Dear Eman,
You bring up a very good point. If some of the continents are formed from ocean crust at the antipode, then they should be made substantially from magnesium iron silicates instead of feldspar silicates. And yet, the continents are made up of feldspar silicates almost entirely.
This is obviously a big miss on my part. I treated the entire crust as though it were uniform ... and it is not.
My theory has Siberia being uplifted several thousand feet from the sea floor 250 MYA. This would mean that the continent would be composed of magnesium iron silicates. It isn't. It is composed primarily of feldspar silicates.
Clearly, my theory will need significant adjusting.
As I review the basis of my theory to begin with, I still find it to be powerfully explanatory. The question is: Can it be sensibly adjusted to reflect this newly realized reality?
I looked at the five uplifted continents that I describe in my book. Four of them can be adjusted without much difficulty (Western Antarctica may involve more work). In fact, the revision may actually be more explanatory for the resulting actions of Eastern North America and Siberia.
My adjusted theory then wouldn't have to account for several thousand feet of uplift. Rather, the uplift would be much lower. Rather than having to uplift to the present height from the depths of the oceans, the uplift would start at the height of existing continental land or continental shelf.
The uplift amount could be fairly small ... certainly not in the range of several thousand feet.
Would there be any uplift at all? I believe that there would be. I don't believe that a continent would shear around a single continuous perimeter (as opposed to splitting up into several radiating pieces) without some uplift involved.
In my view, there would be deformation of the surface of the Earth at the point of impact. I believe that a really large angled impact would transfer this energy in a pulse (not just a wave) through the hydraulic system that is the liquid mantle of the Earth.
Also, I don't believe that the separate continents are just "what they are" and merely "freed" from their bondage in Pangaea in the same shapes that they arrived.
Adjusted Siberia, now uplifted out of the far western (but not quite to the coast) part of Pangaea, would account for the strange sliver of feldspar silicates that is attached to the Pacific Plate to the west of the San Andreas Fault, including Baja California. Otherwise this strange, long sliver would have to be a natural continent that attached itself somehow. How strange would that be?
The adjusted scenario for Siberia and the three other continents would be the same as originally written, except that that the uplift would not be nearly as great, Siberia would be slightly repositioned and there might be an uplifted (but, again, not very much) portion of the continent that would include sea floor basalt (that might be subducted on the continent's directed journey).
The adjusted theory would also have to account for ocean floor "continents", that would move and then be subducted when they ran into feldspar silicate continents. It is statistically unrealistic to think that all major impact antipodal activity is going to somehow involve just the feldspar silicates.
The initial condition of the planet, based on the adjusted theory, would see the feldspar silicates fairly uniformly distributed as almost a surface scum on the hot, liquid surface. As the surface cooled, this relatively even coating of feldspar silicate would be forced to clump together as impacts lifted up directed continents, running them into each other.
I will need to more fully adjust my theory in detail, but I believe that this newly realized reality can be successfully incorporated. But before I rewrite this theory to account for this serious misstep, I would ask you if there are any other significant oversights that I should address.
Thank you for your insights. A theory must deal with reality ... all of it.
Regards,
Ben Fishler
From: MEM <mstreman53@yahoo.com>
To: "geology2@yahoogroups.com" <geology2@yahoogroups.com>
Sent: Wednesday, May 1, 2013 2:56 AM
Subject: Re: [Geology2] Re: The Earth Moved
Dear Ben,
From the perspective of someone who has already studied this in detail there are major un-overcomeable flaws in your hypothesis: Density/bouyancy of felsic vs mafic stock, shock melting dynamics, and lack of felsic minerals not already incorporated in existing continents.
Your theory does not take into account that the continents came in to existance very soon after differentation of the feldspars/silica( Felsic) and magnesium iron silicates( malfic) began circa 4.48± (?) bybp. Owing to their bouyancy differences, the felsic continents have remained floating on the heavier mantle mafic minerals ever since and this WILL always be that way. Continental mass is never subducted and owing to well understood plate tectonic dynamics, mountain building keeps pushing continental materials back up onto the continents themselves and felsic content gets recovered with great efficency.
You likely haven't done the math nor have you modeled it but I if you had you would not see a land mass antipodally but something of a pie-plate melengue of olivine glass derived from the mantle buldged up under an existing continent. We have an example of this on the asteroid Vesta but the scales for something like this happening on earth would be just shy of total core destruction. On vesta almost 1/3 of the asteroid was excavated and opposite that crater is a much less prominent, shallow sloped , buldge. Speaking of core, your impact energy transfer is never going to be one for one antipodally and the core is going to reflect, deflect and, absorb some of the energy. Likely less than 15% of that energy could ever be transfered antipodally even if the earthquake waves traveled with great efficency. A lot would be lost to friction within the planet. You are left with wave energy and not mass movement. High pressures on olivine yield a very compressd form called ringwoodite which is more likely to self absorb the over-pressure rather than produce a crustal blow out of physical mass --on the scale of the known impactors earth has collected anyway.
This hypothetical land form "buldge"--if it could it exist on earth would sink back down into the mantle because its mass density is higher than the surface density. Antipodal impact land formation could not account for any of our continental masses because their basement rocks are already well known to be felsic and bathtub shaped-- not cone shaped filled with malfic minerals. I mentioned source stock for these spash formed continents--that is felsic material lying around ouside an existing crustal system. There is no crustal mineral stock except already used in continental massed to give rise to impact generated continents.
On that basis I suggest you take this idea and see if it doesn't better apply to asteroidal settings. They physics of the earth and the size of the impactors needed but not found, pretty much shoot down this idea you spent so much reasoning on already-- but which you for whatever reason failed to consider the full rhelm of factors against it.
Traditionally when I post a rebuttal to someones pet project I get a range of but-but-buts or a personal attack or Hummph what do you know? yada yada. This time, owing to other obligations and failing vision I can't spend the time rehashing my opinion based on my experience and understanding--it is what it is and I am disinclined to write my own thesis-level reasons in rebuttal. My response was about principles and not through modeling stated values that show the physics in a definite mathmatical evaluation-true-- but I think the hypothesis can be nulled on the principle level alone. If you find a way to model this with realistic assumptions regarding impact energies and material behavior under such an impulse and want to bring that back for discussion then I'll try to get it another honest review (not that it will change existing contintental origin theory). Otherwise this is all I have to say on the topic. As written now, your tretise is but another incomplete theory mainly because your haven't handled all the real life factors that would support or affect your hypothesis --and they are major ones I don't think you can solve but it is your business if you want to pursue them.
One final bit of advice. You clearly have a deeply analytical brain that is dying to be unleashed. Don't unleash it fully until you have a good broad foundation in planetary geology. In this case, it truly is the stuff you don't know which can hurt you. Much of what I have talked about and much I didn't even go into such as the Ringwodite/Spinel zone would have been good to have knowledge of as you started writing.
Bottom Line: Antipodal dynamics do have a basis in planetary science but the continents were not formed by asteroidal collision transfered antipodally.
Regards,
Eman
Sorry my spell checker has stopped working but you bright people can figure it out.
__._,_.___
No comments:
Post a Comment