THE TEMPORARY MISSISSIPPI RIVER 421 



DESCRIPTION OF COURSE OF THE TEMPORARY 

 MISSISSIPPI RIVER 



The advancing Illinoian glacier in crossing into Iowa from the 

 east blocked the valley of Mississippi River and filled it with ice, 

 damming the waters of the great river and necessitating the finding 

 of a new course to the west. The stream found an opening by way 

 of the Maquoketa River Valley and flowed first westward then 

 southward through Goose Lake channel to the valley of Wapsi- 

 pinicon River, and finally over the low divide between Mud and 

 Elkhorn creeks to the valley of the Cedar at Moscow. Thence, 

 continuing southward to the junction of Iowa and Cedar rivers at 

 Columbus Junction, the combined waters of Mississippi, Maquo- 

 keta, Wapsipinicon, Cedar, and Iowa rivers, and those flowing 

 from the edge of the ice, found their pathway obstructed on the 

 one side by the great ice wall of the Illinoian ice sheet and on the 

 other by the Kansan bluffs which stand 120 to 140 feet high. As 

 the waters were unable to find an outlet, they rose and formed a 

 large lake. Finding a low divide at Columbus Junction, the surplus 

 water flowed by a devious course to the valley of Mississippi River 

 below Fort Madison. 



The course of the temporary Mississippi River is best described 

 under the following heads: (i) Goose Lake channel, (2) Mud- 

 Elkhorn-Mud Creek Valley, (3) Cedar River Valley between 

 Moscow and Columbus Junction, and (4) abandoned channel 

 south of Columbus Junction. 



GOOSE LAKE CHANNEL 



Goose Lake Channel (Fig. i), which was first described by 

 McGee,' comprises the northernmost part of the temporary Missis- 

 sippi Valley and lies between Maquoketa River on the north and 

 Wapsipinicon River on the south. The valley is well defined and 

 ranges in width from one to approximately two miles. The valley 

 walls, especially in the northern half, are cut into bedrock and rise 

 from 70 to 200 feet above the flat valley floor, except toward the 

 southern end, where they rise only about 25 feet. At the present 

 time. Goose Lake channel is occupied by two small streams. Deep 



' W J McGee, "The Pleistocene History of Northeastern Iowa," U.S. Geol. Survey, 

 Eleventh Ann. Kept., Part I (1899), p. 392. 



