Glacial Erosion - Freeze-thaw, Plucking

Question # 00574221 Posted By: dr.tony Updated on: 08/13/2017 09:53 AM Due on: 08/13/2017
Subject Geology Topic General Geology Tutorials:
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Experiment 1: Glacial Erosion: Freeze-thaw, Plucking, and
Abrasion
As Agassiz theorized, flowing glaciers carry rocks that scrape across surface bedrock. Glaciers
erode rock three ways. One is by freeze-thaw weathering when glacial meltwater enters
cracks, freezes, and causes the rock to break up. When glaciers move, they may pluck pieces
of larger rocks by clipping a corner, and then taking that piece along with it. The loosened
bedrock scratches underlying bedrock with glacial striations, which are parallel grooves.
Besides freeze-thaw and plucking, abrasion can occur when rocks at the base of the glacier
wear away, polish, scratch, or otherwise mark the bedrock when the advancing glacier grinds
the bedrock surface. In this experiment, students will build a glacier to examine glacial flow,
deposition, and formation of glacial striations. Materials Cardboard (Lab Kit Lid)
Gravel
Ice Mold
Protractor
Ruler
Sand Soap
*Freezer
*Stopwatch
*Water
*You Must Provide. Procedure
1. Measure out 90 mL of sand and 90 mL of gravel and mix.
2. Pour sediment mixture in ice mold. Fill the ice mold with water and freeze.
3. Once the block is fully frozen, take your “glacier” out of the freezer and place it on a
flat surface.
4. Let ice melt enough (about one hour), so it can slide and sediment is exposed.
5. Place the glacier on top of the bar of soap and push exposed sediment one end of
soap to the other. Press firmly enough to make indentations but not destroy the soap.
6. Draw markings left behind on soap in Table 1.
7. Place glacier on top of lab kit lid. Place the cardboard on a slope so that the top of the
slope is elevated by 1 inch.

© 2014 eScience Labs, LLC.
All Rights Reserved 8. Let ice melt and record water flow patterns in Table 1.

9. Note location of sediment left after melting in Table 1. Table 1: Observations
Markings of Soap Water Flow Patterns Sediment Deposition Post-Lab Questions
1. What were the visible features resulting from the movement of the glacier on the
soap and the sloped surface? 2. How did the sediment get into the ice? Is this an example of erosion, weathering, or
both? 3. Explain how the glacier moved and why? If it didn’t move, why? 4. Can you determine the direction of glacial movement from sediments deposited by
meltwater in glaciers found in nature? Is this the same for your glacier? Explain. © 2014 eScience Labs, LLC.
All Rights Reserved 5. How else can you tell the direction of glacial movement? 6. Did glaciers ever come through the area that in which you live? How do you know—
what features express the presence or absence of glaciers? 

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All Rights Reserved
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  1. Tutorial # 00571991 Posted By: dr.tony Posted on: 08/13/2017 09:53 AM
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