2.1 Earths Crust in Motion


Earthquake: shaking and trembling that results from the movement of rock beneath the Earth's surface
Stress: a force that acts on a rock to change its shape or volume
Shearing: stress that pushes a mass of rock in 2 opposite directions
Tension: pulls on crust which stretches rock so that it becomes thinner in the middle
Compression: squeezes rock until it folds or breaks
Deformation: any change in the volume or shape of the Earth's crust
Strike-slip fault: rocks on either side of fault slip past each other sideways with little up and down motions
Normal fault: a fault that is at an angle so one part of the rock lies on top of the fault and the other part of the rock lies below the fault
Hanging wall: the half of the fault lies above the footwall
Footwall: the half of the fault that lies below the hanging wall
Reverse fault: same structure as normal fault but the blocks go in the opposite direction
Fault-block mountain: when normal faults uplift a block of rock a fault-black mountain forms
Folds: bends in rock that forms when compression shortens and thickens the part of Earth's crust
Anticline: a fold in rock that bends upward into an arch
Syncline: a fold in rock that bends downward in the middle to form a bowl
Plateau: a large area of flat land elevated high above sea level


Stress in the Crust

  • stress is what causes rock to change

Types of Stress

  • deformation
    • any change in the volume or shape of the earth's surface
  • shearing
    • can cause rock to break apart or to change shape
  • tension
    • stretches the rock so it's thinner in the middle
  • compression
    • pushes rock together until they compress

Kinds of Faults

  • strike-slip faults
    • the San Andreas fault
  • reverse faults
    • Mount Gould
      • started to form 60 million years ago
  • normal faults
    • the Sandia Mountains

Friction Along Faults

  • friction
    • the force that creates resistance when two things past each other
    • when the friction is high, the rocks won't budge
  • stress can overpower friction
    • when this happens small earthquakes occur

Mountain Building

  • Mountains formed by faulting
    • fault-block mountains form
      • Sierra Nevada, California

Mountains formed by folding

    • folds in the Earth's crust can form mountains
      • two plates collide together which folds the crust
        • Himalayas in Asia
        • Alps in Europe

Anticlines and Synclines

    • anticline
      • the Black Hills of South Dakota
    • syncline
      • the Illinois Basin


    • the Colorado Plateau

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