64 GASPARILLA ISLAND March/April 2019
Canaveral sand commonly exists in very rapidly
permeable soils. It is found along the coast in Peninsular
Florida. Captiva sand forms where the annual temperature
averages about 73 degrees. St. Augustine sand also consists
in very deep, somewhat poorly drained, permeable soils. It
is common in narrow flats and tidal marshes and estuaries
of Peninsular Florida. It originally formed in fill material, as a
result of dredging and filling operations along peninsular
Florida.
Craig Prink, a soil survey leader for the United States Department
of Agriculture based in North Fort Myers, agreed
the dominant soils in the Boca Grande area are Canaveral,
Captiva and St. Augustine. He said an additional type of sand
called Kesson, can also be found in Boca Grande. Kesson is
fine sand that is formed from shell fragments in tidal swamps
and marshes along the Gulf Coast of Florida.
“Close to the beaches and/or estuaries the brackish water
will saturate the sediments with saline water from the Gulf
of Mexico, which affects plant growth and only plants that
tolerate the saline materials will thrive,” Prink said. “Dominant
plants within the tidal zone are mangroves.”
Other elements in the water will precipitate out at the
surface in some cases. So the chemical composition of the
water and soil are in flux and changes over the range of the
tidal periods.
“The marine deposits about 30 to 50 meters away from
the tidal zone will remain more stable, because they are not
exposed to the tidal influence,” Prink said. “Some areas have
been altered for urban uses. These areas will have between
24 to 48 inches of sandy fill material over the existing sand
to bring the area to a higher elevation in an attempt to escape
the water table and/or tidal flooding.”
Depending on the local rock sources and conditions, the
composition of sand is always changing.
Sand on northern Florida beaches has a higher
concentration of quartz.
Technically speaking, sand is finer than gravel and coarser
than silt, with grains between 0.06 and 2.0 mm. Florida’s beach
sand averages about 0.3 mm, but there is much variation
among and within beaches. Finer sands are found on Gulf of
Mexixo beaches and in northeastern Florida and in dunes.
Coarser sands occur on mid-Atlantic beaches.
Source: United States Department of Agriculture Natural
Resources Conservation Services.
G
M
DID
YOU KNOW?
The whitest sands are nearly
100 percent quartz. Amber sands have
aged seashell bits, orange sands are
rusty from iron oxides.
Dark, coarse grains are often
fossilized bone or teeth.
Dark peppering among paler grains is
often ilmenite, an iron titanium oxide.
Many Florida Keys beaches are made
from crunched coral bits
and coralline algae.