Earth's Surface Cracks and Faults
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Questions and Answers

What is the primary cause of earthquakes?

  • Movement of tectonic plates
  • Erosion of soil layers
  • Sudden release of energy in the earth's crust (correct)
  • Volcanic activity beneath the surface

    • Which type of stress causes rocks to be pushed towards each other?

  • Shear stress
  • Bending stress
  • Tensional stress
  • Compressional stress (correct)

    • What movement characterizes a normal fault?

  • Rocks are stretched horizontally
  • Hanging wall moves upward relative to footwall
  • Both walls move parallel to each other
  • Hanging wall moves downward relative to footwall (correct)

    • What type of fault is created when rocks are subjected to shear stress?

    <p>Strike-slip fault (C)</p> Signup and view all the answers

    How is an active fault defined?

    <p>Faults that have generated earthquakes within the last 10,000 years (B)</p> Signup and view all the answers

    What is the distinction of a thrust fault within reverse faults?

    <p>It has a dip less than 45º (B)</p> Signup and view all the answers

    Which fault type involves both shear and compression or tension?

    <p>Oblique-slip fault (D)</p> Signup and view all the answers

    What differentiates inactive faults from active faults?

    <p>Inactive faults may still produce earthquakes in the future (B)</p> Signup and view all the answers

    What is a creep fault characterized by?

    <p>Occurrence without associated earthquake activity (D)</p> Signup and view all the answers

    What defines the Philippine Fault Zone (PFZ)?

    <p>A major tectonic feature across the Philippines (D)</p> Signup and view all the answers

    Which fault type is the Central Mindoro Fault characterized as?

    <p>Right-lateral fault (A)</p> Signup and view all the answers

    What is the focus of an earthquake?

    <p>The location where rocks first rupture (A)</p> Signup and view all the answers

    Which event is NOT a common cause of tsunamis?

    <p>Heavy rainfall (B)</p> Signup and view all the answers

    What magnitude did the strongest recorded earthquake in Southern Chile have?

    <p>9.5 (C)</p> Signup and view all the answers

    Which term describes the breaking surface underground in a fault?

    <p>Fault plane (A)</p> Signup and view all the answers

    What is the epicenter of an earthquake?

    <p>The point on the crust directly above the focus (D)</p> Signup and view all the answers

    Flashcards

    Earthquake

    Shaking and trembling caused by the sudden release of energy in the Earth's crust.

    Fault

    A fracture or break in the Earth's crust.

    Normal Fault

    A fault where the hanging wall moves down relative to the footwall, created by tensional stress.

    Reverse Fault

    A fault where the hanging wall moves up relative to the footwall, created by compressional stress.

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    Strike-Slip Fault

    A fault where rocks move horizontally past each other, created by shear stress.

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    Active Fault

    A fault that has generated earthquakes within the last 10,000 years, and may still continue to do so.

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    Inactive Fault

    A fault that has no record of generating earthquakes in the last 10,000 years, but could still generate one in the future.

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    Stress (geology)

    Force applied to rocks.

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    Creep Fault

    A fault that moves slowly without causing earthquakes.

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    Trench

    A long, narrow depression in the ocean floor.

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    Focus (Hypocenter)

    The point underground where an earthquake's energy releases.

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    Fault Plane

    The surface along which rocks break and slide during an earthquake.

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    Fault Line

    Any edge of the fault plane.

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    Tsunami

    A large wave in the ocean, often caused by earthquakes underwater.

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    Epicenter

    The point on Earth's surface directly above the earthquake's focus.

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    Underwater Earthquake

    Earthquake that occurs beneath the ocean surface and can cause tsunamis.

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    Study Notes

    Earth's Surface Cracks

    • Earthquakes: Sudden releases of energy in Earth's crust cause shaking and trembling.
    • Faults: Fractures or breaks in Earth's crust.
    • Fault zones: Series of associated faults.
    • Stress: Force applied to rocks.
    • Types of Stress:
      • Tensional stress: Rocks stretched apart.
      • Compressional stress: Rocks pushed together.
      • Shear stress: Rocks pushed perpendicular to the axis.

    Faults and Movements

    • Dip: Angle of a fault plane.
    • Dip-slip faults: Faults formed by the dip, including normal and reverse faults.
    • Hanging wall: Part of the fault above the fault plane.
    • Footwall: Part of the fault below the fault plane.
    • Normal Fault: Hanging wall moves down relative to the footwall due to tensional stress.
    • Reverse Fault: Hanging wall moves up relative to the footwall due to compressional stress.
      • Thrust fault: Subtype of reverse fault with a dip less than 45°.
    • Strike-slip fault: Fault movement along the strike (horizontal).
      • Shear: Parallel but opposite movements along the fault plane.
        • Left-lateral strike-slip fault: Leftward movement of one side relative to the other.
        • Right-lateral strike-slip fault: Rightward movement of one side relative to the other.
    • Oblique-slip fault: Movement along both dip and strike directions, combining shearing and compression/tension.

    Active and Inactive Faults

    • Active faults: Generated earthquakes within the last 10,000 years and may continue to do so.
      • Shallow earthquakes occur on active faults.
    • Inactive faults: No record of generating earthquakes in the last 10,000 years, but may generate earthquakes in the future.
    • Creep fault: Fault movement without associated earthquake activity.
    • Trenches: Long, narrow, and steep-sided depressions in the ocean floor.
      • Philippine Trench: Deepest trench in the Philippines, third deepest globally.
    • Philippine Fault Zone (PFZ): Major tectonic feature crossing the Philippines (northwestern Luzon to southeastern Mindanao), 1200 km long, composed of many faults.
      • Central Mindoro Fault: Right-lateral fault marking a slope break.
      • Lubang Fault: Left-lateral fault offshore between Batangas and Mindoro.

    Anatomy of an Earthquake

    • Focus/Hypocenter: Point where rocks first break, releasing seismic energy.

    • Fault plane: Breaking surface underground.

    • Fault line: Edge of the fault plane.

    • Fault scarp: Exposed fault plane above the ground, indicating a fault.

    • Epicenter: Point on Earth's surface directly above the focus; the strongest earthquake point.

    • Types of Earthquake According to Depth of Focus: (related information omitted in the text).

    All About Tsunamis

    • Tsunami: Large volume of water reaching the surface, triggered by underwater events.
    • Causes of Tsunamis:
      • Underwater earthquakes.
      • Volcanic eruptions.
      • Nuclear explosions.
      • Meteors.
      • Underwater landslides.
    • Strong Tsunamis:
      • Tohoku, Sendai (Japan) - March 11, 2011: 9.0 magnitude.
      • Southern Chile - May 22, 1960: Strongest earthquake, 9.5 magnitude.
      • Northwest Sumatra (Indonesia) - December 26, 2004: 9.3 magnitude underwater earthquake.

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    Description

    Explore the dynamics of Earth's surface with a focus on earthquakes, faults, and the various types of stress that act on rocks. This quiz covers essential concepts like dip-slip faults, normal and reverse faults, and the characteristics of stress. Test your understanding of geological processes and fault mechanics.

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