320 likes | 716 Vues
UNDERSTANDING LANDSLIDES. Dr. Walter Hays, Global Alliance For Disaster Reduction . ESSENTIAL KNOWLEDGE FOR SOCIETAL SUSTAINABILITY. A FRAMEWORK FOR UNDERSTANDING THE IMPACTS OF LANDSLIDES ON PEOPLE AND THEIR COMMUNITIES. LANDSLIDES.
E N D
UNDERSTANDING LANDSLIDES Dr. Walter Hays, Global Alliance For Disaster Reduction
ESSENTIAL KNOWLEDGE FOR SOCIETAL SUSTAINABILITY A FRAMEWORK FOR UNDERSTANDING THE IMPACTS OF LANDSLIDES ON PEOPLE AND THEIR COMMUNITIES
LANDSLIDES NATURAL PHENOMENA THAT OCCUR WITH OR WITHOUT HUMAN ACTIVITY
FORCASTING FUTURE EVENTS • The goal is recording, processing, and interpreting geologic changes in time frames of seconds to weeks; i.e., “real- time geology.”
FORCASTING FUTURE EVENTS • Predicting a large volume landslide is important for society, but it depends on long-term monitoring of individual slides.
LANDSLIDES Falls, Topples, Slides, Spreads, Flows
LANDSLIDE HAZARD • Landslides encompass all categories of gravity-related slope failures in Earth materials.
SLOPES • Slopes are the most common landforms. • Although they appear stable and static, slopes are actually dynamic, evolving systems.
SLOPES • Material is constantly moving on slopes at rates varying from imperceptible creep to thundering avalanches and rock falls moving at high velocities.
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.
FORCASTING FUTURE EVENTS • To predict when an earthquake will occur is important for society, but it is not yet feasible because earthquake prediction isn’t.
LAHAR • A lahar is a special “landslide” or mud flow induced by an explosive volcanic eruption.
FORCASTING FUTURE EVENTS • Predicting when a volcano will erupt is important for society, but it depends on knowledge of each volcano’s eruption history.
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.
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.
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.
LANDSLIDE HAZARD: ALASKA • Slope failure was induced by ground shaking of “Quick Clay.”