GEOSCI 106 Lab 8_ Glaciers- MARCH
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University of Wisconsin, Madison *
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106
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Geology
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Dec 6, 2023
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GEOSCI/ENVIR ST 106: Environmental Geology
Lab 8: Glaciers
Assignment Overview:
Glaciers are massive bodies of ice that flow under their own weight from high
elevation to low. Glacier flow represents a significant movement of fresh water in Earth’s hydrologic
cycle, and also strongly contributes to the shape of Earth’s topography. In this lab, you will explore the
processes that drive glacial flow and the ways in which glaciers affect topography.
Instructions:
Fill out each red highlighted field (_________) according to each question’s instructions.
Submission:
To submit the assignment on Canvas, use the following steps:
1.
In Google Docs, generate a PDF: File → Download as → PDF Document
2.
In Google Docs, use Share → Get Shareable Link, and copy the link address
3.
In Canvas, upload your PDF to the assignment.
4.
In Canvas, paste the link address to your Google Doc in the assignment comments.
1
Part I – How do glaciers flow?
Watch the following videos about glaciers and glacial processes and answer the following questions.
BBC:
https://www.youtube.com/watch?v=ghC-Ut0fW4o
National Geographic:
https://www.youtube.com/watch?v=WJgpDyP9ewQ
How does your glacier flow?
https://vimeo.com/133626869
1. (a) From your observations in the videos, do glaciers flow fastest at their sides (i.e., next to the valley
side walls) or in the middle (i.e., away from the side walls)? (1 point)
_After watching the vimeo of the New Zealand glacier I found that glaciers flow the fastest in the middle
away from the side walls.________
(b) In the place(s) where the glacier is flowing more slowly, what makes the ice move more slowly there?
(1 point)
_I think the ice moves slower by the valley walls because there is more friction on ice and rock than there
is with ice on ice in the middle.________
2
Figure 1.
Phase diagram of water. This shows the temperatures and pressures at which H
2
O is a solid
(ice), a liquid (water), and a gas (water vapor).
2. Why can adding pressure to ice make it melt? To accompany your explanation, consider the phase
diagram of water in Figure 1. Here, point A indicates a condition that is at atmospheric pressure (1 atm
on the y-axis) and a temperature below freezing (less than 0°C on the x-axis), conditions like those we
experience in winter in Madison. Download this diagram from the Canvas module (see the file named
“Water phase diagram.png”), and on it draw an arrow starting at point A that shows how ice can melt
under an increase in pressure but no change in temperature, even while remaining at temperature below
0°C. (You are welcome to use whatever application you like to draw an arrow. Recall from an earlier lab
that one way to do this is here in this Google Doc: Place your cursor where you’d like the image to be,
then go to Insert > Drawing > New, and drop the image you’d like to draw on in the resulting window).
Paste your diagram here. (2 points)
Paste your phase diagram here: _
________
Explain why increasing pressure can make ice melt here: _In chemistry we learn that pressure and
temperature are directly related so as one increases, the other also increases. It is because there are more
particles in a tighter space moving around faster and faster which in turn melts the ice.________
3. Do glaciers flow faster with or without meltwater at the base? Why is this? (2 points)
3
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_Faster because as the water melts at the bottom of the glacier it provides a sort of lubricant for the ice to
slide on the ground.________
4. In these videos, crevasses are visible at the surface of the glaciers, indicating that the ice is brittle (i.e.,
it breaks and fractures), and therefore behaves like a solid. This seems to contradict the observation that
glaciers flow downhill, which indicates that the ice behaves like a fluid. What physical processes allow
the ice to flow downhill like a fluid, even though it cracks like a solid at the surface? (2 points)
_It still moves down hill due to the melting water at the base of the glacier that gives it lubrication. It is
the same idea that if you were on ice skates at the top of a hill made of ice, the water melted by your
blades on the surface of the ice cause you to slide downhill.________
Part II – Glacial landforms
5. Describe two processes by which a glacier moves rock or sediment (i.e., erosional or depositional
processes) and the visible evidence left behind by these processes. (2 points)
_One way is through abrasion as the ice at the lower end of the glaciers have rocks and debris inside
making the face rough which takes material off of mountain walls as it passes. Another process is called
plucking when two ice cracks meet up at the bottom of a glacier and pull large amounts of rock with it as
it flows downhill.________
6. In the Canvas lab module, download the Generalized Glacial Geologic Map of Dane County by D.M.
Mickelson, an emeritus professor of UW-Madison. (This can also be found at
https://wgnhs.uwex.edu/pubs/es043plate01/
). What do the black arrows on the map represent? (1 point)
_The small black arrows represent the direction of drumlins, which are small hills that are believed to
have been formed by the streamline movement of a glacier.________
7. Go to Google Maps (
https://www.google.com/maps
), toggle on Terrain mode, and zoom out to the
point where you can see all of Dane County. Zoom in to a few of the streamlined features that are
represented by the black arrows in the Mickelson (2007) glacial geologic map. Pick one of these, and
describe its shape. How can the shapes of these features be used to indicate which direction the ice was
flowing when it was forming these features? (2 points)
4
_On google maps there is a spot west of Sun Prairie where there is said to be black arrows and on the
terrain map you can see evidence of this as there are tree lines and small ponds that follow the same line
that the black arrows did.________
8. Bascom and Observatory Hills (labeled as 41 on the glacial geology map) are on a drumlin. On
Observatory Hill there is a Precambrian metamorphic rock known as a glacial erratic, visible in Google
Street View (
https://goo.gl/maps/24nAgs2QYvWXvVfu8
). A close examination of the rock’s
composition shows that it is not from bedrock around here, but rather came from a metamorphic outcrop
in Canada. How did this rock make this long journey from Canada to our campus? (1 point)
_If you follow the arrows on the map they all point to the southwest. This means the glacier came from
the northeast which explains how the boulder said to come from Canada ended up in Madison.________
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