Whitbeck, R. H., 1871-1939 (Ray Hughes) / The geography and economic development of southeastern Wisconsin
Chapter II. Physical features and climate of southeastern Wisconsin, pp. 5-23 PDF (4.8 MB)
I 10 GEOGRAPHY OF SOUTHEASTERN WIWCONSIN the margin of the glacier when the ice front stood in one place for a long time, while the ice and its load of rock waste kept pushing forward and melting along this near stationary front. Under such a condition great heaps of glacial iriftt were piled up in the form of mounds and hills (Fig. 4). Several ranges of these hills extend north and south in the counties with which this bulletin deals (Fig. 5). In fact, most of the hills and valleys in these counties are due to the unevenness if the glacial deposits. If the glacial drift were all removed from this re- gion, we should have a very different landscape; for the hills, lakes, swamps. and prairies with which we are sow familiar would be gone. There is scarcely a feature of tVe surface of the ground in southeastern Wisconsin which i not due to glaciers-mostly to glacial deposition. Fig. t shows how these mioraines extend parallel to the shore of Lake Michi- gan. The extensive deposits of drift prevent the waters of Lake Michigan from draining southward. By xneans of the Chicago Drainage Canal, some water from Lake Michigan is now conducted southward into the Illinois River and thence into the Mississippi. LAKE MICHIGAN IN THE PAST When the glacier advanced from the north, an arctic climate gripped this region, and the streams changed to ice and ceased to flow. Yet, along the southern margin of the glacier, melting occurred in summer, and streams flowed away toward the south. The river that flowed southward in a valley where Lake Michigan now is, carried away the water from the Lake Michigan lobe of the glacier (Fig. 6). When the cold climate became milder, and the gradual melting of the ice caused the front of the various lobes to retreat, so-called "marginal lakes" were formed. Such a lake was formed at the southern end of the Lake Michigan basin; it is known as Lake Chicago (Fig. 6). This was the beginning of Lake Michigan; as the ice melted back farther and farther, the lake increased in size until it be- came even larger than at present. During this period of en- largement, the lake had different outlets at different times. When the outlet was at Chicago, the lake surface stood at a somewhat higher level than the present surface of Lake Miclhi- ,gan, and low lands along the present margins of the lake were t Glacial drift is the term applied to all kinds of rock waste deposited by glaciers when they melt. It is made up of clay, sand, gravel, bowlders, etc.
Based on date of publication, this material is presumed to be in the public domain.| For information on re-use, see http://digital.library.wisc.edu/1711.dl/Copyright