| A | B |
|---|
| inner core | center of the earth made of solid nickel and iron; it is the most dense |
| outer core | is thought to consist of liquid iron and nickel because S waves can't go through it |
| mantle | below the crust and above the core; plastic like |
| asthenosphere | melted top layer of the mantle; crust floats on it |
| Moho | interface between crust and mantle; earthquake waves speed up here |
| continental drift | an old theory that the continents "float" like rafts on the ocean |
| ocean crust | more dense than continental crust; made of basalt ; thinnest layer of the crust |
| continental crust | less dense than ocean crust; make of granite; thickest part of the crust |
| plate tectonics | crust is broken into plates that move around on the asthenosphere |
| convection cell | circular flow of hot fluid; for example in the mantle |
| divergent | divide apart <- -> |
| convergent | come towards each other -> <- |
| subduction | one plate moves under another plate |
| transform | plates travel or slide alongside each other |
| ridge | formed when two plates diverge |
| trench | formed when two plates collide or converge |
| geosyncline | in a trench, an area where sediments collect |
| Ring of Fire | ring around the Pacific Ocean famous for volacnoes and earthquakes |
| magnetic reversals | magnetic North used to be magnetic South; proves sea floor spreading |
| earthquakes | earth shakes when plates move |
| P waves | primary earthquake waves; fastest; compressional push-pull waves |
| S waves | secondary earthquake waves; slower; shear waves |
