Tieshia Brown Lab 6 Assignment_Online
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Georgia State University *
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1113L
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Geography
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Apr 3, 2024
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Lab 6: Mass Movement
GEOG 1113L – Introduction to Landforms Lab
Name: Quantieshia Brown (Tieshia)
I.
Erosion Due to Gravity
1.
What is mass movement and what is the ultimate purpose of it?
Gravity is a force of erosion that influences the movement of water and causes rocks and soil to move downward. The downward movement caused by gravity is known as mass movement. Mass movement plays a major role in shaping the earth. Sand, rocks, and soil will move downhill until the slope becomes stable.
2.
What is the angle of repose? The angle of repose is the steepest angle at which loose material will not slide downward.
3.
Which of the following does not impact the angle of repose?
A.
Moisture level
B.
Weight
C.
Color
D.
Shape
E.
Size
4.
What factors increase the chance of a landslide?
Heavy rain, deforestation, and earthquakes increase the chances of a landslide. 5.
Creep is a slow form of mass movement that involves the downhill movement of soil. Bent tree trunks may be evidence of this type of mass movement.
II.
Types of Mass Movement
Use your knowledge from the video you just watched and the provided definitions to determine which type of mass movement each of the 10 pictures below shows. Highlight the appropriate answer.
1. Which type of mass movement is shown in the picture above?
A.
Avalanche
B.
Mudflow
C.
Rockfall
D.
Lahar
E.
Creep
F.
Landslide
2. Which type of mass movement is shown in the picture above?
G.
Avalanche
H.
Mudflow
I.
Rockfall
J.
Lahar
K.
Creep
L.
Landslide
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3. Which type of mass movement is shown in the picture above?
A.
Avalanche
B.
Mudflow
C.
Rockfall
D.
Lahar
E.
Creep
F.
Landslide
4. Which type of mass movement is shown in the picture above?
A.
Avalanche
B.
Mudflow
C.
Rockfall
D.
Lahar
E.
Creep
F.
Landslide
5. Which type of mass movement is shown in the picture above?
A.
Avalanche
B.
Mudflow
C.
Rockfall
D.
Lahar
E.
Creep
F.
Landslide
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6. Which type of mass movement is shown in the picture above?
A.
Avalanche
B.
Mudflow
C.
Rockfall
D.
Lahar
E.
Creep
F.
Landslide
7. Which type of mass movement is shown in the picture above?
A.
Avalanche
B.
Mudflow
C.
Rockfall
D.
Lahar
E.
Creep
F.
Landslide
8. Which type of mass movement is shown in the picture above?
A.
Avalanche
B.
Mudflow
C.
Rockfall
D.
Lahar
E.
Creep
F.
Landslide
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9. Which type of mass movement is shown in the picture above?
A.
Avalanche
B.
Mudflow
C.
Rockfall
D.
Lahar
E.
Creep
F.
Landslide
10. Which type of mass movement is shown in the picture above?
A.
Avalanche
B.
Mudflow
C.
Rockfall
D.
Lahar
E.
Creep
F.
Landslide
III.
Angle of Repose
For this activity, you will be using images of sand and gravel to determine the relative angle of repose for each material. Complete the questions that go along with the experiment, as well as the related exercises that follow. Read through the following experiment instructions on the maximum slope at which grains are stable (angle of repose) and utilize the provided images of the results to help you answer the questions. Step 1:
Slowly pour a stream of dry sand into the center of your pan or tray. Do not pack the sand with your hands. Only pour over the top of the pile using the scoop. Avoid disturbing your pile and notice the maximum angle, or steepest slope, of the dry sand. This slope is called the angle of repose.
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Step 2:
Place a pile of damp sand in the center of your pan or tray. You will probably have to scoop the sand instead of pouring it. You can gently pack the pile together but use only gentle pressure. Notice the maximum angle of the damp sand.
Step 3:
With the cup, slowly pour water onto the pile of damp sand and observe what happens to the sand pile as the sand becomes saturated.
Step 4:
Slowly pour the rounded gravel into the center of your tray or pan. Make sure your pile is large enough to get the true angle of repose!
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Step 5:
Slowly pour the angular gravel into the center of your tray or pan. Notice the angle of repose.
1.
Is the dry sand’s angle of repose smaller or larger than the damp sand?
The angle of repose for dry sand is larger than the damp sand. 2.
Which sand – dry or damp – is more likely to move individually down the slope?
The dry sand is more likely to move individually down the slope. 3.
Which sand – dry or damp – is more likely to move in large groups down the slope?
The damp sand is more likely to move in large groups. 4.
Does the saturated sand maintain the damp sand’s angle of repose?
No
5.
Which sediment condition – dry or damp – permits steeper slope angles? Damp sediment condition permits steeper slope angles. 6.
Which sediment condition – dry or damp – lends itself to the most dramatic, quickest, and therefore most dangerous style of slope failure? Explain your reasoning.
The sediment condition that lends itself to the most dramatic, quickest, and most dangerous style of slope failure is dry conditions. This is because dry sediments don’t have much cohesion and can turn into catastrophic failures such as landslides or avalanches. 7.
Suppose a house is built on a slope made of sediment. The slope is slightly greater than the angle of repose. Is this house at risk from mass movement?
Yes, it is at risk from the mass movement because the slope’s inclination exceeds the angle of repose. This means that the sediment is already unstable and prone to sliding and collapsing. 8.
Is the rounded gravel’s angle of repose smaller or larger than the angular gravel?
The rounded gravel’s angle of repose is smaller than the angular gravel. 9.
Compare the angle of repose for the dry sand and the dry gravel. What impact does grain size have on the angle of repose?
The impact that the grain size has on the angle of repose is that the larger grains have a larger angle of repose. It can form a more stable slope because of the increased interlocking and friction between the grains. However, the larger grains provide more contact which allows for better stability and resistance to movement. 10.
Compare the angle of repose for the rounded gravel and the angular gravel. What impact does grain shape have on the angle of repose?
Rounded grains have smoother surfaces which reduces the interlocking causing a smaller angle of repose. Angular grains allow for better interlocking between the grains,
Use the results of the previous experiment and the graphs below to answer the following questions. 11.
In the Seattle area, which four months experience the greatest amount of rainfall?
The four months are November, December, January, and February.
12.
In the Seattle area, which four months experience the highest number of landslides?
The four months that experienced the highest number of landslides are December, January, February, and March.
13.
Thinking about the results of your experiments (especially in Step 3), explain why the peak landslide activity occurs later than the peak rainfall activity.
The peak landslide activity occurs later than the peak rainfall activity because the rainfall loosens the soil which then results in the landslide.
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The USGS has recently developed and tested a model that establishes a precipitation threshold for the Puget Sound Area as it relates to landslides. In this area, landslides tend to occur if the precipitation amount for a 15-day period exceeds a specified level, and that 15-day period is followed by 3 days of rain at certain levels. The graph below shows the Precipitation Threshold for Anticipating the Occurrence of Landslides.
14.
Use the “Draw” tab and red pen to place and label a point on the graph for the following days, and then fill in the remaining column in the table:
Date 15-day cumulative precipitation 3-day cumulative precipitation Landslides expected? (Yes, no, maybe) 1/5/56 4.73 3.38 No 1/6/96 1.27 0.55 Maybe 1/7/96 1.33 1.27 Maybe 2/11/96 4.94 0.07 Maybe 2/21/96 5.87 0.56 Yes