Term
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Definition
| Physical processes we observe today also operated in the past at roughly the same rates and were responsible for the formation of the geologic features we see in outcrops. |
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Term
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Definition
| The age of one geologic feature with respect to another. |
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Term
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Definition
| Age of the feature given in years. |
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Term
| Principle of Original Horizontality |
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Definition
| Sediments on Earth settle out of a fluid in a gravitational field. Typically, the surfaces on which sediments accumulate are fairly horizontal. |
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Term
| Principle of Superposition |
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Definition
| In a sequence of sedimentary rock layers, each layer must be younger than the one below, for a layer of sediment cannot accumulate unless there is already a substrate on which it can collect. |
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Term
| Principle of Original Continuity |
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Definition
| Sediments generally accumulate in continuous sheets. If today you find a sedimentary layer cut by a canyon, then you can assume that the layer once spanned the canon but was later eroded by the river that formed the canyon. |
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Term
| Principle of Cross-Cutting Relations |
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Definition
| If one geologic feature cuts across another, the feature that has been cut is older. |
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Term
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Definition
| The principle that the assemblage of fossil species in a given sequence of sedimentary strata differs from that found in older sequences or in younger sequences. A certain species appears at a certain level and then disappears at a higher level. |
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Term
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Definition
| Such a surface, representing a period a period of non-deposition and possibly erosion. |
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Term
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Definition
| Rocks below an angular unconformity were tilted or folded before the unconformity developed. |
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Term
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Definition
| A type of unconformity at which sedimentary rocks overlie intrusive igneous rocks and or metamorphic rocks. |
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Term
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Definition
| An unconformity parallel to the two sedimentary sequences it separates. |
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Term
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Definition
| USed to describe the vertical location of rock units in a particular area. |
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Term
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Definition
| a sequence of beds of a specific rock type or group of rock types that can be traced over a fairly broad region. |
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Term
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Definition
| The boundary surface between two formations. |
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Term
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Definition
| Age relationship between the strata at one locality and the strata at another. |
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Term
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Definition
| Mysterious period of earth between the birth and 3.8 billion years ago. |
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Term
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Definition
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Term
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Definition
| Complex shell-less invertibrates, Oxygen in the atmostphere, photosysnthesis. |
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Term
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Definition
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Term
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Definition
| Sudden diversification of life, with many new genera appearing over a relatively short interval. |
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Term
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Definition
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Term
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Definition
| Plants and Land Animals (Dinosaurs) |
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Term
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Definition
| Mammals became prominent, humans evolved. |
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Term
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Definition
| Ages are defined by mass extinctions. Meteors, Volcanic Eruptions, Ice Ages. |
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Term
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Definition
| The process of determining numerical age of rocks. |
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Term
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Definition
| Different versions of an element, have the same atomic number but a different atomic weight. |
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Term
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Definition
| Radioactive isotopes are unstable, after a given time, they undergo a change that converts them into a different element. |
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Term
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Definition
| The isotope that undergoes change. |
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Term
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Definition
| The decay product that forms as a result of radioactive decay. |
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Term
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Definition
| Time is takes for half of a group of parent isotopes to decay. |
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Term
When Dating Rocks We Use?
Its Half Life Is? |
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Definition
| When dating rocks, we use uranium, which goes to lead. U→Pb. Which has a half life of 4.4 billion years. |
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Term
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Definition
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Term
| Absolute Dating Measures What? |
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Definition
| • Absolute dating can only measure rocks that cool. Cannot measure sedimentary rocks. To measure sedimentary rocks, set upper and lower limits with crosscutting relationships. |
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Term
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Definition
| Using the naturally reoccurring carbon to date things up to 62000 years old. |
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