Problem of the Week

Chapter 8: Mass Movements, Wind, and Glaciers

Problem of the Week

Slipping and Sliding: Landslides

Extra! Extra! Read all about it!

The Oregonian

Landslides again threaten to close portion of U.S. 101

Saturday, January 8, 2000

"An area along U.S. 101 about 10 miles north of Florence continues to plague travelers with landslides that might close the road through the weekend.

For the second time in a week, more than 50 yards of mud and rocks slid across the highway Thursday and kept it closed through early afternoon Friday. Although the highway was passable later Friday early afternoon, Oregon Department of Transportation officials advised people to find alternate routes."

Muzi.com News: [LatelineNews: 3/12/1998]

Jiangxi Landslides Killed 4 People

"Four people were reportedly killed and three others seriously injured late Sunday night and early Monday morning after they were hit by two landslides in the city of Ruijin in the southern Jiangxi Province, China Daily reported.

The landslides occurred after the area had been pounded by heavy rainfall for three days, affecting 82 villages in 11 townships, blocking local roads and shutting down telecommunications services."

The Atlantic Monthly

January 1, 1999

"The Liquid Earth" by Brenda Bell

"Ground failures of various sorts occur in every state; according to the National Research Council, they annually cause more deaths (twenty-five to fifty) and greater economic loss (roughly estimated at $1.5 billion) than all other natural hazards combined."

Problem:

Background Information

Take a look at these headlines and news excerpts. They are indicative of the fear, unpredictability, and devastation that are characteristic of mass movements, such as land and mudslides. Pretty nasty events, and costly too, don’t you think?

As human populations grow, and our desire to build and live in areas vulnerable to mass movements increases, the risks of economic loss and loss of life will continue to rise. In an effort to reduce the risk from landslides, United States Geological Survey scientists monitor and study conditions in steeply sloped areas. In 1998 a study was performed in an effort to determine the "threshold temperature" after which landslides are most likely to occur in connection with winter snow-melt. The ability to predict the threshold temperature allows the USGS, and other governmental agencies, to issue warnings of increased potential for landslide activity in areas that are susceptible to snowmelt landslides. The early warnings have the potential to save lives and possibly prevent destruction of property.

Analysis:

The graph below was included in the study to present the data collected. Look at the graph, the key, and the explanation below it to determine the following.

First let’s practice reading the graph:

How many landslide events occurred within week 1 at threshold temperature 56^o? What percent would this be?

How many landslide events occurred within week 3 at threshold temperature 56^o? What percent would this be?

Look at the line that records the number of events that occurred within week 3. After the occurrence of which threshold temperature did 21 of the events occur?

At what threshold temperature does the 2-week line intersect with the 3-week line and how many events had occurred at that temperature?

Now,

Imagine you are a member of the research team that performed this study and you must make a recommendation to agencies about when to warn the citizens living in your community about the potential risk of landslides. Following the occurrence of which threshold temperature would you recommend issuing warnings and what evidence would you use to support your recommendation?

Ask your teacher to let you know if your findings agree with what the actual researchers found.