[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: A piece of the bolide?



From: "King, Norm" <nking.ucs@smtp.usi.edu>
 > The March 29, 1996 ... issue of _Science_ has a short note 
 > on the discovery of a 3 mm chip of rock from the K-T layer on the
 > bottom of the Pacific off the west coast of Mexico.  It is rich in
 > iridium, and  contains metallic grains that are up to 87% nickel.
 > ...  but the claim is made that the 
 > survival of a part of the bolide (that's the word they use!) indicates 
 > that it struck at a low angle. 

This seems likely to me.  In a downward impact the force vetors would be
mostly downward, and even the explosive rebound would not have enough
force to drive fragments of the meteorite far enough up to fall outside
the crater zone.

In a low angle impact, even a small upward force could redirect a
fragment into a slightly upwards direction, which combined with its
existing lateral motion, would be sufficient to throw it out.

 >  It is reported that earlier studies of 
 > crater assymmetry suggest that the object came in at about a 30 degree 
 > angle from the southeast.  ...

Also, the assymetry of the long range impact ejecta, which went the
furthest towards the northwest (Canada and the north Pacific).
Alvarez et alii did a rather nice study of the impact dynamics a few
months ago (I forget in which journal) which demonstrated this quite
clearly.

 > If the impact was at a 30 degree angle, would that affect where we would 
 > place an antipode--i.e., are the Deccan basalts still in the right place? 

Whether it does or not, the Deccan volcanism started LONG before the
imapct.  The impact was in the 29R magnetic chron, the Deccan's started
forming in the preceding 30N chron.  The difference is *at* *least*
many hundreds of thousands of years, and possibly extending to more
than a million.

swf@elsegundoca.attgis.com              sarima@netcom.com

The peace of God be with you.