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Faults, Earthquakes & Volcanoes

Faults, Earthquakes & Volcanoes. 56. Faults. Surface along which rocks move when they pass their elastic limit and break. 56. Earthquake. Vibrations produced when rocks break along a fault. 56. Normal Fault.

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Faults, Earthquakes & Volcanoes

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  1. Faults, Earthquakes & Volcanoes

  2. 56 Faults Surface along which rocks move when they pass their elastic limit and break

  3. 56 Earthquake Vibrations produced when rocks break along a fault

  4. 56 Normal Fault Break in rock caused by tension forces, where rock above the fault surface moves down relative to the rock below

  5. 56 Reverse Fault Break in rock caused by compressive forces, where rock above the fault surface moves upward relative to the rock below

  6. 56 Strike-Slip Fault Break in rock caused by shear forces, where rocks move past each other without much vertical movement

  7. 56 Primary (P) – wave Seismic wave that moves rock particles back-and-forth in the same direction that the wave travels

  8. 56 Secondary (S) – wave Seismic wave that moves rock particles at right angles to the direction of the wave

  9. 57 Whose FAULT is it? • STRIKE-SLIP • Side-to-side motion • Happens at TRANSFORM boundaries • Ex. San Andreas Fault Fault Surface

  10. 57 Whose FAULT is it? • NORMAL • Hanging wall moves down • Happens at DIVERGENT boundaries Fault Surface

  11. 57 Whose FAULT is it? • REVERSE (aka THRUST) • Hanging wall moves up • Happens at CONVERGENT boundaries Fault Surface

  12. 58 Earthquakes! • A seismic wave is a wave generated by an earthquake. • There are 3 types of waves: • Primary waves (P-waves) • Secondary waves (S-waves) • Surface waves

  13. Seismic Waves • http://www.classzone.com/books/earth_science/terc/content/visualizations/es1002/es1002page01.cfm

  14. 58 Earthquakes! • Focus is the point BELOW the Earth’s surface where seismic waves start • Epicenter is the point on earth’s SURFACE directly above the focus

  15. 58 Earthquakes! • Liquefaction occurs when wet soil acts more like a liquid during an earthquake

  16. 58 Earthquakes! • Tsunami is a seismic sea wave that begins over an earthquake focus and can be destructive when it hits the shore

  17. What is an Earthquake like? • Earthquake Montage: http://video.nationalgeographic.com/video/environment/environment-natural-disasters/earthquakes/earthquake-montage/ • Earthquake in Japan: http://www.youtube.com/watch?feature=player_embedded&v=x9QNzGY0qxw# • Japan Tsunami: • http://nctr.pmel.noaa.gov/honshu20110311/20110311Houshu.mov

  18. Where do they occur? • http://earthquake.usgs.gov/earthquakes/map/

  19. 59 Earthquake Facts Surface wave EPICENTER Crust FOCUS S-wave Mantle Outer core P-wave Inner core

  20. 59

  21. 59 Earthquake Facts • An earthquake is the vibration, sometimes violent, of the Earth’s surface that follows a release of energy in the Earth’s crust

  22. 59 Earthquake Facts • P-waves push tiny particles of Earth material directly ahead of them or displace the particles behind their line of travel. • Only P-waves travel through the Earth’s molten core. How do we know?

  23. 59 Earthquake Facts • S-waves displace materials at right angles. • They cannot move through the core and are slower than P-waves How do we know?

  24. 59 Earthquake Facts • Surface waves, which travel along the Earth’s surface, create the most noticeable damage (they are the slowest)

  25. 59 Measuring an Earthquake • The vibrations produced by earthquakes are detected, recorded, and measured by instruments called a seismograph

  26. 59 Measuring an Earthquake • We need 3 seismograph station readings to find the focus and epicenter of an earthquake

  27. 59 Measuring an Earthquake • Richter Scale, is a scientific measure of how much energy was released into the Earth

  28. 59 Measuring an Earthquake • Modified Mercalli Scale, is an observational measure of how people experience an earthquake • Mercalli Scale Online

  29. VOLCANOES!

  30. 60 Two Types of Eruptions • Violent/Explosive • Quiet/Flowing

  31. 60 Trapped Gas • Water vapor and carbon dioxide are trapped in magma. • At low pressure, they escape quietly when they reach the surface • At high pressure, they escape violently when they reach the surface

  32. 60 Magma Composition • Basaltic – less silica and very fluid, produces quiet eruptions • Granitic – lots of silica, high water vapor content, and very thick, produces very violent eruptions

  33. 60 Forms of Volcanoes • Shield • Cinder Cone • Composite

  34. 60 Shield Volcanoes • Formed by quiet eruptions • Basaltic lava builds up in flat layers • Gently sloping slides • For example, Hawaii!

  35. 60 Cinder Cone Volcano • Formed by explosive eruptions • Granitic lava thrown high into the air • Lava cools into different sizes of tephra or ash • Steep-sided, loose slopes

  36. 60 Composite Volcano • A mix of the two types • Quiet or violent • Basaltic or granitic • Steep or gentle slopes • Layered with tephra or ash

  37. 60 Parts of a Volcano

  38. 61 Dike • Magma squeezed into VERTICAL cracks

  39. 61 Sill • Magma squeezed into HORIZONTAL cracks

  40. 61 Ring of Fire • Region around the Pacific Ocean with frequent earthquakes and volcanoes

  41. 61 Hot Spot • Isolated volcano not caused by plate tectonics

  42. 61 Caldera • Large crater caused by a violent volcanic eruption

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