Expert: Philip Stahl - 10/20/2004

Question
Hi Philip,
 I have asked this question of other  sites but have not received a response and since you have interests in astronomy and geophysics, you might be the very person to ask! I have a passion for cosmology and astronomy!
In the formation of the planets, material accreted through the debris of the Big Bang, brought together large and small chunks of material and time and gravity and natural physical processes took care of the shaping of the earth over many millions of years. I am wondering, and this is a hypothetical question, if when those larger 'chunks' joined with what was to become the earth, if those under compression and other physical factors might have formed the techtonic plates.
It seems to make sense to me that there would be remaining some underlying structural geological remnants of what took place in our earliest of days! What do you think?!?  

Answer
Hello.

Understanding that this is purely speculative, and not intended to be anything at 'textbook' level (e.g. factual) I think it is *possible* that chunks aggregating to form Earth also yielded the tectonic plates. But not probable.

Current solar system formation theory now posits a much more violent beginning with many, many more collisions - and in a random environment - these would literally be "one on top of another" to form a planet like Earth.

This means the overlaying impacts would make it improbable to have a more or less uniform crust, some 40 miles thick made up of tectonic plates.

Thus, I think it more probable that uneven surface cooling over millions of years from the original high impact regime-object led to the formation of plates. Which would have then been kept active by the earlier formation of a core of molten iron etc. with convective properties. (E.g. upwellings to the surface).

Again, this is all purely conjecture and ought not be take as anything 'engraved in stone'. You asked me what I thought, and I merely provided one possible answer.