25 Jul Geology Homework
1. Which of the following was so unusual about the Oso landslide?
Debris and dirt in the 600 ft high slope spread for an entire mile across the valley
The seismic signal for the event indicated 2 phases of flow
Covered a 1-mile wide stretch of HWY 530
This earth material came off the wall and travelled across the valley in 138 seconds
2. What is regolith?
a. Raw slope left behind after a landslide
b. Chunks that continue to calve off after the landslide
c. Laser-based altimetry
d. Weathered soil on top of bedrock
3. Which of the following statements about mass movements is NOT true?
a. occur in every U.S. state
b. occur wherever there are elevated slopes
c. cause more deaths than floods worldwide
cost the U.S. billions annually
4. New technologies are key to study and estimation of geologic hazards. What is the advantage of lidar (laser-based altimetry) for estimating landslide hazards?
a. It allows geologists to determine how long ago landslides occurred
b. It allows geologists to determine how frequently landslides occurred
c. It allows geologists to model the topography at a high resolution
d. It allows for visualization and mapping of past landslides and their scars below vegetation on the landscape
5. Which of the following new technologies was NOT employed in the case of Oso?
a. Satellite imagery and aerial photography from past years that show changes in the landscape over the past century
b. Thermal cameras that identify bodies of live victims buried at the distal ends of landslides
c. Augmented reality mapping system with pre-disaster aerial photography that shows the layout of the village in 3D
d. Radar and laser beams that measure minuscule movements of the earth’s surface
6. What feature in the landscape is essentially responsible for the recurrence of landslides near Oso?
a. the high porosity of the sand and gravel that make up the 600 ft high valley wall
b. the river and its changing location on the valley floor over time
c. the village built on the slope below the valley wall
d. the position of the coastline and its wave-dominated processes
7. Which part of the Oso slide was fluidized, as detected using seismic instrumentation?
a. The toe of the slide
c. Lower half of the slope (the body)
8. Which factor was least responsible for the rapid flow of the Oso Slide?
a. The elevation of the slope
b. Clay formed an aquiclude underneath the sand and gravel on the slope, so the rainwater couldn’t sink deeper and dissipate
c. Pacific northwest rain (and lots of it!) that caused liquefaction
d. The porosity of the material
9. Which part of a landslide can not support the formation of a lake after the failure occurs?
a. The unconsolidated gaping head and scarp of a landslide
b. The toe of the slide moves out into and fills a river valley
c. The consolidated and hummocky body of the slide
10. How can you use technology combined with your knowledge to avoid buying a home on a past (and still active!) landslide?
a. Walk the property and look for cracks that run perpendicular to the downhill slope as well as hummocky (lumpy and bumpy) ground
b. All of these
c. Look at aerial photos to see how the shape of the slope changed over time
d. Download lidar for your area to look for tell-tale signs of a past slide
e. Walk the property and look for springs that leak to the surface and
suggest an aquiclude at depth
11. Which mitigation measure is sufficient for shallow slides but won’t protect from rockfalls?
a. Gabions (bioengineering and rocks): https://www.youtube.com/watch?v=Pl2cHrHpdYk
b. Catchment fence: https://www.youtube.com/watch?v=N31bJKcaJcw&index=8&list=PLFD9867338D1B7144
c. Protection barrier: https://www.youtube.com/watch?v=QrXV_AXZhF4&index=7&list=PLFD9867338D1B7144
d. Protection facility: https://www.youtube.com/watch?v=Hnl7QF1q51k&list=PLFD9867338D1B7144&index=6
12. Go to this web site, which shows a landslide map (map of mass-movement potential) for the conterminous U.S. (48 states):
Which best describes the areas that have the largest amount of landslides?
a. The potential for landslides is about the same throughout the country.
b. Landslide potential is greatest in the mountainous parts of the country.
c. The southern states, between Texas and Florida, have the highest landslide potential.
d. California has more landslide potential than any other part of the country.