| A | B |
|---|
| fossil | preserved remains or traces of an ancient organism |
| landforms | a feature of topography formed by the process that shaped the Earth's surface |
| evolution | process by which all living things have changed over time |
| relative time (age) | age of rock or organism compared to the age of the rock layers |
| cast | a fossil that is a copy of an organsim's shape formed when minerals seep into the mold |
| absolute time (age) | age of the rock or organism given to the number of years formed |
| law of superposition | states that each layer is older than the rock layer above it (in sedimentary rocks) |
| era | unit of geologic time between the Precambrian and the present |
| period | unit of geologic time in which geologist divide eras |
| epoch | subdivisions of the periods of geologic time scale |
| mass extinction | when many types of living things become extinct at the same time |
