1. failure surface Melissa Beukeboom @

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

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

5. WHY? What helps gravity to win?

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

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

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

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) QUICK CLAYS A SPECIAL CASE!!

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

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

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

16. 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 RIVER

18. 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!  So GRAVITY wins!

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

20. 4. Disturbances include: Volcanoes!

21. 4. Disturbances include: E a r t h q u a k e s ! Volcanoes!

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

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

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

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

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

28. It’s time to slip, slide and away