In 1970, Amos Flora of Flora, Indiana, discovered teeth and...

In $1970,$ Amos Flora of Flora, Indiana, discovered teeth and jawbones while dredging a creek. Scientists discovered that the bones were from a mastodon and that they had lost $77.2 \%$ of their carbon- $14 .$ How old were the bones at the time that they were discovered? (Sources: "Farm Yields Bones Thousands of Years Old," by Dan McFeely, Indianapolis Star, October $20,2008 ;$ Field Museum of Chicago, Bill Turnbull, anthropologist)

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Key Concepts

Carbon-14 Dating

Carbon-14 dating is a method used to determine the age of organic materials by measuring the amount of the radioactive isotope carbon-14 remaining in a sample. As living organisms constantly exchange carbon with the environment, the ratio of carbon-14 to carbon-12 remains relatively constant while alive. When the organism dies, no new carbon-14 is absorbed, and the isotope decays at a known rate, allowing scientists to estimate the time elapsed since death.

Half-life

The concept of half-life refers to the time required for half of the radioactive isotope present in a sample to decay. In the context of carbon-14 dating, knowing the half-life of carbon-14 is crucial because it allows researchers to calculate the age of a sample by measuring how much of the isotope remains compared to its initial concentration.

Radioactive Decay

Radioactive decay is the process by which an unstable atomic nucleus loses energy by emitting radiation. This decay process occurs at a predictable rate, which is characterized by the isotope's half-life. Understanding radioactive decay is fundamental to dating methods such as carbon-14 dating, as it underpins the conversion of remaining isotope percentages into an estimate of the sample's age.

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