Exam 10: Landslides and Slope Failure

-Complete the concept map for number 6.

What would you likely observe if you saw a debris flow?

Use the following information to answer the following questions. There are two main approaches to reducing the risk from landslides; hard and soft. Hard approaches involve construction of retaining walls, slope reduction, and drainage improvements. Soft approaches include zoning restrictions and land use regulations. Read the following mass wasting scenarios to determine if the event involved hard, soft, or both approaches. -City council passes an ordinance preventing a development from building on a historical landslide.

Mudflows and debris flows occur when water and loose materials move down a slope like a thick liquid.

-Complete the concept map for number 3.

Read the following USGS statement and answer this question. USGS Statement on Bluebird Canyon Landslide in Laguna Beach, California In the early morning of June 1, 2005, a landslide began moving in the Bluebird Canyon area of Laguna Beach, California. No rainfall or earthquake activity occurred during or immediately before the landslide movement. This movement is almost certainly related to the extremely heavy winter rains that occurred from December through February. Rainfall from the winter season has been slowly percolating downward through the soil and is gradually raising ground-water levels. As ground water rises, slopes can become unstable and begin to move, even if no rain is presently occurring. The current landslide might enlarge to include areas upslope or other adjacent areas within the next few days and weeks. The continuing infiltration of water from the winter rainy season could trigger other deep landslides in the southern California region over the next few weeks and months. (from www.usgs.gov/homepage/ landslide_laguna.asp) -What direction is the force of friction compared to the surface of a slope?

The term "landslide" applies to several forms of mass wasting.

-What common rockfall feature is pictured at the base of this cliff at Devil's Tower National Park in the image shown above?

Which of the three labeled locations on the topographic map above has the highest risk of mass wasting? (Numbers represent elevation in meters above sea level.)

Slumps occur when soils slowly move down a linear slope.

Creep is the rapid movement of material down a slope.

How and why does saturation change the risk associated with mass wasting of unconsolidated material?

Rockfalls happen when boulders on rocky cliffs dislodge and fall.

Read the following USGS statement and answer this question. USGS Statement on Bluebird Canyon Landslide in Laguna Beach, California In the early morning of June 1, 2005, a landslide began moving in the Bluebird Canyon area of Laguna Beach, California. No rainfall or earthquake activity occurred during or immediately before the landslide movement. This movement is almost certainly related to the extremely heavy winter rains that occurred from December through February. Rainfall from the winter season has been slowly percolating downward through the soil and is gradually raising ground-water levels. As ground water rises, slopes can become unstable and begin to move, even if no rain is presently occurring. The current landslide might enlarge to include areas upslope or other adjacent areas within the next few days and weeks. The continuing infiltration of water from the winter rainy season could trigger other deep landslides in the southern California region over the next few weeks and months. (from www.usgs.gov/homepage/ landslide_laguna.asp) -Which of the following slopes would be at greatest risk for mass wasting?

Rockslides occur when large sheets of rock break free along preexisting, structurally weak surfaces and move down a slope.

Read the following USGS statement and answer this question. USGS Statement on Bluebird Canyon Landslide in Laguna Beach, California In the early morning of June 1, 2005, a landslide began moving in the Bluebird Canyon area of Laguna Beach, California. No rainfall or earthquake activity occurred during or immediately before the landslide movement. This movement is almost certainly related to the extremely heavy winter rains that occurred from December through February. Rainfall from the winter season has been slowly percolating downward through the soil and is gradually raising ground-water levels. As ground water rises, slopes can become unstable and begin to move, even if no rain is presently occurring. The current landslide might enlarge to include areas upslope or other adjacent areas within the next few days and weeks. The continuing infiltration of water from the winter rainy season could trigger other deep landslides in the southern California region over the next few weeks and months. (from www.usgs.gov/homepage/ landslide_laguna.asp) -What prediction do scientists make in this scenario?

-What type of mass wasting is pictured above (photo courtesy USGS)?

-Which form of mass wasting would be most likely after heavy rains on a recently active volcano with significant ash deposits?

-Complete the concept map for number 4.

Use the following information to answer the following questions. There are two main approaches to reducing the risk from landslides; hard and soft. Hard approaches involve construction of retaining walls, slope reduction, and drainage improvements. Soft approaches include zoning restrictions and land use regulations. Read the following mass wasting scenarios to determine if the event involved hard, soft, or both approaches. -A homeowner has the foundation of his house reinforced to lessen the effects of liquefaction.