GEOLOGY OF FLORIDA 287 



TOPOGEAPHY AND ELEVATION 



In topographic detail and surface configuration Florida is by 

 no means lacking in variety. In this respect the state pre- 

 sents much greater diversity than would have been anticipated in 

 view of the fact that the maximum elevation within the state 

 scarcely exceeds 300 feet above sea-level. In the upland section 

 of the state the intimate relation between topography and geology 

 becomes apparent. The limestones under the influence of a heavy 

 rainfall and an excess of humic acids in the ground water have 

 dissolved rapidly, and when lying near the surface have produced a 

 characteristic topography. The lowlands bordering the coast, on 

 the other hand, have been but Httle affected by erosion, and in these 

 areas the surface is perhaps but slightly modified from its original 

 condition. Of the land area of the state, approximately one-half 

 lies below the 50-foot contour line. This belt of land below the 

 50-foot contour includes all of the peninsula south of the northern 

 end of Lake Okeechobee, and in addition a strip of varying width 

 bordering the Atlantic and Gulf coasts. Aside from beach deposits 

 and sand dunes, this belt of country is prevaihngly level. The 

 surface deposits are usually sandy, although, as will be subsequently 

 indicated, limestones underHe considerable areas. 



The higher lands of the interior of the state present for the most 

 part topographic features that are difiicult of description, owing to 

 the apparent irregularity and lack of system of the hills and valleys. 

 Over much of this area the topographic features are the result of the 

 solution of the underlying calcareous deposits, and the prevailing 

 surface configuration includes depressions or solution basins of 

 varying size and depth, and hills of varying size and height. Within 

 the area, the topography of which is controlled by underlying cal- 

 careous deposits, are two subdivisions which are worthy of special 

 mention. These are the "sink-hole region," which lies chiefly along 

 the west slope of the peninsula, and the "lake region," which lies 

 for the most part near to or somewhat east of the center of the 

 peninsula. In the sink-hole region the limestones lie at no great 

 depth. The sinks which form as a result of the solution of the 

 limestones, thus allowing the covering to fall in, usually reach 



