When Nature Strikes: Using Models to Investigate Landslide Triggers
|In this lesson students explore the triggers of landslides using lab materials and online sources to determine the causes of landslides. They apply what they learned to the interpretation of a landslide susceptibility map.
Student worksheet(1 per student)Part 1 materials (per team):
|Developed by NESTA/Windows to the Universe team member Missy Holzer,PhD
|two 45 minute class periods (Note: more time may be needed if students have not used ArcGIS Online previously)
Student Learning Outcomes:
|Hands-on inquiry lab, research, and map interpretation
|This lesson assists learners in developing proficiency in NGSS Performance Expectation MS-ESS3-2 (Analyze and interpret data on natural hazards to forecast future catastrophic events and inform the development of technologies to mitigate their effects.)
- For background information on landslides, watch When Nature Strikes: Landslides. Also explore these topics on the Windows to the Universe website at the links listed below.
- Gather the supplies ensuring there are enough materials and Student worksheet for each team to explore the triggers of landslides.
- Locate images of past landslides and ask students to describe why some regions experience landslides, and others do not. Create a list of their ideas on the board or location where all can see. The list may include angle of repose, soil moisture content, soil compaction, stratigraphy, etc. Tell the students that their goal for the class is to identify what causes landslides using the materials provided. Mention to the students that they may use other materials if they are available.
- Brainstorm with the students what they think are the mechanisms that cause landslides. Review the list, and then tell them that it is the angle of repose which determines if the materials will fall down slope, and it varies by materials and moisture content. However, there are factors that can cause slope instability and therefore trigger the downslope movement of Earth materials. Tell the students that their challenge is to determine the angle of repose of different Earth materials under dry and wet conditions.
- Divide the class into teams of 3 or 4 students. Show them the materials they are to use create a model to identify the angle at which loose materials will slide downslope. Review how to use a protractor to measure an angle. Pass out the student handout. Ask them to read the entire procedure before beginning. They will be collecting data by placing a pile of dry aggregate (about 100 mL or more, depending on the width of the race car track) at one end of the race track while the race track is flat on the cafeteria tray, and slowly raising the end of the track with the aggregate until a bulk quantity of the aggregate slides downslope. The angle of the track is measured, and the data entered in the data table. They repeat this procedure for each of the dry aggregates. After testing the dry aggregates, students will then test damp (grains of sand damp enough that they stick together) and wet (wet enough that the sand grains separate) sand following the same protocol as the dry aggregates. Since the data will be averaged for the class, ensure the students are using the same amount of water to dampen the sand, and to wet the sand. The angle of repose for the dry angles will range between 30-45 degrees for the gravel, approximately 35 degrees for the dry sand, 45 degrees for the wet sand. See the student worksheet for the complete procedure.
- Ask students to put their data into a class data set, and using the class averages they create a bar graph of the data. Assist students with creating the graph. Discuss the results with the class, identifying ways in which their models may or may not closely approximate reality. This would be a good time to talk about the different types of mass movements including rock falls, mudflows, Earthflows, slumps, creeps, and solifluction. Locate images or brief video clips demonstrating these types of mass movements.
- Note: In Part 2 of this lesson it assumes the students previous experience with ArcGIS. If this is not the case, the attached ArcGIS 5 x 5 activity is a good entry activity, and will provide the students with the skills needed to complete this lesson. It is not necessary to create an account to complete this lesson. Students use ArcGIS Online to display the "U.S. Geological Survey - Landslide Susceptibility" data layer, and answer questions related to the data. Students may be assigned certain regions of the country to investigate. They may search for additional landslide layers such as "Aerial Imagery of Oso Slide Area" to investigate the distribution of landslide occurrences across the country. The procedure for this part of the lesson can be found on the student worksheet.
- End the lesson with a discussion about their data from the hands-on portion of the lab compared to what they are finding on the map layer. Discuss the triggers of mass movements such as earthquakes, erosion, volcanic eruptions, groundwater changes, and human activities such as blasting, construction, and deforestation.
ASSESSMENT:The results from Part 1 and Part 2 may be assessed for accuracy and quality. A formative assessment can assess students understanding of cause and effects of landslides, whereas a summative assessment can assess students understanding of the triggers of landslides using models and data in their descriptions.
LAB SAFETY:Students should wear goggles to prevent dust from the dry sand from getting into their eyes. Safe lab practices should always be utilized while performing lab investigations.
CLEAN-UP:Allow wet sand to dry and store all materials for a future lab.
Part 1: Connect with a physics or physical science teacher to tie in the physics concepts related to this activity, such as force of gravity versus friction. This lab activity could be adjusted to explore this relationship when the angle of repose increases. Students can draw models of the relationship as they try different angles to trigger slope failure.
Part 2: Students can identify a location of a recent landslide and write a news release about it, including a map using ArcGIS, results of research about the event, and suggestions for those living near landslide prone areas on how to prepare their homes from damage and how to evacuate should a mass movement occur in their area.
BACKGROUND INFORMATION:The term landslide includes many types of mass movements that vary by moisture and speed at which they move, and occurs when the gravity overtakes the friction that keeps the Earth materials stable. They can be triggered by changes in the groundwater levels, heavy precipitation, erosion, earthquakes, volcanoes, and human activity such as deforestation and blasting. Earth materials resting at the "angle of repose" are stable until a trigger causes slope failure.
RELATED SECTIONS OF THE WINDOWS TO THE UNIVERSE WEBSITE:
- AGU - The Landslide Blog
- Encyclopedia of Earth Landslide page
- TRMM (NASA Tropical Rainfall Measuring Mission) website for potential landslide areas
- USGS Landslide Hazards Program