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What dating method do they use to determine the age of really old fossils?

Yesterday there was news of a 3.3 million year old Australopithecus afarensis fossil from Ethiopia. I'm just curious as to how they ascertain the age. I know it's not carbon-14 dating, that's 2 orders of magnitude beyond its range. It's been a while since I learned about this stuff, so thanks for refreshing my memory.

They measure the decay of other radioactive elements, not carbon. The half life of carbon 14 is only 15,000 years or so. For anything older than that they measure for example, how uranium decays into lead. The article below may help.

This entry was posted on Saturday, November 15th, 2008 at 2:32 pm and is filed under dating. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

6 Responses to “What dating method do they use to determine the age of really old fossils?”

  1. The site I use is match.com The old fossils don't have a picture there.
    References :
    Straight face

  2. Sending the Old fossil on a date with a Blonde, Brunette and a red head – he may react to one of them
    References :
    PG Wodehouse – Jeeves infobase

  3. Looks like there's aluminum, chlorine, calcium & iodine dating…
    http://en.wikipedia.org/wiki/Cosmogenic_isotope#Applications_in_geology_listed_by_isotope
    References :

  4. radioactive dating, using certian elements such as carbon-14, scientists are able to figure out how old a fossil was
    References :
    gr 11 Science

  5. They measure the decay of other radioactive elements, not carbon. The half life of carbon 14 is only 15,000 years or so. For anything older than that they measure for example, how uranium decays into lead. The article below may help.
    References :
    http://en.wikipedia.org/wiki/Rock_dating

  6. check it out on hhp://www.wikipwdia.org
    References :

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