MadSci Network: Earth Sciences |
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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