Landslides - Natural occurring slope Introductions

Landslides

1. UNDERSTANDING UNDERSTANDING
LANDSLIDESLANDSLIDES
Dr. Walter Hays,
Global Alliance For
Disaster Reduction

2. ESSENTIAL KNOWLEDGE FOR ESSENTIAL KNOWLEDGE FOR
SOCIETAL SUSTAINABILITYSOCIETAL SUSTAINABILITY
A FRAMEWORK FOR A FRAMEWORK FOR
UNDERSTANDING THE IMPACTS UNDERSTANDING THE IMPACTS
OF LANDSLIDES ON PEOPLE AND OF LANDSLIDES ON PEOPLE AND
THEIR COMMUNITIESTHEIR COMMUNITIES

3. LANDSLIDESLANDSLIDES
NATURAL PHENOMENA THAT NATURAL PHENOMENA THAT
OCCUR WITH OR WITHOUT OCCUR WITH OR WITHOUT
HUMAN ACTIVITYHUMAN ACTIVITY

4. FORCASTING FUTURE EVENTSFORCASTING FUTURE EVENTS
The goal is The goal is
recording, recording,
processing, and processing, and
interpreting interpreting
geologic geologic
changes in time changes in time
frames of frames of
seconds to seconds to
weeks; i.e., “real- weeks; i.e., “real-
time geology.” time geology.”

5. FORCASTING FUTURE EVENTSFORCASTING FUTURE EVENTS
Predicting a Predicting a
large volume large volume
landslide is landslide is
important for important for
society, but it society, but it
depends on long-depends on long-
term monitoring term monitoring
of individual of individual
slides. slides.

6. LANDSLIDESLANDSLIDES
Falls, Topples, Slides, Falls, Topples, Slides,
Spreads, FlowsSpreads, Flows

7. LANDSLIDE HAZARDLANDSLIDE HAZARD
Landslides encompass all Landslides encompass all
categories of categories of gravity-related gravity-related
slope failuresslope failures in Earth in Earth
materials.materials.

8. SLOPESSLOPES
SlopesSlopes are the most common are the most common
landforms.landforms.
Although they appear stable and Although they appear stable and
static, static, slopes are actually slopes are actually
dynamic, evolving systemsdynamic, evolving systems..

9. SLOPESSLOPES
Material is constantly moving on Material is constantly moving on
slopes at rates varying from slopes at rates varying from
imperceptible creepimperceptible creep to to
thundering thundering avalanches and rock avalanches and rock
fallsfalls moving at high velocities. moving at high velocities.

10. LANDSLIDESLANDSLIDES
Gravity slope failures are triggered Gravity slope failures are triggered
by earthquakeby earthquake ground shaking ground shaking or or
excess precipitationexcess precipitation
The slope does The slope does not not need to be very need to be very
steep for a landslide to occur.steep for a landslide to occur.

11. FORCASTING FUTURE EVENTSFORCASTING FUTURE EVENTS
To predict when To predict when
an earthquake an earthquake
will occur is will occur is
important for important for
society, but it is society, but it is
not yet feasible not yet feasible
because because
earthquake earthquake
prediction isn’t. prediction isn’t.

12. LAHARLAHAR
A lahar is A lahar is a special a special
“landslide”“landslide” or mud flow or mud flow
induced by an explosive induced by an explosive
volcanic eruption.volcanic eruption.

14. FORCASTING FUTURE EVENTSFORCASTING FUTURE EVENTS
Predicting when Predicting when
a volcano will a volcano will
erupt is erupt is
important for important for
society, but it society, but it
depends on depends on
knowledge of knowledge of
each volcano’s each volcano’s
eruption history. eruption history.

15. MOUNT RANIERMOUNT RANIER
Mount Ranier has generated Mount Ranier has generated
more than more than 60 lahars60 lahars during during
the past the past 10,000 years10,000 years..
Many of these occurred Many of these occurred
during periods of during periods of volcanic volcanic
quiescence.quiescence.

16. MOUNT RANIERMOUNT RANIER
Today, Mount Ranier continues Today, Mount Ranier continues
to vent to vent steamsteam and convert its and convert its
andesitic summit into andesitic summit into clayclay..
A plan to A plan to evacuate 50,000 peopleevacuate 50,000 people
has been developed. has been developed.

17. LANDSLIDE HAZARD: ALASKALANDSLIDE HAZARD: ALASKA
THE 1964 PRINCE THE 1964 PRINCE
WILLIAM SOUND WILLIAM SOUND
EARTHQUAKE EARTHQUAKE
TRIGGERED A LARGE TRIGGERED A LARGE
VOLUME LANDSLIDE VOLUME LANDSLIDE
AT TURNAGAIN AT TURNAGAIN
HEIGHTS.HEIGHTS.
MILLIONS OF CUBIC MILLIONS OF CUBIC
METERS OF SOIL AND METERS OF SOIL AND
ROCK MOVED DOWN ROCK MOVED DOWN
SLOPE. SLOPE.

18. LANDSLIDE HAZARD: ALASKALANDSLIDE HAZARD: ALASKA
Slope failure was Slope failure was
induced by induced by
ground shaking ground shaking
of “Quick Clay.” of “Quick Clay.”

22. LANDSLIDE HAZARD: ECUADORLANDSLIDE HAZARD: ECUADOR

25. LANDSLIDE HAZARD: JAPANLANDSLIDE HAZARD: JAPAN

26. LANDSLIDE HAZARD: LANDSLIDE HAZARD:
WASHINGTON STATEWASHINGTON STATE

27. LATERAL SPREADING: JAPANLATERAL SPREADING: JAPAN

29. LATERAL SPREAD: SAN LATERAL SPREAD: SAN
FRANCISCOFRANCISCO