THE SOILS OF FLORIDA. 
53 
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FROST AND FREEZING. 
J •' ... 
Aside from the ordinary changes of temperature, freezing in the 
colder latitudes is an active destructive agent. When water freezes 
it expands with almost irresistible force. The breaks, crevices, and 
pores of rocks are filled with water as a rule, and when this freezes, 
the force of expansion of the water enlarges all such openings, thus 
hastening the decay of the rock. Decay from freezing takes place 
most rapidly as will be apparent, at seasons of the year when alter¬ 
nate freezing and thawing occurs frequently, as when the surface 
rocks thaw during the day and freeze at night. Owing to the mild 
climate this factor in the decay of rocks is of minor importance in 
Florida. 
WIND. 
The wind as a weathering agent might at first thought, seem to be 
of little or no importance, yet under favorable conditions the sand, 
fine gravel, and other materials, carried by the wind may be hurled 
with considerable force against the face of exposed rocks and thus 
gradually wear them away. The wind is most active as an agent of 
decay in the deserts and other sections of slight rainfall. Under the 
action of the wind, the softer materials wear away first. Also, since 
heavier materials carried by the wind are carried close to the ground, 
the base of exposed rocks are worn more rapidly than other parts, 
resulting in fantastic sculpture as seen in some of the desert rocks. 
WATER. 
The agencies mentioned, changes of temperature, frost, and wind, 
all exert a purely mechanical effect in the disintegration of rocks. 
Water, however, in its various phases of activity, acts both mechani¬ 
cally and chemically. Falling as rain, water has but feeble mechani¬ 
cal effect, although in the form of running water a greater mechani- 
% 
cal action is exerted, not by the force of the water alone, but more 
particularly by the force of the impact of materials thrown by the 
current against the face of exposed rocks along the bottom and the 
sides of the stream. The mechanical action of water is in this respect 
analagous to that of the wind. The waves of the sea and of the large 
lakes carry on mechanical erosion by the force of impact of the 
waves beating on the shore. 
