Mass Movements Wasting What are they Mass movements
- Slides: 36
Mass Movements/ Wasting
What are they? Mass movements include: • Landslides • Rock falls • Avalanches • Mud flows • Debris flows • Creep
Anatomy of a rotational landslide
>100 km/year <1 cm/year 0% ~40%
Mass Movements • Material moves downslope due to the pull of gravity • Can happen almost anywhere • Commonly associated with other events (heavy rainfall or earthquakes, for example) and are therefore under-reported • Movements can either be catastrophic (slope failure) or slow and steady (creep) • The rate of the mass movement can be increased by various erosive agents (especially water)
Factors in Slope Stability Gravity Water Earth Materials Triggering Events
Gravity & steepening of a slope
How to cause a landslide: add or subtract a mass …in the wrong place Common when building near slopes Common when building roads
Rotational landslide
Angle of Repose Varies for Different Materials
Water decreases rock/soil cohesion
Water decreases rock/soil cohesion
Water decreases rock/soil cohesion Water circulating underground can dissolve cements that hold sedimentary rocks together
Internal Causes for Slope Failure • • Water (weight & interaction with clay minerals) Decreasing rock cohesion Incompetent/weak material Adverse geologic structures
The Weight of Water • Sedimentary rocks commonly have porosities of 10 - 30% • If pore spaces fill with water, the weight of the material is increased substantially, creating instability
La Conchita, CA March 1995
It happened again in 2004… in exactly the same place…
La Conchita, CA
Debris flows or mud flows • Mass movements that behave like fluids • Unlike slides, flows are not controlled by a failure surface, but instead are dominated by internal movements
Landslides in the Bay Area
1982 San Mateo County
Devil’s slide area on Highway 1 north of Half Moon Bay
Devil’s Slide
Rock Falls
Creep • Downslope movement of soil and uppermost bedrock • Creep happens at too slow of a rate to observe directly • Instead, creep can be identified by it’s effect on objects
Risk factors to increase likelihood of mass movement Gravity - hill slopes more vulnerable (on top of a hill, on the slope, or at the bottom of a hill), modified slopes (road cut, cut flat area to build on, coastal erosion, etc. ) Water - risk is higher when ground is saturated and/or during heavy rains, El Niño events Earth Materials - loose soils (particularly clay-rich) or fractured rock, and old landslides pose greater risk Triggering Events - heavy rain during storm, rain after big storms or fires, earthquakes (when ground is saturated? )…are all triggers
- Antigentest åre
- Mass wasting
- Mass wasting
- Oversteepening
- Subsidence mass wasting
- Cut bank geography
- Mass wasting
- Mass wasting definition
- Mass wasting occurs when____.
- Crescent-shaped cliffs at the head of a slump
- Earthflow
- Mass wasting
- Mass wasting processes
- Axial and locomotor movement
- Sodium correction formula
- The respiratory system just wasting away answer key
- Bitemporal wasting in copd
- Wasting sperm
- Siadh vs di
- Examples of mass movement
- For they not know what they do
- You are not rejected
- Knowledge not shared is wasted
- Rankings: what are they and do they matter?
- Jordan 14
- 2. if we sneak out quietly, nobody notice.
- Grammar rules frustrate me they're not logical they are so
- We seek him here we seek him there
- Moles to grams
- Stoichiometry worksheet #2 (mole-mass mass-mole problems)
- Gravitational mass vs inertial mass
- Convert grams to moles
- Formula mass vs gram formula mass
- Formula mass vs molecular mass
- Formula mass vs molar mass
- Mass/molar mass
- Relative atomic mass of beryllium