Date sent: Thu, 23 Oct 1997 12:46:40 -0400 (EDT)
From: Benny J Peiser <B.J.PEISER@livjm.ac.uk
Subject: CC-DIGEST 23/10/97
CAMBRIDGE-CONFERENCE DIGEST, 23 October 1997
1) MAMMOTH GRAVEYARD
2) JOVIAN SOOT FROM COMETARY IMPACTS?
3) PREDICTIVE ELEMENTS OF LARGE BODY IMPACTS IN GEOLOGICAL HISTORY
4) SHOEMAKER-LEVY 9 AND PLUME-FORMING COLLISIONS ON EARTH
5) MASS HYSTERIA IN ITALY?
from: NEW SCIENTIST, 25 October 1997, p. 27
1) MAMMOTH GRAVEYARD
A violent eruption of the Popocatepetl volcano in central
12.500 years ago trapped a herd of mammoths. While digging a cistern
at the base of a mountain near Popocatepetl last year, construction
workers found the skeletons in a layer of ash 1.3 metres deep. Claus
Siebe of the National Autonomous University of Mexico says the
eruption engulfed areas to the north with a thick layer of ash. Rain
washed the ash down the mountains in a thick slurry that Siebe says
"has the consistency of wet concrete". This week, Siebe told the
Geological Society of America in Salt Lake City that the slurry must
have spread over the plains where the mammoths were grazing. At least
seven died in an area of just 28 square metres.
2) S. Hofner & G. Wuchterl: Jovian soot from cometary impacts?
ASTRONOMY AND ASTROPHYSICS, 1997, Vol.324, No.2, pp.795-798
UNIVERSITY OF VIENNA,INSTITUTE OF ASTRONOMY,
17, A-1180 VIENNA, AUSTRIA
It seems to be widely accepted that the dark spots on Jupiter
by the impacting fragments of comet Shoemaker-Levy 9 are due to dust
particles which have formed immediately after the impacts. However,
the actual nature and origin of these grains is still uncertain. We
propose that they may consist of amorphous carbon and have calculated
the time-dependent formation and growth of such dust particles
assuming an exponential pressure decrease in an adiabatic fireball.
The resulting properties of the grains, e.g. their sizes, are
consistent with observations, The question whether carbon or silicate
grains will form depends critically on the chemical composition of
the Jovian atmosphere. If a carbon-rich environment exists at the
impact sites our model demonstrates that there is enough time to grow
amorphous carbon grains in the fireballs rising immediately after the
J Smith: Predictive elements of large body impacts in geologic history.
GEOLOGISCHE RUNDSCHAU, 1997, Vol.86, No.2, pp.464-470
FREE UNIVERSITY OF AMSTERDAM, INSTITUTE OF EARTH SCIENCE,
OF SEDIMENTARY GEOLOGY, DE BOELELAAN 1085, NL-1081 HV AMSTERDAM,
Large-body impacts cannot be predicted, although the
(size-frequency) of large impacts on the Earth has been worked out,
yielding frequencies of the order of one impact of a l-km body every
500 000 years. Another type of prediction, however, is that
forthcoming from the consequences of a large-body impact. Prediction
as validation of theory. What can be predicted are the consequences
of a large impact, ranging from local and regional ejecta blankets to
global climate changes leading to mass extinctions. It is the
fulfillment of such predictions that has rendered strength to the
impact-extinction theory for the Cretaceous-Tertiary (K/T) boundary,
in contrast to predictions attached to widespread volcanism, such as
at the Deccan traps in India, or sea-level changes.
4) M. B. E. Boslough & D. A. Crawford: Shoemaker-Levy 9 and
plume-forming collisions on Earth. ANNALS OF THE NEW YORK ACADEMY OF
SCIENCES, 1997, Vol.822, pp.236-282
SANDIA NATIONAL LABORATORIES, DEPARTMENT OF COMPUTATION,
MECHANICS, POB 5800, ALBUQUERQUE, NM, 87185
Computational models for the July, 1994 collision of comet
Shoemaker-Levy 9 with Jupiter have provided a framework for
interpreting the observational data. Imaging, photometry, and
spectroscopy data from ground-based, Hubble Space Telescope,
and Galileo spacecraft instruments are consistent with phenomena that
were dominated by the generation of incandescent fireballs that were
ballistically ejected to high altitudes, where they formed plumes
that subsequently collapsed over large areas of Jupiter's atmosphere.
Applications of similar computational models to collisions into
Earth's atmosphere show that a very similar sequence of events should
take place for NEO impacts with energies as low as 3 megatons,
recurring on 100 year timescales or less. This result suggests that
the 1908 Tunguska event was a plume-forming atmospheric explosion,
and that some of the phenomena associated with it might be related
to the ejection and collapse of a high plume. Hazards associated with
plume growth and collapse should be included in the evaluation of the
impact threat to Earth, and opportunities should be sought for
observational validation of atmospheric impact models by exploiting
data already being collected from the natural flux of multikiloton to
megaton sized objects that constantly enter Earth's atmosphere on
annual to decadal timescales.
5) MASS HYSTERIA IN ITALY?
from: Paolo Farinella <firstname.lastname@example.org
I have just read your note on the Italian reactions to the
Umbria-Marche earthquake. Luckily, I am far enough not be affected
directly, but I have been following closely the reports on the media.
In my opinion, the claims of `national psychosis', `mass hysteria'
and `apocalyptic panic' are grossly exaggerated. My impression is
that the 50,000 or so people who are have been forced to sleep in
tents for almost one month due to the continuing quakes are
predictably stressed, and in these conditions some irrational rumors
of `underground volcanos' or `forthcoming big ones' have circulated
-- although they have been promptly contradicted by all the local and
national authorities and no source in the press or the media has
really taken them seriously. The story about Nostradamus is just a
curiosity which has appeared in the popular press, along as many
similar things (horoscopes etc.) which are put around everywhere
(including Britain) in `normal' times. The connection with football
games may be amusing for English readers, but it's the first time I
have seen it made!
I don't intend to deny that in general a connection between
disasters and irrational apocaliptyc beliefs may exist, nor that in
Italy there are many gullible people and even more silly articles in
the press -- but the current earthquake is not really such an
impressive instance of these phenomena.
Paolo Farinella Tel. +39-50-844254 Dipartimento di
Matematica Fax +39-50-844224 Universita` di Pisa Via F. Buonarroti 2
e-mail email@example.com I-56127 Pisa, Italy WWW:
CCCMENU CCC for 1997