From: LARRY KLAES (ljk4@msn.com)
Date: Mon Apr 08 2002 - 08:01:01 PDT
IMPACT EVENTS' KINETIC ENERGY MAY BE KEY TO UNDERSTANDING SEVERITY OF
MASS EXTINCTIONS
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
Geological Society of America
Boulder, Colorado
Contact:
Ann Cairns
Director - Communications and Marketing
acairns@geosociety.org, 303-357-1056
FOR IMMEDIATE RELEASE: April 3, 2002
GSA Release No. 02-19
Impact Events' Kinetic Energy May Be Key to Understanding the Severity of
Mass Extinctions
By Kara LeBeau, GSA Staff Writer
The kinetic energy created by asteroid and comet impacts with the Earth may
be key to linking some impacts with mass extinction events. Michael Lucas, a
geology student at Florida Gulf Coast University, believes that the severity
of four extinction events during the Mesozoic and Cenozoic can be correlated
with the total kinetic energy released by impacts that occur during the
geologic age of the mass extinction.
Lucas will present his findings April 4 at the Geological Society of
America's North-Central Section and Southeastern Section Joint Meeting in
Lexington, Kentucky.
Lucas analyzed the kinetic energy released by 31 of the largest impact
structures from the last 248 million years and correlated them with the
Norian, Tithonian, Late Eocene, and K-T extinction events. The impact energy
released during the geologic ages of each extinction event is at least 10
million megatons of TNT equivalent yield per geologic age. Lucas believes
that this could represent a minimum impact energy required to cause a
global-scale mass extinction. His research results also reveal that
synchronous multiple impact events could also have caused extinctions.
"Approximately ten percent of the impact structures on Earth are doublets or
twin structures, suggesting a nearly simultaneous impact of binary asteroids
or fragmented comets," he said. An example of a twin impact structure would
be the Kara / Ust-Kara twin impact structure in Russia which is about 73
million years old.
CONTACT INFORMATION:
Michael P. Lucas
College of Arts & Sciences
Florida Gulf Coast University
10501 FGCU Blvd. South
Ft. Myers FL 33965 USA
E-mail: mlucas@fgcu.edu
Phone: (941) 590-7225
Abstract available at:
http://gsa.confex.com/gsa/2002NC/finalprogram/abstract_32110.htm
==============
(3) EXTINCTIONS
>From Michael Paine <mpaine@tpgi.com.au>
Dear Benny
The links below may be of interest. Both seem to ignore Luann Becker's
recent work on fullerenes as impact signatures. With Chicxulub-size impacts
we have the frequency (~100 million years) and devastating global
environmental effects (including disturbance of methane hydrate
deposits that the PNAS paper refers to) to account for mass extinctions.
That is not to say that all mass extinctions are necessarily associated with
impacts but it seems to me that they should be considered as prime suspects.
regards
Michael Paine
1.Nature:
http://www.nature.com/nsu/020325/020325-7.html
http://www.nature.com/doifinder/10.1038/416420a
2.Proc. Natl. Acad. Sci.
http://www.pnas.org/cgi/content/abstract/032095199v1
March 26, 2002
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.032095199
Examination of hypotheses for the Permo-Triassic boundary extinction by
carbon cycle modeling.
Robert A. Berner*, Department of Geology and Geophysics, Yale University,
New Haven, CT
06520-8109
The biological extinction that occurred at the Permian-Triassic boundary
represents the most extensive loss of species of any known event of the past
550 million years. There have been a wide variety of explanations offered
for this extinction. In the present paper, a number of the more popular
recent hypotheses are evaluated in terms of predictions that they make, or
that they imply, concerning the global carbon cycle. For this purpose, a
mass balance model is used that calculates atmospheric CO2 and oceanic 13C
as a function of time. Hypotheses considered
include: (i) the release of massive amounts of CO2 from the ocean to the
atmosphere resulting in mass poisoning; (ii) the release of large amounts of
CO2 from volcanic degassing; (iii) the release of methane stored in methane
hydrates; (iv) the decomposition and oxidation of dead
organisms to CO2 after sudden mass mortality; and (v) the long-term
reorganization of the global carbon cycle. The modeling indicates that
measured short-term changes in 13C at the boundary are best explained by
methane release with mass mortality and volcanic degassing contributing
in secondary roles. None of the processes result in excessively high levels
of atmospheric CO2 if they occurred on time scales of more than about 1,000
years. The idea of poisoning by high levels of atmospheric CO2 depends on
the absence of subthermocline calcium carbonate deposition during the latest
Permian. The most far-reaching effect was found to be reorganization of the
carbon cycle with major sedimentary burial of organic matter shifting from
the land to the sea, resulting in less burial overall, decreased atmospheric
O2, and higher atmospheric CO2 for the entire Triassic Period.
* E-mail: robert.berner@yale.edu.
(7) WATCHING THE SKIES, 100 MILLION YEARS AGO
>From Michael Paine <mpaine@tpgi.com.au>
Scientific American, APRIL 2002
http://www.sciam.com/2002/0402issue/040210050fools.html
100,000,000 Years Ago
WATCH THE SKIES?--"At a recent interdisciplinary meeting on the campus of
Pangaea University, researchers discussed with some alarm the mounting
evidence that each of the known mass extinction events may have been caused
by a titanic collision of a comet or asteroid with the
earth. According to recent speculations, such impacts could envelop our
planet in a dense cloud of dust and ash, blocking out the sun, with
disastrous consequences for most life-forms.
"Massive impact scenarios should be of more than academic interest, many of
the gathered scientists said, because a similarly calamitous collision could
occur yet again. 'It's difficult to predict how bad it could be,' remarked
geologist Edward Deinonychus of Gondwana Polytechnic. 'It would surely cause
a huge loss of saurian life, maybe even amounting to 10 percent of the
population. What's more, even aside from its climatic effects, the impact
could ignite a gigantic firestorm. It might destroy every last trace of our
magnificent papier-mâché
cities.'
"Some of the participants at the meeting argued that a future mass
extinction could be averted. 'Our space science is now sufficiently advanced
for us to identify an incoming asteroid decades before its arrival and to
change its course,' said Margaret Dimetrodon of Mount Ararat Observatory. 'I
know it sounds like science fiction. But if we can put a sauropod on the
moon, then we can do this.'
"But support within the government for investing in an asteroid-blasting
scheme remains weak. Echoing sentiments heard throughout Congress, junior
senator Strom Thurmond declared, 'Even if it is a good idea, a big collision
like this might not occur for tens of millions of years. That's more than
enough time for us to get it done. Right now we'd be better off putting our
science funding to more worthwhile uses, like fusion research.'"
Copyright 2002, Scientific American
This archive was generated by hypermail 2.1.2 : Mon Apr 08 2002 - 08:18:42 PDT