1Mass MovementMass movement includes processes that transport large quantities of rock, sediment, soil, etc. down a slope due to gravity. It occurs on most slopes and can range from very slow to very fastTopics:1Types of mass movementFactors that affect the likelihood of mass movementTriggering eventsWhat people can do about it1995 landslide in La Conchita, 2California Photos from U.S. Geological SurveyNext: landslide video1995 landslide in La Conchita, Californiaphoto from U.S. Geological Survey3Recent examples:http://landslides.usgs.gov/recent/?PHPSESSID=n2jadq60bmt2hsv3kiji5l4ku64Ophir Chasma landslide, MarsNASA5Types of Mass movementGradual mass movementCreepRapid mass movement6Landslides - any large, fast mass movementSub-Categories: FallSlideFlowOne type of mass movement can trigger or change into another as it moves downhill. For example, an avalanche may sometimes produce mudflows.27Creep is the slowest type of mass movement. Almost all slopes consisting of unconsolidated material creep a few millimeters up to several centimeters per year. Creep may produce tilting of objects such as fence posts, telephone poles, and retaining walls. It also causes curved trunks in trees on creeping slopes. Fig 11.11 Understanding Earth and NOAA8Types of rapid mass movementGeology - ChernicoffFig 11.8 Understanding9Rockfall is the fastest type of mass movement. It occurs when loose material falls from very steep or vertical slopes.Small rockfall in a road cut in the Blue Mountains of Oregon S. KuehnFig 11.8 Understanding EarthAnother example - boulder on road:http://www.oes.ca.gov/Operational/OESHome.nsf/ALL/EF8986565A9A84FF88256F89006774D4?OpenDocumentUpper part of a slumpGeology - ChernicoffFig 11.16 Understanding Earth10Slump along a roadhttp://pubs.usgs.gov/mf/1999/mf-2325/Slump - a type of slide that separates along a concave surface. Slumps generally do not travel far, and the material within the slump tends to move as a unit and not become mixed. Fig 11.14 Understanding EarthFig 11.13 Understanding Earth11Fig 11.13 Understanding EarthDebris flow or Mud flow- composed of rock debris and mud; includes a lot of water12Debris flow deposits are often poorly sorted and may contain boulders that are larger than normal stream flow can transport. Ancient debris flows can be identified from similar deposits.http://pubs.usgs.gov/fs/2005/31063Mass MovementSome factors that influence or trigger mass movement:• Type of slope material: sand, gravel, clay, bedrock, etc.• How steep the slope is• Amount of waterVi13Illustration: the maximum stable slope angle (angle of repose) for particles of different sizes and shapes.•Vegetation • Presence and orientationof fractures or other zonesof weaknessFig 11.6 Understanding Earth14Figs 11.1, 11.3, 11.4 Understanding Earth15Frequency of landslides and amount of precipitation in the Seattle area. The California coast has a similar correlation between rainfall and landslides.Fire can remove vegetation and decrease slope stability thereby increasing the potential for erosion and mass movementEnhanced erosion following a fire near San Luis Res.16Photo by S. Kuehn, October 2005Fig 11.5 Understanding EarthFractures along sedimentary bedding, Arizona17Photo by S. KuehnFractured volcanic rocks and fallen boulders at Pinnacles National Monument, CAZones of weakness such as fractures and sedimentary layers also contribute to the risk of mass movement18The 1994 Northridge earthquake in Californiatriggered many landslidesUSGS OFR 95-2134Cutting into slopes to build roads and buildings increases the risk of mass movement by making slopes steeper.Small landslide (slump and earthflow) in a roadcut along Hwy 70 in CAPhoto by S. Kuehn191994 landslide near McClures Pass, ColoradoUSGSSmall rockfall in a road cut in the Blue Mountains of Oregon20Construction on steep slopes can put people at greater risk from landslidesChapter 11 Understanding EarthAvoid building on or near slopes that show evidence of a large amount of creepFig 11.11 Understanding Earth and NOAAWhat people can do about mass movement21 22Avoid steep bluffs with unconsolidated sedimentsJanuary, 1997USGS OFR 98-239Watch out for early signs of movement and for evidence of past mass movement. USGS OFR 95-21323Stabilize landslide-prone slopese.g. by build sufficiently strong retaining structures24Keller – Environmental Geology5Installing drain systems to reduce the amount of water in a slope can reduce the risk of landslides.Control water and improve drainage25Shannon & Wilson, Inc.S. Kuehn, 200526Make maps to show where the risk is greatest.see also: http://landslides.usgs.gov/learning/nationalmap/More about landslidesUSGS Landslide Hazards Programhttp://landslides.usgs.gov/Landslide info from VA Dept. of Mines, Minerals, and Energy http://www.dmme.virginia.gov/DMR3/landslides.shtmlVA Natural hazards (business-oriented site)h // /b i /h h / l/ l i /i d f27http://www.vaemergency.com/business/hazthreats/natural/geologic/index.cfmAbout landslides and reducing the risks – WA State Dept. of Ecologyhttp://www.ecy.wa.gov/programs/sea/landslides/prevent/prevent.htmlLandslide info from Calif. Emergency Management Agencyhttp://hazardmitigation.calema.ca.gov/hazards/natural/landslideKelso, WA landslide: amazing photos, landslide video, etc.http://www.nwgeoscience.com/kelso/(Aldercrest is best)130-year history of landslides for La Conchita, Californiahttp://www.geog.ucsb.edu/~jeff/projects/la_conchita/apcg2001_article/apcg2001_article.htmlSouthern California—Debris Flows in Wildfire Areashttp://pubs.usgs.gov/fs/2005/3106/Landslide hazard photos - NOAA Natural Hazard Slide sethttp://www.ngdc.noaa.gov/nndc/struts/results?eq_0=7&t=101634&s=0&d=1Debris-Flow Hazards in the United States-U.S. Geological Survey28eb sowa a ds t e U ted StatesU.S. Geo og ca Su veyhttp://pubs.usgs.gov/fs/fs-176-97/General overview of landslideshttp://wapi.isu.edu/EnvGeo/EG4_mass_wasting/landslide2.htmlcontains a computer-simulated