DELTAS 351 



build a delta with a steep upper surface rising cone-shaped 

 above the water. Many of the deltas in Lake Geneva are 

 of this kind. If the grade is slight, the delta will be sim- 

 ply a continuation of the flood plain of the river. Such 

 is the Mississippi delta. The layers of sediment compos- 



LAKE BRIENZ, FROM ABOVE INTERLAKEN. 



A rapidly eroding stream at the extreme right has built a great delta 

 dividing the ancient lake into two parts. 



ing the delta, slope away from the point where the river 

 enters the still water. Here, as in the alluvial cone, the 

 river is continually silting up its outlet and being forced 

 to seek new channels. In large deltas the river generally 

 enters the sea through several channels or distributaries, 

 as they are called. This is seen in the map of the Missis- 

 sippi delta (page 352). 



