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Ch. 4 Vocab
Term | Definition |
---|---|
Fossil | A trace or the remains of a once-living thing from long ago. |
Original Remains | A fossil that is the actual body or body parts of an organism. |
Ice Core | A tubular sample that shows the layers of snow and ice that have built up over the years. |
Relative Age | The age of an event or object in relation to other events or objects. |
Index Fossil | A fossil of an organism that was common, lived in many areas, and existed only during a certain span of time. Index fossils are used to help determine the age of rock layers. |
Absolute Age | The actual age in years of an event or object. |
Half-Life | The length of time it takes for half of the atoms in a sample of radioactive element to change from an unstable form into another form. |
Uniformitarianism | A theory stating that the processes shaping Earth today, such as erosion and deposition, also shaped Earth in the past, and that these processes cause large changes over geologic time. |
Geological Time Scale | The summary of Earth's history, divided into intervals of time defined by major events or changes on Earth. |