Geology 12
Name: ___________________________
Block: _________
Activity 11-2 Mass Wasting
Mix and Match:
Refer to the following list.
creep
debris flow
talus
slump
angle of repose
landslide
scarp
rock fall
oversteepening
From this list, select the terms which answer the following questions.
1.
Which terms describe some type of mass wasting event?
2.
Which terms describe features that form during mass movements and/or indicate
that a mass movement occurred at some time?
3.
Which terms relate to the role of slope in causing mass movement?
Fill in the Blanks:
4.
The steepest angle that a slope can maintain without collapsing is called the
_________________.
5.
The downslope movement of rock, soil, and other surface materials is collectively
termed _________________
6.
A steep slope is generally _________________ stable than a gentle slope.
7.
Water acts to reduce the _________________ between soil particles.
8.
A _________________ is most likely to happen on very steep slopes when rocks
break loose and tumble down.
9.
A slope that is _________________ to the dip of the underlying sedimentary
bedrock layers may be particularly unstable.
10.
The most common triggering mechanism for slope failure is the shaking due to
_________________ and excessive amounts of _________________.
11.
The accumulation of blocky debris due to rock fall is called
_________________.
12.
Rock _________________ frequently occur when a fairly coherent unit of rock
moves downslope along a bedding plane.
13.
When a _________________ occurs in soil, the block of material tends to move
by rotation, sometimes accompanied by flowing at the base of the block.
14.
When unconsolidated, non-cohesive material moves in a chaotic, disorganized
fashion, the mass movement is classified as a _________________; these are
further characterized by the type of material involved and the rate of motion.
15.
The slowest form of mass movement is appropriately called
_________________.
16.
Large pieces of unconsolidated material tend to have a steeper
_________________ than do small particles.
17.
Movement of earth material that involves more than one type of mass movement
is called _________________ movement.
18.
Highway road cuts and home building on hillsides are activity that can lead to
_________________ of slopes, thereby contributing to landslide potential.
19.
Curved tree trunks and tilted fences and utility poles are evidence that soil
_________________ has occurred and will probably continue to do so.
20.
Thin rock-slide blocks on low-angle slopes can sometimes by anchored by means of
_________________.
True/False Plus:
Indicate if the statement is true or false. If it is false, change the
underlined part(s) to make it true.
21. _____ The force of gravity is responsible for mass wasting.
22. _____ Mass wasting can only occur in steep terrain.
23. _____ Dry loose material cannot accumulate at a steeper angle than the angle of
repose.
24. _____ Water may trigger slope failures by reducing the friction between soil
particles.
25. _____ If the angle of repose of unconsolidated material is exceeded, the material
is likely to become unstable and slide or flow.
26. _____ Vegetation tends to stabilize a slope by binding soil particles together.
27. _____ Loading a slope with large amounts of excavated material tends to compact
the subsurface and increase a slope’s stability.
28. _____ In coastal areas, the undercutting of rock or soil caused by wave action
reduces the slope of sea cliffs and decreases the landslide potential.
29. _____ Once a landslide has occurred in an area, it generally stabilizes and is a
good building site.
30. _____ Removing water by installing subsurface drainage systems is an effective
means of reducing landslide potential in some areas.
31. _____ Cutting highways into mountain slopes tends to decrease the slopes and
reduce landsliding.
32. _____ Reducing the slope angle will reduce the likelihood of a landslide.
33. _____ The occurrence of subsurface clay layers tends to make a steep slope more
stable.
34. _____ In a slide, material acts as a viscous fluid or a plastic.
Drawings and Figures:
35.
Identify the type of mass movement illustrated in the following block diagrams:
a) _______________
b) _______________
d) _______________
c) _______________
e) _______________
Short Answers
36.
37.
Describe how each of the following factors influence mass wasting:
a)
Slope angle
b)
Water content
c)
Overloading (adding weight to the top of the slope)
d)
Vegetation
e)
Bedrock geology
Describe three ways in which a hillside that has a high potential for mass
movement can be stabilized.