| A | B |
|---|
| compressional waves | fastest of the seismic waves. Also called primary waves |
| crust | the hard layer of the rock which covers the outside of the earth. |
| epicenter | located above the focus on the crust of the earth. |
| faults | cracks in the earth's crust |
| focus | origin of an earthquake, which may be miles below the crust |
| igneous rock | rock formed from melted rock which was originally magma |
| inner core | the inntermost core of the earth, consisting of the heaviest elements of iron and nickel |
| lava | magma which is forced up through cracks in the earth's crust and pours fourth from volcanoes |
| mantle | the layer just below the crust |
| magma | the semisolid material in the mantle |
| magnitude | the intensity of an earthquake, usually measured on the Richter Scale |
| metamorphic rock | rock which was once igneous, sedimentary, or metamorphic rock which is physically and sometimes chemically changed due to heat and pressure |
| outer core | layer just below the mantle. |
| pangaea | name of land mass of continents that were grouped together 200 million years ago |
| plate tectonics | the theory that explains the movement of the continents and spreading of the sea floor. |
| richter scale | used to measure the ground motion caused by an earthquake |
| seismic waves | vibrations given off by the violent breaking of rock during an earthquake. |
| secondary waves | slower seismic waves which reach seismographs after P waves |
| surface waves | a seismic wave that slowly travels along the crust of the earth. Also called L waves |
