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Geol 1045 3/22/07Exercise #6 - Quaternary Geology of MinnesotaName____________________________In-class Exercise - Glacial Landforms and Deposits of Minnesota (12 pts)Using the Glacial Till/Topography map (GTT map), the 3-D topographic map of the Upper Midwest, the Quaternary and Bedrock Geology Maps and figures in your Geology of MN Teachers Guide, and the Minnesota at a Glance: Quaternary Glacial Geology pamphlet, answer the following:1. On the GTT map, tills deposited during the retreat of the four main glacial lobes are numbered. Does #1 represent the oldest or youngest till? ____________________(.5 pt)2. What is the glacial landform term for the elongate hills recognizable in the Wadena area (W1 west of R1), the Toimi area (R2-R1 transition), and the area SW of Mille Lacs (view 3D map for better look) what do they tell us about the glacial story? (1 pt) Landform:________________________________Story: _______________________________________________________________________________________________________________________________________________________________3. A) The east-southeast trending topographic high that runs across Wadena 2 till area has one of the highest concentration of lakes in the state outside the BWCA. What is the name of this glacial landform feature (see Fig. 3B in MaaG) _______________________________(0.5 pt)B) The lakes in the BWCA were formed by glaciers scouring depressions into the bedrock. Knowing that bedrock is 200-300 below the surface in western Minnesota, what is the likely origin of these lakes? (1 pt) _________________________________________________________________________________________________________________________________________________________4. Lake Mille Lacs is a pro-glacial lake dammed behind what moraine formed from what ice lobe? (1 pt) Moraine____________________, Ice Lobe _______________________5. Superior Lobe Till is distinctively red colored and sandy, whereas Des Moines Lobe till is typically gray and clay rich. Why would this be the case? (1 pt.) __________________________________________________________________________________________________________________________________________________________________________________________________________6. The Des Moines 2 till of the Grantsburg moraine is much more reddish colored than other Des Moines lobe tills. Why would this be the case? (0.5 pt) _______________________________________________________________________________________________________________________________7. The St. Louis Sublobe was a late surge of ice from the NW corner of the state coming off the Des Moines Lobe. One interesting characteristic of the till from this sublobe (D4) is that it changes color from gray to reddish to the southeast. What might explain this? (1 pt) _____________________________________________________________________________________________________________________________________________________________________________________________8. The locations of some of the larger glacial lakes (now drained) are shown in figure 4 of the MN at a Glance handout. How would you describe the landscape of these glacial lakebeds and what kind of sediment (clay, sand, gravel, mixed, limestone) would you expect to find in these areas? (1 pt)Landscape______________ ____________________, Sediment ____________________________9. What glacial landforms are the scalloped ridges in the Des Moines lobe (D3) especially evident south of the Iowa border (view in 3D) (0.5 pt)__________________________________________________How do features like this form? (1 pt)______________________________________________________________________________________________________________________________________10. Check out the wedge-shaped topographic high in northeast South Dakota in 3D. This feature is called the Couteau du Prairie. Do you have an idea as to how this might have formed? (1 pt) ____________________________________________________________________________________________________________________________________________________________________11. Notice that in the vicinity of Mankato, the Des Moines glacial lobe was diverted to the south, and then the Minnesota River was diverted to the north. Is there anything about the bedrock geology that might have caused this diversion? (1 pt) _________________________________________________________________________________________________________________________________________12. Notice the deeply incised landscape of southeastern and southwestern Minnesota. This is an area calledthe Driftless area. It is thought that glaciers did not pass over these areas at least in the most recent glacial episodes. What might have cause the deep erosion of the area? (1 pt)


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U of M GEOL 1045 - Glacial Landforms exercise

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