dating rocks & fossils. will you go out with me no! i’m far too old for you!
TRANSCRIPT
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Dating Rocks & Fossils
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Dating Rocks & Fossils
Will you go out
with meNO!
I’m far too old for you!
![Page 3: Dating Rocks & Fossils. Will you go out with me NO! I’m far too old for you!](https://reader036.vdocument.in/reader036/viewer/2022083008/56649f4e5503460f94c70102/html5/thumbnails/3.jpg)
Relative dating
• The nearer the surface a stratum of rock is, the younger the fossils it contains.
• The age of a fossil can be estimated if you can accurately date rock strata above and/or below
• “Index fossils” dated at one site may be used to estimate ages of fossils found at another site
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Radiometric techniques
Carbon dating• Living things take in some C-14 which is
produced at a (nearly) steady rate in the upper air.
• C-14 decays to C-12 at a constant rate.• By measuring how much C-14 is left in a
once living thing we can find ages up to about 50,000 years
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Radiometric techniques (cont’d)Potassium – Argon dating• When rock melts it loses all the gas it
contains. • Once it cools, potassium-40 in the lava
decays radioactively at a known rate to form argon-40 gas.
• By measuring the amount of Ar-40 in volcanic rock, ages from over 10,000 to millions of years can be found.
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Radiometric techniques (cont’d)
Uranium series decay• Using uranium’s decay to other elements it
is possible to date corals and shells up to about 1 million years.
Fission track• Tracks left in volcanic rock, glass or
pottery by radioactive decay of uranium can be used to find ages from 1000 years to 100 million years.
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Electron Spin Resonance (ESR)
• Electronic charges produced by radioactivity in surrounding rocks can be trapped in a fossil such as teeth or bones
• The older the fossil the more charges in it. This can be measured by ESR spectroscopy
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Genome Analysis• DNA sequencing: The more similar the DNA
of 2 species/groups, the more closely they are related
• Mitochonrial DNA (mtDNA). Passed on from mother only. Mutations occur at a steady rate so it can show how closely groups are related and how long ago they separated.
• Y chromosome DNA. Passed on from father to sons only. Not prone to much change so can be used to trace ancestry and relationships..