SOME FEATURES OF THE CHANNEL OF THE MISSISSIPPI 
RIVER BETWEEN LANSING AND DUBUQUE, AND 
THEIR PROBABLE HISTORY. 
BY SAMUEL CALVIN. 
The courses followed by the major streams of the interior of the 
North American continent during Paleozoic and Mesozoic times, 
can not now be pointed out with any high degree of certainty. The 
numerous upwarps and twistings to which the continental ridge 
was subjected, caused large portions of what is now North America 
to be at times abo.ve the sea, at other times below, and the drainage 
was shifted from area to area, from one direction to another. 
During a period as recent as the late Cretaceous the drainage of 
the middle Northwest flowed westward into a great sea that over- 
lapped the western part of Iowa and extended away to the Sierras 
of California. There were no Rocky mountains such as we now 
know, for it was not until the close of the Cretaceous that the 
ridges of the' Rockies, as a whole, rose above the waters; not until 
this event took place, could there be a Mississippi valley with ex- 
tensive surfaces sloping from mountain chains on the east and west 
toward a central axis ; not till then could the master stream of the 
continent enter upon its permanent career. 
During practically the whole of the Tertiary period the axial 
part of the Mississippi valley was low; the Gulf of Mexico ex- 
tended to the mouth of the Ohio ; the great river and its immediate 
tributaries meandered sluggishly on a base-levelled plain. Toward 
the close of the Tertiary, however, there occurred a succession of 
disturbances, not violent, whereby the central part of the valley 
was elevated to a height of probably 2,000 feet above tide at what 
is now the northeastern corner of Iowa. All the streams were 
quickened by the uplift, and corrasion of the channels proceeded 
with more or less energy until grade was again reached and the 
drainage courses were adjusted to the new conditions. Corrasion 
and upward movement were so balanced that, in general, the 
streams continued to follow their previous winding courses and en- 
trenched their old meanders. This fact is well illustrated by the 
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