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.