4 4 Deformation
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4 4 Deformation






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4 4 Deformation 4 4 Deformation Presentation Transcript

  • Chapter 4 Plate Tectonics 4-4 Deforming the Earth’s Crust
  • Essential Questions/Learning Goals:
    • How does stress affect the Earth’s crust?
    • Describe the three major types of folds.
  • Science Terms:
    • Compression
    • Tension
    • Folding
  • Section Introduction:
    • What is stress?
      • The amount of force per unit of area on a substance.
  • Deformation
    • What is deformation?
      • Changes in a rock’s shape due to stress
        • De = “undo”
        • Form = “shape”
        • – tion = “process of”
  • Compression
    • What is compression?
      • Stress that squeezes rocks together
    • What kind of boundary has compression?
      • Convergent boundaries.
  • Tension
    • What is tension?
      • Stress that stretches rocks.
    • What kind of boundary has tension?
      • Divergent
  • Folding
    • What are folds?
      • Bends in rocks due to stress.
  • Types of Folds
    • The two most common types of folds are:
      • Anticlines:
        • Upward folds (arches)
      • Synclines:
        • Downward folds (troughs)
  • What is a monocline fold?
    • A fold that has both ends of the fold still horizontal.
    • There is a middle portion that bends downwards.
  • Monocline fold
  • How big are folds?
    • Folds can be as large as mountains
    • Or
    • As small as centimeters
  • Faulting
    • Essential Question:
      • How are the three types of faults different from each other?
    • Science Term
      • Fault
  • What is a Fault?
    • A break in rocks where one rock slide past the other
  • Fault Illustration
    • What are the pieces of broken rock on each side of the fault called?
      • Fault blocks.
    • Two types:
      • Footwall
      • Hanging wall
  • Footwall
    • The block of rock beneath the fault
      • You can climb up the footwall
  • Hanging Wall
    • The block of wall above the fault.
        • You could stand underneath a hanging wall.
  • Normal Faults
    • How do the fault blocks move in a Normal Fault?
      • The hanging wall slides down the foot wall
    • What kind of stress makes a Normal Fault?
      • Tension
    • What kind of boundary are you likely to find a Normal Fault at?
      • Divergent Boundary
  • Reverse Faults
    • How do the fault blocks move in a Reverse Fault?
      • The hanging wall slides up the footwall
    • What kind of stress makes a Reverse Fault?
      • Compression
      • What kind of boundary are you likely to find a Reverse Fault at?
        • Convergent
  • Telling the Difference Between Faults
    • How can you tell the difference between a normal fault and a reverse fault?
      • If you look at the rock layers, you can tell how the hanging wall and footwall have moved.
  • Strike Slip Faults
    • How do the fault blocks move in a strike slip fault?
      • The blocks grind and slide past each other horizontally
      • Example of a strike slip fault
        • San Andreas Fault
  • Plate Tectonics and Mountain Building
    • What kinds of mountains are built by Plate Tectonics?
      • Folded mountains
      • Fault-block mountains
      • Volcanic mountains
  • Folded Mountains
    • How are these mountains formed?
      • Plates colliding at a…
        • Convergent boundary
      • Examples:
        • Appalachian, Alps, Himalayas.
  • Fault-Block Mountains
    • How are these mountains formed?
      • Tension pulling huge blocks of rocks apart.
        • Gravity causes the hanging wall to slide down the footwall
          • Normal faulting
  • Fault-Block Mountains
    • Shape?
      • Can be very jagged and sharp looking.
    • Example:
      • Tetons in Wyoming
  • Volcanic Mountains
    • How are these mountains formed?
      • When plates collide and one is…
        • Subducted
      • The melted crust rises to form volcanic mountains
  • Volcanic Mountains
    • Where are most volcanic mountains formed?
      • At plate boundaries such as….
        • Subduction zones
  • What is the Ring of Fire ?
    • It is the plate boundaries that are found around the Pacific Ocean
  • Uplift and Subsidence
    • What type of motion occurs in the crust in uplift and subsidence?
      • Vertical movement
    • Uplift?
      • Upward movement of blocks of rock
        • May or may not be deformed by stress
    • Subsidence?
      • Downward movement of blocks of rock
        • Usually are not deformed by stress.
  • Uplifting of Depressed Rocks
    • Rocks that have been pushed down by the weight of glaciers will rise upwards after the glacier has melted away.
    • This is called…
      • Rebound
    • Does deformation occur?
      • No.
  • Subsidence of Cooler Rocks
    • As rocks cool, they take up less…
      • Space or volume
    • What does this mean for the height of mountains?
      • They shrink!
  • Subsidence of Cooler Rocks
    • Where does this occur?
      • Mid ocean ridges.
        • As the rocks get further from the MOR, the rocks cool and become more dense causing the ridges to become lower.
  • Tectonic Letdown
    • What happens to the crust when you stretch it?
      • It will sink lower
      • This creates a…
        • Rift zone
  • Tectonic Letdown
    • What kind of boundary does this occur at?
      • A divergent boundary
    • What kind of fault occurs here?
      • Normal faults.