GLACIAL DRIFTS IN MINNESOTA 
393 
thus easily comparable to the Nebraskan, and with the Kewatin 
drift of the Wisconsin stage. Comparison is made first of all 
with the- latter, because it is so well seen at the surface. Materials 
of the two drifts are so much alike that they are not readily dis¬ 
tinguished the one from the other when out of geologic associa¬ 
tion and when certain age marks of the Kansan fail. Their 
source, direction of glacial movement to and out of Minnesota 
are so similar that the difference in size of the two glaciers is the 
chief matter of contrast, the Kansan being much wider and of 
course longer than the Wisconsin Kewatin glacier. The Kansan 
is not so wide, however, as the Nebraskan glacier appears to have 
been at the south boundary line of Minnesota, and it is remarkable 
if, as generally believed, it reached farther south than the first 
glacier did. 
The oncoming of the Kansan glacier must, of course, have 
found the surface conditions of Minnesota different from those 
that the Nebraskan glacier met. As already explained, the Ne¬ 
braskan glacier probably built no high moraines even across the 
main valleys and also built none of the still higher outwash plains, 
as the Wisconsin glacier did. Evidence, both direct and indirect, 
is lacking to indicate that any of the main drainage valleys were 
blockaded here during the Nebraskan stage of glaciation. During 
the erosion interval, the valleys undoubtedly became clear of 
drift; and if for some other reason they were silted up, the 
drainage in front of the oncoming Kansan glacier was free. But, 
otherwise, there were boulder-strewn hills from the remnants of 
the eroded Nebraskan till, and no doubt many minor valleys 
with gravelly erosion terraces and bottoms, to cross. The rem¬ 
nants of Nebraskan till, also, were in part perched, no doubt, 
where they had to be pushed over and incorporated in the Kansan 
till — hence the great difficulty in many cases in distinguishing 
Kansan from Nebraskan till. From somewhere, probably central 
Minnesota, the Kansan glacier gathered up a great number of 
enormous granitic boulders, also. 
The Kansan glacier made many local outwash fans in front of 
itself as it advanced, such as the conspicuous one near Goodhue, 
and of these some were simply buried under ground-moraine and 
left, while others, by bedding of the gravel back into the ice, 
