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LANDSLIDES!

LANDSLIDES!. failure surface. Melissa Beukeboom @. What is a landslide?. GRAVITY. FRICTION. Gravity is the force that pulls everything toward the centre of the Earth. Friction between soil particles must RESIST the pull of gravity. Tug of War. GRAVITY WINS!!. When a landslide occurs….

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LANDSLIDES!

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  1. LANDSLIDES! failure surface Melissa Beukeboom @

  2. What is a landslide?

  3. GRAVITY FRICTION Gravity is the force that pulls everything toward the centre of the Earth Friction between soil particles must RESIST the pull of gravity Tug of War

  4. GRAVITY WINS!! When a landslide occurs….

  5. WHY? What helps gravity to win?

  6. 1. Type of sediment 2. Erosion 3. Water content in soil 4. Disturbances like: • Earthquakes • Volcanic eruptions • Machinery, traffic, mining

  7. SOIL Let’s take a closer look! 1. Type of Rock Particles (a.k.a. Sediment) ROCK PARTICLES a.k.a. SEDIMENTS WATER AIR ORGANIC MATTER

  8. ROCK PARTICLES • Rocks are weathered (broken down) by water, wind, and ice into smaller and smaller pieces called SEDIMENTS • Main types of SEDIMENTS: • gravel • sand • silt • clay

  9. 1. Type of Rock Particles (a.k.a. Sediment) Gravel and sand grains are very angular in shape. Their sharp edges hold on to each other, increasing FRICTION and fighting GRAVITY.

  10. What happens to these sediments when a landslide occurs?

  11. 1. Type of sediment (continued) • Clay particles are flat and fit together very tightly. • This prevents water from moving between clay particles easily. • Water pressure can build up in slopes made of clay.

  12. 1. Type of sediment (continued) A SPECIAL CASE!! QUICK CLAYS

  13. QUICK CLAYS IN ONTARIO TYRRELL SEA CLAY Northern Ontario & Quebec Ottawa & Quebec LEDA CLAY OR CHAMPLAIN SEA CLAY We are here! Do we have quick clays in Ontario? YES!

  14. 2.0 x 10-9m or 0.000000002 m – that’s small!!! Cardhouse Structure

  15. Until the structure is disturbed!! 1. Type of sediment (continued) • The card house structure makes quick clay very stable….

  16. RIVER RIVER RIVER RIVER RIVER RIVER 2. Erosion • When a slope is over-steepened, it becomes unstable • Rivers erode the base of slopes and make them too steep…making it unstable

  17. So GRAVITY wins! 3. Water Content • Too much water added to soil, pushes the sediment particles apart. • The particles lose contact with each other…therefore they lose FRICTION!

  18. So GRAVITY wins! 4. Disturbances • Disturbances also push particles apart, causing them to lose contact with each other • They lose FRICTION, so….

  19. 4. Disturbances include: Volcanoes!

  20. 4. Disturbances include: Volcanoes! Earthquakes!

  21. 4. Disturbances include: Earthquakes! Volcanoes! Construction

  22. 4. Disturbances include: Earthquakes! Volcanoes! Construction Heavy Traffic

  23. 4. Disturbances include: Earthquakes! Volcanoes! Construction Deforestation Heavy Traffic

  24. GRAVITY to win! Let’s re-cap… Landslides occur when the land is unstable…allowing Instability depends on: • The type of sediment • Water content in the soil • Erosion over-steepening the slope • A major disturbance

  25. When a landslide occurs… • It can be fast or slow • It can look like “the wave” or falling dominos To conclude…here is a bit humour… • The “domino effect” Imagine the people are sediment particles

  26. It’s time to slip, slide and away The End!

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