| A | B |
|---|
| Geology | The study of rocks and minerals. |
| Geologic Time Scale | An outline of earth's history, arranging events in the order in which they occurred. |
| Era | The largest division of geologic time. |
| Theory | A general principle or set of principles that explains facts or events of the natural world. |
| Law | A sequence of natural events occurring with unvarying uniformity under the same conditions. |
| Fossils | A record of past life in the form of a track, a trace, or the remains of organisms preserved in rock. |
| Index Fossil | A fossil of an organism that lived in many places, but over a short time period; used to date the rock layer in which it is found. |
| Trilobite | An index fossil that is a hard-shelled invertebrate that lived about 570 million years ago. |
| Ammonite | A shelled invertebrate. |
| Extinct | No longer in existence. |
| Relative Dating | The process of determining that one event occurred before or after another. |
| Radio Metric Dating | A technique that uses radioactivity to find the ages of certain rocks. |
| Half Life | The amount of time needed for one-half of the atoms in a radioactive element to decay. |
