26 FLORIDA GEOLOGICAL SURVEY TENTH ANNUAL REPORT. 
TOPOGRAPHY AND GEOLOGY. 
E. H. SELLARDS. 
The uplands in this area include a plain or plateau which is 
highest at the north or northwest, where it reaches an elevation of 
from 300 to about 325 feet above sea. The plain as now preserved 
slopes to the south, east and southeast. The slope to the south, es- 
pecially just east of the Apalachicola river, may approximate the 
original dip slope of the plain. The slope to the east and southeast 
possibly has been somewhat accentuated by surface erosion and 
removal of the disintegrated materials by surface wash. The av- 
erage rate of slope of the plain from the State line to the Gulf is 
approximately 300 feet in 60 miles, or an average of about 5 feet 
per mile. 
This plain is cut across by the Apalachicola and the Ocklocknee 
rivers, and is cut into by the numerous streams tributary to these 
rivers. The most rugged land of this area is that which borders the 
Apalachicola river in Gadsden and the northern part of Liberty 
counties. The plateau here rises from the river abruptly. The 
small streams tributary to the Apalachicola river have cut short 
deep channels back into the plateau, producing over a small area 
the most hilly section found in Llorida. 
STREAM VALLEYS. 
This area presents some topographic features of exceptional 
interest. The two principal streams, the Apalachicola river on the 
west and the Ocklocknee river on the east, each have a northeast- 
southwest course through the northern half of this area and, in 
this part of their course, both streams have developed pronounced 
bluffs on their left or east banks. This is notably true of the larger 
of these streams, the Apalachicola river. The bluffs immediately 
on the east side of this river rise to an elevation of as much as 
from 150 tq 225 feet above the river valley. On the west side., on 
the contrary, the banks are low and the rise to the high land is 
very gradual. This lack of symmetry is due in part to the fact 
that the streams are working down the dip of the formations which 
is to the south and southeast. Hence they impinge more strongly 
on their left than on their right bank. Another and perhaps a 
