52 FLORIDA GEOLOGICAL SURVEY—FOURTH ANNUAL REPORT. 
The formations found in Florida from which the soils are derived 
are of sedimentary origin. Since there are many different kinds of 
sedimentary rocks the soils from them are necessarily varied. More¬ 
over, the character of the soil is determined not alone by the for¬ 
mation from which derived, but also by the climatic, drainage and 
other conditions to which it has been subjected. Distinct formations 
if similar in character may give rise to similar soils. Conversely, a 
single formation under varying conditions may give rise to various 
soils. If the writer’s views as to the origin of the sandy soils of the 
interior of the State are correct, soils in Florida referred to the 
Norfolk, Portsmouth, and Orangeburg series are in some instances 
derived from one and the same formation, the differences in the soils 
being due to the different topographic and drainage conditions 
under which they have accumulated. 
DISINTEGRATION OF ROCKS. 
Soils result from the decay and disintegration of rocks. Active 
among the agencies of decay are: Changes of temperature; frost or 
freezing; wind; water; animals; and plants. Through the continued 
activity of these agencies, solid rocks crumble to dust, the residue 
forming the mineral constituents of soils. The combined effect of all 
these agencies is known as weathering, and all rocks when exposed 
at the earth’s surface are subjected to this process. 
CHANGES OF TEMPERATURE. 
Changes of temperature of rocks result in alternate contraction 
and expansion, thus widening existing breaks and joints, loosening 
the rocks and permitting the entrance of water, which finds its way 
more readily through the rock. In dry climates rocks heated to a high 
temperature during the day cool rapidly at night. Under the influence 
of heat rocks expand, and the sudden cooling and contraction of the 
exterior crust upon the still heated and hence expanded interior sets 
up strains which frequently disrupt and break the crust. Then, too, 
rocks consist usually not of one but of several minerals, and each 
mineral has its own coefficient of expansion and contraction and 
hence contracts and expands when heated, at a slightly different 
rate from the associated minerals. Thus the different parts of the 
rock are subjected to strains, which loosen the minerals and let 
water enter more freely, thus hastening decay. 
