Mass Wasting Earth Science Tarbuck and Lutgens Chapter 4 Pages 102 112 Mass Wasting The downslope movement of rock regolith and soil under the direct influence of gravity Gravity is the controlling force Mass Wasting Important triggering factors Saturation Oversteepening Removal of vegetation Ground vibrations Important triggering factors Saturation of the material with water Destroys particle cohesion Water adds weight Important triggering factors Important triggering factors Oversteepened slopes Oversteepened slopes Unconsolidated granular particles assume a stable slope called the angle of repose Stable slope angle is different for various materials Oversteepened slopes are unstable Undercutting by streams Undercutting by human interference Addition of material to top of slope Natural deposition Human caused construction 1 Important triggering factors Mass Wasting Types of mass wasting processes Removal of anchoring vegetation Wildfires Drought Development logging Defined by The material involved The movement of the material Ground vibrations from earthquakes Types of mass wasting processes Defined by the material involved Debris Mud Earth Rock Types of mass wasting processes Defined by the movement of the material The rate of the movement Fast Slow Types of mass wasting processes Defined by the movement of the material The character of the movement Fall Slide Flow Forms of mass wasting Slump Rockslide Debris flow Earth flow Creep Solifluction 2 USGS Landslide Types Types of mass wasting http pubs usgs gov fs 2004 3072 fs 2004 3072 html Forms of mass wasting Slump diagram Slump Rapid movement along a curved surface Occur along oversteepened slopes Slump Government Hill AK 1964 http walrus wr usgs gov geotech radaraapg fig4 html http www physicalgeography net fundamentals 10x html 3 Government Hill AK seismic cross section Forms of mass wasting Rockslide Rapid Blocks of bedrock move down a slope Cousin to Rockfall http walrus wr usgs gov geotech radaraapg fig5 html Rockslide diagram Nevado Huascar n Peru 1970 Buried two towns 18 000 killed Geologists warned government of potential http landslides usgs gov html files landslides slides slide5 htm Gros Ventre rockslide diagram http www goldengatephoto com WestUS wyother html grosventre Gros Ventre landslide photo 4 Slide Lake Wyoming Sherman Glacier Rock Avalanche March 1964 http www uwsp edu geo projects geoweb participants dutch VTrips GrosVentre HTM Rock Fall Rock Fall July 1996 Yosemite http landslides usgs gov html files landslides slides slide9 htm http sts gsc nrcan gc ca geoscape vancouver graphics mountain1 gif Forms of mass wasting Debris flow mudflow Rapid flow of debris with water Confined to channels Dry areas with heavy rains Lahar composed of volcanic materials 5 Snohomish County WA January 2006 US 50 Sierra Nevadas California 1997 http www komotv com stories 41527 htm http landslides usgs gov monitoring hwy50 index php La Conchita California La Conchita California Spring 1995 No one injured or killed February 2005 http landslides usgs gov html files landslides slides slide21 htm La Conchita 2005 Slide Mountain Nevada 1983 http landslides usgs gov html files landslides slides slide2 htm http www redcross org article 0 1072 0 312 3943 00 html 6 Debris flow damage Lahar debris flow Nevado del Ruiz Toutle River Debris Flow http pubs usgs gov fs fs 176 97 fs 176 97 html Eruption of Nevado del Ruiz http volcanoes usgs gov Hazards What Lahars RuizLahars html http landslides usgs gov html files landslides slides slide13 htm http volcanoes usgs gov Hazards What Lahars RuizLahars html Confluence of lahars Nevado del Ruiz http volcanoes usgs gov Hazards What Lahars RuizLahars html 1 Armero site Nevado del Ruiz http volcanoes usgs gov Hazards What Lahars RuizLahars html Philippine Landslide 2006 http www alertnet org thenews pictures MAN52D htm Forms of mass wasting Scar of Philippine landslide Earthflow Rapid or slow Typically occur on hillsides in humid regions Water saturates the soil Liquefaction associated with earthquakes and clay soils http news yahoo com news tmpl story u 060219 481 xbm10202190643 Hollywood Hills CA January 2005 http www cnn com interactive weather 0501 gallery storms frameset exclude html 2 Niigata Japan 1964 Anchorage AK 1964 http www owlnet rice edu sehh AlaskaEQ Alaska Sci EQScience http www ce washington edu liquefaction selectpiclique nigata64 tiltedbuilding jpg Alaska 1964 http www ce washington edu liquefaction selectpiclique alaska64 landslideintowater jpg http walrus wr usgs gov geotech radaraapg fig5 html Sheffield Dam 1925 Location of Sarno Italy Santa Barbara County Earth quake caused flow http www ce washington edu liquefaction selectpiclique dams sheffielddam1 jpg 8 Forms of mass wasting Creep Slow movement of soil and regolith downhill Causes fences and utility poles to tilt Some visible effects of creep Creep Bedrock curled due to creep mass wasting Creep http www ngdc noaa gov seg hazard slideset 6 6 140 slide shtml Forms of mass wasting Curved trunks due to soil creep Solifluction Slow movement in areas underlain by permafrost Upper active soil layer becomes saturated and slowly flows over a frozen surface below http classes colgate edu dkeller geol101 massw images creep1 jpg 9 Ground subsidence in Alaska due to solifluction Solifluction Lobes http piru alexandria ucsb edu collections geography3b misc solifluction lobes jpg 5b1 5d jpg Measuring ground movement Mass Wasting Potential EXPLANATION LANDSLIDE INCIDENCE Low less than 1 5 of area involved Moderate 1 5 15 of area involved High greater than 15 of area involved LANDSLIDE SUSCEPTIBILITY INCIDENCE Moderate susceptibility low incidence High susceptibility low incidence High susceptibility moderate incidence Mass Wasting Potential Mass Wasting EXPLANATION LANDSLIDE INCIDENCE Low less than 1 5 of area involved Moderate 1 5 15 of area involved High greater than 15 of area involved LANDSLIDE SUSCEPTIBILITY INCIDENCE Moderate susceptibility low incidence High susceptibility low incidence High susceptibility moderate incidence The downslope movement of rock regolith and soil under the direct influence of gravity Gravity is the controlling force Important triggering factors Saturation of the material with water Oversteepening Devegetation Vibration 10
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