Earth Science: Geology, the Environment, and the UniverseChapter 8:
Mass Movements, Wind, and GlaciersProblem of the WeekSlipping 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
56o? What percent would this be?
- How many landslide events occurred within week 3 at threshold temperature
56o? 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.
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Figure 2: http://geohazards.cr.usgs.gov/pubs/ofr/98-124/ |