faults, earthquakes & volcanoes
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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. - PowerPoint PPT PresentationTRANSCRIPT
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Faults, Earthquakes & Volcanoes
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Faults
Surface along which rocks move when they pass their elastic limit and break
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Earthquake
Vibrations produced when rocks break along a fault
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Normal Fault
Break in rock caused by tension forces, where rock above the fault surface moves down relative to the rock below
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Reverse Fault
Break in rock caused by compressive forces, where rock above the fault surface moves upward relative to the rock below
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Strike-Slip Fault
Break in rock caused by shear forces, where rocks move past each other without much vertical movement
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Primary (P) – wave
Seismic wave that moves rock particles back-and-forth in the same direction that the wave travels
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Secondary (S) – wave
Seismic wave that moves rock particles at right angles to the direction of the wave
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Whose FAULT is it?
• STRIKE-SLIP– Side-to-side motion– Happens at TRANSFORM boundaries– Ex. San Andreas Fault
Fault Surface
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Whose FAULT is it?
• NORMAL– Hanging wall moves down– Happens at DIVERGENT boundaries
Fault Surface
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Whose FAULT is it?
• REVERSE (aka THRUST)– Hanging wall moves up– Happens at CONVERGENT boundaries
Fault Surface
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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
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Seismic Waves
• http://www.classzone.com/books/earth_science/terc/content/visualizations/es1002/es1002page01.cfm
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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
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Earthquakes!
• Liquefaction occurs when wet soil acts more like a liquid during an earthquake
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Earthquakes!
• Tsunami is a seismic sea wave that begins over an earthquake focus and can be destructive when it hits the shore
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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
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Where do they occur?
• http://earthquake.usgs.gov/earthquakes/map/
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Earthquake Facts59
Inner core
Outer core
Mantle
CrustFOCUS
EPICENTER
Surface wave
P-wave
S-wave
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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
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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?
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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?
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Earthquake Facts
• Surface waves, which travel along the Earth’s surface, create the most noticeable damage (they are the slowest)
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Measuring an Earthquake
• The vibrations produced by earthquakes are detected, recorded, and measured by instruments called a seismograph
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Measuring an Earthquake
• We need 3 seismograph station readings to find the focus and epicenter of an earthquake
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Measuring an Earthquake
• Richter Scale, is a scientific measure of how much energy was released into the Earth
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Measuring an Earthquake
• Modified Mercalli Scale, is an observational measure of how people experience an earthquake
• Mercalli Scale Online
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VOLCANOES!
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Two Types of Eruptions
• Violent/Explosive• Quiet/Flowing
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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
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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
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Forms of Volcanoes
• Shield• Cinder Cone• Composite
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Shield Volcanoes
• Formed by quiet eruptions • Basaltic lava builds up in flat layers• Gently sloping slides • For example, Hawaii!
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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
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Composite Volcano
• A mix of the two types • Quiet or violent• Basaltic or granitic• Steep or gentle slopes• Layered with tephra or ash
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Parts of a Volcano60
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Dike
• Magma squeezed into VERTICAL cracks
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Sill
• Magma squeezed into HORIZONTAL cracks
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Ring of Fire
• Region around the Pacific Ocean with frequent earthquakes and volcanoes
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Hot Spot
• Isolated volcano not caused by plate tectonics
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Caldera
• Large crater caused by a violent volcanic eruption
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