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Unformatted text preview: This page last updated on 11-Nov-2011 EENS 2040 Natural Disasters Tulane University Prof. Stephen A. Nelson Mass Movements and Mass Movement Processes Mass Movements and Their Human Impacts Mass Movement is defined as the down slope movement of rock and regolith near the Earth's surface mainly due to the force of gravity. Mass movements are an important part of the erosional process, as it moves material from higher elevations to lower elevations where transporting agents like streams and glaciers can then pick up the material and move it to even lower elevations. Mass movement processes are occurring continuously on all slopes; some act very slowly, others occur very suddenly, often with disastrous results. Any perceptible down slope movement of rock or regolith is often referred to in general terms as a landslide . Landslides, however, can be classified in a much more detailed way that reflects the mechanisms responsible for the movement and the velocity at which the movement occurs. As human populations expand and occupy more and more of the land surface, mass movement processes become more likely to affect humans. The table below shows the impact of mass movement processes on human life over the last century. Year Location Type Fatalities 1916 Italy, Austria Landslide 10,000 1920 China Earthquake triggered landslide 200,000 1945 Japan Flood triggered landslide 1,200 1949 USSR Earthquake triggered landslide 12,000-20,000 1954 Austria Landslide 200 1962 Peru Landslide 4,000-5,000 1963 Italy Landslide 2,000 1970 Peru Earthquake related debris avalanche 70,000 1985 Columbia Mudflow related to volcanic eruption 23,000 1987 Ecuador Earthquake related landslide 1,000 1998 Nicaragua Debris avalanche and mudflow tirggered by heavy rains during Hurricane Mitch ~2,000 2001 El Salvador Earthquake-induced landslide 585 2006 Philippines Rain triggered debris avalanche >1100 Mass Wasting Processes 11/11/2011 Page 1 of 6 In a typical year in the United States, landslides cause over $2 billion in damages and 25 to 50 deaths. In other countries, especially less developed countries, the loss is usually higher because of higher population densities, lack of zoning laws, lack of information about mass movement hazards, and lack of emergency preparedness. Between 1969 and 1993, worldwide, landslides caused an average of about 1550 deaths per year. Knowledge about the relationships between local geology and mass movement processes can lead to better planning that can reduce vulnerability to such hazards. Thus, we will look at the various types of mass movement processes, their underlying causes, factors that affect slope stability, and what humans can do to reduce vulnerability and risk due to mass movement hazards....
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