Re: Great size and oxygen content of the atmosphere

["King, Norm" <nking.ucs@smtp.usi.edu>]

John Schneiderman wrote (Date: 01/26/96; 8:51a):

>On Thu, 25 Jan 1996, Gary Bull wrote:

>> There was a theory that the oxygen content of the earth's atmosphere 
was 
>> greater when very large dinosaurs roamed the earth, enabling them to 
grow 
>> large.  Can't remember anything else about the theory or whether it 
was 
>> disproved (or unprovable).  

>During a Historical Geology class the professor stated during the 
>Cretaceous, cocoliths (calcium carbonate critters) were so numerous that 

>the oxygen to carbon dioxide ratios became inbalanced, producing a 
higher 
>than normal oxygen levels.

>Check out an introductory Historical Geology textbook and take a look...

Your professor's statement is absurd.  We don't know how numerous 
Cretaceous coccoliths were in the seas (i.e., how many there were per 
cubic meter of water).  We only know how dense they are in Cretaceous 
sediments.  Furthermore, the world is a complex, dynamic system.  You 
can't just change one aspect of the environment and expect everything 
else (except what you're trying to explain, of course) to stay the same.  
This reminds me of a statement by Mark Twain about tremendous conjectures 
in science from trifling investment of fact (I can't remember the words, 
but you've probably seen it). Unfortunately, he was right.  We often see 
hypotheses based upon hypotheses, devised solely to explain other 
hypotheses.

Richard Owen may have been the first to propose that the Mesozoic 
atmosphere was denser and richer in oxygen than today's.  It was his way 
of explaining how dinosaurs could have been designed for high activity 
levels (i.e., built like mammals) in spite of being "cold-blooded," with 
the respiratory inefficiency that entails.  It also allowed him to 
explain how huge pterosaurs could fly--the air was much denser and could 
more easily support them.  This "secondary" dense air hypothesis doesn't 
need to be seriously entertained today, because the hypotheses upon which 
it was, in turn, based are in serious question (to put it mildly).  Now, 
if you can come up with compelling evidence for dense air or high oxygen 
content during the Mesozoic (or for some part of it?), aside from any 
preconceived desire to find dense air in the Mesozoic, then you've got 
something! 


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Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu