184 
FLORIDA STATE GEOLOGICAL SURVEY. 
most one known to the writer being Pine Island, in the Everglades back 
of Fort Lauderdale, six miles from their eastern margin. The belt of 
country containing the prominent dunes south of West Palm Beach 
probably in no place exceeds five miles in width. 
On the west coast of southern Florida dunes are not nearly so nu¬ 
merous as on the east coast and are more irregularly distributed; like 
the east coast dunes, they are found near the shore, rather than inland. 
The best developed dune-system on the west coast, seen by the 
writer, is the one that covers parts or the whole of several islands near 
Caximbas Pass. It extends east from the south end of Caximbas Island 
in a disconnected line having somewhat the shape of the Greek letter 
_n_ , the total length being about eight miles. Just back of Caximbas 
postoffice at the west end of the system there is a dune about thirty-five 
feet high. A mile to the northeast is another ridge having a maximum 
height of sixty feet, and said to be the highest in the system. 
There are no dunes on the islands near the mouth of Caloosahat- 
chee River, where from the configuration of the present coast line they 
might be expected, although a high beach ridge forms the backbone of 
Captiva Island. Between the mouth of the Caloosahatchee and Cax¬ 
imbas there are said to be two dunes, one on a small inner key near 
Estero, the other, much larger, on the mainland about half way be¬ 
tween Marco and Naples. 
South of Caximbas there are no dunes, not even back of the ten 
mife stretch of sandy beach at Cape Sable and none along the southern 
edge of the mainland from Cape Sable eastward. 
It will be noted from this brief account of the distribution of the 
South Florida dunes that while their arrangement is in some way 
related to the present coast line, the relation is not a definite one. The 
high ridges lie back from the ocean and from the Gulf, yet extend but 
a few miles inland. Those lying on keys rise out of mangrove swamps 
where dune building is an impossibility; those near open water, like 
the dune back of Jupiter Light usually have a protecting key between 
them and the ocean and have a fringe of mangroves along the shore. 
Perhaps the most noteworthy feature of the dunes of southern 
Florida is the slight movement of the sands today. Cleared of pine 
timber and palmetto scrub they grow good pineapples, but even when 
bare the sands are little moved by the prevailing winds. While the 
blasts of a hurricane may have some effect there is certainly nowhere 
in southern Florida any such movement of sand as is characteristic of 
dunes in active growth; there is no leeward march overwhelming trees 
and threatening dwellings; no such sand drift as can be seen at Cape 
Henry, Virginia, and at other points on the Atlantic coast. Instead 
of burying forests the dunes of southern Florida where not cleared, 
are covered with large pine trees. In short they are quiescent. 
