Landslides/Mass Wasting

H.E.W_Exam.3

Mass Wasting

Another term for Landslides

Landslides

downslope movement o’ material

Forces acting on Slope

Driving Forces; Resisting Forces

Driving Forces

(shear stress) force exerted on slope→ weight

Resisting Forces

(shear strength) force that tries to resist pull o’ gravity

Resisting force = winning tug o’ war w/ gravity

material stays

Resisting force = getting its a-s-s dragged :( → Driving force stronger

slope fails, material slides

Primary reason for Mass Wasting

*Water*

Slope material→ saturated w/ water

Empty pores = filled w/ water, looses friction, (yucky mud/very wet sand)

Cohesion

water gives sed grains supa powas (surface tension & electrostatic attraction) & the mineral surfaces + water molecules are able to combine (Voltron, hi-yah!!)

Landslide ingredients

Material o’ slope; Loose sed/soil; Layered rock parallel to slope

Material o’ slope

What slope is made of can affect stability, ex: clay

Why clay bad for slope

act like liquid when disturbed/shaken (EQ!!)

Loose Unconsolidated Sediment/Soil on slope

is prone to tumbling and fracturing off (no duh)

Layered Rock Parallel to (under) Slope

is more susceptible to sliding cuz it’s not a stable foundation :( (probably needs therapy tbh)

Angle of Repose

Slope gets cut off for the night→ angle = max steep slope can be

If Slope don’t quit slinging steepness after Angle of Repose

slope = more susceptible to mass wasting events, slope fails (L alcoholism)

Angle Repose depends on

material of slope→ stable vs unstable gets diff angles

Scarp

aftermath exposed, underlying material on top of hill-side

Toe

Where scarp material comes to rest at bottom

Mass Movement =

speed & type of movement behavior

Types of Mass Movements

Slides; Flows; Free-Fall

Slides

movement o’ sturdy block material along weak plane

Types of Slides

Rockslide; Debris/Mud Slide; Slump

Flows

movement o’ loose material mixed w/ water = fluid motion

Types of Flows

Creep; Earthflow; Mudflow; Debris Flow

Free-Fall

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Landslide button pushers

Sudden, Heavy Rainstorms; EQ Shocks; Loading; Steepening Slope; Removing Vegetation

Sudden, Heavy Rainstorms

increase water→ entering & adding weight to slope.

Climates affect Landslides how

diff climates = diff amounts of precipitation

Types of Climates that affect Landslides

Humid/Tropical; Arid Regions

Humid & Tropical Region Climates

more precipitation = watery landslides

Arid Region Climates

usually dry = only rockfalls; heavy rainfall (flash flooding) as result→ debris flows