plate tectonics and earthquakes
DESCRIPTION
Plate Tectonics and Earthquakes. Brittle vs. Ductile Deformation. Brittle. Ductile. Bends when stressed. Breaks when stressed. Brittle vs. Ductile Deformation. Deformation is dependent on: 1. Temperature (Cold or Hot) 2. Composition (Soft or Hard) 3. Strain Rate (Fast or Slow). - PowerPoint PPT PresentationTRANSCRIPT
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Plate Tectonics and Earthquakes
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Brittle vs. Ductile Deformation
Brittle• Breaks when stressed
Ductile• Bends when stressed
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Brittle vs. Ductile Deformation
Deformation is dependent on:
1. Temperature (Cold or Hot)2. Composition (Soft or Hard)3. Strain Rate (Fast or Slow)
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Brittle vs. Ductile Deformation
How does the Milky Bar deform when stressed?
a. What if we froze it?
b. What if we heated it?
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Plate Tectonics
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Plate Tectonics
• Crust – Uppermost part of the Earth• Lithosphere – Crust and Upper Part of Mantle• Mantle• Core
Convection
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Major Plates
• Major Plates– North American– South American– Eurasian– African– Pacific– Antarctic– Indoaustralian
• Others to note• Juan de Fuca• Nazca• Arabian• Caribbean
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Types of Plate Boundaries
• Divergent (Tension)– Mid-Ocean Ridges
• East Pacific Rise• Mid-Atlantic Ridge
• Convergent (Compression)– Subduction Zone– Cascade Mountains – Himalayan Mountains
• Transform (Shear)– San Andreas Fault
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Divergent Boundaries
• Mid Ocean Ridgeshttp://www.youtube.com/watch?v=t-ctk4KR-KU
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Convergent Boundaries
• Subduction Zone – One Plate goes under the other plate
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Convergent Boundaries• Subduction – Ocean/Continental – Andes
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Transform Boundaries
• Shear motion• Plates slide past each
other• San Andreas Fault
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Western UShas all three!
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Earthquakes
• Occur on Faults– a break in the rock of the crust where rock
surfaces slip past each other (displacement has occurred)
• Measured on the Moment Magnitude Scale– Logarithmic scale
• Change 1 magnitude - 32 times more energy
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Earthquakes
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Earthquakes
• Focus (hypocenter) - the location inside the earth where the first rupture of the earthquake took place
• Epicenter- the point on the Earth’s surface that is directly above the focus (hypocenter)
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Faults - Brittle
• Hanging Wall(Top)/Foot Wall(Bottom)• Normal Faults• Reverse Faults
– Thrust Faults
• Strike-Slip Faults– Left and right lateral
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Models of Faults
High Fives
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Folds - Ductile
• Anticline – oldest rocks in the middle
• Syncline – youngest rocks in the middle
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California Seismicity
http://earthquake.usgs.gov/earthquakes/recenteqscanv/
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California Seismicity
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Seismic Waves
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Seismic Waves
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Fold and Fault Model
• Compression!• What types of faults will we see?• What else do you see?
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Earthquake Preparedness• Have a pair of shoes next to the bed
– Due to broken glass from windows or other debris
• Create Post-Disaster Kit– One at home and one in your car
• Drop, Cover, Hold On– Do not run to the doorway, find something to get
underneath
• Don’t forget about aftershocks!• K-12 Earthquake Lesson Plans
http://www.scec.org/education/k12/eclakit/index.html
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Tsunamis• A tsunami is a series of sea waves most
commonly caused by an earthquake beneaththe sea floor
• In the open ocean, tsunami waves travel at speeds of up to 600 miles per hour
• The first wave is often not the largest• Successive waves may be spaced many
minutes (up to 30-40 mins) apart and continue arriving for a number of hours
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Tsunamis
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Tsunamis
• Since 1812, the California coast has had 15 tsunamis with wave heights higher than three feet; seven of these were destructive
• The worst tsunami resulted from the 1964 Alaskan earthquake and caused 12 deaths and at least $17 million in damages in northern California (2011 tsunami’s damages have not been totaled yet)
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What to do!
• If you feel a serious earthquake, and you are near the shoreline:
• Get inland and up as soon as possible. – 100 ft in elevation or higher– 2 miles or more inland
• If the tide recedes, get away fast.• Inform others to get to safety
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Forces
• F=ma• Force = mass * acceleration• Units:
– N (Newtons) = kg * m/s2
– 1 Kilogram = 2.2 lbs– 1 Meter = 3.28 feet = 100 cm = 1000 mm– Gravity = 9.8 m/s2
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Forces
• Forces have both magnitude (size) and direction
• Unequal forces will cause a change in velocity
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Forces
• Examples:– Box on table (steady state)– Box in hand (steady state)– Box in hand (change in forces)– Pushing a large box (static and kinetic friction)– Tension– Compression
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Forces
• Examples:– Strike-slip faults: Stick slip
• Forces and friction
– Normal faults:• Tension
– Reverse faults:• Compression