MadSci Network: Earth Sciences
Query:

Re: Seemingly high elevation of Seahorse Key on the Gulf Coast?

Date: Wed Dec 15 11:10:47 2004
Posted By: David Smith, Director of Professional Development
Area of science: Earth Sciences
ID: 1102002817.Es
Message:

Although I could not find any definitive statements on a variety of web 
sites, it does seem most likely that Seahorse Key is simply a drowned dune 
and the reason it sticks higher than other nearby keys is that the dune, 
when formed, was higher than other nearby features.  Large coastal dunes 
are a feature of the modern Florida coast, for example:
 http://beachesofsouthwalton.com/blue_mountain.asp

During the last glacial maximum (the last pulse of what is commonly called 
the Ice Age), about 10,000 years ago, sea level was lower, which means the 
shoreline was in a location that is now underwater.  Large dunes would 
likely have formed along such a shore and would then have been innundated 
by rising sea level as the ice sheets melted back.  Although some erosion 
would be inevitable as sea level rose, dunes that had been stabilized by 
vegitation would be relatively resistant to erosion and could form 
relatively stable islands.  

Another factor that may have contributed (and this is really speculation - 
I have no information to back this up) is sediment supply from the Suwanee 
River.  IF sediment from the river is carried into the Cedar Keys area by 
longshore currrents (wave-driven currents that move parallel to the 
shoreline), then that could offset any erosion and further stabilize the 
islands.

Hope this helps,

David Smith, Ph.D., Geologist & Director of Professional Development
Da Vinci Discovery Center of Science and Technology, Bethlehem PA



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