Forces that Shape Earth: Earthquakes VOCABULARY
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Stress- a force that acts on rock to change its shape or volume
Tension- stress that stretches rock so that it becomes thinner in the middle
Compression- stress that squeezes rock until it folds or breaks
Shearing- stress that pushes masses of rock in opposite direction in a sideways movement
Normal fault- a type of fault where the hanging wall slides downward; caused by tension in the crust
Hanging wall- the block of rock that form the upper half of a fault
Footwall- the block of rock that forms the lower half of a fault
Reverse fault- a type of fault where the handing wall slides upward; cause by compression in the crust
Strike-slip fault- a type of fault in which rocks on either side more paste each other sideways with little up and
down motion
Anticline- an upward fold in rock formed by compression of Earth’s crust
Syncline- a downward fold in rock formed b compression in Earth’s crust
Plateau- a large area of flat land elevated high above sea level
Earthquake- the shaking that results from the movement of rock beneath Earth’s surface
Focus- the point beneath earth’s surface where rock breaks under stress and causes an earthquake
Epicenter- the point on Earth’s surface directly above an earthquake’s focus
P waves-seismic waves that compress and expand in the ground
S waves-seismic waves that vibrate from side to side as well as up and down
Surface waves- a type of seismic wave that move the ground up and down or side to side
Mercalli scale- a scale that rates earthquakes according to their intensity and how much damage they cause at a
particular place.
Magnitude- the measurement of an earthquakes’ strength based on seismic waves and movement along faults
Richter scale- a scale that rates an earthquakes magnitude based on the size of its seismic waves.
Seismograph- a device that record ground movement caused by seismic waves as they move through earth
Moment magnitude scale- a scale that rates earthquakes by estimating the total energy related by an
earthquake
Seismogram-the record of an earthquakes seismic waves produce by an seismograph