| A | B |
|---|
| axis | imaginary line that passes through the Earth’s center and its North |
| conservation | saving or protecting natural resources |
| core | Earth’s hottest layer; center of the Earth made of molten rock |
| crater | holes on the surface of a moon or a planet formed when meteors |
| crust | the outer layer of the Earth; made of solid rock |
| eclipse | what occurs when one object passes through the shadow of another |
| erosion | the process of moving sediment from one place to another |
| fossil fuel | a fuel formed from the remains of once-living organisms |
| fossils | the remains or traces of past life found in the Earth’s crust |
| gravity | the force that pulls all objects in the universe toward one another |
| igneous rock | rocks made from cooled magma beneath the Earth’s surface or |
| inexhaustible resource | a resource that cannot be used up |
| lava | magma that pours out of a volcano onto the Earth’s surface |
| limited resource | a resource that will eventually be used up |
| magma | hot, soft rock from the Earth’s lower mantle |
| mantle | the layer of rock beneath the Earth’s crust |
| metamorphic rock | rocks changed in form by great heat or pressure |
| minerals | naturally occurring substances within the Earth |
| natural resource | any of the useful minerals and other materials that people take |
| nonrenewable resource | a resource that cannot be replaced once it is used |
| orbit | the path a heavenly body takes as it revolves around a star or a |
| rotate | to turn completely around, such as the Earth rotating on its axis |
| renewable resource | a resource that is replaced as it is used |
| revolve | to travel in a closed path |
| rock cycle | the cycle in which rocks change over time and under certain |
| satellite | any natural body, like the moon, or artificial object that orbits |
| sedimentary rock | rocks formed from particles that have been deposited by ice, water, |
| telescope | an instrument that magnifies distant objects |
| weathering | the process of breaking rock into soil, sand or other tiny pieces |
