Question | Answer |
Earthquake | vibrations produced when rocks break along a fault |
Fault | surface along which rocks move when they pass their elastic limit and break |
Focus | in an earthquake, the point below Earth's surface where energy is released in the form of seismic waves |
Primary waves | seismic wave that moves rock particles back-and-forth in the same direction that the wave travels |
Secondary waves | seismic wave that moves rock particles at right angles to the direction of the wave |
Surface waves | seismic wave that moves rock particles up-and-down in the backward rolling motion and side-to-side in a swaying motion |
Epicenter | point on Earth's surface directly above and earthquake's focus |
Seismograph | instrument used to register earthquake waves and record the time that each arrived |
Richter scale | a scale used to measure the magnitude of an earthquake |
modified Mercalli scale | a scale used to measure the amount of damage that occurred during an earthquake |
volcano | opening in Earth's surface that erupts sulfurouse gases, ash, and lava; can form at Earth's plate boundaries, where plates move apart or together, and at hot spots |
vent | opening where magma is forced up and flows out onto Earth's surface as lava, forming a volcano |
crater | steep-walled depression around a volcano's vent |
Hot spot | the result of an unusually hot area at the boundary between Earth's mantle and core that forms volacoes when melted rock is forced upward and breaks through the crust |
Shield volcano | broad, gently sloping volcano formed by quiet eruptions of basaltic lava |
cinder cone volcano | steep-sided, loosely packed volcano formed when tephra falls to the ground |
composite volcano | volcano built by alternating explosive and quiet eruptions that produce layers of tephra and lava; found mostly where Earth's plates come together and one plate sinks below the other |
tephra | bits of rock or soldified lava dropped from the air during an explosive volcanic eruption; ranges in size from volcanic ash to volcanic bombs and blocks |