Term
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Definition
-most common technique is Radiometric Dating
-way of determing date of mineral (crystallization or cooling) |
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Term
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Definition
- actual number of years passed since rock formed
(closed system-not always true in nature) |
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Term
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Definition
-contain electrons, protons, neutrons
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Term
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Definition
-atoms of an element have same # of protons
-but different # of neutrons
-atomic # same
-idenfied by mass number-sum of neutron & protons
-are unstable and said to be radioactive
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Term
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Definition
Composite Column
-chronological order
-succession of known strata
-fitted together by fossils or evidence of relative age |
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Term
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Definition
-are unstable
-decay in 3 processes; most useful for dating rocks |
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Term
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Definition
-lose an electron from the nucleus
-changes a neutron to (proton)
N↓P↑
(atomic # goes down) |
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Term
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Definition
-nucleus may gain an electron
-changing a proton (to an neutron)?
-decreases # protons |
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Term
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Definition
-lose 2 protons & 2 neutrons
-reduces mass number by 4
-reduces atomic number by 2
-happends in isotopes with large atomic #
(because they more N & P)
(helium atom or alpha particle) |
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Term
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Definition
-radioactive decay measured
-time required for half of the parent atoms in a sample to decay into daughter atoms.
-expressed in time units
-time needed to reduce parents in 1/2
(50% parent & 50% daughter)-1 half life
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Term
| Ability to date rock depends on |
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Definition
a. fiding a mineral containing the useful istopes
b. determing that the nineral formed when the rock formed
c. our ability to measure samll amounts of useful istopes |
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Term
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Definition
-useful for young minerals
(carbon works back to 70,000-100,000 yrs) |
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Term
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Definition
| -not useful for young minerals ut works well for oldest minerals |
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Term
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Definition
-major difference geoglist & most scientists is their attitude about time
a "long" time may not be important unless it is > 1 millions years |
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Term
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Definition
| divisions worldwide stratgraphic column based on on variation in perserved fossil |
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Term
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Definition
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Term
| Parent atom/Daughter atom |
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Definition
| parent atom going under radioactive decay product that comes from it is daughter atom |
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Term
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Definition
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Term
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Definition
- use natural radioactive isotopes
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Term
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Definition
-not all rocks can be dated by radiometric methods
-datable materials (such volcanic flows/ash beds and ingneous intrustions) often used to bracket episodes in earths history and arrive at ages |
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Term
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Definition
Paleozoic=old life
Mesozoic=middle life
Cenozoic=recent life |
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Term
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Definition
-phanerozioc eon divided into periods
-fossils contained in equivalent rocks |
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Term
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Definition
-interval into which geologic time is divided
(4 of them) |
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Term
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Definition
-oldest eon
-earliest time unit in earths history
-present on other planets and moons |
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Term
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Definition
-after hadean
-oldest rocks we know of on earth
-microscopic life forms |
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Term
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Definition
-follow Archean
-rocks evidence of multicelled organisms (lack preservable parts)
-not well known |
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Term
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Definition
-periods are subdivded
-subdivision of fossil record |
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Term
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Definition
-time divided into periods of predominalty normal polarity
-or predominantly reserved polarity |
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