Earthquakes

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Earthquakes
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What is an Earthquake?

• The shaking and trembling that results from the
  movement of rocks in the Earths crust.

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What does the plate movement create?

• Powerful forces that squeeze or pull the rock in
  the crust.
• These forces are examples of stress, a force that
  acts on rocks to change its shape or volume.

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Three Types of Stress

• Shearing
• Tension
• Compression

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What is shearing?

• Stress that pulls rock in two opposite directions.

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What is tension?

• It pulls on the crust, stretching rock so that it
  becomes thinner in the middle.
• It occurs where two plates are moving apart.

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What is compression?

• It squeezes the rock until it folds or breaks.

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What is deformation?

• It is any change in the volume or shape of
  Earths crust.

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What are faults?

• It is a break, or crack in the Earths crust
  where the crust slips past each other.
• They occur along plate boundaries, where forces
  of plate motion compress, pull, shear the crust
  so much that it breaks.

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What are the main types of faults?

• Strike-slip faults
• Normal faults
• Reverse faults

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What are strike slip- faults?

• Rocks on either side of the fault slip past each
  other sideways with little up or down motion.
• It forms the transform boundary.

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What is a normal fault?

• It is at an angle, so that one rock block lies
  above the fault, while the other lies below the
  fault.
• Above- hanging wall
• Below- footwall

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What are reverse faults?

• Produced by compression.
• Has the same structure as a normal fault but the
  blocks of rock move in opposite directions.

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What is friction?

• It is the force that opposes the motion of one
  surface as it moves across another surface.
• Friction occurs because surfaces are not smooth.
• It determines how a fault moves.

15
How does mountain building occur?

• Normal faults can uplift a block of rock, a
  fault-block mountain forms.
• Collisions of two plates can cause compression
  and folding creating folded mountains.

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What are anticlines and synclines?

• An anticline is an upward fold or bend in a rock.
  
• A syncline is a downward fold or bend in a rock.

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What is a plateau?

• It is a large area of flat land elevated high
  above sea level.