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Re: antipodal effects

Paul wrote:-

> I once did some calculations on a 65mybp palaeoglobe (based on the Terra
> Mobilis program) and the land closest to the opposite side of the world to
> Chixalub at that time was Broome, Western Australia. In reference to an
> earlier, similar post by Dave Carlisle, India was some distance from the
> opposite side of the world at that time. Not only was Australia much closer
> to the antipodal impact site, there are no flood basalts of that age in
> that area.
I'm sorry that I have not been following this conversation as I have 
been rather busy :-) collecting dinosaurs in Scotland and I will soon be
 away again to lecture in France :-#

They way I see it (if this has not already been covered) is that the 
impact of an asteroid/comet is unlikely to have an antipodal effect.  
It is like a mosquitoe crash landing on a tomato..... might dent the 
skin, but doesn't produce an antipodal blip.  If the asteroid/comet 
was the size of the moon, however, then there might have been an 
antipodal effect similar to a marble bouncing off a tomato.  Even if 
the asteroid/comet penetrated the crust, the effect would be similar 
to an earthquake, or a nuclear explosion (more likely as the seismic 
waves would be equal in all directions) to form doughnut and circular 
shadow zones by refraction (at least that is my guess based on the 
internal structure of the Earth). 

What do you think David?  How wrong am I?