| A | B |
|---|
| asthenosphere | plastic-like layer of Earth on which the lithospheric plates float |
| batholith | largest intrusive igneous rock body that forms and solidifies underground |
| caldera | large, circular-shaped opening formed when the top of a volcano collapses |
| 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 |
| continent | one of the seven great divisions of land on the globe |
| continental drift | Wegener's hypothesis that all continents were connected, then drifted apart |
| convection current | current in Earth's mantle that transfer eat in Earth's interior, driving force for tectonics |
| converge | to come together |
| crater | steep-walled depression around a volcano's vent |
| crest | the highest point of a wave |
| dike | igneous rock feature formed when magma is squeezed into a vertical crack |
| diverge | to move apart |
| earthquake | vibrations produced when rocks break along a fault |
| epicenter | point on Earth's surface directly above an earthquake's focus |
| extrude | to force or push out |
| 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 |
| hot spot | result of an unusually hot area at the boundary between Earth's mangle and core that forms volcanoes |
| intrude | to enter by force; cut in |
| lava | molten rock material flowing from volcanoes |
| liquefaction | occurs when wet soil acts more like a liquid during an earthquake |
| lithosphere | rigid layer of Earth about 100 km thick, made of the crust and part of upper mantle |
| magma | hot, melted rock material beneath Earth's surface |
| magnitude | measure of the energy released during an earthquake |
| normal fault | break in rock caused by tension forces |
| Pangaea | large ancient landmass composed of joined continents |
| plate tectonics | theory that Earth's crust and upper mantle are broken into plates that float and move |
| primary wave | seismic wave that moves rock particles back and forth in the same direction that the wave travels |
| reverse fault | break in rock caused by compressive forces |
| seafloor | portion of Earth's crust that lies beneath ocean waters |
| seafloor spreading | Hess's theory that new seafloor is formed when magma is forced upward toward the surface |
| secondary wave | seismic wave that moves rock particles at right angles to the direction of the wave |
| seismic wave | wave generated by an earthquake |
| seismograph | instrument used to register earthquake waves and record the time that each arrived |
| shield volcano | broad, gently sloping volcano formed by quiet eruptions of basaltic lava |
| sill | igneous rock feature formed when magma is squeezed into a horizontal crack |
| strike-slip fault | break in rock caused by shear forces |
| surface wave | seismic wave that moves rock particles rolling or swaying motion |
| tephra | bits of rock or solidified lava dropped from the air during an explosive volcanic eruption |
| transform | to convert or change |
| tsunami | seismic sea wave that begins over an earthquake focus, can be highly destructive when it reaches shore |
| vent | opening where magma is forced up and flows out as lava |
| volcanic neck | solid igneous core of a volcano left behind after the softer cone has been eroded |
| volcano | opening in Earth's surface that erupts sulfurous gases, ash, and lava |
| wave | rhythmic movement that carries energy through matter and space |
