| Term | Definition |
| core | The inner most layer of the earth |
| mantle | The middle layer of earth, semi-liquid (or plastic-like) |
| crust | The thin outer layer of the earth |
| density | How tightly packed the molecules are within an object |
| tectonic plates | Large sections of the earth's crust |
| convection current | The cycle of rising and sinking particles within the mantle due to changes in temperature and density; cause the tectonic plates to move |
| magma | Hot, semi-fluid material found underneath the surface of the earth; can form igneous rock |
| lava | Hot, semi-fluid, molten rock that comes out from volcanoes or other large openings in the earth's crust |
| convergent boundary | Boundary created when two plates collide, resulting in subduction (destroys some of the earth's crust) |
| divergent boundary | Boundary created when two plates pull apart from each other, resulting in an opening between the plates where magma rises and cools (creates new crust) |
| transform boundary | Boundary created when two plates move horizontally past each other with little vertical motion |
| subduction | One plate slides underneath another plate |
| metamorphic | Rock formed when exposed to extreme heat and pressure; rock that has changed form |
| igneous | Rock formed in or near a volcano when magma/lava or ash hardens to become rock |
| sedimentary | Rock formed when little bits of "stuff" (sediment) harden to become rock |
| weathering | Breaking down of rock and the earth's crust due to forces in the atmosphere like running water (rain), wind, chemicals, etc. |
| erosion | Gradual destruction of an object by forces within earth's atmosphere like wind, running water, chemicals, etc. |
| volcano | Typically a hill or mountain with a central vent from which magma/lava, pieces of rock, ash, and gas escape; usually (95% of the time) form on the along plate boundaries |
| trench | Forms at a subduction zone (convergent boundary) under water; some of the deepest parts of the ocean |
| mid-oceanic ridge | The longest mountain range in the world; all along the center of the Atlantic Ocean; formed by active volcanoes through sea floor spreading |
| sea-floor spreading | Occurs at a divergent boundary under water; two plates pull apart, magma rises and cools, creating new land (what formed the Atlantic Ocean) |
| rift | A large, long valley on a continent; formed at a divergent boundary; small volcanoes are typical as magma rises and cools (ex: African Rift Valley) |
| hotspot | A weak spot in the middle of a tectonic plate where magma surfaces; forms a volcano (ex: Hawaii & Yellowstone) |
| fault | A crack in the Earth's crust |
| reverse fault | A fault where one side is driven on top of the other; caused by compression stress (force pushing together) |
| normal fault | A fault where one side moves down compared to the other side; caused by tension stress (force pulling apart) |
| strike-slip fault | A fault where two sides move horizontally with respect to each other (caused by shearing stress (force of sliding past each other) |