98 RESOURCES OF SOUTHERN ALABAMA. 



Topography and drainage. 



The topography of southern Alabama is very diversified, 

 ranging from the steep and rugged Buhrstone ridges, some 

 of which are over 200 feet above the nearest creeks or 

 rivers, to the comparatively smooth post-oak flatwoods, the 

 gently undulating lime-sink region with its numerous, un- 

 drained depressions, the flood-plain of the Mobile River with 

 its intricate network of channels, and the low flat country 

 on the west shore of Mobile Bay. 



Most of the surface features seem to be the result of 

 normal erosion, and the ridges are generally determined by 

 hard strata or by gravel beds. On account of the prevailing 

 southward dip of the strata the north slopes of the ridges 

 are usually steeper than the south slopes, forming promi- 

 nent inland-facing escarpments (cuestas) in many places. 

 The effects of solution of underlying limestone are seen in 

 several caves (one of which is near the southeastern corner 

 of Covington County) and' a few large springs, and in some 

 of the ponds and sinks of the eastern red hills and the lime- 

 sink region. Wave work is well exhibited in the cliffs fac- 

 ing the bays on both sides of southern Baldwin County, and 

 wind work in the dunes along the coast. Some if not most 

 of the ponds in the southwestern pine hills may represent 

 mere irregularities in the surface when it was originally 

 deposited beneath the sea, for there is no limestone or other 

 soluble rock within several hundred feet of the surface there, 

 as far as known. The larger rivers are bordered in many 

 places by flat terraces a mile or more in width, presumably 

 representing ancient flood-plains. 



STREAMS. 



The larger streams take fairly direct courses to the 

 Gulf of Mexico. Only two of the rivers cross the black belt 

 before entering the area here described. The westernmost, 

 the Tombigbee, traverses it for 100 miles or so, and one of 

 its branches drains a large area of the coal fields, too. The 

 other, the Alabama, has its head-waters partly in the Appa- 

 lachian Valley and partly in the Piedmont, and probably 

 carries down nearly as much fertility as the Tombigbee. The 

 Chattahoochee, on the eastern border of the State, origi- 

 nates entirely in the Piedmont, and on the southern slopes 

 of the Blue Ridge, and passes very little limestone anywhere 



