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 itRecent examples:Hwy 410 in Washington State buriedhttp://seattletimes.nwsource.com/html/localnews/2010044629_webmudslide11m.html19 Killed in Brazil2http://www.cbsnews.com/stories/2010/01/01/world/main6045455.shtmlUSGS list of major landslides by yearhttp://landslides.usgs.gov/recent/?PHPSESSID=n2jadq60bmt2hsv3kiji5l4ku61995 landslide in La Conchita, 3California Photos from U.S. Geological SurveyNext: landslide videoOphir Chasma landslide, MarsNASA4Types of Mass movementGradual mass movementCreepRapid mass movement5Landslides - 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.6Creep 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 NOAA27Types of rapid mass movementGeology - ChernicoffFig 11.8 Understanding8Rockfall 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 Earth9Slump 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 Earth10Fig 11.13 Understanding EarthDebris flow or Mud flow- composed of rock debris and mud; includes a lot of water11Debris 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/2005/3106Mass MovementSome factors that influence or trigger mass movement:• Type of slope material: sand, gravel, clay, bedrock, etc.• How steep the slope is• Amount of wateri12Illustration: 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 Earth313Figs 11.1, 11.3, 11.4 Understanding Earth14Frequency 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.15Photo by S. Kuehn, October 2005Fig 11.5 Understanding EarthFractures along sedimentary bedding, Arizona16Photo 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 movement17The 1994 Northridge earthquake in Californiatriggered many landslidesUSGS OFR 95-213Cutting 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. Kuehn181994 landslide near McClures Pass, ColoradoUSGSSmall rockfall in a road cut in the Blue Mountains of Oregon419Construction 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 movement2021Avoid steep bluffs with unconsolidated sedimentsJanuary, 1997USGS OFR 98-239Watch out for early signs of movement and for evidence of past mass movement. USGS OFR 95-21322Installing drain systems to reduce the amount of water in a slope can reduce the risk of landslides.Control water and improve drainage23Shannon & Wilson, Inc.S. Kuehn, 2005Stabilize landslide-prone slopese.g. by build sufficiently strong retaining structures24Keller – Environmental Geology525Make 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 f26http://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 Survey27DebrisFlow Hazards in the United StatesU.S. Geological Surveyhttp://pubs.usgs.gov/fs/fs-176-97/General overview of landslideshttp://wapi.isu.edu/EnvGeo/EG4_mass_wasting/landslide2.htmlcontains a computer-simulated