GETSI Teaching Materials >Surface Process Hazards > Unit 3: Understanding landslide factors
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Unit 3: Understanding landslide factors

Sarah Hall (College of the Atlantic)
Becca Walker (Mt. San Antonio College)

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Summary

How do slope characteristics and magnitude of forces dictate whether or not a slope will fail? Can environmental and built characteristics change the magnitude of these forces? In this unit, students qualitatively and quantitatively consider the impact of slope angle, driving force, and frictional force on mass-wasting potential. A map activity prompts students to think about how climatic, tectonic, and geologic factors, as well as population and land use characteristics can influence mass-wasting potential.

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Learning Goals

Unit 3 Learning Outcomes

  • Students will describe three physical components that contribute to mass-wasting potential and relate these components to changing landscape characteristics.
  • Students will apply known environmental and built attributes of landscapes to compare relative mass-wasting potential for different regions.

Unit 3 Teaching Objectives

  • Cognitive: Provide a conceptual framework for identification of the physical and environmental characteristics that contribute to an area's mass-wasting potential.
  • Behavioral: Facilitate students' abilities to calculate the forces and stresses that contribute to driving and resisting forces in a geologic system.

Context for Use

The content in Unit 3 is appropriate for introductory geology, hazards, and other geoscience courses; sophomore-level courses in which geodesy and/or geomorphology/surface processes are being introduced; or non-geoscience courses where infrastructure planning, Earth hazards, and/or the nature and methods of science are being investigated. Unit 3 activities can be adapted to serve small- or large-enrollment classes and can be executed in lecture and lab settings as an in-class activity in which students work in small groups, a lab exercise, or as part of a ~2-week investigation of the use of geodesy to understand surface process hazards and decision-making using the entire Surface Process Hazards module.

This unit follows Unit 2: Reading the landscape on identifying landscape features using topographic, lidar hillshade, and aerial imagery data and precedes Unit 4: Anatomy of a tragic slide–Oso Landslide case study on determining relationships between landscape features and types of mass-wasting events. If the entire 2-week module will not be used, we recommend pairing Unit 3 with Unit 4: Anatomy of a tragic slide–Oso Landslide case study to give students the opportunity to use geodetic data to identify landscape features associated with a slow slip mass-wasting event and classify low, medium, and high-risk areas based on landscape characteristics.

Description and Teaching Materials

Before coming to class, students need to have a general understanding of the concept of hazard versus risk. As a brief preparation exercise, we suggest Activity 1.1 from the Hazard and Risk exercise, part of the InTeGrate project's Natural Hazards and Risks: Hurricanes module.

Part 1: Interactive lecture and student exercise on the physics of mass wasting

Using free body diagrams with vectors to illustrate slope angle, driving force, frictional force, and the concept of stress, students are introduced to the physical factors that contribute to mass wasting. Options for implementation include interactive lecture followed by in-class exercise or starting with the in-class exercise and interspersing individual lecture slides throughout the in-class exercise.

Part 2: Classroom activity on natural and built characteristics that influence mass-wasting potential

After an interactive lecture on cohesion and internal friction as contributors to the strength of a medium, students will review the factors that increase driving forces and increase resisting forces in the second part of the in-class activity.

Using the same study areas as in Unit 2, students consider environmental and built factors for these study areas and color a hillshade image of the study area to indicate two areas of high mass-wasting potential, two areas of moderate mass-wasting potential, and two areas of low mass-wasting potential, providing justifications for their choices. Students should be given hillshade maps to draw on. Maps illustrating various environmental (geology, geomorphology and hydrology, climate) and built (population density, land use) attributes of the study areas are displayed in the classroom during this portion of the activity.

  • Student exercise and answer key
  • Study site maps files
    • Poster pdf format
      • All study site map sets in a zipped file Unit 3 Part 2 all pdf maps (Zip Archive 263MB Oct22 20)
        Each study area PDF map set has hillshade, hillshade + rivers, satellite image, topographic, slope, and aspect maps, as well as maps related to things like population, geology, and seismic hazard. Not all the maps are needed for the assignment but are provided to increase options and flexibility.
      • Study sites individually:
        • Northern Washington (includes Seattle area and Oso Landslide, 22 March 2014); Northern Washington Maps Unit 3-4 (Acrobat (PDF) 41.3MB Oct22 20)
        • Southern Washington (includes 1998-99 Kelso slow slip event and Mount Saint Helens and its eruption and debris flow, 18 May 1980); Southern Washington Maps Unit 3 (Acrobat (PDF) 41.3MB Oct22 20)
        • Upstate New York (includes Tully Farms Road—Tully Farm slide, 27 April 1993); NY Maps Unit 3 (Acrobat (PDF) 66.1MB Oct22 20)
        • Utah (includes Salt Lake City Bingham Mine slide and Thistle–Thistle slide, 13-18 April 1983); Utah Maps Unit 3 (Acrobat (PDF) 77.9MB Oct22 20)
        • Alaska (includes Prince William Sound Earthquake-triggered underwater slide and tsunami, 27 March 1964); Alaska Maps Unit 3 (Acrobat (PDF) 41.7MB Oct22 20)
    • Unit 2 Google Earth Version Maps (Zip Archive 34.8MB May28 17) can be used again in this exercise for satellite imagery, hillshade, slope, and aspect maps of the study sites.

Part 3: Class check-in

Ask the students to break into small groups and brainstorm ideas about mass-wasting mitigation and preparedness options. Here are some potential questions to pose to the students:

  • What do you already know about the topic of mass wasting in the region where you live? Do you think mass wasting should be considered one of the main geohazards of your region?
  • Think briefly about the place where you live, what are some potential environmental and built factors that may influence landslide potential?
  • What are some mass-wasting mitigation or preparedness measures you have encountered, either in your own community or that you have heard about in other regions?
  • Given what you know now about the forces involved in mass-wasting events, do you think some of the mass-wasting case studies we have examined so far (Yungay Peru; San Fratello, Italy; Yosemite, CA) were avoidable or predictable? In what ways?
  • What strikes you the most about what you have learned about mass-wasting hazards so far?

Conclude with a brief class discussion.

Teaching Notes and Tips

  • If you have not already and would like to give your students a little more context about geodesy data in general and the lidar and InSAR methods in particular, you could use this short presentation. (Note: InSAR data are actually used in Unit 4: Anatomy of a tragic slide–Oso Landslide case study but lidar data are used throughout the module.)
    Introduction to Geodesy and Surface Process Hazards Presentation (PowerPoint 2007 (.pptx) 14.7MB Jul11 17)
    Introduction to Geodesy and Surface Process Hazards Presentation
    Click to view

  • For students who have not taken a physics/mechanics class and/or trigonometry, Part 1 of the unit could be daunting. You could consider working through some (or most, or all) of the problems together, either as a series of think-pair-shares, in small groups with frequent whole-group checkins, or as a whole group. The think-pair-share and small group strategies will likely use more class time but will cater better to differences in student completion time.
  • Similar to the landscape scavenger hunt in Unit 2, numerous strategies exist for implementing Part 2 of this unit. You may choose to have all students complete all study areas, but it is also feasible to use a format in which each group of students completes one study area, then shares their results with other groups of students who worked with different study areas. Alternatively, all study areas could be provided for students and they have a choice on which study area(s) to complete. Regardless, time should be allotted for the whole-group discussion/wrap-up to summarize results and consider commonalities and differences among study areas regarding the environmental and built characteristics that contribute to mass wasting susceptibility.
  • You can use some hands-on examples if you have a long enough class period. For example:
    • bring in sand and have students touch dry, moist, and saturated sand
    • have examples of clay, sand, and gravel for students to look at and pour water through to observe sorting, roundedness, and porosity.
    • show the effects of water on a sloping surface with the classic "Soda can experiment"
  • http://www.geo.cornell.edu/geology/classes/Geo101/structure/structure_s00.pdf
  • http://structuralgeology.50webs.com/pageb7.htm

Assessment

Formative assessment:

We have embedded several questions into the interactive lecture slides that can be used as formative assessment in real time. In addition, several questions in the in-class exercises for Part 1 and Part 2 require students to share the results of their calculations with their peers (for example, calculating masses of uniform volumes of sand, limestone, and basalt) and contribute ideas during the brainstorming portions that could be reported out to the class.

Summative assessment:

Level 1 example: Name three physical factors that change the driving forces and/or the resisting forces on a slope. For each factor that you name, state whether the factor increases or decreases the likelihood of the slope to fail.

Scoring, assuming that this is a 6-point question:
1 point for each acceptable factor named (3 points total)
1 point for each correct characterization of the factor's influence on mass-wasting potential (3 points total)

Level-2 example: Question 12 from the Part 2 in-class exercise. Students are provided with a hillshade image of one of the study areas and aerial imagery, topo map, geologic map, population density map, and seismic hazard maps from the study area. Based on their knowledge of physical factors that contribute to mass-wasting potential and how these factors are influenced by environmental and built characteristics, students shade two areas of high mass-wasting potential, two areas of moderate mass wasting potential, and two areas of low mass-wasting potential on their hillshade image. They must also provide a written justification explaining how they made their decisions regarding high, moderate, and low mass-wasting potential.
Unit 3 Level-2 Example scoring rubric (Microsoft Word 2007 (.docx) 82kB Jun11 17)

Level 3 example: Upon the conclusion of Unit 3 in-class exercises, students (likely working in pairs or small groups) will prepare a 5-7 minute "case study" presentation on one of the four study areas that they have looked at in the context of landscape features and relative mass-wasting potential. Students should plan to cover the following information in their presentation: type of mass-wasting event (schematic drawing), date/time/location of the event, damage caused by the event, description of the different factors leading to the event, and other physical parameters (volume, velocity, or duration of event).

Unit 3 Level-3 Summative Assessment (Microsoft Word 2007 (.docx) 315kB Jun13 17)
Unit 3 Level-3 Example scoring rubric (Microsoft Word 2007 (.docx) 109kB Jun11 17)

Note that we define Level 1, Level 2, and Level 3 assessments throughout the module based on Bloom's Taxonomy levels and examples of skills/tasks/actions involved in answering the question. Level 3 corresponds to higher-level cognitive tasks. Additional details in the Guide to GETSI Assessment Levels 1, 2, and 3 (Microsoft Word 2007 (.docx) 304kB Jun11 17)

References and Resources

Math teaching support

Supplementary information on geodesy and surface processes

Lidar data sources

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This module is part of a growing collection of classroom-tested materials developed by GETSI. The materials engage students in understanding the earth system as it intertwines with key societal issues. The collection is freely available and ready to be adapted by undergraduate educators across a range of courses including: general education or majors courses in Earth-focused disciplines such as geoscience or environmental science, social science, engineering, and other sciences, as well as courses for interdisciplinary programs.
Explore the Collection »