ESO 170 Material past the midterm
1. Why is a 5 m-high tsunami wave much more devastating than a 5 m-high wind wave at the coastline?: A 5 m-
high tsunami wave is more devastating because it carries a huge volume of water, travels fast, and floods inland for
longer distances, causing massive destruction, unlike wind waves that break quickly and affect only the surface
2. What are factors that increase the likelihood of a landslide occurring?: - Increasing the slope angle
- Add to the mass of the material
- Shaking the slope
- Reducing friction
3. How does increasing the slope angle increase the likelihood of a landslide occurring?: Increasing the slope angle
makes the slope steeper, which increases the downslope gravitational force acting on the material. This reduces the
stability of the slope by decreasing the resisting forces (friction and cohesion), making it more likely for the material to
overcome these forces and result in a landslide.
4. How does adding mass to the slope increase the likelihood of a landslide occurring?: Adding mass to a slope,
such as water, buildings, or vegetation, in- creases the gravitational force acting on the slope. This additional load
increases the downslope driving force, making it more likely to exceed the resisting forces (friction and cohesion),
thereby triggering a landslide.
5. How does shaking the slope increase the likelihood of a landslide occur- ring?: Shaking the slope, such as during
an earthquake, disturbs the stability of the slope by temporarily reducing friction and cohesion between particles. This
can weaken the slope material, destabilize it, and trigger a landslide by increasing the downslope driving forces relative
to the resisting forces.
6. How does reducing friction for the slope increase the likelihood of a land- slide occurring?: Reducing friction
on a slope decreases the resisting force that holds the material in place. With less friction, the downslope driving force
becomes more likely to overcome the resisting force, increasing the likelihood of a landslide.
7. Explain how the Case of Vargas, Venezuela (1999) shows how of water increases the likelihood of landsliding:
Water seeps into soil or rock, filling pore spaces and increasing pressure, which reduces friction and weakens slopes.
The Vargas Tragedy (Venezuela, 1999) saw heavy rains saturate slopes, causing catastrophic debris flows.
8. Explain how the case of Oso, Washington (2014) shows how of the addition of water weight increases the
likelihood of a landslide occurring: Water adds weight to a slope, making it unstable and more likely to fail. In Oso,
Washington (2014), rainfall saturated the ground, adding weight that triggered a deadly landslide.
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, ESO 170 Material past the midterm
9. Explain how the case of Oso, Washington (2014) shows how of water erosion can increase the likelihood of a
landslide: The 2014 Oso landslide in Washington demonstrated how water erosion can increase landslide likelihood by
undercutting the base of a slope. The nearby Stillaguamish River eroded the slope's toe over time, removing support and
destabilizing the slope. Heavy rainfall saturated the soil, further reducing cohesion and increasing its weight, ultimately
leading to the catastrophic collapse.
10.Where on a landslide would the head scarp be located?: The head scarp is located at the top of the landslide,
where the ground has broken away, forming a steep, exposed surface.
11.Where on a landslide would the transverse cracks be located?: Transverse cracks are located across the surface
of the landslide, typically behind the main scarp, running perpendicular to the direction of movement.
12.Where on a landslide would the toe be located?: The toe of a landslide is located at the bottom, where the
displaced material accumulates and spreads out.
13.Where is the basal failure surface of a landslide?: The basal failure surface is located at the base of the landslide,
where the sliding material separates from the stable ground below.
14.What type of landslide is depicted in the Module D practice question?: Ro- tational landslide
15.Why did many people choose not to evacuate Montecito on the night of the disaster, even when
advised?: Many Montecito residents chose not to evacuate before the January 2018 mudslides because they
underestimated the
danger, believed warnings were exaggerated, or were confused by evacuation maps. Some also felt safe because their home
were outside the mandatory evacuation zones.
16.What were the triggers and preconditions for the 1999 Varga (Venezuela) debris flow: Triggered by rainfall
Pre-conditions of this disaster were repeated tectonic uplift and weak metamorphic bedrock
17.What was the precondition and trigger for the 2008 China landslide?: Steep angles which caused a landslide
after an earthquake
18.What were the preconditions and the triggers for the 2007 Pe Ell Landslide in Washington State: Trigger was
rainfall of the great coastal storm of 2007
Pre-conditions include the surface geology and steepened slopes due to the under- cutting of the slope during highway
construction and logging of the hill
19.Explain the 2018 Palu earthquake mudslide: a lateral spread triggered by solid liquefaction due to human
2/
11
1. Why is a 5 m-high tsunami wave much more devastating than a 5 m-high wind wave at the coastline?: A 5 m-
high tsunami wave is more devastating because it carries a huge volume of water, travels fast, and floods inland for
longer distances, causing massive destruction, unlike wind waves that break quickly and affect only the surface
2. What are factors that increase the likelihood of a landslide occurring?: - Increasing the slope angle
- Add to the mass of the material
- Shaking the slope
- Reducing friction
3. How does increasing the slope angle increase the likelihood of a landslide occurring?: Increasing the slope angle
makes the slope steeper, which increases the downslope gravitational force acting on the material. This reduces the
stability of the slope by decreasing the resisting forces (friction and cohesion), making it more likely for the material to
overcome these forces and result in a landslide.
4. How does adding mass to the slope increase the likelihood of a landslide occurring?: Adding mass to a slope,
such as water, buildings, or vegetation, in- creases the gravitational force acting on the slope. This additional load
increases the downslope driving force, making it more likely to exceed the resisting forces (friction and cohesion),
thereby triggering a landslide.
5. How does shaking the slope increase the likelihood of a landslide occur- ring?: Shaking the slope, such as during
an earthquake, disturbs the stability of the slope by temporarily reducing friction and cohesion between particles. This
can weaken the slope material, destabilize it, and trigger a landslide by increasing the downslope driving forces relative
to the resisting forces.
6. How does reducing friction for the slope increase the likelihood of a land- slide occurring?: Reducing friction
on a slope decreases the resisting force that holds the material in place. With less friction, the downslope driving force
becomes more likely to overcome the resisting force, increasing the likelihood of a landslide.
7. Explain how the Case of Vargas, Venezuela (1999) shows how of water increases the likelihood of landsliding:
Water seeps into soil or rock, filling pore spaces and increasing pressure, which reduces friction and weakens slopes.
The Vargas Tragedy (Venezuela, 1999) saw heavy rains saturate slopes, causing catastrophic debris flows.
8. Explain how the case of Oso, Washington (2014) shows how of the addition of water weight increases the
likelihood of a landslide occurring: Water adds weight to a slope, making it unstable and more likely to fail. In Oso,
Washington (2014), rainfall saturated the ground, adding weight that triggered a deadly landslide.
1/
11
, ESO 170 Material past the midterm
9. Explain how the case of Oso, Washington (2014) shows how of water erosion can increase the likelihood of a
landslide: The 2014 Oso landslide in Washington demonstrated how water erosion can increase landslide likelihood by
undercutting the base of a slope. The nearby Stillaguamish River eroded the slope's toe over time, removing support and
destabilizing the slope. Heavy rainfall saturated the soil, further reducing cohesion and increasing its weight, ultimately
leading to the catastrophic collapse.
10.Where on a landslide would the head scarp be located?: The head scarp is located at the top of the landslide,
where the ground has broken away, forming a steep, exposed surface.
11.Where on a landslide would the transverse cracks be located?: Transverse cracks are located across the surface
of the landslide, typically behind the main scarp, running perpendicular to the direction of movement.
12.Where on a landslide would the toe be located?: The toe of a landslide is located at the bottom, where the
displaced material accumulates and spreads out.
13.Where is the basal failure surface of a landslide?: The basal failure surface is located at the base of the landslide,
where the sliding material separates from the stable ground below.
14.What type of landslide is depicted in the Module D practice question?: Ro- tational landslide
15.Why did many people choose not to evacuate Montecito on the night of the disaster, even when
advised?: Many Montecito residents chose not to evacuate before the January 2018 mudslides because they
underestimated the
danger, believed warnings were exaggerated, or were confused by evacuation maps. Some also felt safe because their home
were outside the mandatory evacuation zones.
16.What were the triggers and preconditions for the 1999 Varga (Venezuela) debris flow: Triggered by rainfall
Pre-conditions of this disaster were repeated tectonic uplift and weak metamorphic bedrock
17.What was the precondition and trigger for the 2008 China landslide?: Steep angles which caused a landslide
after an earthquake
18.What were the preconditions and the triggers for the 2007 Pe Ell Landslide in Washington State: Trigger was
rainfall of the great coastal storm of 2007
Pre-conditions include the surface geology and steepened slopes due to the under- cutting of the slope during highway
construction and logging of the hill
19.Explain the 2018 Palu earthquake mudslide: a lateral spread triggered by solid liquefaction due to human
2/
11
