can explain these in a young-Earth framework, I'd like to hear
it.
So would Michael and I! Could you please describe the strata, if any,
between the bottom of the Alberta reefs and the Precambrian?
Bill
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