Landslide Classification Flashcards
definition of landslides
movement of a mass of rock, debris, or earth down a slope.
are landslides limited to land?
no, can be submarine
ground subsidence, collapse, ice falls or snow avalanches are all examples of landslides. TRUE/FALSE
False. they are not landslides
are landslides 100% human initiated?
nope, they are part of the natural landscape forming. They are “accelerated erosion” if you will.
main landslide causes
- Natural (rivers, streams, waves)
- weathering
- geological (weak materials, e.g. rock)
- rainfall
- earthquake
- human activity (slope modification)
what important things must be recorded in a landslide event?
- topographic location
- site details
- size of landslide feature
- material type
- activity
- potential for future movement
- photos
how are landslides classified?
- mechanism of failure (mode of movement)
- type of material (rock and soil types)
why do landslides need to be classified?
different landslides move at different speeds
whats depth of failure surface in a shallow, and a deep-seated landslide
shallow < 5m
deep-seated > 5m
trigger of most shallow landslides is…
rainfall
deep seated triggered by….
faults, shears, etc.
4 main types of landslide
- falls
- slides
- avalanches (not snow)
- debris flows
falls
masses of rocks, soil, or debris moving rapidly down very steep slopes, by freefall or bouncing and rolling
slides
rock, soil or debris sliding down planes of weakness (bedding, joints, faults, etc.)
avalanches
rock and debris. Very rapid and long-run on steep slopes for than 200m high. Can be wet or dry flows or falls
debris flows
high sediment concentrations (like wet concrete)
are debris floods landslides?
nope.
coarse soils debris size
> 2mm
different types of landslide movement
- slides
- rotational
- translational - spreads
- flows
- complex
landslide scar
source area and debris trail
main scarp
steep slope at the head of the slide (visible part of the failure surface)
tension cracks
located upslope of main scarp.
hummocky ground
irregular ground surface, results from shear and compression in the displaced material
Is there a difference between rainfall and earthquake induced landslide occurrence?
earthquake induced are more likely on steep rock slopes ( would’t be any soils there - too steep)
active landslides
currently moving or moved in the last year
3 inactive landslide classifications
- dormant - causes and potential for movement remain
- Stabilised - remedial measures have stopped movement
- Relict - developed under different conditions - prehistoric
name of an inactive landslide that starts to move again
reactivated
- eroded rounded and subdued features
- main scarp eroded and well vegetated
- hummocky and irregular ground with ponds.
What is being described here?
Relict landslide
dormant landslide
causes and potential for movement remain
