1. Earth’s Structural Key Elements & the Hazards of Plate Movement AICE EM: Lithosphere Key Content 1 & 2

2. Before We Begin, You Need to Understand These Terms: Convection Currents Density

4. Convection Currents Cause Motion Demo – through water Demo – through air Picture drawing an arrow from the base of the fountain up and out in any direction that the water flows. This is the possible path for convection currents. When you see the next slide, it is a cross section of the planet.

5. The Earth’s Crust Is Made Up of a Mosaic of Huge Rigid Plates: Tectonic Plates

6. The Evidence In 1912 Alfred Wegener - hypothesis of continental drift – Fossil Evidence (dinosaurs & coal measures) – Evidence form rock formations – Climatic Evidence Originally opposed b/c the mechanism was disproved

7. Mid-Ocean Ridges

8. MORs – How They Cause Sea-Floor Spreading

9. More Evidence Paleomagnetism – Normal polarity – Reversed polarity – MORs have alternating magnetic fields

10. Continents in Motion

11. Sea-floor Spreading Also Causes Motion Lithosphere sits on top of moving asthenosphere

12. Boundary Types Convergent Divergent Transform Constructive Destructive Conservative

13. Note location of MOR, rift valley, oceanic & continental crust

14. Note: ocean trench, active volcano, magma, subduction zone. Why subduction occurs Oceanic & Continental plates Oceanic & Oceanic Plates

16. What type of boundary is found between the South American plate and the African plate? What surface features are most often at boundaries of this type?

17. Chapter 10 The Supercontinent Cycle

18. Earthquakes Wave properties Wave characteristics Body waves (P wave & S wave) Surface waves (L waves) Note focus, epicenter, direction of seismic waves Shallow focus – Intermediate – 60 – 300 km. Deep focus – up to 700 km. Surface to 40 mi. (60 km)

19. Fig. 14-8, p. 350 Liquefaction of recent sediments causes buildings to sink Two adjoining plates move laterally along the fault line Earth movements cause flooding in low-lying areas Landslides may occur on hilly ground Shock waves Epicenter Focus

20. Seismic Waves

21. P wavesS

22. Earthquakes Occur at All Boundaries

23. Fig. 14-5, p. 348

24. Earthquake scales Richter scale – Measures ground motion to determine strength (magnitude) Moment magnitude scale – Measures strength based on area size that the fault moved, average distance that fault blocks move, and rigidity of blocks in fault zone – The greater the number, the stronger the (E). < 2.5 not felt by people – 6.9 Kobe, Japan 1995 Modified Mercalli scale – Based on intensity and effect felt / damage to structure (I – XII)

25. Tsunamis Caused by an epicenter located on the ocean floor Also caused by underwater landslide which was activated by an earthquake

26. Fig. 14-11, p. 352 Earthquake in seafloor swiftly pushes water upwards, and starts a series of waves Waves move rapidly in deep ocean reaching speeds of up to 890 kilometers per hour. As the waves near land they slow to about 45 kilometers per hour but are squeezed upwards and increased in height. Waves head inland causing damage in their path. Undersea thrust fault Upward wave Bangladesh India Thailand Sri Lanka Malaysia Earthquake Sumatra Indonesia December 26, 2004, tsunami Burma

28. Volcanoes Activity occurs when…(3 answers)

29. Fig. 14-7, p. 349 Extinct volcanoes Eruption cloud Ash Ash flow Lava flow Mud flow Landslide Central vent Magma conduit Magma reservoir Solid lithosphere Upwelling magma Partially molten asthenosphere Acid rain

30. VOLCANIC ERUPTIONS Difference between magma & lava is… – Oceanic crust tends to create Mafic lava (Mg & Fe) Low viscosity quiet eruptions (basaltic eruptions) – Continental crust tends to make Felsic lava (silicates) Sticky, high viscosity explosive eruptions Explosive eruptions: – Trapped dissolved gasses Leads to acidic atmospheric pollution (SO 2, H 2 S, CO 2 ) – Pyroclastic material Volcanic ash, dust, stones, bombs, blocks

32. Volcanic eruption sequence Steam explosions (phreatic explosions) Explosive eruption of magma Eruption cloud Pyroclastic flows Lava flows Lava fountains Volcanic debris & mudflow (lahars)

33. Predicting Eruptions & Reducing Loss Earthquake activity – Magma pressure – Temperature changes Activity patterns – Geologic measurements – Measuring Devices Historical records Don’t live there at all Evacuate