GEOLOGY BETWEEN APALACHICOLA AND OCKLOCKNEE RIVERS, 2J 
more effective cause for the high bluffs on the east side is found 
in the history of the development of the tributaries. Those trib- 
utaries that flow with the dip extend their course inland more rap- 
idly than those that work against the dip. Those streams flowing 
with the dip receive a better and more constant supply of water 
from springs than do the other streams. This increased supply of 
water facilitates both the extension and the deepening of the 
stream channels. The greater development of the drainage sys- 
tem is accompanied by an increased amount of erosion and surface 
wash. In this way the average land level on the west or northwest 
side of the main stream has been more rapidly reduced than on 
the east side. Instead of the typical V-shaped valleys, the streams 
in this area, for the most part, are bordered on one side by bluffs, 
more or less pronounced, while on the other side, the. land rises 
gradually to the plateau level. 
STEEPHEADS. 
s 
A characteristic feature of this topography is the development 
of what is known locally as “steepheads.” These steepheads are 
due to the *fact that indurated sands and sandy clays overlie slightly 
indurated sands and clays and shell marls. The surface waters pass 
into the earth and, upon reaching the underlying clay or marl beds, 
emerge, as springs. The indurated sandy clays near the surface 
stand up vertically, while the softer sands, at a greater depth 
where the springs emerge, wash easily. The result is the forma- 
tion of a nearly vertical bluff, at the base of which springs emerge 
supplying small streams. This bluff or streamhead assumes in time 
a semi-circular form, which is the “steephead.” The steephead 
thus formed is retained by the stream as it gradually extends its 
way back into the plateau. The depth of the steephead from the 
plateau is usually from 50 to 60 or more feet, depending upon the 
depth at which the ground waters emerge as springs. 
