| A | B |
|---|
| crust | The outermost solid layer of the Earth. |
| mantle | The thick layer of the Earth that contains most of the Earth's mass. |
| core | The innermost layer of the Earth. |
| inner core | a solid, iron ball |
| lithosphere | Earth's crust and the solid part of the mantle. |
| continental drift | the theory that continents drifted apart in the past and continue to do so today. |
| plate tectonics | The theory that the Earth's lithosphere is broken into about 20 moving plates. |
| plate boundaries | areas where two plates meet |
| fault | a break in the Earth's crust |
| spreading boundaries | plates move away from one another causing magma to rise through the cracks |
| fracture boundaries | plates slide past one another often causing earthquakes |
| colliding boundaries | two plates push against one another causing mountains |
| pangaea | whole Earth, one large continent |
| convection | in the mantle, the rising and falling of hot melted rock that circles around over and over |
