Mass Wasting Mass Wasting Mass Wasting Important triggering factors The downslope movement of rock, • Saturation regolith, and soil under the direct influence of gravity • Oversteepening • Removal of vegetation Gravity is the controlling force • Ground vibrations Important triggering factors Important triggering factors Important triggering factors Saturation of the material with water Oversteepened slopes Oversteepened slopes • Destroys particle cohesion • Unconsolidated granular particles assume • Undercutting by streams • Water adds weight a stable slope called the angle of repose • Undercutting by human interference • Stable slope angle is different for various • Addition of material to top of slope materials • Natural—deposition • Oversteepened slopes are unstable • Human-caused--construction Types of mass wasting Important triggering factors Mass Wasting processes Types of mass wasting processes • Removal of anchoring vegetation Defined by Defined by the material involved • Wildfires • The material involved • Debris • Drought • The movement of the material •Mud • Development, logging •Earth •Rock • Ground vibrations • from earthquakes 1 Types of mass wasting Types of mass wasting processes processes Forms of mass wasting •Slump Defined by the movement of the material Defined by the movement of the material • Rockslide The character of the movement The rate of the movement • Debris flow •Fall •Fast • Earth flow • Slide •Slow • Creep •Flow • Solifluction USGS Landslide Types of mass wasting Types Forms of mass wasting Slump • Rapid movement along a curved surface • Occur along oversteepened slopes • http://pubs.usgs.gov/fs/2004/3072/fs-2004-3072.html Slump—diagram Slump Government Hill, AK • 1964 • http://walrus.wr.usgs.gov/geotech/radaraapg/fig4.html • http://www.physicalgeography.net/fundamentals/10x.html 2 Government Hill, AK Forms of mass wasting Rockslide—diagram seismic cross section Rockslide • Rapid • Blocks of bedrock move down a slope Cousin to Rockfall • http://www.kmtr.com/mediacenter/[email protected],[email protected],4200@video. kmtr.com,[email protected],[email protected]&navCatId=5&2=2 • http://walrus.wr.usgs.gov/geotech/radaraapg/fig5.html Elkton, Oregon, March 4, 2006 Elkton, Oregon, March 4, 2006 Nevado Huascarán • Peru 1970 • Buried two towns • 18,000 killed • Geologists warned government of potential • http://www.kmtr.com/news/local/story.aspx?content_id=010798AE-AF2F-41D5-93F5-120A64493D45 • http://www.kmtr.com/news/local/story.aspx?content_id=010798AE-AF2F-41D5-93F5-120A64493D45 http://landslides.usgs.gov/html_files/landslides/slides/slide5.htm • http://www.goldengatephoto.com/WestUS/wyother.html#grosventre Gros Ventre rockslide--diagram Gros Ventre Slide Lake, Wyoming landslide—photo • http://www.uwsp.edu/geo/projects/geoweb/participants/dutch/VTrips/GrosVentre.HTM 3 Sherman Glacier Rock Rock Fall Rock Fall Avalanche, March 1964 • July 1996 • Yosemite • http://landslides.usgs.gov/html_files/landslides/slides/slide9.htm • http://sts.gsc.nrcan.gc.ca/geoscape/vancouver/graphics/mountain1.gif Snohomish County, WA Forms of mass wasting January 2006 Debris flow (mudflow) • Rapid flow of debris with water • Confined to channels • Dry areas with heavy rains • Lahar composed of volcanic materials • http://www.komotv.com/stories/41527.htm US 50, Sierra La Conchita, La Conchita, California Nevadas, California California 1997 • Spring 1995 • No one injured or killed • February 2005 • http://landslides.usgs.gov/html_files/landslides/slides/slide21.htm http://landslides.usgs.gov/monitoring/hwy50/index.php 4 La Conchita, 2005 Slide Mountain, Nevada, 1983 Debris flow damage http://landslides.usgs.gov/html_files/landslides/slides/slide2.htm • http://www.redcross.org/article/0,1072,0_312_3943,00.html Toutle River Debris Flow Nevado del Ruiz Lahar debris flow • http://landslides.usgs.gov/html_files/landslides/slides/slide13.htm • http://pubs.usgs.gov/fs/fs-176-97/fs-176-97.html • http://volcanoes.usgs.gov/Hazards/What/Lahars/RuizLahars.html Eruption of Nevado del Ruiz Confluence of lahars, Nevado del Ruiz Armero site, Nevado del Ruiz • http://volcanoes.usgs.gov/Hazards/What/Lahars/RuizLahars.html • http://volcanoes.usgs.gov/Hazards/What/Lahars/RuizLahars.html • http://volcanoes.usgs.gov/Hazards/What/Lahars/RuizLahars.html 5 Philippine Landslide, 2006 Scar of Philippine landslide Forms of mass wasting 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 • http://www.alertnet.org/thenews/pictures/MAN52D.htm Earthflow—diagram Hollywood Hills, CA Niigata, Japan, 1964 • January 2005 • http://www.cnn.com/interactive/weather/0501/gallery.storms/frameset.exclude.html • http://www.ce.washington.edu/~liquefaction/selectpiclique/nigata64/tiltedbuilding.jpg Anchorage, AK 1964 liquefaction damage Alaska, 1964 1964 • http://www.owlnet.rice.edu/~sehh/AlaskaEQ/Alaska_Sci/EQScience • http://www.ce.washington.edu/~liquefaction/selectpiclique/alaska64/landslideintowater.jpg • http://walrus.wr.usgs.gov/geotech/radaraapg/fig5.html • Hyperlink to sand boil liquefaction http://walrus.wr.usgs.gov/geotech/images/TIsandboils.mov 6 Sheffield Dam, 1925 Forms of mass wasting Cause of creep—frost heave Santa Barbara Creep County • Slow movement of soil and regolith downhill Earth-quake • Causes fences and utility poles to tilt caused flow • http://www.ce.washington.edu/~liquefaction/selectpiclique/dams/sheffielddam1.jpg Some visible effects of creep Creep Creep • Bedrock curled • Curved due to creep trunks mass wasting due to soil creep • http://classes.colgate.edu/dkeller/geol101/massw/images/creep1.jpg • http://www.ngdc.noaa.gov/seg/hazard/slideset/6/6_140_slide.shtml Ground subsidence in Forms of mass wasting Solifluction Lobes Alaska due to solifluction Solifluction • Slow movement in areas underlain by permafrost • Upper (active) soil layer becomes saturated and slowly flows over a frozen surface below • http://piru.alexandria.ucsb.edu/collections/geography3b/misc/solifluction_lobes_jpg%5b1%5d.jpg 7 Mass Wasting Potential Mass Wasting Potential Measuring ground EXPLANATION LANDSLIDE INCIDENCE EXPLANATION Low (less than 1.5% of area involved) movement Moderate (1.5%-15% of area involved) LANDSLIDE INCIDENCE High (greater than 15% of area involved) Low (less than 1.5% of area involved) Moderate (1.5%-15% of area involved) LANDSLIDE SUSCEPTIBILITY/INCIDENCE Moderate susceptibility/low incidence High (greater than 15% of area involved) High susceptibility/low incidence High susceptibility/moderate incidence LANDSLIDE SUSCEPTIBILITY/INCIDENCE Moderate susceptibility/low incidence High susceptibility/low incidence High susceptibility/moderate incidence Mass Wasting 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 8.