Hi,
The one source I could find (in a hurry,
admittedly, said oxygen content at the end of
the Permian dropped to a "mere 16%"
instead of the 20% we enjoy today. That
16% at sealevel would be the equivalent
of 20% O2 air at 12 psi. Into the early
Triassic, it dropped to 12%, the equivalent
of 20% O2 air at 9 psi.
Care has to be taken interpreting the
oxygen drops as "one half" or "one quarter,"
because the oxygen content at the beginning
of the Permian was 30%! Plant life had pumped
up the oxygen content faster than animal life
could use it up. At the same time, plants were
depleting the rich CO2 atmosphere (100 times
more CO2 than today) and cooling the planet
off by 10 degrees C.
Since atmospheric pressure in Denver,
Colorado (altitude 5,280 feet, marked right
there on the famous step!), is only 12.2 psi,
I can only suggest the Denver List Members
flee for their lives before a Permian-like extinction
overtakes them! (Those living at 10,000 feet
presumably have already perished in horrible
gasps by now...)
On top of Mount Everest, the pressure
has fallen to one-third of an atmosphere, or
about 5 psi, the equivalent of 6-7% O2 air at
sealevel. And it's true that you'll meet no Permian
reptiles on top of Mt. Everest and few humans
without an O2 tank either. (It has been done
without supplemental O2 but it's mean and
damaging.)
We worry so much about CO2 that it's easy
to forget how dangerous a high-oxygen environment
can be. The present Earth biosphere would be in
peril if O2 content rose above 28%. Spontaneous
and easily kindled "natural" fires would rage across
the planet at unstoppable speed all the time, I mean,
continuously. The rapidity of combustion in a 28%
O2 environment would make even the "tame"
human uses of fire very hazardous.
The Late Permian had a very hot climate, the
warmest mean annual temperature in geological
history. If you average out climates on the long
scale (1,000,000 years) and ignore those little
100,000 year fluctuations, the planet's climate
flops back and forth between an ice age average
of 22 degrees C. (70 F) and a greenhouse average
of 31 C (90 F) and always has... Except for
the Late Permian when the mean annual temp of
the Earth soared to 34-35 degrees C., the only
time in a billion years it's done that.
As Elton so rightly pointed out, the interior of
the one continent became the greatest desert ever.
With an average temperature of 105 F and a noon
summer temp of 140-150 F, no plant or animal life
existed there, in a region covering almost 40% of
the Earth's land area. Another 25% of the planet
was cooler but so arid as to be lifeless also. The
only lively places were near the poles.
One continent to a planet is not a good
arrangement. (Fortunately, we don't have worry
about this, as it will take another 250 million
years or more for tectonics to re-assemble
another single-continent world.)
As a general trend, the decline in oxygen
content during the Permian spelled big trouble for
the primitive reptiles and the therapsids, but the
notion that this (and the oceanic problem of loss
of oxygenated shallows) could culminate in a
disastrous crisis of "Sick Earth Syndrome" from
which life almost perished is hard to reconcile
with the fact such processes both preceded and
followed the extinction for many millions of years.
There is no doubt that the world was very
vulnerable at the end of the Permian from a whole
variety of environmental stresses. Maybe the Permian
Whacker wasn't that much bigger than other impactors
but just had a disporportionate effect on the world.
What I detect is an idea designed to appeal to
minds already persuaded to regard Global Warming
as a kind of "sick" Earth symptom and to regard
CO2 as a poisonous pollutant. The "Sick Earth"
theory fits the same model of how to look at the
world, and just as wrongly, or at least is being
promoted by the press in that way.
Sterling K. Webb
----------------------------------------------------------
----- Original Message -----
From: "Mr EMan" <[EMAIL PROTECTED]>
To: "Meteorite Mailing List" <[email protected]>
Sent: Saturday, October 21, 2006 11:25 PM
Subject: Re: [meteorite-list] P-T Extinction: 'SickEarth' Book
Recommendation
What a segway! Based on what I read there was evidence
of a sick earth but Peter Ward's research showed a
very rapid extinction of land animals.
I just finished reading "Gorgon: The Monsters That
Ruled the Planet Before Dinosaurs and How They Died in
the Greatest Catastrophe in Earth's History" by Peter
Ward. Ward spent decades studing the Permian
Extinction in the Karoo district of South Africa.
Ward was a specialist in the K-T extinction and looked
kept an eye out for a similar impact component. The
book is an account of the trials and tribulations of a
geologist trying to do science, make a living, and
raise a new family in the wilderness. The snobbbey and
blood-letting amongst researchers is insightful to the
way other researchers posion the pond in other fields.
The science is pretty neat. The book is rarely
predictible.
Far too many dimentions to describe but the book is
cheap online and a must read for anyone interested in
the life of a geologist and novel solutions to solve
obsticles.
Ward's observations were that the land amimals that
survived and flourished ultimately were the ones which
had a bone structure that allowed for a flexible and
greater lung capacity--side slung arms aka
lizard-like. Research supported that there was a
plunge in oxygen levels such that it was like moving
from sea level to 12000ft. Part of the overall
observation is that Gondwana moved over the south pole
and in the ensuing ice age, sea level moved beyond the
already meger contentinal shelves cutting shallow
water habitat to nill killing the plankton bloom. The
sea based food chain collapsed along with the oxygen
production. There was a scarcity of land plants in the
Permian besause so much of the land mass was at the
interior of a massive water deprived landlocked
soiless landscape. Life in the Triassic remained meger
until the Breakup of Pangea opened up more shore line
to the interior.
The Siberian trapps at that time were above the
Artic(North) not far from where they are today.
For a book description:
<http://www.amazon.com/Gorgon-Paleontology-Obsession-Greatest-Catastrophe/dp/0670030945?tag2=gp04-20>
Or Google Gorgon Ward Book.
Regards,
Elton
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