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39 Cards in this Set
- Front
- Back
What does gravity cause?
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The downward movement of landslides and subsiding ground.
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What are some external causes of slope failure?
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1) Steepeing the slope by faults or fault movements.
2) Removing support from low on the slope. 3) Adding mass high on the slope as in sediment deposition. |
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What is the cause of a landslide?
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Loading the head and reducing the toe.
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What is an internal cause of slope failure?
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Inherently weak materials such as clay.
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Whats the problem with clay?
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It is too small, and too thin and weathers easily under low pressure and low temperature.
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Where is most feldspar found and how is it formed?
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Found in granite and is formed under high pressure and temperature.
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How does unloading occur?
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Clay breaks off through weathering and pressure is removed.
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What does the mechanical stregnth of rock depend on?
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10-15% of the rock with the smallest grain size.
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What is another internal cause of slope failure?
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Water
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What are some roles of water?
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It is absorbed and adsorbed by clay materials. Since it is polar it can be effected electrostatically.
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How does water cause slope failure?
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Water can dissolve some of the minerals that bind rocks as well as eroding loos materials.
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How does water weaken earth materials?
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1) Decreasing cohesion
2) Subsurface erosion 3) Creating pressure in pore spaces. 4) Weight 5) Interplay of clay materials |
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What is another internal cause of slope failure?
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Decrease in cohesion
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What is the final internal cause of slope failure?
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Adverse geologic structures.
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What triggers mass movements?
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Heavy rains, Earthquakes, Thawing frozen ground, construction projects of humans.
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What is the slowest but most widespread type of mass movement?
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Creep
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What is creep and where are its effects most noticible?
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Movement of soil and upper most bedrock, its effects are most noticible on trees and fences.
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How does rock and soil move by creep?
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Expansion and contraction, the soils swell and then shrinks
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Why is the contraction occuring?
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Because of the pull of gravity
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What is the shrinking caused by?
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The soil thawing, drying, cooling and gravity pulling.
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What is a fall?
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Elevated rock masses seperate along joints, bedding or other weaknesses.
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What are the main causes of a fall and how does it ususally occur.
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Gravity, earthquakes and people, occurs extremely rapidly and under dry conditions.
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What are slides? What is the main cause of them.
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Movements above one or more failure surfaces. Gravity is the main cause.
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What is a rotational slide and how does it typically occur?
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Slump is a roational slide in which the head moves down and typically backwards.
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What are transitional slides?
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Masses that move down and out by sliding on surfaces of weakness.
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What are the three outcomes of transitional slides?
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1) They remain basically coherent.
2) They may deform and disintegrate. 3) They may spread laterally when the underlying material fails and flows.q |
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How do flows behave and what are some different types of them?
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They move like fluids, names for them are Loess flow, earthflow, mudflow, debris avalanche, lahars.
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In what ways do avalanches move?
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Creep, fall, slide and flow
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How do avalanches occur?
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From triggers such as earthquakes or people, accumulation high on the slopes loads the head and sets the stage for failure.
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What is the top speed for an avalanche?
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230 mph
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What are the three outcomes of transitional slides?
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1) They remain basically coherent.
2) They may deform and disintegrate. 3) They may spread laterally when the underlying material fails and flows.q |
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How do flows behave and what are some different types of them?
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They move like fluids, names for them are Loess flow, earthflow, mudflow, debris avalanche, lahars.
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In what ways do avalanches move?
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Creep, fall, slide and flow
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How do avalanches occur?
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From triggers such as earthquakes or people, accumulation high on the slopes loads the head and sets the stage for failure.
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What is the top speed for an avalanche?
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230 mph
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What is subsidence?
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The ground moves down and either sags gently or drops catastrophically as voids.
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What material often involved with subsidence causes the collagpse of roads built on top?
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Limestone
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What in rock helps support the weight of overlying rock?
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Fluids
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What happens when water or oil are squeezed or pumped out of pores in rock or grains?
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The pore pressure casues the grains to move together and they are compacted.
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