CHAPTER X 
RIVER AND LAKE DEPOSITS 
River DEposIts 
Transportation of Sediment. — By actual measure- 
ment, the quantity of material carried mechanically by 
the Mississippi, and dumped into the Gulf of Mexico, 
amounts annually to about 200,000,000 tons. This, 
if accumulated on a space with an area of a square 
mile, would form a prismatic block 268 feet high. 
In addition to this great mass of sediment, the 
Mississippi is also carrying a load of chemically dis- 
solved mineral. Thus the drainage area of the Mis- 
sissippi is slowly lowered, and the Gulf of Mexico 
filled. The great-delta at the mouth of the Missis- 
sippi (Fig. 97) shows how important is this work of 
carrying and filling. 
The Arkansas, which annually carries about 6,800,000 
tons in solution past Little Rock, is also carrying about 
21,400,000 tons of sediment. This represents an 
amount removed by the river, which, in the course of 
about 9400 years, is equal to the removal of a foot 
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