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Science Study Guide-Chapter 4
Terms in this set (26)
A force that acts on a rock to change its shape or volume
The stress force that pulls on the crust and thins rock in the middle
The stress force that squeezes rock until it folds or breaks
Stress that pushes a mass of rock in two opposite directions
The fault that cuts through rock at an angle so that one block of rock sits over the fault while the other block of rock lies under the fault
The block of rock that sits over the fault
The block of rock that lies under the fault
Has the same structure as a normal fault, except the blocks of rock move in the reverse direction
The rocks on either side of the fault slip past each other sideways, with little up or down motion
A large area of flat land elevated high above sea level
The shaking and trembling that results from the movement of rocks beneath Earth's surface
The area beneath Earth's surface where rocks that were under stress begin to break or move
The point on Earth's surface directly above the focus
Seismic waves that compress and expand the land like an accordion
Seismic waves that vibrate the land from side to side or up and down
Move more slowly than P and S waves but can produce sever ground movements
An instrument that is used to measure and record an earthquake's seismic waves
Modified Mercalli Scale
Rates the amount of shaking from an earthquake
A single number that geologists assign to an earthquake based on the earthquake's size
Moment magnitude scale
Geologists use this scale to rate the total amount of energy released from an earthquake
What are the three types of stress? Describe each.
Tension-Rock in the crust is stretches, like a warm piece of bubblegum, and makes the rock in the middle thinner. Tension occurs where two plates pull apart (divergent boundary)
Compression-When one plat pushes against another, it can squeeze the rock until in folds or breaks, like a giant teach compactor. Compression occurs where two plates come together (convergent boundary)
Shearing-When stress pushes a mass of rock in two opposite directions, this can cause the rock to break and slip apart or to change its shape. Shearing occurs where two plates slip past each other in opposite directions (transform boundary)
How does each type of stress change the shape and volume of the rock?
Rocks are hard, but the movement of Earth's plates can create strong forces that slowly bend or fold rocks like a caramel candy bar. Like the candy bar, some rocks only bend and stretch when a strong force is applied to them, but, beyond a certain limit, all rocks in Earth's crust break. These forces are called stress. Stress changes a rock's shape or volume. Geologists express stress as force/unit area. Since stress increases as force increases, stress adds energy to the rock, and it it stored in the rock until the rock changes its shape or breaks.
What are the three types of faults? Describe each.
Normal faults-Form where rock is pulled apart by tension in Earth's crust. The fault cuts through rock at an angle, so that one block of rock sits over the fault and the other lies under the fault. The block of rock that sits over the fault is the hanging wall, which moves downward relative to the footwall, which is the rock that lies under the fault, Normal faults occur where two plates diverge, or pull apart.
Reverse faults- Has the same structure as a normal fault, but the rocks move in reverse direction, so the hanging wall moves up relative to the footwall. Reverse faults form where compression pushes the rock of the crust together.
Strike-slip faults-Produced by shearing. The rocks on either side of the fault slip past each other sideways, with little up or down motion. A strike-skip fault that forms the boundary between two plates is a transform boundary.
Which types are associated with which types of faults?
Tension = normal fault (divergent boundary), compression = reverse fault (convergent boundary), and shearing = strike-slip fault (transform boundary)
How do faults form?
When enough stress build up in a rock, it can cause the rock to break, therefore a fault is created. Most faults occur along plate boundaries, where the forces of plate motion push/pull the crust until it breaks.
What causes the formation of anticlines and sync lines?
An anticline is a fold in a rock that bends upward in an arch shape, and a sync line is a fold in a rock that bends downward to form a V shape. They both form in places where compression forces have folded the crust.
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