Take a look at Florida Google Maps. Do you see all those thin strips of land off the coast, which consequently contain our most famous beaches? Yup, those are barrier islands. Without them Florida would be a very different place. So, how did they come to be?
Formation Theories
Offshore Bar Theory
Spit Accretion Theory
This theory says barrier islands are formed by sediment from longshore drift. The drift accumulates to form a spit—a strip of land, connected to the mainland, that juts out into the water. Then, subsequent storm waters would break the spit from the mainland, creating a barrier island. This theory was first introduced by American geologist, Grove Karl Gilbert, in 1885.
- Mainland Beach
- Ocean
- Longshore drift carrying sediment
- Waves crashing into the longshore drift, churning the sediment
- Swash (turbulent layer of water that washes up on the beach after a wave breaks, moving the sediment around.
- Backwash; the sediment is carried out, sometimes building up a spit
Submergence Theory
This theory says water moves in on coastal ridges and separates them from the mainland. This theory was popularized by American geologist William John McGee (not to be confused with Travis McGee) in 1890.
It is debatable which theory holds true, as barrier island formation takes a very, very long time. But lately, scientists are beginning to think barrier islands are formed by a combination of the above theories. Hmmm…so what do you think?
For further reading, check out Barrier Islands of the Florida Gulf Coast Peninsula.
Sources:
“Barrier Islands.” 2FLA. Retrieved 9 Sept. 13. http://www.2fla.com/barrier_islands.htm
“Barrier Islands and Barrier Beaches.” Glencoe. Retrieved 6 Sept. 13. <http://www.glencoe.com/sec/science/cgi-bin/splitwindow.cgi?top=http://www.glencoe.com/sec/science/top2.html&link=http://www.salemstate.edu/~lhanson/gls214/gls214_barrier_isl.htm>
Snyder, Richard A. “Flora and Fauna of Northwest Florida.” University of West Florida. 20 June 08. 6 Sept. 13. <http://www.uwf.edu/rsnyder/ffnwf/barrier/barrier.html>
(updated 09/22/2019)
