R. Ohio R. A. This map shows the Great Lakes and the familiar present-day pattern of rivers. Quaternary ice sheets played a major role in creating this pattern. sauri R. Upper Lower Missouri R. Teays R. ohio B. Reconstruction of drainage systems prior to the Ice Age. The pattern was very different from today, and the Great Lakes did not exist. Mississ Red R. R. Missouri Mississippi R. Red R.

Compare the two parts of Figure 4.20 and identify
three major changes to the flow of rivers in
the central United States during the Ice Age.