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Earth’s Structural Key Elements & the Hazards of Plate Movement

Earth’s Structural Key Elements & the Hazards of Plate Movement. AICE EM: Lithosphere Key Content 1 & 2. Before We Begin, You Need to Understand These Terms:. Convection Currents Density. Convection Currents Cause Motion.

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Earth’s Structural Key Elements & the Hazards of Plate Movement

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  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

  3. Convection Currents Cause Motion 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. • Demo – through water • Demo – through air

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

  5. 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

  6. Mid-Ocean Ridges

  7. MORs – How They Cause Sea-Floor Spreading

  8. More Evidence • Paleomagnetism • Normal polarity • Reversed polarity • MORs have alternating magnetic fields

  9. Continents in Motion

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

  11. Boundary Types • Convergent • Divergent • Transform • Constructive • Destructive • Conservative

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

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

  14. 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?

  15. Chapter 10 The Supercontinent Cycle

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

  17. 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 Focus Epicenter Fig. 14-8, p. 350

  18. Seismic Waves

  19. P waves S

  20. Earthquakes Occur at All Boundaries

  21. Fig. 14-5, p. 348

  22. 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) 9.5

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

  24. 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. Waves move rapidly in deep ocean reaching speeds of up to 890 kilometers per hour. Earthquake in seafloor swiftly pushes water upwards, and starts a series of waves Undersea thrust fault Upward wave Bangladesh Burma India Thailand Malaysia Sri Lanka Earthquake Indonesia Sumatra December 26, 2004, tsunami Fig. 14-11, p. 352

  25. Volcanoes • Activity occurs when…(3 answers)

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

  27. 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 (SO2, H2S, CO2) • Pyroclastic material • Volcanic ash, dust, stones, bombs, blocks

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

  29. 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

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