Types of Mass Movement

Why is mass wasting important? What Is Mass Wasting? Mass movement or mass wasting refers to several processes that have the following in common: 1. Downslope movement of rock or weathered material 2. Movement is due to pull of gravity 3. There is no flowing medium (water, air or ice) that carries the material *Generally, mass wasting occurs when gravitational forces exceed frictional or shear forces (strength) of material.   Why is mass wasting important? Processes represent a significant hazard to property and people Need to identify where and under what conditions these processes occur Avoid construction in areas prone to mass wasting or attempt to prevent mass wasting

Driving force behind Mass Wasting: 1. Weight (amount) of material on slope 2. Resistance of the material 3. Steepness of slope 4. Saturation (water holds particles together, but too much water acts as a lubricant) 5. Biological factors such as vegetation 6. Triggers (weakened planes) Possibly triggered by: 1.  Earthquake 2. Construction work (blasting) 3. Flooding   

How are Mass Movement events classified? 1. Type of material that moves 2. Nature of movement (slide, flow, or fall) 3. How fast material moves: Creep: slow and steady movement of small particles Flows (mudflows): materials move as though they are a thick liquid Slides: rapid movement of a block of rock, soil, and debris; also called debris avalanches Slumps: rapid slide of materials along a curved surface Avalanches: landslides that occur in mountainous areas with thick accumulations of snow Rock falls: Sporadic, rapid movement of large, loose materials  

Free movement Earth material move in blocks, creating large pile of debris Solids mix with water and move downward in a circular pattern, spreading out

Fall Avalanche Slide Flow Slump Creep Velocity of Movement

Most common mass wasting types Avalanche Slump Creep Flow Rockslide Deposits of Mass Wasting Mass wasting produces sediment deposits. These deposits commonly contain a wide range of sizes of particles (they are "unsorted"). The deposits do not show layering (they are "unstratified")

How do mass movements affect people? Humans contribute to mass movement through activities such as road and building construction and poor land maintenance (ie septic tanks) Humans and property are also in potential danger of mass movement events, especially in areas of steep slopes, supersaturated soils, and natural triggers like tectonic plate movement How do we prevent mass movement? This is NOT possible. A better question is “how do we lessen the effects” of mass wasting? 1.      Remove weight from slope 2.     Vegetation 3. Drainage systems to divert running water 4.     Cables and anchoring systems (steel likes and fences)

Pertinent Web Sites Disaster Finder (NASA) A complete index to the best disaster Web sites on the Internet. Geologic Hazards—Landslides (USGS) A great site from the Landslides Hazards Group of the United States Geological Survey (USGS) that conducts research, gathers information, responds to emergencies and disasters, and produces scientific reports and other products for a broad-based user community. Glossary of Soil Science An extensive glossary of soil science terms from the Canadian Soil Information System. Landslides (USGS) Landslide information from the United States Geological Survey (USGS). Mass Wasting Links This Central Michigan University site maintained by Dr. Mark Francek lists several good links to Web sites containing information relative to topics discussed in the chapter. Mass Wasting Links (Houghton Mifflin) Links to several mass wasting sites, including class lecture notes, arranged by topic. National Cooperative Soil Survey National Cooperative Soil Survey provides a dynamic resource of soils information for a wide range of needs. National Landslide Information Center (USGS) The National Landslide Information Center (NLIC) is responsible for distributing information about landslides to the lay public, researchers, planners, and local, state, and federal agencies. Recent Landslide Events (USGS) A listing with descriptions and explanations of recent landslide events from the United States Geological Survey (USGS).