| A | B |
|---|
| crust | outermost, least dense layer |
| lithosphere | large sections of Earth's crust and upper mantle |
| mantle | largest, thickest layer, below crust |
| asthenosphere | plastic-like layer at top of mantle |
| outer core | liquid layer below mantle |
| inner core | solid, center layer of Earth |
| density | compares mass and volume |
| seismic waves | energy waves; spread out in all directions from epicenter |
| Primary (P) waves | longitudinal waves; travel fastest |
| Secondary (S) waves | transverse waves; arrive at seismograph after P waves |
| surface waves | form when P and S waves reach surface; causes ground to shake |
| seismograph | instrument used to detect and measure seismic waves |
| seismogram | jagged lines produced on paper by seismic waves |
| epicenter | point on Earth's surface above focus of earthquake |
| focus | point where rock breaks releasing seismic energy |
| triangulation | using records from 3 seismograph stations to lockate epicenter |
| igneous rocks | formed by cooling and hardening of molten rock |
| intrusive | igneous rocks which form from magma below the surface |
| extrusive | igneous rocks formed on surface from cooled lava |
| metamorphic rocks | formed from existing rocks due to heat and pressure |
