[Coral-List] impact of beachrock on beach erosion

[Eugene Shinn]

Barbara,

I have beat on and cored a lot of beach rock over the years. In the 
Persian Gulf it can form in one

or two years and creates natural harbors for fishing villages. And then 
there is Bimini where some "alternative thinkers" speculate the 
submerged beach rock offshore is the remains of Atlantis. See paper below:

/Shinn, Eugene A., 2009, The mystique of beachrock, International 
Association of Sedimentology Special Publication No. 41, 19-28/

True beachrock is especially resistant to erosion, however, in many 
places in the Bahamas

beach dunes cemented by calcite can be mistaken for true beachrock. 
Percolation or rainwater

causes cementation in beach dunes and because of past sea level rise can 
now be found in the

intertidal zone.That rock is often mistaken for true beach rock but is 
quite different. It is softer

and easily broken and eroded. However, true beach rock is very hard. If 
you go to Loggerhead

Key in the Dry Tortugas you can see extensive layers of intertidal beach 
rock still forming along

the west side of the island. The rock there contains water pipes that 
were placed in soft intertidal

beach sand for the Carnegie research institute lab back in 1904-1905. 
This island most likely

would have been washed away long ago if not for the beach rock armor 
that is still

forming. The same can be said for much of the swimming beach at Bimini 
in the Bahamas. If

you have true beach rock it probably should not be removed. Gene

-- 


No Rocks, No Water, No Ecosystem (EAS)
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E. A. Shinn, Courtesy Professor
University of South Florida
College of Marine Science Room 221A
140 Seventh Avenue South
St. Petersburg, FL 33701
<eugeneshinn at mail.usf.edu>
Tel 727 553-1158
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