Geocentric Science

Mass wasting is defined as the downhill movement of sediment due to gravity. There are several important forces that determines whether or not an object will move. There is a downward force and an opposing frictional force (upward force). Depending on which force is greater (the downward force or the frictional force), will determine if the object or sediment will move. If the frictional force is greater than the downward force, the object remains stationary.

1. How does the slope of a hill affect mass wasting?

   Answer: As the slope gets steeper, there is a greater downward force. This increases the chances of mass wasting.

2. What is the angle of repose?

   Answer: The angle of repose is defined as the steepest angle that sediment will remain stable. The size, shape, and density of the sediment influence the angle of repose. Once the angle is exceeded, mass wasting (or a landslide) will occur.

3. What is a landslide?

   Answer: A landslide is a general term used for any mass wasting event. There are several types of both rapid mass wasting as well as slow mass wasting.

4. What are examples of rapid mass wasting?

   Answer:

   - Rockfalls: Rock pieces are broken off by weathering and fall down the steep slopes of a mountain. Rockfalls are common along highways or in mountainous areas.

   - Rockslides (or Block slides): Occur on less steep slopes than rockfalls. During a rockslide, debris slides downward and are often triggered by heavy rains (the water provides a smooth surface for the debris to move over) or earthquakes (sediment is broken apart and become unstable).

   

   - Slumps: Masses of rock or soil slides down the cliff in one slab (or piece). Slumps occur because the sediment slides down a curved plane of weakness.

   - Mudflows: Are mixtures of rock, soil and water. Mudflows typically occur after heavy rains and over surface that has little or no vegetation (the vegetation holds the soil in place).

5. What are examples of slow mass wasting?

   Answer: Slow mass wasting typically occurs in more humid areas where the slopes are covered in vegetation. The vegetation holds the soil and sediment together. However, mass wasting will occur, but will occur much more slowly.

   - Earthflow: A shallow layer of soil and sediment slowly slides downwards.

   

   - Soil Creep: Vegetation and surface features (such as fences and walls) moves downhill extremely slowly. Frost action is one of the main contributors to soil creep.