Landslide Lab teaching notes

About these notes

Landslide Lab is a hillside and a mountain. In summer, rain soaks into a forested hill above a road and houses, and the student watches the water rise in the soil, sees where the hill is closest to sliding, changes the hill, and watches it let go. In winter, the student builds the snowpack a day at a time, reads it in a snow pit, and watches slab avalanches. Under both is one balance: the pull of the weight down the slope against the grip that holds it.

It is written for 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. That standard's clarification names mass wasting. MS-ESS2-2 names rapid landslides among the processes that change Earth's surface. No NGSS standard names avalanches; the winter side is the same balance with snow, and it is where the forecasting lives.

One period: the hill

1. Ordinary rain (5 minutes) Everyone presses Rain. Watch the side cut in the corner: the blue layer is water rising in the soil from the rock up. The hill holds: at its weakest, the grip is 1.38 times the pull.
2. Read the colors (5 minutes) The hill turns green, yellow and red. Ask why the hollow is closest to sliding when the same rain fell everywhere. Water from the whole hill drains into it underground.
3. The big storm (5 minutes) Pick the Big storm and Rain. It holds, only barely: 1.04. Ask what would push it over.
4. Change the hill (15 minutes) Clear the trees on the hollow, then the big storm again. Four slides run; the biggest falls 170 m and runs 350 m, crosses the road and reaches a house. Undo, then try cutting the road deeper instead: the bank slumps onto the road, and the hollow holds. Groups can each try one change and report.
5. The tray (10 minutes) Raise dry sand, damp sand and soaked sand in the tilt tray: about 34, 45 and 19 degrees. A little water helps, a lot hurts.

A second period: winter and a forecast

1. Build a winter (15 minutes) Click Winter. Add Snow, Clear night, Clear night, Heavy snow, Heavy snow, and play the days one at a time, looking at the snow pit after each. The clear nights grow frost feathers on top; the snow buries them. On day five six slopes let go on their own.
2. Send a skier (5 minutes) Up the trees: nothing happens, because thick trees anchor the snow and the crest is gentle. Across the bowl: the skier's weight breaks the buried layer. About 9 in 10 people caught in avalanches set them off themselves or were with someone who did.
3. Forecast (20 minutes) Click Forecast. Each student reads the last days' weather, digs three pits, rates the danger in three bands, names the problem and picks a route, then publishes. Tomorrow plays, and the check names the pit that showed the danger or the one they missed. Then the summer forecast: walk the hill, mark the houses to leave, and send the warnings.

The tray, beside the real lab

The tilt tray is the classroom slope-stability lab: a tray of material on a hinge, raised slowly, recording the angle where the first grains roll and the angle where all of it lets go. Do it for real too: a baking dish or a box lid of sand, a protractor, and a spray bottle.

• Dry sand: the first grains roll at 31 degrees and all of it goes at 34.
• Damp sand: it stands to about 45 degrees, because a little water pulls the grains together, like a sandcastle.
• Soaked sand: it flows at about 19 degrees, because the water pushes the grains apart.
• Round gravel rolls sooner than sand, at about 31 degrees. Soil held by grass roots stands steepest of all.

What students get wrong, and where the app answers it

What the app simplifies, on purpose

• The soil is one layer over rock, and a slide goes down to the rock. Real soils come in layers, and deep slides can go far below the soil.
• Rain soaks in evenly across each kind of ground. The forest's roots are set low in the range measured in real old forests, so a soaked, cleared hollow tells its story.
• Logging takes effect at once: the next storm comes a few years later, after the roots have rotted.
• The snowpack is built from a few simple rules, the same on every slope facing one way at one height. Its avalanche problems are storm slabs, wind slabs and persistent slabs only.
• The danger ratings come from the app's own cutoffs, not a forecaster's judgment. Routes are checked for slopes on them a skier would set off, not for avalanches from the slopes above.
• The hill and the mountain are made up, and their numbers are the right size, not a forecast for any real place. The app is not a tool for judging a real slope. To go into avalanche terrain, take an avalanche course, read the local avalanche forecast, and carry rescue gear with people trained to use it.

Grades 2 to 5, middle school and high school

The forecast, the sheet and the setup

Each forecast comes from the student's own seed, so no two students share an answer, unless you choose the same forecasts for everyone in Setup. Then the answer key lists the first five forecasts of each season: the true danger in each band, the problem, the routes no slope on which a skier would set off, what was hidden in each summer valley, and which houses the slides reached.

The sheet fills itself from what the student did: the tray runs, the hill's storms and slides, the winter's days and avalanches, and the forecasts. Its questions appear once the student has done what each is about, and Hand in waits until every one is answered. In Setup you choose the level, how many checks a forecast allows (2 to 5), which questions the sheet asks, and up to ten of your own. Set it up once and hand the project out as the starter.

Standards

• MS-ESS3-2: natural hazards, forecasting and mitigation; mass wasting is named in its clarification.
• MS-ESS2-2: geoscience processes at different speeds; rapid landslides are named in its clarification.
• 4-ESS2-1: weathering and erosion by water and vegetation; slope, vegetation and water are named as variables.
• 2-ESS2-1: comparing solutions that slow or prevent water from changing the land.
• HS-ESS3-1: natural hazards and human activity; mass wasting is named.
• Texas TEKS 3.10(C) names landslides among rapid changes to Earth's surface. Utah SEEd 5.1.5 names landslides among the events to design solutions for.

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