Lab 10 - Glacial Geology of Wisconsin
docx
keyboard_arrow_up
School
University of Texas *
*We aren’t endorsed by this school
Course
3359
Subject
Geology
Date
Dec 6, 2023
Type
docx
Pages
4
Uploaded by CountSalmon1601
GLACIAL GEOLOGY OF DANE COUNTY
Instructions:
Answer the following questions
using the Glacial Geology of Dane County
(Mickelson, 1979) map
provided by your TA.
Before you begin, look over the map and
familiarize yourself with the legend, scale, etc.
1.
Note the long linear features southwest of
Madison-- the dark green regions denoted on the
map as “em”.
a) What are these features? (1pt)
-
These features are called End moraines. They are ridges (100 feet to 1 mile wide)
marking the terminal zone of a glacier. Usually is composed of till (material
deposited directly by ice) but often includes poorly sorted stratified material in
places. Surface generally hummocky, containing kettles in places, and often littered
with boulders.
b.) How are they formed? (1 pt)
-
End moraines form at the snout (edge) of a glacier, and they are mostly debris that has
accumulated by plucking and abrasion, has been pushed by the front edge of the ice, is
driven no further and instead is deposited in a heap.
c.) Which of these two features is oldest--which one formed first, the one farther
NE or the one farther SW? (1 pt)
-
The feature to the southwest is the one that formed first and is the oldest as it is
Early Woodfordian (approx. 22,000 years B.P. to 17,000 years B.P.)
d.) Which is the terminal end moraine, and which is the recessional end moraine?
(1pt)
-
The recessional end moraine is the dark green feature labelled EM and the terminal
end moraine is the pale yellow feature.
2.
Find the approximate location of the State Capitol and Bascom Hill.
a.) What are the glacial features that these buildings are on? (1 pt)
-
The state capitol and Bascom hill are roughly 43°4'W 89°23 N both buildings on a
ground moraine and a Drumlin.
b.) What does the pattern of these features (their orientation) across the map tell
you about the direction of glacial ice flow over Dane County? (2 pt)
-
By looking at the drumlin and ground moraine pattern we can assess that the
direction of glacial ice flow is moving in the northeast direction. This is noticeable
because the glacial till beings to tail off and more drumlins start to accumulate in the
northeastern direction.
3.
Note the distribution of the light blue and white lacustrine plain (lp) deposits.
These
lacustrine sediments were deposited 17,000-13,000 years ago in glacial lakes Yahara and
Middleton.
a.)
How do you know that the glacial lakes were larger than lakes we see today in
the Madison area? (2 pt)
-
When glacial material filled the Yahara valley, it dammed the Yahara River’s previous
course, allowing large glacial lakes to form as glacial melt water collected on the
2
landscape. Eventually the lakes’ waters broke through some of the dams, and the
supply of melt water decreased as the glacier retreated, leaving behind the Yahara
lakes there right now.
b.) What was the ultimate fate of glacial lakes Yahara and Middleton? (2 pt)
-
The retreating glaciers caused smoothing over the landscape that had been
previously eroded creating a new younger landscape. What is now left of the Yahara
due to the rounds of deposition, erosion, and glaciation, is a landscape influenced by
eroded bedrock foundation and pre-glacial valleys, but with topography that has
been subdued by the flattening, scouring, and valley-filling power of ice.
4.
Note the pale yellow (not bright yellow) and light green-blue units (labeled a) in the
SW portion of the map (0.5 pt each):
a.)
What are the names of these two units?
a.
Yellow unit = Bedrock, Windblown Silt and Residuum in Driftless
Area
b.
Blue unit = Alluvium, Colluvium in Driftless Area
b.)
On a geologic map, units are described in the legend from the youngest (at the
top) to the oldest (at the bottom).
Which of the two units is older?
Which is
younger?
What are the ages of these two units? (2 pt)
a.
The Yellow unit (Bedrock, Windblown Silt and Residuum in Driftless
Area) is the older of the two units being pre-woodfordian period (more
than 22,000 years old). The Blue unit is the younger unit being from the
Holocene geologic period (approximately 10,000 years B.P. to present)
c.)
Based on the presence of these two units, can you tell whether this area was
glaciated or not?
How? (2 pt)
3
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
a.
No because Bedrock, Windblown Silt and Residuum lacks evidence of glacial
depositing and since
Retreating glaciers leave behind drift composed of silt,
clay, sand, gravel, and boulders since both of these units are in the driftless
area there is no evidence of it being glaciated.
d.)
If this area was not glaciated, what term would one use to describe the area? (1
pt)
a.
Driftless area
5.
What causes the formation of the ice-contact stratified deposits listed below? (1 pt
each)
a.
Drumlins – are formed by the streamlined movement of glacial ice sheets
across rock debris, or till.
b.
Kettles - form when a block of stagnant ice detaches from a glacier.
6.
Name two types of glacial features found in Dane County that are depositional glacial
landforms. (1 pt)
-
Ice contact stratified deposits and Drumlins.
4