Introduction to Mass Movement Charity I. Mulig-Cruz

Definition Mass Movement (aka mass wasting) Refers to the downslope movement of material under the direct influence of gravity.

Caution “… although many people, including geologists, use the term (landslide), the word landslide has no specific definition in geology. Rather, it should be considered as a popular nontechnical term to describe all relatively rapid forms of mass wasting, including those in which sliding does not occur.” Earth Science by Tarbuck and Lutgens

Cause vs. Trigger of Mass Movement Triggers Controlling force of mass movement. There is only one cause – GRAVITY. An event that initiates the downslope movement. Not the sole cause of the mass wasting event, but just the last of many causes.

Triggers of Mass Wasting Oversaturation of material with water Torrential rain, melting of snow caps, over irrigation, leaking septic tanks Over-steepening of slopes Angle of inclination approaches (or is greater than) the angle of repose Under-cutting, road excavation, mining Overloading

Triggers of Mass Wasting Removal of anchoring vegetation Or replacement with vegetation with shallower root systems Ground vibrations Natural (earth quake and volcanic eruptions) and man-made (construction work and passing vehicles)

Factors Affecting Mass Wasting Slope Angle/ Steepness of Slope Weathering and Climate Water Content Vegetation Geomorphology/ Nature and structure of slope materials

Classification of Mass Movement Rate of Movement Type of Movement Materials Rapid/ Fast Slow Fall Slide Flow Creep Solifluction Rock Debris Soil