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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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Presentation Transcript
faults

56

Faults

Surface along which rocks move when they pass their elastic limit and break

earthquake

56

Earthquake

Vibrations produced when rocks break along a fault

normal fault

56

Normal Fault

Break in rock caused by tension forces, where rock above the fault surface moves down relative to the rock below

reverse fault

56

Reverse Fault

Break in rock caused by compressive forces, where rock above the fault surface moves upward relative to the rock below

strike slip fault

56

Strike-Slip Fault

Break in rock caused by shear forces, where rocks move past each other without much vertical movement

primary p wave

56

Primary (P) – wave

Seismic wave that moves rock particles back-and-forth in the same direction that the wave travels

secondary s wave

56

Secondary (S) – wave

Seismic wave that moves rock particles at right angles to the direction of the wave

whose fault is it

57

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

Fault Surface

whose fault is it1

57

Whose FAULT is it?
  • NORMAL
    • Hanging wall moves down
    • Happens at DIVERGENT boundaries

Fault Surface

whose fault is it2

57

Whose FAULT is it?
  • REVERSE (aka THRUST)
    • Hanging wall moves up
    • Happens at CONVERGENT boundaries

Fault Surface

earthquakes

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
seismic waves
Seismic Waves
  • http://www.classzone.com/books/earth_science/terc/content/visualizations/es1002/es1002page01.cfm
earthquakes1

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
earthquakes2

58

Earthquakes!
  • Liquefaction occurs when wet soil acts more like a liquid during an earthquake
earthquakes3

58

Earthquakes!
  • Tsunami is a seismic sea wave that begins over an earthquake focus and can be destructive when it hits the shore
what is an earthquake like
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
where do they occur
Where do they occur?
  • http://earthquake.usgs.gov/earthquakes/map/
earthquake facts

59

Earthquake Facts

Surface wave

EPICENTER

Crust

FOCUS

S-wave

Mantle

Outer core

P-wave

Inner core

earthquake facts1

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
earthquake facts2

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?

earthquake facts3

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?

earthquake facts4

59

Earthquake Facts
  • Surface waves, which travel along the Earth’s surface, create the most noticeable damage (they are the slowest)
measuring an earthquake

59

Measuring an Earthquake
  • The vibrations produced by earthquakes are detected, recorded, and measured by instruments called a seismograph
measuring an earthquake1

59

Measuring an Earthquake
  • We need 3 seismograph station readings to find the focus and epicenter of an earthquake
measuring an earthquake2

59

Measuring an Earthquake
  • Richter Scale, is a scientific measure of how much energy was released into the Earth
measuring an earthquake3

59

Measuring an Earthquake
  • Modified Mercalli Scale, is an observational measure of how people experience an earthquake
  • Mercalli Scale Online
two types of eruptions

60

Two Types of Eruptions
  • Violent/Explosive
  • Quiet/Flowing
trapped gas

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
magma composition

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
forms of volcanoes

60

Forms of Volcanoes
  • Shield
  • Cinder Cone
  • Composite
shield volcanoes

60

Shield Volcanoes
  • Formed by quiet eruptions
  • Basaltic lava builds up in flat layers
  • Gently sloping slides
  • For example, Hawaii!
cinder cone volcano

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
composite volcano

60

Composite Volcano
  • A mix of the two types
  • Quiet or violent
  • Basaltic or granitic
  • Steep or gentle slopes
  • Layered with tephra or ash
slide38

61

Dike
  • Magma squeezed into VERTICAL cracks
slide39

61

Sill
  • Magma squeezed into HORIZONTAL cracks
ring of fire

61

Ring of Fire
  • Region around the Pacific Ocean with frequent earthquakes and volcanoes
hot spot

61

Hot Spot
  • Isolated volcano not caused by plate tectonics
caldera

61

Caldera
  • Large crater caused by a violent volcanic eruption
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