[Coral-List] Seismic testing info for time ecott

Gene Shinn eshinn at marine.usf.edu
Tue May 15 15:07:56 EDT 2007

Dear Time Ecott, Modern seismic testing is done with what are called 
air guns. 500 to 2000 psi air is released suddenly to create a signal 
that penetrates the bottom and bounces off various layers to make a 
picture of the underlying stratigraphy. Think of a fish finder on a 
larger scale. In the 1970s I swam to within 12 feet of one that was 
firing and made 16 mm movies.  It did not affect my ears but was a 
heck of a jolt to my chest.  Normally there would be a dozen or more 
firing simultaneously. That is much more severe. I filmed them from 
about 40 ft away...as close as you would want to get.  Nevertheless 
they are no threat to coral reefs.
     Before air guns came into use the sound source was dynamite and 
or ammonium nitrate (fertilizer similar to Oklahoma City Bomb) That 
makes a terrible multi-frequency jolt much stronger than air guns. It 
will kill fish 100 ft away.
In the early 1950s thousands of 50 lb charges were shot on the bottom 
up and down the Florida Keys..They were mostly shot on the bottom in 
the marine grass areas in Hawk Channel. Look at any old Florida Keys 
aerial photography (1950s through 1960s) and you will see hundreds of 
evenly spaced 50-ft-diameter bare areas in the turtle grass. By the 
1970s they had healed over and were no longer visible.  The staging 
area was a place called the Dynamite Docks on the east side of north 
Key Largo. You may still find the place mentioned on maps and wonder 
why it was called that.  Also, boomers (electronic plates that act 
like a woofer or think of a inner city boom car) are used for high 
resolution seismic investigation such as those used to determine the 
thickness of Holocene  sand, mud and coral reefs. They do no harm to 
fish or corals.
    I know nothing about the pingers used by the Navy that have 
recently  been implicatedf  with mammal deaths.

No Rocks, No Water, No Ecosystem (EAS)
------------------------------------ -----------------------------------
E. A. Shinn, Courtesy Professor
University of South Florida
Marine Science Center (room 204)
140 Seventh Avenue South
St. Petersburg, FL 33701
<eshinn at marine.usf.edu>
Tel 727 553-1158---------------------------------- 

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