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8ES Chp 6:Earthquake
8th Grade Earth Science Chapter 6: Earthquakes Coach Leach
Term | Definition |
---|---|
earthquake | A measurable movement of the earth's crust. |
stress | Any force exerted on an object. |
compression | A contact force that acts to squeeze or crush an object or substance. |
tension | Forces that act to pull an object apart. |
shear | Forces acting in opposite directions on different parts of the same object or substance. |
divergent boundary | The margin between two tectonic plates that are moving away from each other. |
convergent boundary | The margin between two tectonic plates that are moving toward each other. |
transform boundary | The margin between two tectonic plates that are sliding in opposite directions parallel to the margin. |
strain | Any change in the shape of a solid due to stresses exerted on the material. |
joint | A crack in a rock that shows no indication of motion on either side of the crack. |
fault | A joint or crack in rock where the rock on both sides of the joint have moved relative to each other. |
strike | The compass direction of the horizontal plane of the surface of a fault face or rock stratum. |
dip | The angle of slope of a fault face or stratum, measured from the horizontal plane. |
dip-slip fault | A fault whos main motion is parallel its dip direction. |
normal fault | A dip-slip fault in which the upper body of rock drops relative to the body of rock. |
reverse fault | A dip-slip fault in which the upper body of rock slides upward relative to the lower body of rock. |
strike-slip fault | A fault along which the main movement is horizontal, or parallel to the fault's strike; also called a transform fault. |
seismometer | An instrument that detects the movement of the earth due to seismic waves. |
P wave | The first earthquake wave that reaches a seismic station from an earthquake; these waves are the fastest seismic waves, passing through all parts of the earth's interior and tend to be the least destructive. |
S wave | The second earthquake wave that reaches a seismic station from an earthquake; they don't pass through the earth's core and are much more destructive than primary waves. |
surface wave | One of several kinds of earthquake waves that travel only along the surface of the earth; they are slower than P or S waves and far more destructive. |
focus | The point of an earthquake's origin deep within the earth. |
epicenter | The location on the earth's surface directly above an earthquake's focus. |
Richter scale | A scale that rates the magnitude of the intensity of an earthquake. |
magnitude | In seismology, it is a measure of an earthquake's energy. |
intensity | In earthquakes, it is a measure of the damage that an earthquake causes using the Modified Mercalli Intensity scale |
tsunami | A far-reaching, devastating water wave caused by seismic activity. |
buoyant force | The upward force that a fluid exerts on an object in the fluid. |