What causes Mass Movement?

1. What causes Mass Movement? Landforms can change through the processes involving Wind, ice, and water and through the force of gravity.

2. Variables that influence Mass Movement • Material’s weight • Material’s resistance to sliding or flowing • Trigger (earthquake) • Water – too much or too little Movement occurs when the forces working to pull material down a slope are stronger than the material’s resistance to sliding.

3. Creep Slowest movement Observe structures to determine If creep has occurred

4. Flows • Flow as if it was liquid • Common in volcanic regions as lahars • Can happen in semi-arid regions with sudden • Rapid intense rainfalls – southern California

5. Landslides • Happens when a thin block of loose soil separates from the bedrock. • Common on steep slopes • Often triggered by earthquakes

6. Slump • When the mass of material in a landslide rotates and slides along a curved surface. • Can be triggered by earthquakes

7. Avalanches • Landslide where there is thick accumulation • of snow. • Usually occur on slopes at least 35 degrees • 10,000 / year • Snow can melt and refreeze into a layer of ice. When • snow falls on top it can become too heavy and slide • down as an avalanche.

8. Rock Falls Common on road cuts and rocky Shorelines Prevention: road walls, vegetation And rock cages.

9. Mass Movement Prevention • Digging trenches to divert water around a slope and control drainage. • Steel nets & fences • Educate people about the problems of building on steep slopes

10. How to prevent soil erosion • Reforestation – trees reduce the flowing water. Roots absorb the water & hold the soil together. • Grasses & vegetables – grass has thick roots, wind carries the topsoil away without grass. • Contour Plowing – plowing across a slope following its elevation contour lines. Creates a water break to prevent rill erosion. • Strip Cropping – alternating planting grasses & crops. Grasses that remain after the crops hold the soil together.

11. Wind Erosion & Transport • Suspension – strong wind cause particles • to stay airborne for long distances • Saltation – bouncing motion of particles. Most sand transport by wind. • Abrasion – particles rub against the surface of rocks. Rocks become pitted, grooved, and polished. Rocks shaped by wind –blown sediments are called ventifacts.

12. Where is wind erosion a problem in North Carolina?

13. Glaciers – Two Types Valley Glaciers – occurs when a growing ice mass becomes too heavy to maintain its shape & begins to flow like a thick liquid. Continental Glaciers – cover broad continent sized areas

14. Anatomy of a Glacier