Dating
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
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| measured by man directly | Time
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| heart beats | Time
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| pendulum swings | Time
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| atomic cyclic vibrations | Time
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| redefined in 1967 | Time
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| 9,192,631,770 vibration cycles of a cesium atom | second
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| rotation of the Earth | day
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| lengthening 1 sec/year | variable
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| 1.5 Ga day | 11 hours
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| 20 hours - based on daily growth rings | 400 Ma day
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| moon around the Earth | month
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| Earth around the Sun | year
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| changes in growth cycles | seasons
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| because the Earth is inclined on its axis | seasons
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| produces growth rings in plants | seasons
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| bristle cone pines in the southwest U.S. | example of growth rings
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| oldest known trees | >5000 yrs.
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| used to calibrate 14C dates | trees
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| produces growth rings in animals | seasons
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| tidal control | claims
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| fish scales | growth rings
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| scallop growth bump | growth rings
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| high erosion, low erosion cycles | varves
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| back to ~15,000 years b.p. | glacial
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| more cycles in the past indicates shorter days in the past | growth rings
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| salt in the ocean | major argument on Earth age
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| 1899,Irish physicist estimated - Earth age ~99.4 million years old | Joly
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| ocean thought initially salty | refuted
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| cooling rate of the Earth | major argument on Earth age
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| middle 1860s -a physicist | Lord Kelvin
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| time necessary to cool from a liquid | Lord Kelvin
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| Earth age 10-20 million | Lord Kelvin
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| radioactive heating discovered 1896 | Becquerel
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| sediment deposition rate since fossils appeared | major argument on Earth age
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| total thickness versus rate of accumulation137,195 0.305m/1000 years | sediment deposition rate
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| >450 million years old | fossil bearing rocks
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| age estimates based on radioactive decay estimates | major argument on Earth age
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| spontaneous breakup of the atomic nuclei of certain unstable substances | radioactivity
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| discovered in 1896 by Becquerel - French physicist | radioactivity
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| isolated energy producers from Uranium | Curies
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| 1898 - Curies discovered Radium, atomic number 88 | Radium
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| radioactive disintegration | decay
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| nuclei of helium atoms | alpha particles
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| 2 protons | helium
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| 2 neutrons | helium
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| electrons | beta particles
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| electromagnetic radiation | (gamma) rays
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| - like light but with a very short wavelength | gamma rays
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| unstable elements | radioactive isotopes
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| spontaneous decay of individual particles is unpredictable | radioactive isotopes
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| decay of half of the atoms is statistically predictable | radioactive isotopes
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| (t1/2) - time it takes for half of the atoms of an isotope to disintegrate | half-life
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| (ln 2)/l; where l = decay constant | t1/2
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| varies from fractions of a second to billions of years | t1/2
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| a constant relating the instant rate of radioactive decay of a radioactive species to the | decay constant
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| naturally -in our atmosphere (14C) | cosmic radiation
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| in the laboratory | cosmic radiation
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| absolute dates | Isotopic Dating
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| based on Parent/Daughter ratio when the decay is known | Isotopic Dating
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| requires a closed system | Isotopic Dating
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| no parent or daughter product can leave the system | closed system
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| changes based on particle emissions/capture | Isotopic Dating
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| parent nucleus loses an alpha particle | alpha particle emission (nucleus of helium atom)
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| daughter atomic number is 2 lower | alpha particle emission (nucleus of helium atom)
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| daughter atomic weight is 4 lower | alpha particle emission (nucleus of helium atom)
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| parent nucleus loses a beta particle | beta particle emission (electron)
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| neutron changes to a proton in the nucleus | beta particle emission (electron)
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| daughter atomic number is 1 higher | beta particle emission (electron)
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| daughter atomic weight is the same | beta particle emission (electron)
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| parent nucleus gains a beta particle | electron capture
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| proton changes to a neutron in the nucleus | electron capture
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| daughter atomic number is 1 lower | electron capture
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| daughter atomic weight is the same | electron capture
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| 14C dating - Carbon - Nitrogen - 1/2 life 5,730 years | Carbon dating
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| in atmosphere 14N + e --> 14C + H | Carbon dating
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| 14C + O2 --> 14CO2 into plants and animals | Carbon dating
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| dates 14C/12C after death | Carbon dating
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| normal methods good to ~40,000 years | Carbon dating
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| accelerator dates to ~100,000 years | Carbon dating
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| tree rings used to calibrate dates | Carbon dating
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| 14C production assumed constant through time | Carbon dating
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| 14C disappears at the 1/2 life rate- 14 14 6 C --> 7 N - " decay | Carbon dating
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| Earth age = 4.6 billion | Uranium-Lead dating
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| 1/2 life = 713 million to 4.5 billion years | Uranium-Lead dating
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| dated oldest rocks on Earth | Uranium-Lead dating
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| Zircon U/Pb age - 4.06 Ga | oldest rocks
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| Northwest Territories of Canada | oldest rocks
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| gneissic rock type (Acasta Gneiss) | oldest rocks
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| 1/2 life 48.8 b.y. | Rubidium-Strontium dating
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| discovered 1948 | Potassium-Argon dating
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| 1/2 life = 1.3 b.y. | Potassium-Argon dating
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| 40Ar/39Ar method | Potassium-Argon dating
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| argon loss at 50-200o C | Potassium-Argon dating
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| metamorphism resets the atomic clock | Potassium-Argon dating
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| usually igneous rocks dated- biotite, others | Potassium-Argon dating
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| 1/2 life 106 b.y. | Samarium-Neodymium dating
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| 1/2 life = 13.9 b.y. | Thorium-Lead dating
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| global | MAGNITUDE
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| Cenozoic; specific events in time | TIME
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| CaCO3; water in ice cores; mineral specific | MINERALOGY
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| ice volume and climate | CAUSE
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| evaporation and precipitation fractionation | INTERPRETATION
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| diagenetic problems; organism specific, | ANALYTICAL
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| good | PRECISION
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| cycles - Cenozoic; event specific | UTILITY
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| measured using mass spectrometers | oxygen isotopes
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| rare isotopes | 180
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| common isotope | 160
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| lighter 16O more readily | during evaporation
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| heavier 18O is left behind and concentrated | during evaporation
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| ice is light-isotope enriched | during glaciation
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| oceans become heavier | during glaciation
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| in general, marine organisms concentrate 18O | during glaciation
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| some organisms fractionate isotopes | problems with fractionating
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| salinity causes local isotope anomalies | problems with fractionating
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| temperature decreases and organisms concentrate 18O | problems with fractionating
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| first identified by Urey in 1947 | fractionation
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| method established by Emiliani beginning in 1954 | fractionation
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| (1967) estimated paleotemperatures | Shackleton
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| (1973) established $18O to 120 Ka | Shackleton and Opdyke
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| record pushed back beyond 2 Ma | Shackelton
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| (1984) | Imbrie and others
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| established a well dated $18O composite to 780 Ka | Imbrie and others
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| back to 500 k still used today as established in 1984 | Imbrie and others
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| based on 5 marine cores | Imbrie and others
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| showed Milankovitch periods | Imbrie and others
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| precession at ~20 kyr | orbital
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| obliquity at ~40 kyr | orbital
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| at ~100 kyr | eccentricity
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| the state of the atmosphere at a place and time as regards heat, cloudiness, dryness, sunshine wind, rain, etc., | weather
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| the weather conditions prevailing in an area in general over a long period - classically defined as 30 yrs | climate
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| of/or relating to the entire Earth as a planet | global
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| as used by geologists represents the temperature, rainfall and wind over thousands of years | Global Climate
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lmulke1
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