GLACIAL LAKE MAUMEE. 341 



The larger scale of the forms in this district as compared with modern features of similar 

 origin points to some interesting conclusions relating to the conditions which existed at that 

 time. It was stated above that most of the rampart ridges seem to be related to the time of the 

 highest Maumee beach. It is worthy of note that the conditions were more favorable for on- 

 shore movement of the ice then than at later times, for, when the continental ice sheet first with- 

 drew from this ground and Lake Maumee first occupied it, the slopes from the lake bottom 4 or 5 

 miles offshore to the land surface a few miles back of the shore were more even and uniform than 

 they have been at any later time, because they had not then been modified either by surf -wasting- 

 offshore or by the building of beach ridges on shore. Hence, the first ice cakes that were blown 

 on shore met less resistance and probably pushed farther up the slope than any of the later ones. 

 As the surf-wasted bench became more pronounced in its development and the beach ridges 

 larger and more bulky, the conditions favoring the shoving of ice floes above the shore line 

 grew less marked. For this reason the highest of the ramparts and those farthest back were made 

 first and the series down the slope to the northwest were made successively later. The older 

 ridges generally contain more clay than the later ones. Some of the fragments and bent ends 

 indicate displacements amounting to a mile or more, and in some places the displacement may 

 have been even greater. 



As the shore of Lake Maumee westward into Indiana is of the same character and the 

 beaches westward from Delphos show very little modification of the kind here described, it 

 seems certain that the westerly and northwesterly winds were the chief forces that produced the 

 on-shore shoving of the ice. That part of the shore that faces the northwest or north-northwest- 

 shows the strongest development of ramparts. The shoving seems to have been done mainly 

 from the west-northwest or in a direction slightly oblique to the slope. This, of course, had 

 the effect of reducing the relative degree of inclination of the slope up which the ice moved and 

 facilitated the process. In general the bent ends and sinuosities seem best accounted for by 

 shoving from the west-northwest. 



If the beachlike clayey ridges of this district are in fact ice ramparts and were produced in 

 the way here suggested, their magnitude and the scale of the movements involved in then- dis- 

 placement seem to require thicker ice in the ice cakes or floes on Lake Maumee than occurs on 

 any modern lakes. Ice at least 5 to 10 feet thick seems indispensable to the validity of the 

 explanation here offered. But a greater thickness of the winter's ice on Lake Maumee might 

 be expected in the glacial period when the front of the continental ice sheet was probably not 

 more than 40 or 50 miles away. It is not impossible that a more detailed study of these forms 

 would lead to more definite conclusions as to the thickness of the ice at that time. 



After the surf-worn bench offshore became strongly developed, on-shore shoving of the ice 

 ceased to be so important, but apparently it did not cease to play a part in determining the com- 

 position of the beach ridge in some localities. The middle beach ridge a mile or two east of Del- 

 phos is composed largely of clay, and the upper ridge in Van Wert was found by Mr. Leverett 1 

 to contain clay. In all probability these characters are due to the same process of on-shore 

 shoving of floating ice by the wind — an action which, though strong enough to push much clay 

 up onto the beach, was too feeble to break or displace the ridge as it had done formerly. The 

 lowering of the lake level from the highest to the middle Maumee beach reduced the offshore 

 depth and tended to favor a renewal of rampart making. But the slope back from the water's 

 edge was less favorable, being steeper than formerly, and probably caused the ice cakes to 

 break up against the beach ridge. 



OTHER GLACIAL RAMPARTS. 



Somewhat similar effects on a smaller scale may have been produced hi other locabties 

 in the Great Lakes area. Some may be associated with the Whittlesey, Arkona, and Warren 

 beaches in the flat regions in Ohio north and northeast of the district here described. In the 

 Quanicassee region at the southeast side of Saginaw Bay some of the heavy ridges may be largely 



1 Mon. U. S. Geol. Survey, vol. 41, 1902, p. 72S. 



