UNDERSTANDING LANDSLIDES

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UNDERSTANDING LANDSLIDES
Dr. Walter Hays, Global Alliance For Disaster
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ESSENTIAL KNOWLEDGE FOR SOCIETAL SUSTAINABILITY

• A FRAMEWORK FOR UNDERSTANDING THE IMPACTS OF
  LANDSLIDES ON PEOPLE AND THEIR COMMUNITIES

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LANDSLIDES

• NATURAL PHENOMENA THAT OCCUR WITH OR WITHOUT
  HUMAN ACTIVITY

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FORCASTING FUTURE EVENTS

• The goal is recording, processing, and
  interpreting geologic changes in time frames of
  seconds to weeks i.e., real- time geology.

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FORCASTING FUTURE EVENTS

• Predicting a large volume landslide is important
  for society, but it depends on long-term
  monitoring of individual slides.

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LANDSLIDES

• Falls, Topples, Slides, Spreads, Flows

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LANDSLIDE HAZARD

• Landslides encompass all categories of
  gravity-related slope failures in Earth
  materials.

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SLOPES

• Slopes are the most common landforms.
• Although they appear stable and static, slopes
  are actually dynamic, evolving systems.

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SLOPES

• Material is constantly moving on slopes at rates
  varying from imperceptible creep to thundering
  avalanches and rock falls moving at high
  velocities.

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LANDSLIDES

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

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FORCASTING FUTURE EVENTS

• To predict when an earthquake will occur is
  important for society, but it is not yet feasible
  because earthquake prediction isnt.

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LAHAR

• A lahar is a special landslide or mud flow
  induced by an explosive volcanic eruption.

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FORCASTING FUTURE EVENTS

• Predicting when a volcano will erupt is important
  for society, but it depends on knowledge of each
  volcanos eruption history.

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MOUNT RANIER

• Mount Ranier has generated more than 60 lahars
  during the past 10,000 years.
• Many of these occurred during periods of volcanic
  quiescence.

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MOUNT RANIER

• Today, Mount Ranier continues to vent steam and
  convert its andesitic summit into clay.
• A plan to evacuate 50,000 people has been
  developed.

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LANDSLIDE HAZARD ALASKA

• THE 1964 PRINCE WILLIAM SOUND EARTHQUAKE
  TRIGGERED A LARGE VOLUME LANDSLIDE AT TURNAGAIN
  HEIGHTS.
• MILLIONS OF CUBIC METERS OF SOIL AND ROCK MOVED
  DOWN SLOPE.

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LANDSLIDE HAZARD ALASKA

• Slope failure was induced by ground shaking of
  Quick Clay.

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LANDSLIDE HAZARD ECUADOR
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LANDSLIDE HAZARD JAPAN
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LANDSLIDE HAZARD WASHINGTON STATE
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LATERAL SPREADING JAPAN
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LATERAL SPREAD SAN FRANCISCO