Re: Chicxulub's Antipode (Re: cause of death at KT)

["James R. Cunningham" <jrccea@bellsouth.net>]

Phillip Bigelow wrote:

> On Fri, 01 Sep 2006 22:09:18 +0200 David Marjanovic



> - Tsunamic effects would have been minor, because North and South America
> would have blocked the waveform from the paleo Pacific

Why?  If I remember correctly, the isthmus of Panama didn't exist at that
time, if so, there was a direct connection to the Pacific.

> - What about reentering ejecta?  It was probably no worse than elsewhere
> on the globe.  Keep in mind that just because some material went
> suborbital or fully orbital doesn't *require* that the material must fall
> at the antipode.  It could fall just about anywhere on Earth,

It can, but a substantial fraction will fall near the antipode (or rather the
antipode displaced by about 45 minutes). I'd expect quite a concentration of
ejecta near the displaced antipode.

> which is
> dictated by the ejecta's altitude (ejecta in low Earth orbit will reenter
> sooner; higher orbits may take hundreds of years to degrade to reentry).

I believe it would be mostly sub-orbital stuff that would nail the antipode.

> Let's assume for the sake of argument that the Chicxulub antipode was
> occupied by sea floor rather than by dry land. Is this part of the sea
> floor still preserved?  If it is, and if the site can be located, would
> it would be worthwhile to drill into into it and see what types of
> faulting patterns characterize a mega-converging seismic event at an
> antipode?

That's a darned good suggestion.

> I'm thinking of the structural geology seen at the antipode of the
> Caloris [impact] Basin on Mercury and the structural geology seen at the
> antipode of the Stickney Crater on Phobos.  Not to mention the antipodal
> structures on Mimas.

And a couple of the larger craters on the Moon.