Geol 1045
Exercise #6 - Quaternary Geology of Minnesota
3/22/07
Name____________________________
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 called
the 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) ___________________
_________________________________________________________________________________