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Mass Wasting. What is Mass Wasting? The downslope movement of slope material. Gravity is the key to mass wasting. Landslides are mass wasting

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  • Mass Wasting

  • What is Mass Wasting?The downslope movement of slope material.

    Gravity is the key to mass wasting.

    Landslides are mass wasting.

  • ColluviumThe term colluvium describes the angular pieces of rock that are moved by mass wasting [contrasting with alluvium or water moved rock.]

  • Weathering, then DetachmentSolid rock must first weather.

    Then, the weathered rock must detach.

  • Lots of ways to organize processesthat influence peopleCreepRock Fall 3. Topple

    4. Rotational Slump5. Translational Slide (Block Glide)6. Rock slide7. Flows

  • Key is gravity

  • Order Present1. Creep2. Rock Fall 3. Topple4. Rotational Slump5. Translational Slide ( & Block Glide)6. Rock slide7. Flows

  • Soil Creep

  • In the wetting or freezing soil zone

  • Very Slow, mm/yr to cm/yr

  • Very Slow, mm/yr to cm/yr

  • rock fall

  • rock fall

  • rock fall

  • rock fall produces talus, oftenTalus Cones atAngle of Repose

  • Detachment and Gravity Fallnot limited to rocks

  • How do you discuss this?

  • topple

  • Top falls, butbottom stays

  • Rotational Slump

  • Laguna Beach

  • Laguna Beach

  • Translational Slide

  • Translational Slide at Torrey Pines

  • Snow Avalanches Often Start As Translational Slides, that then flow

  • Often Occur in Same Places: Avalanche Chutes

  • 3 Strategies: Avoid, Engineer, Ignore

  • Engineer

  • MostlyIgnore

  • Rock Slide

  • Gros Ventre Rock Slide

  • Madison Canyon Slide

  • crushed dolomite stayed on top

  • Army Corp Prevent Disaster

  • Attabad Pakistan (Hunza River)

  • Steep Jointing - Set Stage

  • Spillway Creation & Widening:Race to Avoid Bursting the Dam

  • More added, keep widening

  • Marcus Rockslide in Scottsdale

  • Virtual Field Trip to Marcus Slide

  • Can occur elsewhere there is steep jointing, and weathered granite on slick, fresh joint faces

  • Flows, mudflow (few rocks)

  • Flows, mudflow (few rocks)

  • Flows, debris flow (more rocks mixed with mud)

  • KOA Campground

  • Slide Mountain, Nevada

  • La Canada, California

  • Debris flows can occur in Phoenix

  • Earth flow, slower & thicker

  • Why? What Causes Mass Wasting?GRAVITY!! Steeper slopes = more likely

  • Steep Slopes One Reason why California experiences problemAz CanToo

  • Undercutting steepens the slope,wave action in this case

  • Undercutting steepens the slope,stream action in this case

  • Undercutting steepens the slope,stream action in this case

  • Undercuttingcan be from earlier mass wasting

  • Human activities dangerous around steep slopes: Telegraph Hill 2007

  • Or from construction

  • Oversteepening from from new fault scarp

  • Hard caprock creates situation where weaker material erodes away until slope is so steep that caprock erodes

  • Whole idea of a Mesa relies onundercutting by erosion of weaker rock

  • Another Reason: Weak Material

  • Palos Verdes: Weak & Undercut

  • Best solution: land use that can be disturbed, like a golf course

  • Another Reason: Weak Material

  • Weakness can be a joint (fracture) in a strong rock

  • Weakness can be a joint (fracture): but orientation is important

  • Lots of water

  • Lots of water (rain, snowmelt)

  • Lots of water (rain, snowmelt)Exert pore pressure

  • Reaches thixotropic behavior(solid, then liquify into plastic)

  • Get some corn starch

  • Result: Liquifaction

  • Liquifaction leads to flows (debris flows, mudflows, earthflows)

  • Entire valley filled with mud

  • Russian Roulette

  • Alaska Landslide from 1980 Quake

  • Earth Shaking (earthquakes, or even bouncing large trucks)

  • 1970 Earthquake

  • disaster

  • Earthquake & Moisture: Las Colinas, El Salvador Disaster (2001)

  • Earthquake in Wet Winter: Future California Disaster

  • Blackhawk Landslide Example

  • Shaking can be from volcanic eruption, case of Mt Shasta

  • Big Az Concern: Fire & Hydrophobic soils

  • Cave Creek Complex Fire

  • Forest Wildfires: Idaho

  • Los Alamos Fire

  • Online Video/AnimationsMass Wasting and Landslide Animationshttp://serc.carleton.edu/NAGTWorkshops/visualization/collections/mass_wasting.html

  • Net Effect: Slow, Steady Inevitable

    Not just in southern California. British Columbia! Imagery seen in this presentation is courtesy of Ron Dorn and other ASU colleagues, students and colleagues in other academic departments, individual illustrations in scholarly journals such as Science and Nature, scholarly societies such as the Association of American Geographers, city,state governments, other countries government websites and U.S. government agencies such as NASA, USGS, NRCS, Library of Congress, U.S. Fish and Wildlife Service USAID and NOAA.