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LD ES - Ch 6
LD Earth Science - Chapter 6 - Interpreting Earth's History
| Term | Definition |
|---|---|
| Absolute Age | Age of a rock unit, a fossil, or an event expressed in units of time, such as years |
| Absolute Time Scale | Geologic time that uses numerical time units ( years ) |
| Carbon 14 | Radioactive form of the element carbon that has been used to determine the absolute age of recent fossils & geologic events |
| Correlation | Matching rock layers in different locations by age or by rock types |
| Decay Product | Element produced by the decay of a radioactive isotope |
| Decay Product Ratio | Ratio between the mass of a radioactive element & its decay product |
| Era | Large division of geologic time such as the Mesozoic Era |
| Evolution | Principle that through Earth's history, living things have changed in form from a few simple organisms to a great diversity of organisms |
| Extrusion | Rocks formed from lava that solidifies quickly at Earth's surface |
| Fold | Layers of rock that have been bent by forces within Earth |
| Geologic Time Scale | Divisions of Earth's history originally based on observations of fossil evidence; now, through the use of radioactive isotope measurements , it has changed form a relative scale to an absolute scale |
| Half-life | Time for half the atoms in a radioactive sample to change to the decay product |
| Index Fossil | Fossil found over a large geographic area but which existed for a brief period of geologic time |
| Intrusion | Molten, liquid rock (magma) pushed into cracks within Earth's crust; a body of coarse-grained igneous rock formed by slow cooling within Earth |
| Isotope | Form of a element with more or fewer neutrons then other forms of the same element |
| Law of Superposition | Principle that the lowest layer in a sequence of rock strata must have been deposited before the layers above, unless the rock strata have been turned upside down |
| Mass extinction | Extinction of a large number of species |
| Original horizontally | Principle that all sedimentary layers were originally flat |
| Orogeny | Process of mountain building caused by forces within Earth |
| Period | Subdivision of an era |
| Radioactive | Emission of energy rays or nuclear particles due to the breakdown of an unstable isotope |
| Relative Age | Comparative age; age expressed as before or after other events without specifying the age in units |
| Relative Time Scale | Time scale that indicates whether the object in question is older or younger then something else |
| Superposition | Principle that the lowest layer in a sequence of rock strata must have been deposited before the layers above, UNLESS the rock strata have been turned UPSIDE DOWN |
| Tilted Sedimentary layers | Beds of rock (usually sedimentary) thought to have been deposited horizontally that have been pushed into a different inclination (angle), usually by motions of Earth's crust |
| Unconformity | Gap in geologic record caused by the erosion of sediments or rock followed by new deposition |
| Uniformitarianism | Principal that most geologic events of the past are similar to processes that occur in the present |
Created by:
desilva13
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