Allan Shumaker asked:

"My question is - did anyone see it"

The answer to that questions falls into the realm of the controversy over
the validity of various Pre-Clovis Sties, i.e. Topper Site, and when people
first arrived in North America.

Charles O'Dale in "My Aerial Explorations of Terrestrial Meteorite Craters"
at [ottawa.rasc.ca] stated:

"- Sutton (1985) used thermoluminescence techniques to
determine an age of 49000 +/- 3000 years;
- Phillips et al (1991) used cosmogenic 36-chlorine
techniques to determine an age of 49700 +/- 850 years, and;
- Nishiizumi et al. (1991) used in situ production of
10-berilyum and 26-aluminum to determine a minimum
age of 49200 +/- 1700 years."

All of the dating technique used provide a consistent date somewhere
around 49,000 BP plus or minus the error of the dating method used.

The actual fireball would have engulfed anything with 10 km of the impact.
Within 3 km of the impact, the winds would have been more than 2,000 km
per hour and hurricane force winds would have extended as far as 20 to 40
km from the crater (Kring 1997). The "kill zone" would have extended
about 10 km from the rim with serious injury and possible death happening
to anyone within an area extending 25 km from the crater. If the meteorite
came in at a slower speed and the impact produced less energy than
previosuly calculated, the distance that the fireball, winds, and
overpressure extended from the rim the crater would have been shorter
than calculated by Kring (1997) and given above by a small amount along
with the resulting "kill" and "injury" zones.

A table of impact effects can be found in "Damage by Impact -- the Case
at Meteor Crater, Arizona" by Linda M.V. Martel at [solarsystem.nasa.gov]

Given that the fireball would have been visible for at least a couple of
hundred kilometers outside the "kill zone" around the crater, the question
becomes whether anyone was in the area at the time of impact. Because of
the age of Meteor Crater (Barringer Crater), the answer to Shumaker's
question lies right in the middle of the unresolved controversy of when
and where the first people migrated into North America. I will let other
more knowledgable people comment on their opinions about that question.

References on the dating of Barringer Crater / Meteor Crater are:

Nishiizumi, K. Kohl, C. P., Shoemaker, E. M., Arnold,
J. R., Klein, J., Fink, D. and Middleton,R. 1991 In
situ 10Be-26Al exposure ages at Meteor Crater, Arizona.
Geochimica et Cosmochimica Acta, vol. 55, pp. 2699-2703.

Phillips, F. M. Zreda, M. G., Smith, S. S., Elmore, D.,
Kubik, P. W., Dorn, R, I. and Roddy, D. J. 1991 Age and
geomorphic history of Meteor Crater, Arizona, from
cosmogenic 36Cl and 14C in rock varnish. Geochimica et
Cosmochimica Acta, vol. 55, pp. 2695-2698.

Sutton, S. R., 1984, Thermoluminescence age of Meteor
Crater, Arizona. Meteoritics. vol. 19, no. 4, pp. 317-318

Sutton, S. R., 1985, Thermoluminescence measurements
on shock-metamorphosed sandstone and dolomite from
Meteor Crater, Arizona; 2, Thermoluminescence age
of meteor crater. Journal of Geophysical Research. B,
vol. 90, no. 5, pp. 3690-3700.

Other references cited:

Kring, D. A., 1997, Air blast produced by the Meteor Crater
impact event and a reconstruction of the affected environment.
Meteoritics and Planetary Science. vol.32, pp. 517-530.

The original reference to this post is:

Melosh, H. J. and Collins, G. S. 2005, Planetary science:
Meteor Crater formed by low-velocity impact. Nature.
vol. 434, no. 7030, pp. 157-158. doi:10.1038/434157a

Other web pages are:

1. "Meteor Crater, Northern Arizona, USA" at [www.meteorite.com]

and 2. "Barringer" at [www.unb.ca]
.
Yours,

Paul H.
Baton Rouge, LA



Edited 12 time(s). Last edit at 03/12/2005 12:50PM by Paul H..