Ch 3-1 Geologic Time
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18 terms
Terms | Definitions |
|---|---|
 Cambrian period | Time span from 542 million years ago to 488 million years ago, marked by the appearance of complex life-forms |
| Fossil | Preserved remains or evidence of a past living organism |
| Geologic time scale | Visual record of Earth's history, with the individual units based on changes in the rocks and fossils |
| Half-life | Time required for half of the amount of a radioactive parent element to decay into a stable daughter element |
| Principle of superposition | States that in rock layers that have not been folded or deformed, the oldest rock layers are on the bottom; gives the relative age of rock layers |
| Radioactive Decay | Process by which an element naturally changes into another |
| Adaptation | A characteristic that improves an species developed over time that helps them survive in a particular environment |
| Extinct | No longer alive; occurs when all individuals of a species are dead |
| Phanerozioc eon | Geologic time from 542 million years ago to present, marked by the appearance of larger , more complex organisms |
| Trilobite | Extinct marine arthropod characterized by a three-lobed body |
| Achaean eon | Time span from 4 to 2.5 billion years ago, during which Earth had its first solid surface |
| Hadean eon | Time span covering the first 640 million years of Earth's history |
| Occur | To come into being; as an event; to come to pass |
| Great Oxygenation Event | Rise of atmospheric oxygen during the Proterozoic eon, harming organisms that had evolved in an oxygen-poor environment |
| Proterozoic eon | Time span from 2.5 to 0.542 billion years ago, during which large landmasses formed on Earth |
| Protocontinents | Small landmasses that formed on Earth during the Achaean eon |
| Salt | Ionic crystalline compound |
| Thermal Energy | Moves from one place to another because of differences in temperature |
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