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Posted By:
Hal Brown
Date Posted:
Nov 15, 2007
Description:
A barrier island is just a string of sand keeping the brown water from overtaking the emerald water.
Barrier islands are built of sand washed into the gulf by rivers. The sand dumped into this part of the gulf by the Apalachicola River was once part of the Appalachian Mountains. Of course the eroding mountains don’t get here so much anymore because of dams on the river. Now with the restrictions on river flow due to the drought in Georgia and thirsty folks in Atlanta, it will be lucky to flow at all. In fact, the Apalachicola oysters may very well disappear with the increasingly salty water. Good thing I don’t like oysters…..but I do like the beaches!
The barrier islands cover most of the Gulf coast. Worldwide, however, they constitute only 15% of the world’s coastlines.
There are two primary theories as to how barrier islands form, and one that has never been demonstrated.
The oldest theory has wave action concentrating sand in shallow water along the coastline. Waves start cresting on the sandbar, dumping their load. As the sand emerges in the intertidal zone, opportunistic vegetation may be established trapping even more sand and building dunes. This process has actually been observed around Florida over a period of decades.
Another theory has barrier islands developing as an extension of the mainland. Violent storms breach the attachment and islands are formed. This has been observed along the Gulf coast where hurricanes have isolated portions of the sandy spits as in the case of Petit Bois Island.
The third theory is that the barrier islands are just dune lines buried by a rising sea. It’s a good idea, but no one has been interested enough to make verifying observations over a period of several thousand years.
Rising sea levels are actually no good for barrier islands. When sea levels rose rapidly after the last ice age (averaging 1 to 2 cm per year), barrier islands would have been difficult to find. The rate of rise is actually ten times as fast as sea level has been rising for the past 7,000 years. Not coincidently, the barrier islands are less than 7,000 years old.
Date Taken:
Nov 15, 2007
Place Taken:
Santa Rosa Island, FL
Owner:
Dan Nickens
File Name:
11_Sand_String.jpg - Photo HTML
Full size - <img src="/show.php?splash=SZUFP0000h">
Medium - <img src="/show.php?splash=SZUFP0000m">
Thumbnail - <img src="/show.php?splash=SZUFP0000s">
Category:
289, An Indirect Relocation
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